Also, I've heard of some engines producing their bhp and max torque at the same RPM, is there any specific reason why this sometimes happens, but not always? Is it all down to valve timing?
Something I'm not quite clear on, If I understand you correctly you would accelerate faster holding the RPM at which you get max torque, regardless of the gear you're in? Ex. If I'm entering the freeway, my truck makes 300 lb/ft of torque @ 3200 RPM. To get up to highway speed ASAP, is it best to hold the engine at that RPM and build speed, or just let it go up to about 4k, when it will shift up and fall back to 1750 and continue like that?
@EngineeringExplained Well i never said it was the same thing but for sure the one depends of the other. A nice easy way to show it, would be with a long crankshaft and a short one...that shows both torque and HP in each case...
@EngineeringExplained Ok! I thought about it before and understood it completely,so i wanted to get online an correct my self..
What i wanted to say is that the point where the highest torque of an engine is,is the most officient way to drive it in terms of energy you give and energy you get,so every hp you get before or after that,it may be less or more,but in order of consumption/torque it wont be officient...
the 5252 mark confused me a little bit...Is this just a theoretical number?
@StefSyros Umm, well the number is based on the definition of horsepower. 1 hp = 33000 ft/lb-min / (2*pi) = 5252. And based on the equation, this is where the two will always meet. However, it is important to note the HP and Torque are measuring different things, they do not have the same unit. So saying they're "the same" at 5252 rpm isn't really accurate, it's just where it occurs.
So..simple said,at 5252 rpm its the most officient way to opperate any kind of ICE,cause then you get the best analogy of torque/HP for the minimum possible fuel??
I mean,everything less than 5252 would give you off course less fuel consumption,but you wont get the maximum amound off power from it??And everything more than that would produce more power ok,but with more energy needed to produce it??
@StefSyros Uhh I wouldn't necessarily say that. At greater RPMs, there is an increase in friction. The more friction you have, the less efficient your engine is. I believe there are some hybrids that have a setup with the engine running at a constant rpm, and I think they're in the 2000-3000 rpm range, this being this specific engine's most efficient range.
Those numbers are at different RPM, so no. If they were at the same RPM, then yes, you could solve for them. But when companies post their figures they use the highest torque (typically at a lower RPM than hp) and the highest HP figure.
@Nathan21h Haha, unfortunately I'm an engineer, not a mechanic. I'm trying to learn but your shop is still much more capable than I when it comes to working on your car.
@TheRekcabOfTheD I wish it was that simple. As much as I wish only the metric system existed, unfortunately America is still far too stubborn to change. I will try my best to switch it, but in many examples it's just the way it is in the real world so it's what I'm forced to use.
@EngineeringExplained I have hope, the only thing I love more than the metric system is America, and nothing would make me happier than to see them together.
@TheRekcabOfTheD I hope my comments did not come off as demanding, I am, by no means trying to tell you how to run your videos, you do a much better job than I every could, I'm just trying to broadcast the usefulness of the metric system, I apologize for anyconfusion and than you again for your videos.
Riddle me this, why can't your common "muscle" car aka mustang and camaros rev pass oh say 7k rpm? where as Hondas are spitting out cars that come 7500+ rpm redline stock and can even go pass it with a tune
@hazyazn Engine size and engineering. Smaller engines with shorter strokes can rev higher, and have less mass in the pistons, meaning less inertia to overcome with each stroke of the engine. DOHC provides a great advantage over pushrod (OHV) because the inertia of the pushrods causes valve float at high rpm. Mustangs have switched over. Not sure about Camaros, I think they're still OHV. Corvettes are still OHV as well. But engine size is just as critical, smaller being with higher revs.
@EngineeringExplained O great explanation, I heard somebody at a car meet said Hondas have titanium valve springs so they can rev higher, not sure if its true though. Your response makes more sense.
the difference between torque and horsepower..... horsepower defines how fast you will hit the wall and torque, how much you will make the wall move.....
trust me......we face it first hand, racing on Indian Roads . ...lol ... you turn perfect, hit a pot hole.... and you are not so perfect anymore.....
we always expect pot holes at entry> apex > n exit of every corner we take..... + traffic + pedestrians + dumb animals....
its much more perfect,its interesting,challenging. and UNFORGIVING \m/
@nixonbrappp22 The power band is simply an rpm range for which your producing maximum horsepower/torque. And this idea can be applied to any engine, 2 stroke, 4 stroke, rotary, etc.
@yodavoodo Low, in comparison to the amount of torque it produces when compared with smaller engines. Truck engines do not rev high, as there is too much inertia preventing that from safely occurring. And if the revs are low, the torque will be a greater number than the hp. Don't simply compare the two numbers though, obviously, as the units are different.
Hey man im interested in getting in the automotive engineering field. I'm very unsure of which route i should take. and guidance you can provide will be much appreciated. feel free to email me.
Good math, but for people that don't plan on being engies, torque is how much weight you can move, horse power is how fast you can move it.. the most basic explanation I have. Again, great explanation to those that can understand it.
@zozlimits Mechanical. It has its ups and downs. Thermo is awesome, and explains so much practical knowledge. Vibrations, dynamics, controls... it gets rough.
i stay up til 6am and click a video in my 'suggested' list and notice a bunch of other comments about people watching this video really late at night O_o
nice video by the way, thanks for the explanation!
@ABC5060 It's difficult to explain in a comment, but basically you want to keep your engine running within the power band. Many engines will have a loss of power for the last 1000 or so RPM before redline, so people say to shift gears then. This isn't logical. If you shift gears at peak hp, your engine rpm will drop too low. Ideally you can shift when downshifting produces the same net force on the wheels as the current gear. This doesn't always occur, so you can just shift at redline.
i'm not taking engineering classes yet but between the comparison of the truck and sports car, did you mean to say the output of the wheel or the wheels rpm instead of rev? because if you think of it, a trucks good friend to create greater torque is keeping the engine at a high rpm and the wheels at a low rpm, thats why 18 wheelers have like 10 shifts (i don't really know how many but many more than the average car) because they need to keep their engines reved high?
@williamred1 The engine revs in large trucks are high relative to the engine's capabilities, but not in comparison to car engines. The reason they have so many gears is to keep the engine within its power band, which can sometimes be only 500 rpm differences. Large trucks may never rev over 2500 rpm, yet my car will easily rev to 6000. Truck engines produce large amounts of torque, but since they are large inertia prevents high revs (relative to cars). Hope this clears things up.
oh i see what your saying. sometimes i don't trust what people say since theyre only human as i am even whats in the books was written by educated humans who got there knowledge out of experiments. this is what i was thinking: you have two exact engines, one has a high gear diference (first gear only) say 1:8 and the other has a gear ratio of 1:2. you place a big load on both engines, the first engine can take it. engine two needs to increase rpm by bigger gear ratio.
so thats what had me with questions, i see how a bigger engine revs low but i did not see how if you needed more torque, simply reduce the engines speed, <that would not make sense, a bigger stronger engine that revs low does make sense. you still wanna keep the revs as high as the engine can safely make to keep the torque at the wheels greater
So, it means that having more torque when climbing your engine can be on 1500rpm and there is still power. If I am wrong please give me an example about torque.
@SuperTauta They rev high to create a lot of power from a small engine (ultimately to save weight/size). Smaller engines have less total inertia, and can be built to rev at much greater limits than larger engines.
you gave the same example of a body builder and a sprinter to explain torque and hp as i give to people. great. and your videos are very good. for a layman hp can be the ability to have the maximum possible rotating force (torque) that an engine can produce for a longer range of rpm or an engine can have more hp if it is able to keep up its maximum torque to a longer range of rpm, i mean upto higher rpms. i am sorry. my english isnt very good.
interesting video! what is 'power band' and is it directly related to the torque/hp relationship i.e. does it inhabit a specific domain on the torque/hp graph? hope i'm making some kind of sense.
@jdis Power band is just referring to the RPM range for which the engine is producing adequate horsepower/torque. For example between your maximum torque and your maximum hp (say one's 3000 and the other's 6000) your power band would be between the two. For racing you want to keep the gearing so that power remains inside the power band as you shift gears, so you can achieve max acceleration.
Dude, you definitely are gonna be the guy that helps me understand the concepts of intricate car techs :D just watched auto bs manual and this one. Gonna check the rest out. Thanks for doing these and keep on! :D
A better mind experiment would be this: say you have a 3000 lb vehicle and you want it to accelerate as quickly as possible. Would you rather have an engine that makes 500 lb-ft at 6000 rpm or one that makes 250 lb-ft at 18000 rpm? (Like F1 motor). Use these examples to move to how gearing would allow the low-torque motor to slaughter the high-torque motor even though vehicle weight is equal. And maybe some discussion of logical and ergonomic shift points. Then viewers might learn something.
@rokjoke It is an excellent example, but I wouldn't have gone so far to say "then viewers might learn something." People on YouTube are at many different levels. Some may learn a lot from this video, others might not hear anything new. Some of my videos are very basic, and others more complicated, as I attempt to appeal to a large audience.
Actually the analogy is pretty lame. MoronAntidote's post from a month ago is right on. Wheel torque is all that matters, and any discussion that claims to explain automotive torque vs. HP and does not talk about gearing is not really going to explain anything. So people fall back of "rules of thumb" that just make them sound ignorant.
@rokjoke Looking back, the analogy wasn't such a good idea; what I implying is that many vehicles with high torque that are geared low tend to be heavy, so added weight affects them little, where as small engines have lower torque, but rev higher, and are used in lighter vehicles where additional weight makes a large impact. What I was hoping to bring across for the rest of the video though is that the two are ultimately related, which many people do not seem to understand.
@ZajoSTi Yes, it comes from 33,000 (from the definition of HP) divided by 2*pi (for the number of radians in one revolution). It applies to all stand alone internal combustion engines without hybrid powertrains.
I am doing an aviation engineering apprenticeship, but I still love learning about car engines and all this stuff is still relevant.
The way you explain it makes me instantly click and go 'Ohhhhh', whereas elsewhere, I have read pages on this type of thing, but in minutes you have me completely getting it. Love the analogy's too, they really help the understanding. There'll always be a job in teaching for you, my friend! A natural talent.
@EngineeringExplained It is not always the case that torque and horsepower will cross at 5252 RPM on a dyno chart. A special case is that I can take a brushed DC electric motor connected to motor speed controller with active current limit capability and have it accelerate a flywheel such that if you could measure the torque it would be constant from zero to some cut off point which is dependent on motor back EMF and your supply voltage and then the torque curve will roll off as 1/X. cont..
@EETechs For instance I could make a brushed DC motor have the torque and horsepower intersect at 3,000 RPM with active current limit (current source basically), but have the torque curve roll off as 1/X beyond 3,000 RPM in which case at 5,252 RPM they will never intersect.
@EngineeringExplained No problem bro! I have a request though! Do you think you could do a video explaining twin over head cams, over head cams etc, I honestly have no idea and I definitely think you're the man for the job of explaining.
@tackiee9 Don't worry about your English, it's fine! Horsepower = energy, cc = volume. The units are unrelated. (Newton-meters per second vs meters cubed)
Thank you so much for this video. I am fascinated by engines, but i didn't quite get the Horsepower to torque ratio until I saw this. I'm failing math class but I when I saw the formulas you had on your white board there I pulled out my Ti-84, though of my car's torque and did some algebra. haha thank you so much!
Could i just ask you to emphasise to people that the G force they feel is 'proportional' to the torque curve at the wheels, not the engine torque or horsepower. The engine torque is quite meaningless by itself, because it is modified by the gearbox and final drive, but losses withstanding, it does determine what people 'feel'. Torque is a force, and hence produces thrust. Horsepower is not a force, and does not magically 'take over' at some point as some people seem to imagine. Think wheel TQ!
Help me out: If Horsepower is more important for a sports car, then why is torque so emphasized in Mustangs, Corvettes, etc? They aren`t going to be hauling big loads anyway.
@pointman127 Depending on the RPMs that the engine is capable of, it is irrelevant whether you have more torque or more horsepower. Both can accelerate equally if the gearing is manipulated correctly. A high torque low revving engine can accelerate equal to a high hp high revving engine if the gearing is correct. Many times American sports cars are high torque with lower redlines where as cars from Japan for instance are high revving, so they give the hp figure.
An often overlooked engineering principle in this case is the 'area under the curve', in this case the torque curve. You could have twice the rev range and half the torque and achieve the same area. All you'd do is shorten the final drive ratio by a factor of 2 and you'd have the same wheel torque. In reality, torque curves aren't flat, but a high revving race engine can have more area under the shift-shift portion than a low revving engine of the same max HP.
This is an area where diesels fall down, because their torque curves are tall but not very broad, falling rapidly to their low rev limit, whereas race tuned petrol engines can maintain their torque to within a smaller margin of their rev limit, hence larger area under the shift-shift torque range. They don't need low rev torque after launch if the driver uses his gears, but diesels need low rev torque, because they have limited rev range, falling torque and taller gearing.
if you have a decent grasp of mathematics it may help to you understand the relationship further if its mentioned that the graph of an engines horsepower (HP along the y-axis and RPMs along the x-axis) is a function, f(x), while the function creating the graph of the engines torque is the derivative of the HP function. so, if HP = f(x), then ft/lbs = f '(x)
@kiithsjet2 Your Calculus will not work for DC electric motors which make max torque WITHOUT rotating. Therefore, you need to set limitations to your function, else it is not correct.
@EETechs doesnt matter where torque is made. a function that creates the graph of torque output is the derivative of the function that creates the graph of horsepower output. and calculus isnt mine, it was 'created' way before i was even around.
@kiithsjet2 Then find the derivative of zero horsepower then...That is where it will get you. See with brushed DC motors you can never know the magnitude of the stall torque by finding the derivative of zero horsepower. That is why your function will not work unless you specify set conditions with limits.
@EETechs this is for engines that create power based on pulses of torque per given unit of time.this does not include dc motors. theyre not even engines. thats why theyre called motors. my comment was correct. your comment has no business here. just as magnetic flux density has no meaning or existence in the internal combustion engine universe, chemical reactions and exhaust temperatures have no meaning or existence in the electric motor universe. i really dont know what your trying to say here.
@kiithsjet2 I have nothing to say because you finally limited your function to a correct prime mover. :) I was not trying to harass you, I was just wishing you would admit that you did not include set conditions in which your function is valid. On a test if you did not specify the conditions to which your function can work then I would have counted that whole problem wrong on a test if I graded it. Did not mean to inconvenience you.
@EETechs the information i provided was intended to supplement people who were directed to this specific video while seeking a greater understanding of torque/hp relationships in internal combustion reactions. the understanding that the information i provided was to pertain specifically to internal combustion engines was already pre-established by the subject matter of the video.
@kiithsjet2 Power ( W ) = Torque ( N x m ) x Angular velocity (rad / s) = Torque ( N x m ) x ( 6.28 x RPM ) all divided for 60. This is true for all kind of motors. DC motors have high torque at low rpm...Internal combustion engines doesn't have high torque at low rpm...They need gears for multiplying torque ---> and so reducing speed...BECAUSE (Torque) x (Angular velocity) = (Power)
Lets do an example. Say you have two engines both at 200hp. One however has 150lb-ft of torque and the other has 250lb-ft of torque. But both are geared to redline at exactly the same speed (the higher torque engine redlining at a lower engine speed and the lower torque engine redlining at a higher engine speed) If you were to measure the force at the wheels for both of these engines, you would find identical forces.
@joeslimon So what are you implying with the example? Also, if these vehicles were to be carrying a load, are you saying they would still accelerate at the same rate (assuming base weights the same, even though this would not occur)?
@EngineeringExplained If the vehicles had identical weights, powers and redlined at the same speeds they would both accelerate the same regardless if they were both given 1000lbs of load. The gearbox simply amplifies the torque of the engine with less torque, since the engine with less torque can rev higher you can get away with a more aggressive gear ratio. In the end 200hp at 60mph will always be 1250lbs of tractive force minus drive train losses regardless of the base engines torque.
Imagine a 200lb cyclist pushing down on the pedals of a bicycle with 1 foot long cranks. The input is sinusoidal so it's not 200lb.ft, but it's not far off that of say a 1.6L petrol engine. Do you think he could propel a car to 100mph? Of course not, because he can only pedal at a few tens of rpm, so he only produces a fraction of 1hp. You'd have to gear the car so short to allow him to move it in the first place that his top speed would be tiny. All TQ - no HP.
You're welcome. Some years ago i was troubled by the lack of understanding on the internet regarding torque/horsepower, so as an engineering type i decided to write my own simulator in excel. I learned a great deal from it and can now say i have a complete understanding, but i also learned that it's virtually impossible to explain it using words alone. People just seem to want to treat the two separately (wrong), but not consider gearing, weight and aerodynamics.
@MoronAntidote Yes, it's very true and very frustrating. I've received numerous messages asking what setup people should have for different causes. I recently uploaded a video on torque and gears because it seems there is a big lack of understanding that a torque from a small gear greatly increases when the force is applied to a larger gear. How does your simulator work/what types of parameters can you adjust?
Well it's a long time since i wrote it, but it started with an engine torque curve at 100rpm intervals. Gear ratios, final drive ratio, weight, aerodynamic drag and frontal area were all variable. The calculations were based on 4th order runge kutta integration, and the engine torque and rpm were linearly interpolated (good enough). I used a crude method for clutch and tire slip, and allowed you to select launch rpm. Weight transfer too i think. Was quite accurate.
Oh yeh, and one thing i found most interesting was a feature that indicated the optimum shift rpm, which actually changed slightly with gear and vehicle speed.
@MoronAntidote Ahh, very useful! I've pretty much assumed it's best at redline, but it's logical that in higher gears when acceleration takes a greater amount of time, the time to shift could be moved back at a lower rpm.
It depends on the spacing of the ratios. The maximum acceleration is always at the peak torque for any given gear, but as soon as you reach the point where the wheel torque in the next gear is equal to the wheel torque in the current gear, you might as well downshift. The reason being that engine torque always heads south somewhat before redline.
As i'm sure you know, high revving, high horsepower engines tend to have close ratio boxes, and this allows you to keep them on the boil. It's the obvious choice for a race car, since low end torque only matters at the starting line. Build an engine for high end torque and use a close ratio box, and you're always in the portion of the torque curve with largest area under it. Once moving, the fastest car is the one with the largest area under the shift-shift torque curve.
I never stated engine torque. I merely stated torque, which is transferred throughout the system.
As to race cars, low end torque can also beneficial, if you are able to put out the same power at a lower engine speed you will be able to conserve fuel and take fewer pit-stops. i.e. in the 24hour endurance races like lemans (which is one of a few reasons why the Audi diesels have been dominating this series).
Torque isn't 'transfered' through the system unchanged. Only horsepower could be claimed to be transfered, because gearing doesn't change the product of output torque and rpm, though there is a loss due to friction. The low rpm you're talking about is a characteristic of diesel fuel/engines. Your argument does not apply to petrol engines. They're not conserving fuel by revving lower, it's just an inherent limitation of diesel fuel/engines. More energy per gallon but low rev limit.
An engine which outputs the same power at low rpm as it does at high rpm is basically broken. Power is the product of torque and rpm, and the only way the power could be the same at low and high rpm, is if the torque was a downward slope. You're not making sense.
Are you trolling me? I never said anything about torque transferring through the system unchanged.
Lower revs will be more fuel efficient, since they allow for a more complete burn of fuel and it will reduce the amount of energy lost through friction. This is why ice power plants rev at very slow rates. This is why the 8.4L engine in the viper puts out a higher kW/(L/100km) ratio then almost every other car on the market.
Stating lower revs will be universally more fuel efficient is ignorant. It depends very much on the engine design and fuel. I'm not trolling you, i just don't like bullshit.
Why do you think F1 engines are designed the way they are? A light weight high revving engine with high rpm torque is optimal for race performance. Basic physics determines this.
Yes, all engines show a fall in torque as their volumetric efficiency limitations are reached. Different story!
I never stated the hp/liter ratio. I find that ratio to be rather useless as it doesn't really describe anything useful about the car. The ratio I stated compares overall power output to the fuel economy of an engine. The ratio increases with increased torque, and also increases with increased fuel efficiency.
If you wanted an imperial version of the ratio, multiply hp and mpg together. The viper can net 22mpg, and 600hp. So together it yields about 13,200 hp*mpgs compared to a 911 turbo s which gets 530hp and 23mpg or only 12,190hp*mpgs. Clearly the viper can get more power out of a certain gas mileage.
you can't even explain why it's a poor performer, sure you can cite a ratio, but you don't even know how that ratio affects the engine. The worlds most efficient engines have very low hp/liter ratios, does this mean they are poor performers? I mean, if you want a ratio that cites just performance, you should do a hp/lb ratio of just the engine... at least that weight number means something that affects how the vehicle handles...
How the fuck would you know? You don't actually give people the chance to reveal what they know before you attempt to shoot them down with sweeping generalisations. There are many measures of performance as we both know! I find this stuff pretty easy tbh, but one thing i have learned is that you can't adequately explain it in a few words on youtube. Designing/programming electronics for engine managements or industrial lasers is harder than the basics you're talking about mate.
F1 engines are designed for performance yes, but due to the short nature of the races fuel economy isn't much of a concern for them. So higher performance and poorer fuel economy is beneficial. In a lemans race or any endurace race where fuel economy plays a relative importance, high strung engines are less beneficial.
This video is about torque and horsepower, not a platform for some blow-hard to get on his soapbox about economy of diesel vs petrol engines in Lemans. Jesus.
lemans is used as an example to disprove your theory regarding low end torque being of little importance. This has everything to do about torque and horsepower.
Lemans or any other over-simplistic example will never serve as an explanation, let alone disproof of a basic principle, especially when stated out of context. You're just letting your ego get the better of you. Nobody can generalise in written english about this and get away with it, because it involves physics calculations based on lots of differently varying parameters (no problem here). Comparing diesel and petrol engines without looking at the big picture is a fool's game.
also... do you think that it is volumetric efficiency that limits an engines speed? I daresay it isn't, with the right valve and ignition timing, the next thing that limits an engines torque will be flame path speed and getting complete combustion in shorter and shorter time intervals. Which is why engines with more and/or smaller combustion chambers will rev far higher. I should mention component strength also limits engine strength lest you attack me on that point...
No i don't think it's the only limiting factor. Are you trying to put words in my mouth? You seem to be trying to stray from the original topic in order to wave your e-peen. You know full well that my reference to volumetric efficiency was in relation to a stock engine. We both know how it could be improved, but as far as this discussion is concerned, you're just muddying the waters. Stay on topic.
On topic being, hp derived at lower engine speeds are more efficient. I was originally arguing to your point where you said the only time a race car needs low range torque is when launching. I'm arguing against this point and stating that the lower this peak power number is, the longer the car can race per gallon of fuel. So low range torque is very important, especially in endurance style races where fuel economy is a larger factor.
Ah i get it. You're just yet another person that doesn't seem to get the fact that it's not about engine torque, it's about power to weight ratio. Those diesels sure produce lots of torque, but they don't rev very high do they? So, what about the horsepower in comparison to the rest of the pack? Is it similar? If so, did you consider all they needed to do was gear appropriately? If power to weight is similar, then fair enough, but who cares if diesel is more economical?
No you don't get it. I am the one who realizes that 500hp is 500hp regardless of the engine speed it occurs at. I'm the first one to post that on this topic.
The diesel lemans cars have similar power to weight ratios due to engine restrictions. The lower frictional losses and more complete fuel burn and higher compressions ratios help keep them out of the pits longer. And thus allow them to win.
No you're not the first person to realise or post this simple and obvious fact. If you read my posts you'll realise that i'm well aware that horsepower to weight ratio is the best indicator. I have no idea why you think this is news to me to be honest.
I agree that frictional losses are proportional to rpm, but whether or not they achieve a better fuel burn than a properly optimised petrol engine is open to debate. Diesels inherently require higher compression ratios.
Yes, I am the first person. I posted that in this topic 2 weeks ago! lol
higher compression ratios lead to better efficiency. Longer cycle times (i.e. lower speeds) allow for more energy to be extracted from the fuel. This isn't debatable either.
And you think you're revealing anything new? Why do you attempt to argue with things people didn't say, by assuming they don't know it? I was never talking about efficiency, and trying to misrepresent my statements by shifting them into the realm of oranges as opposed to apples is just silly. As i said, stay on topic.
Try considering the AREA under the torque curve. After launch, it's the area under the shift-shift portion that matters, whether diesel or petrol.
And you actually have the arrogance to believe you're the first person to reveal this? My god, you need to be slapped. The math is so old and so simple, i can't believe you said that. So sad :(
Couldn't you just explain it as torque is the twisting force of the wheels where as power is the amount of energy that is used? You can have a lot of force at the wheels while standing, but you won't have any energy output.
Also, I find your analogies a little off. 1000lbs will affect a sports car more because it will change the power to weight ratio of the sports car more then a truck. Not because of a difference in torque.
@joeslimon Yes, torque is the twisting force, and hp is the amount of energy used. I explained it the way I did because I felt like it was an easier way of understanding it. Hp is the amount of torque supplied per unit time. The greater this number is, the faster the car will accelerate.
Perhaps I am off on my analogies, though they seem accurate to me. Yes, power to weight is extremely important in acceleration, as is gearing, but vehicles with higher torque seem to perform better under load.
Engine torque is not the twisting force at the wheels. It is always rated at the flywheel.
The torque at the wheels is modified by the gearbox and final drive. The gearing is chosen according to the rev range of the engine, so a high torque low revving engine can be matched by a low torque high revving engine, as far as wheel torque is concerned. Wheel torque is what produces thrust and therefore determines acceleration when weight is considered.
one last question. more torque= faster acceleration whereas more more hp= higher top speed? and why does having more torque, pulling the lever harder help accelerate a car faster?
@ichigokillsyou Once again, torque and hp are more related than you are making them out to be. An F1 car will accelerate faster than a Camaro SS even though the Camaro has much more torque. The F1 has more hp and weighs a lot less. Power to weight is much more important for acceleration than high hp/torque figures. Higher speeds rely heavily on power and aerodynamics. Perhaps watch my video "Car Gears - Explained" which discusses why torque is greater in first gear (from a stop).
Can you tell me what I am saying is correct? from a standstill, the car with more torque accelerates quicker at a lower rpm because the car generates power quicker because the there is more force pulling down on the lever. for the sports car, where there is less torque, less force is pulling down on the lever, less power is being generated. the sports car starts to accelerate much quicker at higher rpm because now the engine has more momentum and less torque is needed to keep spinning it?
@ichigokillsyou Not exactly. You need to look at the relationship between hp and torque. HP*5252 = T*RPM. Now from this relationship you can see that HP increases as RPM increases, assuming the torque remains the same. This is why F1 cars can produce HP numbers like 700 hp etc.. from 200 ft-lb (torque) engines. When the car is revving at 18,000 rpms it's hp is over 3x it's torque (18,000/5252 = 3.43). Think of RPMs as a multiplier. The higher the rpm, the more hp, and faster your car is.
@ichigokillsyou Sure: Drag racing with a trailer attached to the back or not. Lets say a a Ford F-250 diesel vs. an Acura Integra type R. With the trailers attached, the integra doesn't have the torque to pull the trailer, and so it will lose the "race." With the trailers unattached, the integra's power to weight advantage will allow it to cross the line first, even though the truck has more torque. Now there are many other factors involved (gearing, aerodynamics, etc...) but the model works.
thank you for your explanation between torque and horsepower. I know have a better understanding of the two terms. however, I still have one question. In a drag race with no rolling start, I hear a lot of people say that the car with more torque will pull ahead faster than the car with less torque. How does that work? But with no rolling start, the car with the higher hp will win.
@ichigokillsyou I'm not positive of more torque or more hp and which is more advantageous, but there are several other deciding factors in rolling vs. stopped. From a standstill, more powerful cars may have a difficult time putting all their power down (preventing wheelspin), where as the same cars from a rolling start can apply it much more easily. A rolling start is more of a car comparison where a non rolling start is more of a driver comparison (assuming all other variables are equal).
nicely done, however, your entire explanation is based on the fact that all your viewers are well versed on the area of phisics, which might not be true.
Awesome videos! Just subscribed
MK3504 5 days ago
great videos
William9alex 1 week ago
you earned yourself a sub! ,fair play good work
andrewcovie 1 week ago
@andrewcovie Woohoo! Thanks!
EngineeringExplained 1 week ago
Also, I've heard of some engines producing their bhp and max torque at the same RPM, is there any specific reason why this sometimes happens, but not always? Is it all down to valve timing?
desertfox2020 2 weeks ago
Something I'm not quite clear on, If I understand you correctly you would accelerate faster holding the RPM at which you get max torque, regardless of the gear you're in? Ex. If I'm entering the freeway, my truck makes 300 lb/ft of torque @ 3200 RPM. To get up to highway speed ASAP, is it best to hold the engine at that RPM and build speed, or just let it go up to about 4k, when it will shift up and fall back to 1750 and continue like that?
desertfox2020 2 weeks ago
@EngineeringExplained Well i never said it was the same thing but for sure the one depends of the other. A nice easy way to show it, would be with a long crankshaft and a short one...that shows both torque and HP in each case...
Ok i get the 5252 number...thx
StefSyros 2 weeks ago
@EngineeringExplained Ok! I thought about it before and understood it completely,so i wanted to get online an correct my self..
What i wanted to say is that the point where the highest torque of an engine is,is the most officient way to drive it in terms of energy you give and energy you get,so every hp you get before or after that,it may be less or more,but in order of consumption/torque it wont be officient...
the 5252 mark confused me a little bit...Is this just a theoretical number?
StefSyros 2 weeks ago
@StefSyros Umm, well the number is based on the definition of horsepower. 1 hp = 33000 ft/lb-min / (2*pi) = 5252. And based on the equation, this is where the two will always meet. However, it is important to note the HP and Torque are measuring different things, they do not have the same unit. So saying they're "the same" at 5252 rpm isn't really accurate, it's just where it occurs.
EngineeringExplained 2 weeks ago
So..simple said,at 5252 rpm its the most officient way to opperate any kind of ICE,cause then you get the best analogy of torque/HP for the minimum possible fuel??
I mean,everything less than 5252 would give you off course less fuel consumption,but you wont get the maximum amound off power from it??And everything more than that would produce more power ok,but with more energy needed to produce it??
I dont know if i understood it right..
StefSyros 2 weeks ago
@StefSyros Uhh I wouldn't necessarily say that. At greater RPMs, there is an increase in friction. The more friction you have, the less efficient your engine is. I believe there are some hybrids that have a setup with the engine running at a constant rpm, and I think they're in the 2000-3000 rpm range, this being this specific engine's most efficient range.
EngineeringExplained 2 weeks ago
there is a car that has 412 HP and 390 torque, can you solve for RPM?
MustangTogunner 2 weeks ago
@MustangTogunner Is it a 2011 Mustang GT?
Those numbers are at different RPM, so no. If they were at the same RPM, then yes, you could solve for them. But when companies post their figures they use the highest torque (typically at a lower RPM than hp) and the highest HP figure.
EngineeringExplained 2 weeks ago
lesson learned: dont carry heavy stuff in a sports car..eats away the HP.
question: formula is divide by 33,000, then it changes to 5252..how so?
MustangTogunner 2 weeks ago
@MustangTogunner 33,000/(2*pi), the 2*pi being the radians in one revolution, just a unit conversion.
EngineeringExplained 2 weeks ago
man i need you to work on my car you seem to know you stuff and my shop doesnt
Nathan21h 3 weeks ago
@Nathan21h Haha, unfortunately I'm an engineer, not a mechanic. I'm trying to learn but your shop is still much more capable than I when it comes to working on your car.
EngineeringExplained 3 weeks ago
@EngineeringExplained i got a 1996 camaro rs and cant really find any good way to supercharge it or put a turbo on it let alone finding one
Nathan21h 3 weeks ago
I love your videos, but you have got to use the metric system.
TheRekcabOfTheD 3 weeks ago
@TheRekcabOfTheD I wish it was that simple. As much as I wish only the metric system existed, unfortunately America is still far too stubborn to change. I will try my best to switch it, but in many examples it's just the way it is in the real world so it's what I'm forced to use.
EngineeringExplained 3 weeks ago
@EngineeringExplained I have hope, the only thing I love more than the metric system is America, and nothing would make me happier than to see them together.
TheRekcabOfTheD 2 weeks ago
@TheRekcabOfTheD I hope my comments did not come off as demanding, I am, by no means trying to tell you how to run your videos, you do a much better job than I every could, I'm just trying to broadcast the usefulness of the metric system, I apologize for anyconfusion and than you again for your videos.
TheRekcabOfTheD 2 weeks ago
If I were as smart as your little finger, my parents would be proud. I am not, so they are not.
RTSchofield 3 weeks ago
@RTSchofield Nonsense! Have you seen my handwriting? Clearly my fingers are stupid.
EngineeringExplained 3 weeks ago
Riddle me this, why can't your common "muscle" car aka mustang and camaros rev pass oh say 7k rpm? where as Hondas are spitting out cars that come 7500+ rpm redline stock and can even go pass it with a tune
hazyazn 3 weeks ago
@hazyazn Engine size and engineering. Smaller engines with shorter strokes can rev higher, and have less mass in the pistons, meaning less inertia to overcome with each stroke of the engine. DOHC provides a great advantage over pushrod (OHV) because the inertia of the pushrods causes valve float at high rpm. Mustangs have switched over. Not sure about Camaros, I think they're still OHV. Corvettes are still OHV as well. But engine size is just as critical, smaller being with higher revs.
EngineeringExplained 3 weeks ago
@EngineeringExplained O great explanation, I heard somebody at a car meet said Hondas have titanium valve springs so they can rev higher, not sure if its true though. Your response makes more sense.
hazyazn 3 weeks ago
Simple yet emphatic explanation. Gratefully yours
SuperGogoX 3 weeks ago
the difference between torque and horsepower..... horsepower defines how fast you will hit the wall and torque, how much you will make the wall move.....
trust me......we face it first hand, racing on Indian Roads . ...lol ... you turn perfect, hit a pot hole.... and you are not so perfect anymore.....
we always expect pot holes at entry> apex > n exit of every corner we take..... + traffic + pedestrians + dumb animals....
its much more perfect,its interesting,challenging. and UNFORGIVING \m/
rajasoumyajit 4 weeks ago
10k rpm.. must be a civic lol
chrisinator13 1 month ago
Great explanation bro... Some people on here are Dicks..
INGKaYo 1 month ago
Quick question; Anyone feel free to chime in
Why is it that 2-strokes dont have powerbands*, where as a 4-stroke does?
nixonbrappp22 1 month ago
@nixonbrappp22 The power band is simply an rpm range for which your producing maximum horsepower/torque. And this idea can be applied to any engine, 2 stroke, 4 stroke, rotary, etc.
EngineeringExplained 1 month ago
@EngineeringExplained I like your video except for your analogy, have you ever seen a sprinter?Their built like bodybuilders.
NHLGUITARMAN 1 month ago
@NHLGUITARMAN You should see my body. Sorry, too far.
EngineeringExplained 1 month ago
so a truck with 600 ft lbs of torque has low hp?? dont think so
yodavoodo 1 month ago
@yodavoodo Low, in comparison to the amount of torque it produces when compared with smaller engines. Truck engines do not rev high, as there is too much inertia preventing that from safely occurring. And if the revs are low, the torque will be a greater number than the hp. Don't simply compare the two numbers though, obviously, as the units are different.
EngineeringExplained 1 month ago
Hey man im interested in getting in the automotive engineering field. I'm very unsure of which route i should take. and guidance you can provide will be much appreciated. feel free to email me.
paulpatlan13 1 month ago
very nice analogy.. keep it up
triplexindia 1 month ago
F-150 - driven by footballers; M3 - bonkers
McWeslyF1 1 month ago
Good math, but for people that don't plan on being engies, torque is how much weight you can move, horse power is how fast you can move it.. the most basic explanation I have. Again, great explanation to those that can understand it.
bgomusicco 1 month ago
@EngineeringExplained what kind off studies do you need to know to become a mechanical engineer? it has always for me been a career choice.
saintmark3 1 month ago
you'll be great, what kind of engineer are you? is it fun?
zozlimits 1 month ago
@zozlimits Mechanical. It has its ups and downs. Thermo is awesome, and explains so much practical knowledge. Vibrations, dynamics, controls... it gets rough.
EngineeringExplained 1 month ago
i stay up til 6am and click a video in my 'suggested' list and notice a bunch of other comments about people watching this video really late at night O_o
nice video by the way, thanks for the explanation!
Benlucky13 2 months ago
The math was to much for me, but the last minute was very clear ^^ tnx!
Elbisrever 2 months ago
So in drag racing do lunch and shift gears at the higher RPM or the higher Torque?
BTW, Great vids, Keep it up!!!
ABC5060 2 months ago
@ABC5060 It's difficult to explain in a comment, but basically you want to keep your engine running within the power band. Many engines will have a loss of power for the last 1000 or so RPM before redline, so people say to shift gears then. This isn't logical. If you shift gears at peak hp, your engine rpm will drop too low. Ideally you can shift when downshifting produces the same net force on the wheels as the current gear. This doesn't always occur, so you can just shift at redline.
EngineeringExplained 2 months ago
@EngineeringExplained Thanks for the reply!!!
ABC5060 2 months ago
@EngineeringExplained
i'm not taking engineering classes yet but between the comparison of the truck and sports car, did you mean to say the output of the wheel or the wheels rpm instead of rev? because if you think of it, a trucks good friend to create greater torque is keeping the engine at a high rpm and the wheels at a low rpm, thats why 18 wheelers have like 10 shifts (i don't really know how many but many more than the average car) because they need to keep their engines reved high?
williamred1 1 month ago
@williamred1 The engine revs in large trucks are high relative to the engine's capabilities, but not in comparison to car engines. The reason they have so many gears is to keep the engine within its power band, which can sometimes be only 500 rpm differences. Large trucks may never rev over 2500 rpm, yet my car will easily rev to 6000. Truck engines produce large amounts of torque, but since they are large inertia prevents high revs (relative to cars). Hope this clears things up.
EngineeringExplained 1 month ago
@EngineeringExplained
oh i see what your saying. sometimes i don't trust what people say since theyre only human as i am even whats in the books was written by educated humans who got there knowledge out of experiments. this is what i was thinking: you have two exact engines, one has a high gear diference (first gear only) say 1:8 and the other has a gear ratio of 1:2. you place a big load on both engines, the first engine can take it. engine two needs to increase rpm by bigger gear ratio.
williamred1 1 month ago
@EngineeringExplained
so thats what had me with questions, i see how a bigger engine revs low but i did not see how if you needed more torque, simply reduce the engines speed, <that would not make sense, a bigger stronger engine that revs low does make sense. you still wanna keep the revs as high as the engine can safely make to keep the torque at the wheels greater
williamred1 1 month ago
So, it means that having more torque when climbing your engine can be on 1500rpm and there is still power. If I am wrong please give me an example about torque.
kushtrimm3 2 months ago
3:26 is this the reason why formula one engines rev so high @ 18 000 rpm ? for a total weight of about 700 kg ?
SuperTauta 2 months ago
@SuperTauta They rev high to create a lot of power from a small engine (ultimately to save weight/size). Smaller engines have less total inertia, and can be built to rev at much greater limits than larger engines.
EngineeringExplained 2 months ago
you gave the same example of a body builder and a sprinter to explain torque and hp as i give to people. great. and your videos are very good. for a layman hp can be the ability to have the maximum possible rotating force (torque) that an engine can produce for a longer range of rpm or an engine can have more hp if it is able to keep up its maximum torque to a longer range of rpm, i mean upto higher rpms. i am sorry. my english isnt very good.
faziljaved 2 months ago
great video....
avdcruis 2 months ago
Ha, I'm 3rd grade student of mechanical engineering, and I have never noticed that torque line crossing HP line at 5252RPM :D
nejckra 2 months ago
thankyou!!! great video!
ir3a11ydontn0 2 months ago
Thank you so much :D
GUPPIESrAWSOME 2 months ago
Great explanation. This kid will go far
RFID666 2 months ago 13
Thank you for the great and yet very simple explanation ..The body builder and the sprinter example cleared things up,,keep up those good vids.
camry4ever 2 months ago
you are legit. Just watched your torque converter video and now thisand i understand so much better now thank you
villani27 2 months ago
note to self. don't watch this at 3 am.
MrAxmea 2 months ago
@MrAxmea Fluffy kitten videos are probably a better option at 3 in the morning.
EngineeringExplained 2 months ago 8
@MrAxmea smart kid.....just like me lol
marijuanamanbigfoot 2 months ago
@MrAxmea or 7am!!
StuartMcMahon65 2 months ago
interesting video! what is 'power band' and is it directly related to the torque/hp relationship i.e. does it inhabit a specific domain on the torque/hp graph? hope i'm making some kind of sense.
jdis 2 months ago
@jdis Power band is just referring to the RPM range for which the engine is producing adequate horsepower/torque. For example between your maximum torque and your maximum hp (say one's 3000 and the other's 6000) your power band would be between the two. For racing you want to keep the gearing so that power remains inside the power band as you shift gears, so you can achieve max acceleration.
EngineeringExplained 2 months ago 2
Dude, you definitely are gonna be the guy that helps me understand the concepts of intricate car techs :D just watched auto bs manual and this one. Gonna check the rest out. Thanks for doing these and keep on! :D
StreetRazorZ 3 months ago
@StreetRazorZ Thanks! I shall keep on!
EngineeringExplained 2 months ago
A better mind experiment would be this: say you have a 3000 lb vehicle and you want it to accelerate as quickly as possible. Would you rather have an engine that makes 500 lb-ft at 6000 rpm or one that makes 250 lb-ft at 18000 rpm? (Like F1 motor). Use these examples to move to how gearing would allow the low-torque motor to slaughter the high-torque motor even though vehicle weight is equal. And maybe some discussion of logical and ergonomic shift points. Then viewers might learn something.
rokjoke 3 months ago
@rokjoke It is an excellent example, but I wouldn't have gone so far to say "then viewers might learn something." People on YouTube are at many different levels. Some may learn a lot from this video, others might not hear anything new. Some of my videos are very basic, and others more complicated, as I attempt to appeal to a large audience.
EngineeringExplained 3 months ago
Actually the analogy is pretty lame. MoronAntidote's post from a month ago is right on. Wheel torque is all that matters, and any discussion that claims to explain automotive torque vs. HP and does not talk about gearing is not really going to explain anything. So people fall back of "rules of thumb" that just make them sound ignorant.
rokjoke 3 months ago
@rokjoke Looking back, the analogy wasn't such a good idea; what I implying is that many vehicles with high torque that are geared low tend to be heavy, so added weight affects them little, where as small engines have lower torque, but rev higher, and are used in lighter vehicles where additional weight makes a large impact. What I was hoping to bring across for the rest of the video though is that the two are ultimately related, which many people do not seem to understand.
EngineeringExplained 3 months ago
What's the deal with the 5252 RPM? Is it valid for every engine?
ZajoSTi 3 months ago
@ZajoSTi Yes, it comes from 33,000 (from the definition of HP) divided by 2*pi (for the number of radians in one revolution). It applies to all stand alone internal combustion engines without hybrid powertrains.
EngineeringExplained 3 months ago
I am doing an aviation engineering apprenticeship, but I still love learning about car engines and all this stuff is still relevant.
The way you explain it makes me instantly click and go 'Ohhhhh', whereas elsewhere, I have read pages on this type of thing, but in minutes you have me completely getting it. Love the analogy's too, they really help the understanding. There'll always be a job in teaching for you, my friend! A natural talent.
ballbagjosh 3 months ago
@ballbagjosh Thank you so much, this means a lot, honestly!
EngineeringExplained 3 months ago
@EngineeringExplained It is not always the case that torque and horsepower will cross at 5252 RPM on a dyno chart. A special case is that I can take a brushed DC electric motor connected to motor speed controller with active current limit capability and have it accelerate a flywheel such that if you could measure the torque it would be constant from zero to some cut off point which is dependent on motor back EMF and your supply voltage and then the torque curve will roll off as 1/X. cont..
EETechs 3 months ago
@EETechs For instance I could make a brushed DC motor have the torque and horsepower intersect at 3,000 RPM with active current limit (current source basically), but have the torque curve roll off as 1/X beyond 3,000 RPM in which case at 5,252 RPM they will never intersect.
EETechs 3 months ago
@EETechs Thanks for the tip, did not know that!
EngineeringExplained 3 months ago
@EngineeringExplained No problem bro! I have a request though! Do you think you could do a video explaining twin over head cams, over head cams etc, I honestly have no idea and I definitely think you're the man for the job of explaining.
Cheers.
ballbagjosh 3 months ago
@ballbagjosh Fortunately I already have a video on it. Search my channel for "DOHC vs SOHC vs OHV." Should answer your question quite well!
EngineeringExplained 3 months ago
@EngineeringExplained My understanding has been fulfilled, Love this channel!
ballbagjosh 3 months ago
this...helped....ALOT
cartzar 3 months ago
diffrence of cc and hp? please
tackiee9 3 months ago
@tackiee9 cc = cubic centimeters. A 100cc engine is a 0.1 Liter engine. This unit is generally used for smaller engines.
EngineeringExplained 3 months ago
@EngineeringExplained thank you
tackiee9 3 months ago
@EngineeringExplained thanks & can you please tell me like 1 horsepower = how many cc's ? please ? and sorry for my worst english :)
tackiee9 3 months ago
@tackiee9 Don't worry about your English, it's fine! Horsepower = energy, cc = volume. The units are unrelated. (Newton-meters per second vs meters cubed)
EngineeringExplained 3 months ago
awesome video thanks for the explanation
accin88 4 months ago
Thank you so much for this video. I am fascinated by engines, but i didn't quite get the Horsepower to torque ratio until I saw this. I'm failing math class but I when I saw the formulas you had on your white board there I pulled out my Ti-84, though of my car's torque and did some algebra. haha thank you so much!
NoNoMoreTalk 4 months ago
Could i just ask you to emphasise to people that the G force they feel is 'proportional' to the torque curve at the wheels, not the engine torque or horsepower. The engine torque is quite meaningless by itself, because it is modified by the gearbox and final drive, but losses withstanding, it does determine what people 'feel'. Torque is a force, and hence produces thrust. Horsepower is not a force, and does not magically 'take over' at some point as some people seem to imagine. Think wheel TQ!
MoronAntidote 4 months ago
@MoronAntidote Good thinking, I'll include this in the description.
EngineeringExplained 4 months ago
Help me out: If Horsepower is more important for a sports car, then why is torque so emphasized in Mustangs, Corvettes, etc? They aren`t going to be hauling big loads anyway.
pointman127 4 months ago
@pointman127 Depending on the RPMs that the engine is capable of, it is irrelevant whether you have more torque or more horsepower. Both can accelerate equally if the gearing is manipulated correctly. A high torque low revving engine can accelerate equal to a high hp high revving engine if the gearing is correct. Many times American sports cars are high torque with lower redlines where as cars from Japan for instance are high revving, so they give the hp figure.
EngineeringExplained 4 months ago
@EngineeringExplained Thanks for explaining!
pointman127 4 months ago
@EngineeringExplained
An often overlooked engineering principle in this case is the 'area under the curve', in this case the torque curve. You could have twice the rev range and half the torque and achieve the same area. All you'd do is shorten the final drive ratio by a factor of 2 and you'd have the same wheel torque. In reality, torque curves aren't flat, but a high revving race engine can have more area under the shift-shift portion than a low revving engine of the same max HP.
MoronAntidote 4 months ago
@MoronAntidote
This is an area where diesels fall down, because their torque curves are tall but not very broad, falling rapidly to their low rev limit, whereas race tuned petrol engines can maintain their torque to within a smaller margin of their rev limit, hence larger area under the shift-shift torque range. They don't need low rev torque after launch if the driver uses his gears, but diesels need low rev torque, because they have limited rev range, falling torque and taller gearing.
MoronAntidote 4 months ago
if you have a decent grasp of mathematics it may help to you understand the relationship further if its mentioned that the graph of an engines horsepower (HP along the y-axis and RPMs along the x-axis) is a function, f(x), while the function creating the graph of the engines torque is the derivative of the HP function. so, if HP = f(x), then ft/lbs = f '(x)
kiithsjet2 4 months ago
@kiithsjet2 Your Calculus will not work for DC electric motors which make max torque WITHOUT rotating. Therefore, you need to set limitations to your function, else it is not correct.
EETechs 3 months ago
@EETechs doesnt matter where torque is made. a function that creates the graph of torque output is the derivative of the function that creates the graph of horsepower output. and calculus isnt mine, it was 'created' way before i was even around.
kiithsjet2 3 months ago
@kiithsjet2 Then find the derivative of zero horsepower then...That is where it will get you. See with brushed DC motors you can never know the magnitude of the stall torque by finding the derivative of zero horsepower. That is why your function will not work unless you specify set conditions with limits.
EETechs 3 months ago
@EETechs this is for engines that create power based on pulses of torque per given unit of time.this does not include dc motors. theyre not even engines. thats why theyre called motors. my comment was correct. your comment has no business here. just as magnetic flux density has no meaning or existence in the internal combustion engine universe, chemical reactions and exhaust temperatures have no meaning or existence in the electric motor universe. i really dont know what your trying to say here.
kiithsjet2 3 months ago
@kiithsjet2 I have nothing to say because you finally limited your function to a correct prime mover. :) I was not trying to harass you, I was just wishing you would admit that you did not include set conditions in which your function is valid. On a test if you did not specify the conditions to which your function can work then I would have counted that whole problem wrong on a test if I graded it. Did not mean to inconvenience you.
EETechs 3 months ago
@EETechs the information i provided was intended to supplement people who were directed to this specific video while seeking a greater understanding of torque/hp relationships in internal combustion reactions. the understanding that the information i provided was to pertain specifically to internal combustion engines was already pre-established by the subject matter of the video.
kiithsjet2 3 months ago
@kiithsjet2 Power ( W ) = Torque ( N x m ) x Angular velocity (rad / s) = Torque ( N x m ) x ( 6.28 x RPM ) all divided for 60. This is true for all kind of motors. DC motors have high torque at low rpm...Internal combustion engines doesn't have high torque at low rpm...They need gears for multiplying torque ---> and so reducing speed...BECAUSE (Torque) x (Angular velocity) = (Power)
maxmidiwave 3 months ago
Lets do an example. Say you have two engines both at 200hp. One however has 150lb-ft of torque and the other has 250lb-ft of torque. But both are geared to redline at exactly the same speed (the higher torque engine redlining at a lower engine speed and the lower torque engine redlining at a higher engine speed) If you were to measure the force at the wheels for both of these engines, you would find identical forces.
joeslimon 5 months ago
@joeslimon So what are you implying with the example? Also, if these vehicles were to be carrying a load, are you saying they would still accelerate at the same rate (assuming base weights the same, even though this would not occur)?
EngineeringExplained 5 months ago
@EngineeringExplained If the vehicles had identical weights, powers and redlined at the same speeds they would both accelerate the same regardless if they were both given 1000lbs of load. The gearbox simply amplifies the torque of the engine with less torque, since the engine with less torque can rev higher you can get away with a more aggressive gear ratio. In the end 200hp at 60mph will always be 1250lbs of tractive force minus drive train losses regardless of the base engines torque.
joeslimon 5 months ago
@EngineeringExplained
Imagine a 200lb cyclist pushing down on the pedals of a bicycle with 1 foot long cranks. The input is sinusoidal so it's not 200lb.ft, but it's not far off that of say a 1.6L petrol engine. Do you think he could propel a car to 100mph? Of course not, because he can only pedal at a few tens of rpm, so he only produces a fraction of 1hp. You'd have to gear the car so short to allow him to move it in the first place that his top speed would be tiny. All TQ - no HP.
MoronAntidote 4 months ago
@MoronAntidote Great analogy, thanks.
EngineeringExplained 4 months ago
@EngineeringExplained
You're welcome. Some years ago i was troubled by the lack of understanding on the internet regarding torque/horsepower, so as an engineering type i decided to write my own simulator in excel. I learned a great deal from it and can now say i have a complete understanding, but i also learned that it's virtually impossible to explain it using words alone. People just seem to want to treat the two separately (wrong), but not consider gearing, weight and aerodynamics.
MoronAntidote 4 months ago
@MoronAntidote Yes, it's very true and very frustrating. I've received numerous messages asking what setup people should have for different causes. I recently uploaded a video on torque and gears because it seems there is a big lack of understanding that a torque from a small gear greatly increases when the force is applied to a larger gear. How does your simulator work/what types of parameters can you adjust?
EngineeringExplained 4 months ago
@EngineeringExplained
Well it's a long time since i wrote it, but it started with an engine torque curve at 100rpm intervals. Gear ratios, final drive ratio, weight, aerodynamic drag and frontal area were all variable. The calculations were based on 4th order runge kutta integration, and the engine torque and rpm were linearly interpolated (good enough). I used a crude method for clutch and tire slip, and allowed you to select launch rpm. Weight transfer too i think. Was quite accurate.
MoronAntidote 4 months ago
@EngineeringExplained
Oh yeh, and one thing i found most interesting was a feature that indicated the optimum shift rpm, which actually changed slightly with gear and vehicle speed.
MoronAntidote 4 months ago
@MoronAntidote Ahh, very useful! I've pretty much assumed it's best at redline, but it's logical that in higher gears when acceleration takes a greater amount of time, the time to shift could be moved back at a lower rpm.
EngineeringExplained 4 months ago
@EngineeringExplained
It depends on the spacing of the ratios. The maximum acceleration is always at the peak torque for any given gear, but as soon as you reach the point where the wheel torque in the next gear is equal to the wheel torque in the current gear, you might as well downshift. The reason being that engine torque always heads south somewhat before redline.
MoronAntidote 4 months ago
@MoronAntidote
As i'm sure you know, high revving, high horsepower engines tend to have close ratio boxes, and this allows you to keep them on the boil. It's the obvious choice for a race car, since low end torque only matters at the starting line. Build an engine for high end torque and use a close ratio box, and you're always in the portion of the torque curve with largest area under it. Once moving, the fastest car is the one with the largest area under the shift-shift torque curve.
MoronAntidote 4 months ago
@MoronAntidote
All other things being equal ofc ;)
MoronAntidote 4 months ago
@MoronAntidote
I never stated engine torque. I merely stated torque, which is transferred throughout the system.
As to race cars, low end torque can also beneficial, if you are able to put out the same power at a lower engine speed you will be able to conserve fuel and take fewer pit-stops. i.e. in the 24hour endurance races like lemans (which is one of a few reasons why the Audi diesels have been dominating this series).
joeslimon 4 months ago
@joeslimon
Torque isn't 'transfered' through the system unchanged. Only horsepower could be claimed to be transfered, because gearing doesn't change the product of output torque and rpm, though there is a loss due to friction. The low rpm you're talking about is a characteristic of diesel fuel/engines. Your argument does not apply to petrol engines. They're not conserving fuel by revving lower, it's just an inherent limitation of diesel fuel/engines. More energy per gallon but low rev limit.
MoronAntidote 4 months ago
@joeslimon
An engine which outputs the same power at low rpm as it does at high rpm is basically broken. Power is the product of torque and rpm, and the only way the power could be the same at low and high rpm, is if the torque was a downward slope. You're not making sense.
MoronAntidote 4 months ago
@MoronAntidote
Are you trolling me? I never said anything about torque transferring through the system unchanged.
Lower revs will be more fuel efficient, since they allow for a more complete burn of fuel and it will reduce the amount of energy lost through friction. This is why ice power plants rev at very slow rates. This is why the 8.4L engine in the viper puts out a higher kW/(L/100km) ratio then almost every other car on the market.
Also, most torque curves drop off at higher revs.
joeslimon 4 months ago
@joeslimon
Stating lower revs will be universally more fuel efficient is ignorant. It depends very much on the engine design and fuel. I'm not trolling you, i just don't like bullshit.
Why do you think F1 engines are designed the way they are? A light weight high revving engine with high rpm torque is optimal for race performance. Basic physics determines this.
Yes, all engines show a fall in torque as their volumetric efficiency limitations are reached. Different story!
MoronAntidote 4 months ago
@MoronAntidote
I never stated the hp/liter ratio. I find that ratio to be rather useless as it doesn't really describe anything useful about the car. The ratio I stated compares overall power output to the fuel economy of an engine. The ratio increases with increased torque, and also increases with increased fuel efficiency.
joeslimon 4 months ago
@joeslimon
If you wanted an imperial version of the ratio, multiply hp and mpg together. The viper can net 22mpg, and 600hp. So together it yields about 13,200 hp*mpgs compared to a 911 turbo s which gets 530hp and 23mpg or only 12,190hp*mpgs. Clearly the viper can get more power out of a certain gas mileage.
joeslimon 4 months ago
@joeslimon
That's all just meaningless bollocks. The viper engine is a poor performer given its capacity - end of story.
MoronAntidote 4 months ago
@joeslimon
Just as well you didn't because it's poor.
You value something i don't. I value something you don't. Don't get bent out of shape because we appreciate different aspects of an engine.
MoronAntidote 4 months ago
@MoronAntidote
you can't even explain why it's a poor performer, sure you can cite a ratio, but you don't even know how that ratio affects the engine. The worlds most efficient engines have very low hp/liter ratios, does this mean they are poor performers? I mean, if you want a ratio that cites just performance, you should do a hp/lb ratio of just the engine... at least that weight number means something that affects how the vehicle handles...
joeslimon 4 months ago
@joeslimon
How the fuck would you know? You don't actually give people the chance to reveal what they know before you attempt to shoot them down with sweeping generalisations. There are many measures of performance as we both know! I find this stuff pretty easy tbh, but one thing i have learned is that you can't adequately explain it in a few words on youtube. Designing/programming electronics for engine managements or industrial lasers is harder than the basics you're talking about mate.
MoronAntidote 4 months ago
@MoronAntidote
F1 engines are designed for performance yes, but due to the short nature of the races fuel economy isn't much of a concern for them. So higher performance and poorer fuel economy is beneficial. In a lemans race or any endurace race where fuel economy plays a relative importance, high strung engines are less beneficial.
joeslimon 4 months ago
@joeslimon
This video is about torque and horsepower, not a platform for some blow-hard to get on his soapbox about economy of diesel vs petrol engines in Lemans. Jesus.
MoronAntidote 4 months ago
@MoronAntidote
lemans is used as an example to disprove your theory regarding low end torque being of little importance. This has everything to do about torque and horsepower.
joeslimon 4 months ago
@joeslimon
Lemans or any other over-simplistic example will never serve as an explanation, let alone disproof of a basic principle, especially when stated out of context. You're just letting your ego get the better of you. Nobody can generalise in written english about this and get away with it, because it involves physics calculations based on lots of differently varying parameters (no problem here). Comparing diesel and petrol engines without looking at the big picture is a fool's game.
MoronAntidote 4 months ago
@MoronAntidote
also... do you think that it is volumetric efficiency that limits an engines speed? I daresay it isn't, with the right valve and ignition timing, the next thing that limits an engines torque will be flame path speed and getting complete combustion in shorter and shorter time intervals. Which is why engines with more and/or smaller combustion chambers will rev far higher. I should mention component strength also limits engine strength lest you attack me on that point...
joeslimon 4 months ago
@joeslimon
No i don't think it's the only limiting factor. Are you trying to put words in my mouth? You seem to be trying to stray from the original topic in order to wave your e-peen. You know full well that my reference to volumetric efficiency was in relation to a stock engine. We both know how it could be improved, but as far as this discussion is concerned, you're just muddying the waters. Stay on topic.
MoronAntidote 4 months ago
@MoronAntidote
On topic being, hp derived at lower engine speeds are more efficient. I was originally arguing to your point where you said the only time a race car needs low range torque is when launching. I'm arguing against this point and stating that the lower this peak power number is, the longer the car can race per gallon of fuel. So low range torque is very important, especially in endurance style races where fuel economy is a larger factor.
joeslimon 4 months ago
@MoronAntidote
sorry *limits torque at high revs*
joeslimon 4 months ago
@joeslimon
Oh, and please tell me the specific horsepower of the viper. I'm aware of production engines with at least 120hp per liter.
MoronAntidote 4 months ago
@MoronAntidote
Without forced induction that is.
MoronAntidote 4 months ago
@joeslimon
Ah i get it. You're just yet another person that doesn't seem to get the fact that it's not about engine torque, it's about power to weight ratio. Those diesels sure produce lots of torque, but they don't rev very high do they? So, what about the horsepower in comparison to the rest of the pack? Is it similar? If so, did you consider all they needed to do was gear appropriately? If power to weight is similar, then fair enough, but who cares if diesel is more economical?
MoronAntidote 4 months ago
@MoronAntidote
No you don't get it. I am the one who realizes that 500hp is 500hp regardless of the engine speed it occurs at. I'm the first one to post that on this topic.
The diesel lemans cars have similar power to weight ratios due to engine restrictions. The lower frictional losses and more complete fuel burn and higher compressions ratios help keep them out of the pits longer. And thus allow them to win.
joeslimon 4 months ago
@joeslimon
No you're not the first person to realise or post this simple and obvious fact. If you read my posts you'll realise that i'm well aware that horsepower to weight ratio is the best indicator. I have no idea why you think this is news to me to be honest.
I agree that frictional losses are proportional to rpm, but whether or not they achieve a better fuel burn than a properly optimised petrol engine is open to debate. Diesels inherently require higher compression ratios.
MoronAntidote 4 months ago
@MoronAntidote
Yes, I am the first person. I posted that in this topic 2 weeks ago! lol
higher compression ratios lead to better efficiency. Longer cycle times (i.e. lower speeds) allow for more energy to be extracted from the fuel. This isn't debatable either.
joeslimon 4 months ago
@joeslimon
And you think you're revealing anything new? Why do you attempt to argue with things people didn't say, by assuming they don't know it? I was never talking about efficiency, and trying to misrepresent my statements by shifting them into the realm of oranges as opposed to apples is just silly. As i said, stay on topic.
Try considering the AREA under the torque curve. After launch, it's the area under the shift-shift portion that matters, whether diesel or petrol.
MoronAntidote 4 months ago
@joeslimon
And you actually have the arrogance to believe you're the first person to reveal this? My god, you need to be slapped. The math is so old and so simple, i can't believe you said that. So sad :(
MoronAntidote 4 months ago
@EngineeringExplained
Sorry i meant to reply to joeslimon.
MoronAntidote 4 months ago
Couldn't you just explain it as torque is the twisting force of the wheels where as power is the amount of energy that is used? You can have a lot of force at the wheels while standing, but you won't have any energy output.
Also, I find your analogies a little off. 1000lbs will affect a sports car more because it will change the power to weight ratio of the sports car more then a truck. Not because of a difference in torque.
joeslimon 5 months ago
@joeslimon Yes, torque is the twisting force, and hp is the amount of energy used. I explained it the way I did because I felt like it was an easier way of understanding it. Hp is the amount of torque supplied per unit time. The greater this number is, the faster the car will accelerate.
Perhaps I am off on my analogies, though they seem accurate to me. Yes, power to weight is extremely important in acceleration, as is gearing, but vehicles with higher torque seem to perform better under load.
EngineeringExplained 5 months ago
@joeslimon
Engine torque is not the twisting force at the wheels. It is always rated at the flywheel.
The torque at the wheels is modified by the gearbox and final drive. The gearing is chosen according to the rev range of the engine, so a high torque low revving engine can be matched by a low torque high revving engine, as far as wheel torque is concerned. Wheel torque is what produces thrust and therefore determines acceleration when weight is considered.
Power to weight is key.
MoronAntidote 4 months ago
Fantastic video!
aidanthedealer 5 months ago
one last question. more torque= faster acceleration whereas more more hp= higher top speed? and why does having more torque, pulling the lever harder help accelerate a car faster?
ichigokillsyou 6 months ago
@ichigokillsyou Once again, torque and hp are more related than you are making them out to be. An F1 car will accelerate faster than a Camaro SS even though the Camaro has much more torque. The F1 has more hp and weighs a lot less. Power to weight is much more important for acceleration than high hp/torque figures. Higher speeds rely heavily on power and aerodynamics. Perhaps watch my video "Car Gears - Explained" which discusses why torque is greater in first gear (from a stop).
EngineeringExplained 6 months ago
Can you tell me what I am saying is correct? from a standstill, the car with more torque accelerates quicker at a lower rpm because the car generates power quicker because the there is more force pulling down on the lever. for the sports car, where there is less torque, less force is pulling down on the lever, less power is being generated. the sports car starts to accelerate much quicker at higher rpm because now the engine has more momentum and less torque is needed to keep spinning it?
ichigokillsyou 6 months ago
@ichigokillsyou Not exactly. You need to look at the relationship between hp and torque. HP*5252 = T*RPM. Now from this relationship you can see that HP increases as RPM increases, assuming the torque remains the same. This is why F1 cars can produce HP numbers like 700 hp etc.. from 200 ft-lb (torque) engines. When the car is revving at 18,000 rpms it's hp is over 3x it's torque (18,000/5252 = 3.43). Think of RPMs as a multiplier. The higher the rpm, the more hp, and faster your car is.
EngineeringExplained 6 months ago
can you set up two racing scenarios where having more torque and having more hp respectively prove to be more advantageous?
ichigokillsyou 6 months ago
@ichigokillsyou Sure: Drag racing with a trailer attached to the back or not. Lets say a a Ford F-250 diesel vs. an Acura Integra type R. With the trailers attached, the integra doesn't have the torque to pull the trailer, and so it will lose the "race." With the trailers unattached, the integra's power to weight advantage will allow it to cross the line first, even though the truck has more torque. Now there are many other factors involved (gearing, aerodynamics, etc...) but the model works.
EngineeringExplained 6 months ago
@EngineeringExplained Thank you for the explanation
ichigokillsyou 6 months ago
thank you for your explanation between torque and horsepower. I know have a better understanding of the two terms. however, I still have one question. In a drag race with no rolling start, I hear a lot of people say that the car with more torque will pull ahead faster than the car with less torque. How does that work? But with no rolling start, the car with the higher hp will win.
ichigokillsyou 6 months ago
@ichigokillsyou I'm not positive of more torque or more hp and which is more advantageous, but there are several other deciding factors in rolling vs. stopped. From a standstill, more powerful cars may have a difficult time putting all their power down (preventing wheelspin), where as the same cars from a rolling start can apply it much more easily. A rolling start is more of a car comparison where a non rolling start is more of a driver comparison (assuming all other variables are equal).
EngineeringExplained 6 months ago
nicely done, however, your entire explanation is based on the fact that all your viewers are well versed on the area of phisics, which might not be true.
But still, a valid explanation nonetheless.
Beef1188 6 months ago