With direct fuel injection in gas engines, would the engine have a higher compression ratio? Would it be more similar to a diesel engine in that sense? More torque and better fuel economy?
@EngineeringExplained cool... now i appreciate better why diesel engines in race cars like those on the audi les mans cars are such a big deal. Thanks!
Your "explaination" would leave a lot of folks thinking that all Diesels were 4-stroke.. completely excludes one of the principal differences in operation too, air restriction vs. fuel restriction
@doktorbimmer Correct. Honestly I didn't expect this video to be very popular, and didn't include many differences. I just wanted to get the main point that one is ignited with a spark, and the other uses compression for combustion. But yes, diesels adjust amount of fuel going into the cylinder for power, gasoline engines adjust the amount of air.
@EngineeringExplained Thanks for your reply. Apart from the ignition source its a major difference between the two engine types thats almost always omitted from explainations like these. The different types of controls lead to very different air-fuel ratios and both engines react very differently to lean or rich AFRs, combustion temps respond to AFR in a completely opposite manner.
@doktorbimmer Yep. I took an internal combustion course at my university. I believe the A/F mixture for gasoline was around 14.6 ideally (+/- 0.5) and for diesel the range was something like 18-70. 70 being idle with very little fuel consumption, 18 being with the pedal down. Our professor also said that stoichiometric for diesel is around 15:1, but is rarely used. I found that interesting.
@bloximonkey Do they? Different applications, either choice could be a viable option. I wouldn't say gasoline has higher performance. They can hit higher rpms, since they use lower compression ratios and typically lighter materials, and many times smaller engines, but there's a diesel that can match the specs for most cases.
@G30RG3walker Diesels have glow plugs for cold starts, just to heat the cylinders a bit on top of the heat generated from compression. As far as the fuel type, I'm not positive, but I would assume diesel is more predictable as far as auto-ignition, in the sense that at a certain temperature combustion will occur.
@EngineeringExplained Not all Diesel engines use glow plugs, generally found only in automotive applications.
Some Diesel engines have been design to use gasoline for fuel, the US military purchased tens of thousands of vehicles with "multi-fuel" engines capable of burning D1,D2, JP-4, JP-8, Avgas or even ordinary gasoline.
@G30RG3walker Ignition tempature (the temp at whitch a fuel ignites without any spark) Octane refers to a fuels resistance to "knock" or pre-ignition, octane also relates dirctly to speed (rate of burn) and peak combustion tempature. Cetane is used to rate Diesel type fuels in similar ways but mainly how easily it ignites when cold.
Glow plugs are not required but insure fast reliable ignition even if the temp is to low to for fast "clean" start-up, without clagging lots of noise and smoke
@aussiebug1970 Moving on, GM was working on a gas engine that didn't use spark plugs. This was accomplished by a high CR. what they found out was that the gas engine was behaving like a diesel one. (no top-end) the solution to this; spark plugs that only ignite at high speed for highway passing power. Why is this engine not in production? because like any trucker or drag racer would tell you, high CR engines are LOUD. GM feared no one would buy a car with it in it.
I know you think that diesel engines are more efficient but in reality, not having spark plugs give a car no top end, it would have no power to pass on the highway. GM was trying to make a gas engine without spark plugs and they came to the same conclusion. and ultimately the engine had to have spark plugs that would work only for the highway.
@Hondaminican You're a bit confused. The diesel engine "compression ignition" - the fuel lights up in the hot air (high compression ratio) as soon as it's injected. A gasoline engine has the fuel and air pre-mixed and the spark lights the fuel. You can NOT (quote) "make a gas engine without spark plugs" (unquote) - a gasoline engine must have an ignition source (spark plugs). Modern diesel engines do have a good "top end", and also have better torque at lower revs.
@aussiebug1970 EE's opinion is that the diesel cycle is more efficient than the otto cycle. I say, no its not. because its the diesel engines omission of spark plugs is what makes it such a dud in the highway. Now, all modern diesels have turbo, but if you get a chance to drive a non-turbo diesel engine then you'll know what i mean by no top-end.
@Hondaminican If I said cycle, I meant engine. Diesel engines are more efficient since they have higher compression ratios, and diesel fuel is more energy dense.
@Hondaminican You are still confused. The 4-stroke diesel IS AN OTTO CYCLE engine - which is defined as a "compressed gas internal combustion 4 stroke engine". Both gasoline and diesel engines fit this. Gas engines use light fuels and need spark plugs - diesels use heavier fuel and use compression ignition. I OWN three diesel trucks with non-turbo engines, and I also drive interstate car-carriers with turbo engines, so I have a good comparison. I prefer the non-turbo engines.
@aussiebug1970 "Gas engines use light fuels and need SPARK PLUGS - diesels use heavier fuel and use COMPRESSION ignition." you clearly just agreed with me. diesels & gas engines use a different cycle. diesels don't have spark plugs like i said for the 3rd time and someone tried creating a gas engine that didn't use spark plugs as well.. what part am i confused of? now in a gas engine if you run a 15:1 CR you're going to have ignition just like in a diesel.
@Hondaminican quote "diesels & gas engines use a different CYCLE." unquote. Wrong again - both engines use the same Otto cycle - just different IGNITION systems for different fuels. quote "now in a gas engine if you run a 15:1 CR you're going to have ignition just like in a diesel." unquote. I think you're confusing detonation with compression ignition. Gasoline is designed to resist self-ignition (octane rating), but diesel is designed to self-ignite easily (cetane rating).
@Hondaminican What saying is you don't understand the basic differences of the Diesel and Otto engine.. 4 stroke gas and Diesel have the exact same 4 cycles!!! Gasoline burns MUCH faster than Diesel, Diesel auto ignites more easily than gasoline, octane vs. cetane. Diesels are still more effiecent gasoline engines with the same CR because Diesels intake a full air charge EVERY INTAKE STROKE and can extract more energy (work) per BTU than gasoline because it burns more slowly.
@13sfaustino Most Diesels do not have glow plugs at all, there use mostly limited to automotive or light truck use. Some Diesels use intake manifold heaters or no preheating at all.
dude I freakin LOVE your videos! I'm a freshman engineer and I find it really tough to understand parts of physics unless they're explained in a simple way like this...my lecturer seems to think everyone in the class already has a degree in physics... keep up the good work :D :D
@awesomeness2571 For cold starts a glow plug is used. It heats inside the combustion chamber, and with the added heat from compression, the temperature is great enough for combustion.
@EngineeringExplained im just confusing about this glow plug, do the glow plug glowing while the engine is running? or glow plug used only for cold starts?
@awesomeness2571 glow plugs (duramax, powerstroke, etc.) or a grid heater (cummins) once the engine is running the glow plug is no longer needed and it stops
am i correct that the diesel engine compresses pure air while the gasoline engine compresses mixture of air and gas? pls reply .. tnx! your videos are very useful tnx to you!
@cadetAJ18 Yes, you are correct. No need to say please haha! Though some gasoline engines (especially newer ones) use direct injection, in which the air is compressed without fuel and it is sprayed in at different times to optimize power/efficiency.
@EngineeringExplained thank you so much for the answer.. i am a marine engineering student graduating this semester and your videos are helping me a lot.. what video are you planning to do next?
That was an excellent explanation of the differences between petrol and diesel. Cleared up a few "knowledge gaps" nicely. Was also interested in the advantage a diesel has over petrol in avoiding issues such as pre-ignition.
I'd be interested to hear your explanation of 2-stroke diesel v/s 4 stroke as is the case with railway locomotives.
one question, how come there is that knocking sound in most diesel engine?
mrbigtian 2 days ago
In university, I studiy french litterature, I've got no engeneering background but this video helps a lot. Thank you Sir !
Reda8861 1 week ago
With direct fuel injection in gas engines, would the engine have a higher compression ratio? Would it be more similar to a diesel engine in that sense? More torque and better fuel economy?
Thanks
hashimola 2 weeks ago
That is really great video. Excellent knowledge passing skill
nenadusa3 2 weeks ago
so is that why most diesel engines are made of cast iron instead of aluminum? to deal with the higher pressures and temperatures of the compression?
jcnbw01 2 weeks ago
@jcnbw01 Yes, exactly.
EngineeringExplained 2 weeks ago
@EngineeringExplained cool... now i appreciate better why diesel engines in race cars like those on the audi les mans cars are such a big deal. Thanks!
jcnbw01 2 weeks ago
Your "explaination" would leave a lot of folks thinking that all Diesels were 4-stroke.. completely excludes one of the principal differences in operation too, air restriction vs. fuel restriction
doktorbimmer 1 month ago
@doktorbimmer Correct. Honestly I didn't expect this video to be very popular, and didn't include many differences. I just wanted to get the main point that one is ignited with a spark, and the other uses compression for combustion. But yes, diesels adjust amount of fuel going into the cylinder for power, gasoline engines adjust the amount of air.
EngineeringExplained 4 weeks ago
@EngineeringExplained Thanks for your reply. Apart from the ignition source its a major difference between the two engine types thats almost always omitted from explainations like these. The different types of controls lead to very different air-fuel ratios and both engines react very differently to lean or rich AFRs, combustion temps respond to AFR in a completely opposite manner.
doktorbimmer 4 weeks ago
@doktorbimmer Yep. I took an internal combustion course at my university. I believe the A/F mixture for gasoline was around 14.6 ideally (+/- 0.5) and for diesel the range was something like 18-70. 70 being idle with very little fuel consumption, 18 being with the pedal down. Our professor also said that stoichiometric for diesel is around 15:1, but is rarely used. I found that interesting.
EngineeringExplained 4 weeks ago
And why do gasoline engines have higher performance?
bloximonkey 1 month ago in playlist More videos from EngineeringExplained
@bloximonkey Do they? Different applications, either choice could be a viable option. I wouldn't say gasoline has higher performance. They can hit higher rpms, since they use lower compression ratios and typically lighter materials, and many times smaller engines, but there's a diesel that can match the specs for most cases.
EngineeringExplained 1 month ago
what does the type of fuel either diesel or gas have to do with it and why do diesels have glow plug instead of spark plugs or is that right
G30RG3walker 1 month ago
@G30RG3walker Diesels have glow plugs for cold starts, just to heat the cylinders a bit on top of the heat generated from compression. As far as the fuel type, I'm not positive, but I would assume diesel is more predictable as far as auto-ignition, in the sense that at a certain temperature combustion will occur.
EngineeringExplained 1 month ago
@EngineeringExplained Not all Diesel engines use glow plugs, generally found only in automotive applications.
Some Diesel engines have been design to use gasoline for fuel, the US military purchased tens of thousands of vehicles with "multi-fuel" engines capable of burning D1,D2, JP-4, JP-8, Avgas or even ordinary gasoline.
doktorbimmer 1 month ago
@doktorbimmer Really thats cool!
WarlDogg 3 weeks ago
@EngineeringExplained thanks man good shit
G30RG3walker 1 month ago
@G30RG3walker Ignition tempature (the temp at whitch a fuel ignites without any spark) Octane refers to a fuels resistance to "knock" or pre-ignition, octane also relates dirctly to speed (rate of burn) and peak combustion tempature. Cetane is used to rate Diesel type fuels in similar ways but mainly how easily it ignites when cold.
Glow plugs are not required but insure fast reliable ignition even if the temp is to low to for fast "clean" start-up, without clagging lots of noise and smoke
doktorbimmer 1 month ago
Ford's coyote 5.0 in the mustang runs an 11 to 1 compression, NASCAR engines run even higher...
wbc564 1 month ago
@wbc564 Mazda's Mazda3 with skyactive has a compression ratio of up to 14:1, depending on the model. Untouchable for a car at that price.
EngineeringExplained 1 month ago
@aussiebug1970 Moving on, GM was working on a gas engine that didn't use spark plugs. This was accomplished by a high CR. what they found out was that the gas engine was behaving like a diesel one. (no top-end) the solution to this; spark plugs that only ignite at high speed for highway passing power. Why is this engine not in production? because like any trucker or drag racer would tell you, high CR engines are LOUD. GM feared no one would buy a car with it in it.
Google this ^^
Hondaminican 1 month ago
I know you think that diesel engines are more efficient but in reality, not having spark plugs give a car no top end, it would have no power to pass on the highway. GM was trying to make a gas engine without spark plugs and they came to the same conclusion. and ultimately the engine had to have spark plugs that would work only for the highway.
Hondaminican 1 month ago
@Hondaminican You're a bit confused. The diesel engine "compression ignition" - the fuel lights up in the hot air (high compression ratio) as soon as it's injected. A gasoline engine has the fuel and air pre-mixed and the spark lights the fuel. You can NOT (quote) "make a gas engine without spark plugs" (unquote) - a gasoline engine must have an ignition source (spark plugs). Modern diesel engines do have a good "top end", and also have better torque at lower revs.
aussiebug1970 1 month ago
@aussiebug1970 EE's opinion is that the diesel cycle is more efficient than the otto cycle. I say, no its not. because its the diesel engines omission of spark plugs is what makes it such a dud in the highway. Now, all modern diesels have turbo, but if you get a chance to drive a non-turbo diesel engine then you'll know what i mean by no top-end.
Hondaminican 1 month ago
@Hondaminican If I said cycle, I meant engine. Diesel engines are more efficient since they have higher compression ratios, and diesel fuel is more energy dense.
EngineeringExplained 1 month ago
@Hondaminican You are still confused. The 4-stroke diesel IS AN OTTO CYCLE engine - which is defined as a "compressed gas internal combustion 4 stroke engine". Both gasoline and diesel engines fit this. Gas engines use light fuels and need spark plugs - diesels use heavier fuel and use compression ignition. I OWN three diesel trucks with non-turbo engines, and I also drive interstate car-carriers with turbo engines, so I have a good comparison. I prefer the non-turbo engines.
aussiebug1970 1 month ago
@aussiebug1970 "Gas engines use light fuels and need SPARK PLUGS - diesels use heavier fuel and use COMPRESSION ignition." you clearly just agreed with me. diesels & gas engines use a different cycle. diesels don't have spark plugs like i said for the 3rd time and someone tried creating a gas engine that didn't use spark plugs as well.. what part am i confused of? now in a gas engine if you run a 15:1 CR you're going to have ignition just like in a diesel.
Hondaminican 1 month ago
@Hondaminican quote "diesels & gas engines use a different CYCLE." unquote. Wrong again - both engines use the same Otto cycle - just different IGNITION systems for different fuels. quote "now in a gas engine if you run a 15:1 CR you're going to have ignition just like in a diesel." unquote. I think you're confusing detonation with compression ignition. Gasoline is designed to resist self-ignition (octane rating), but diesel is designed to self-ignite easily (cetane rating).
aussiebug1970 1 month ago
@aussiebug1970 well i didn't use the correct terminology but I'm sure you understood what i was saying...
Hondaminican 1 month ago
@Hondaminican What saying is you don't understand the basic differences of the Diesel and Otto engine.. 4 stroke gas and Diesel have the exact same 4 cycles!!! Gasoline burns MUCH faster than Diesel, Diesel auto ignites more easily than gasoline, octane vs. cetane. Diesels are still more effiecent gasoline engines with the same CR because Diesels intake a full air charge EVERY INTAKE STROKE and can extract more energy (work) per BTU than gasoline because it burns more slowly.
doktorbimmer 1 month ago
@aussiebug1970 part 2. in fact unless you use a racing fuel, you are going to have a lot of pre-ignitions and your knock sensor would go nuts.
Hondaminican 1 month ago
wow. brilliant :D im making a high school documentary about biodiesel so i needed to make sure i understood my engines :)
slb711isScott 1 month ago
@slb711isScott Glad I could help! You going to post your video when you finish?
EngineeringExplained 1 month ago
@EngineeringExplained yes i will but it wont be on this channel. i can comment on this video when its up in mid february from that channel
slb711isScott 1 month ago
Thank you so much! This helped so much!
Anoush13 1 month ago
I was always curious about these two.....Thanks man!
Medicalv911 1 month ago
tx man
khalidelbatni05000 1 month ago
excellent vieo
stretchout100 1 month ago
Very good video. Thank you.
niceday2dayman 2 months ago
@awesomeness2571 Diesel engines use glow plugs
13sfaustino 2 months ago
@13sfaustino Most Diesels do not have glow plugs at all, there use mostly limited to automotive or light truck use. Some Diesels use intake manifold heaters or no preheating at all.
doktorbimmer 1 month ago
dude I freakin LOVE your videos! I'm a freshman engineer and I find it really tough to understand parts of physics unless they're explained in a simple way like this...my lecturer seems to think everyone in the class already has a degree in physics... keep up the good work :D :D
SchizophrenicKishan 2 months ago
Nicely done!
eneoeneo 2 months ago
if there is no spark plug in a diesel engine, how do you start a diesel engine?
awesomeness2571 2 months ago
@awesomeness2571 For cold starts a glow plug is used. It heats inside the combustion chamber, and with the added heat from compression, the temperature is great enough for combustion.
EngineeringExplained 2 months ago
@EngineeringExplained im just confusing about this glow plug, do the glow plug glowing while the engine is running? or glow plug used only for cold starts?
brakehorsepower1 1 month ago
@brakehorsepower1 Just starts. Once the engine heats up it's not needed.
EngineeringExplained 1 month ago
@EngineeringExplained ...cool... =)
brakehorsepower1 1 month ago
@awesomeness2571 glow plugs (duramax, powerstroke, etc.) or a grid heater (cummins) once the engine is running the glow plug is no longer needed and it stops
hudsonjamesc 1 month ago
I totally love your videos...simple and great ones. Well done
kaeminator 2 months ago
simple answer pls regarding with the difference between diesel engine and gasoline egine.. pls reply asap.. tnx!
cadetAJ18 3 months ago
@cadetAJ18 What? Umm, gasoline uses a spark for ignition, diesel uses compression. Is that what you're asking?
EngineeringExplained 3 months ago
@EngineeringExplained okay tnx for the answer..
am i correct that the diesel engine compresses pure air while the gasoline engine compresses mixture of air and gas? pls reply .. tnx! your videos are very useful tnx to you!
cadetAJ18 3 months ago
@cadetAJ18 Yes, you are correct. No need to say please haha! Though some gasoline engines (especially newer ones) use direct injection, in which the air is compressed without fuel and it is sprayed in at different times to optimize power/efficiency.
EngineeringExplained 3 months ago
@EngineeringExplained thank you so much for the answer.. i am a marine engineering student graduating this semester and your videos are helping me a lot.. what video are you planning to do next?
cadetAJ18 3 months ago
@cadetAJ18 Uh possible RWD vs FWD, torque steer, PDCS. Voting is on facebook, search EngineeringExplained.
EngineeringExplained 3 months ago
@EngineeringExplained may i have a request? pls discuss Internal Combustion Engine and External Combustion Engine..
cadetAJ18 3 months ago
That was an excellent explanation of the differences between petrol and diesel. Cleared up a few "knowledge gaps" nicely. Was also interested in the advantage a diesel has over petrol in avoiding issues such as pre-ignition.
I'd be interested to hear your explanation of 2-stroke diesel v/s 4 stroke as is the case with railway locomotives.
Excellent Job. Thanks for posting.
251CE 3 months ago
Nice job Bro! It was truly clear and complete. Thank you :)
MiladUniversity 4 months ago
i was able to run a weed eater off diesel fuel, kerosine, barbeque lighter fluid and sea foam
mrsmashthings 4 months ago
Can you explain how a super charger works?
techno1246 4 months ago
@techno1246 Yes, I was actually planning on doing that this week! Thanks for the tip!
EngineeringExplained 4 months ago
man u should teach classes T-up
jsbcomp 4 months ago
very nice, clear presentation. sub'd
YeTenuousUmbrae 4 months ago
excellent info, thanks a lot!
quitraindrop 6 months ago
very well explained i understood this quickly you did a much better presentation than thoes assholes at general motors
lukeplusmusic 7 months ago
@lukeplusmusic Thanks, good to hear!
EngineeringExplained 7 months ago
awesome info. thanks!
tylercall358 7 months ago