1966 Plymouth Barracuda Startup, 273 V8

[KISSARMYHQ]

my first car, but mine was a pale yellow and had a straight six . Car looks to have a lot of potential, what happened to it ?

[loungecruz]

nice ride

[MisterWatWatWat]

My dad had a 'Cuda just like that. Beautiful cars.

[markbotv3]

the 273 2bbl is rated at 180hp at a peasly 1600 rpm at 4000 rpm it produces 235...now the comando 4bbl is rated at 235 but actually produces 275 horse and with a larger carb is good for 305 hp compression ratio is about 10.5 to one and if high test lead gas is used 25 to 30 mpg is pretty common...only 17mpg with 87 no lead gas with lots of dieseling at shut off. one of mopars most underated motors of all time

[MoPar7055]

I call bullshit, to make 180hp at 1600rpm you have to make 591 ft/lbs of torque mathematically. This whole post is full of BS.

[markbotv3]

nope only need 260 ft/lbs with 10.5 comp pistons to make 180 hp at 1600 rpm...when you came up with your 591 torque figure where you going off the wheels, the output shaft , or the flywheel...horsepower ratings have been taken at all three locations at different eras throughout the years.

[MoPar7055]

It doesn't matter, HP = (tq * RPM) / 5252 Do the math and you will see that 180 hp at 1600 rpm is ridiculous.

[markbotv3]

lol on paper mabey. but the cam grind also makes a difference at where the power band is. take the same engine and replace the cam with different grinds torque changes very little if at all and the horse power goes up or down accordingly

[MoPar7055]

Dude it doesn't matter, if an engine produces 180 hp at 1600 rpm it makes 591 ft/lbs of torque. It doesn't matter if it is an electric motor or a big block v8. This is always true.

[markbotv3]

ok so lets run your formulae on an factory 318 2bbl circa 1976...allpar lists figure of 150 horsepower at 4000 rpm with 255 torque....255x4000/5252= 194.21 horse power. a difference of 44.21 horsepower. your formulae might get you in the ball park but its not a do all be all...heck we used to guestimate for 60s era the following formulae CUBIC INCH MINUS 100

[MoPar7055]

Factory figures are often wrong for one thing. For another thing peak torque and peak HP are often measured at two different RPMs so the formula wouldn't work in that case. You said it was at 4000 rpm but I bet that peak torque is at a different rpm then peak HP on that engine.

[markbotv3]

correct it was rated at 1600 rpm but when you run your formulae it comes out to be 77.68...off by an even greater amount. but i do agree with you factory ratings are usually fudged. which is the reason i said the 273 is an underated engine...but it doesnt take no 500lb ft of torqe to make 180 hp your not taking into account vollumetric efficiency. that raises or lowers horsepower and leaves torque unchanged.

[MoPar7055]

It does take 591 ft/lbs of torque to make 180 hp at 1600 rpm. Now if you're turning 5252 rpm it only takes 180 torque to make 180 horsepower. If you are turning at 6000 rpm it takes even less.

[markbotv3]

but again that is all on paper. your not taking into account the breathing capabilities of the motor. most 60s era engines couldnt rev to 6000 rpm and still generate power. they would lose 33% from 4000 to 6000. now a dodge neon 2.0 would make 150 horsepower at 5600 rpm with 133 ft/lb of torque it has a vollumetric efficiency of 120% to a 273s (4.5L) VE of 85% the torque curve on the 60s engines was always at the bottom end

[MoPar7055]

It doesn't matter, volumetric efficiency, none of that matters. You said specifically that the engine produces 180 HP at 1600 RPM, I don't care what the VE is, it can't be done without also producing 591 ft/ lbs of torque at the same 1600 RPM. Now those old engines may operate under a certain RPM, whatever, all you said was that it makes 180 HP at specifically 1600 RPM and therefore it must also produce 591 ft/lbs of torque to do so.

[MoPar7055]

No you can't change the horsepower at a certain rpm without changing the torque at that same rpm. If you do increase the horsepower without changing torque it's because the peak horsepower and peak torque are now being measured at two different RPMs.

[markbotv3]

ok when you apply your 5252 formulae are you going at peak torque or peak horsepower?

[MoPar7055]

Type in dyno graph into google images and look at how the HP and TQ always crosses at 5252 rpm. Look at how there is more torque than HP when under 5252 rpm and how there is more HP than torque when above 5252 rpm. It is always like this regardless of cam grinds, VE etc.

[markbotv3]

ok i think i see whats going on...when i say 180hp at 1600...its not peak horsepower. peak is somewere in the 4700 rpm range. they rated the motor at peak torque to get the smaller hp number to keep insurance bean counters happy. ok do your formula again assuming 4700 peak rpm and 290 torque. you should come up with a figure around the 230 range...which is what its actually producing. not what is being advertised.

[MoPar7055]

If an engine makes 290 tq at 4700 RPM then it also produces 259.5 HP at exactly 4700 RPM which is not far off.

[markbotv3]

259 sounds a bit high

[MoPar7055]

I am not sure if you understand an engine does not produce one certain torque or horsepower number, as the RPMs rise the numbers are constantly changing with RPM. At any different RPM the horsepower and torque will be different.

[MoPar7055]

Now you are changing things around on me, I never said it requires 591 ft/lbs of torque to make 180 HP. I only said it requires 591 ft/lbs of torque to make 180 HP at 1600 RPM.

[markbotv3]

but that dyno pull torque was droping and so was horsepower. but at 1600 it was WAAAAAY less than 591 torque and horsepower wouldnt be too far off from 180 at 1600rpm. anyway my whole point is the factory rated this engine at 180hp and 260 torque...im saying they actually produce 230 hp and 290 torque...the only way we can prove or dis prove is to put one on the dyno if im off at the 1600rpm mark it wouldnt be by much.

[MoPar7055]

You would actually be off by alot, the formula is always right, if a dyno graph dissagrees with it then the dyno graph is wrong. Keep in mind that tq and HP are in a way defined by this formula atleast when it is applied to rotary motion.

[markbotv3]

ok at what rpm would a 500horse power engine make 180hp. assuming peak hp is 6000 rpm and peak torque is 4000rpm

[MoPar7055]

You gave me the wrong variables I can't calculate that. The only way I could calculate that is if it constantly made the same torque value all throughout the RPM range then I could tell you at what RPM it makes 180HP.

[markbotv3]

also your not taking into account time...a low torque engine takes longer to reach any given rpm than a high torque engine especialy under a load.

[MoPar7055]

You are bringing in variables that are not factors here. For example If I told you I had a 50/50 mixture of methanol and water in that jar and you said, is that a 50/50 mixture measured by gallons? Pints? Ounces? It doesn't matter, a 50/50 mixture is a 50/50 mixture.

[markbotv3]

or assuming again the factory figure of 260 torque at 1600 what is the hp at 1600?

[MoPar7055]

That would be 79 HP.

[markbotv3]

oops typo 380 torque at 1600rpm for that motor estimate

[MoPar7055]

I'm telling you it ain't so, you can't have 380 torque and 180 HP both at 1600 RPM.

[MoPar7055]

You can actually use that formula to estimate how much an engine is underrated by but the factory TQ rating would have to be accurate unlike the HP rating and you would have to know what the TQ rating was at the peak HP rpm. Unfortunately you usually don't know this because peak TQ and RPM are usually at two different RPMs and if they tell you that it makes 300 HP at 5000 rpm they usually don't tell you what the TQ is at that same RPM. However there are actually ways around this albeit complicat

[markbotv3]

ok i found a dyno run on the interwebb...this guys motor makes 448hp at 6000 and 448 torque at 4000...but at 3000 rpm torque is 420 and hp is 241...i wish they would of done the 1600rpm range but guessing torque would be 300 and hp 180

[MoPar7055]

Do you see how the lower the RPM is the higher the torque is compared to horsepower? Look at how after 5252 the horsepower is always higher than torque. Always. At 5252 they cross. If you go as low as 1600 RPM the torque will be way higher than horsepower.

[MoPar7055]

If RPM is a constant then horsepower is a function of torque meaning there is only 1 value of HP for each value of TQ no matter what. Even if it's a different engine, any engine that makes 180 HP at 1600 rpm must have 591 ft/lbs of torque at 1600 RPM.

[MoPar7055]

If an engine makes 400 horsepower that means it only makes 400 horsepower at one certain point in the RPMs everywhere else the number will be lower.

[markbotv3]

ok lets say there is a car that runs the 1/4 mile in 15.4 secs at 93mph. where you check the horsepower at flywheel output shaft or wheels changes the horsepower number. but the performance is unchanged. explain that brainiac lol

[MoPar7055]

That's because horsepower is lost through the drivetrain due to friction. It has nothing to do with it. When rpm stays a constant there is a relationship between HP and TQ. Look at a dyno graph, you will see that before 5252 rpm there is always more torque than HP and after 5252 rpm there is always more HP than torque. At 5252 they cross.

[markbotv3]

the horse power isnt "lost" as you say because performance is unchanged. the number is lower because of the location of the reading.

[MoPar7055]

You are wrong, horsepower is lost due to friction in the drivetrain. This explains why an engine makes more horsepower when measured at the crank then at the wheels.

[markbotv3]

my point is its not "losing" horsepower simply because your taking the readings at different locations your just changing the number...now pull a wire off then yes you are losing horsepower. and performance would suffer

[MoPar7055]

The engine itself may not be losing horsepower. But there is horsepower lost on its transfer from the engine to the wheels.

[markbotv3]

ok lets look at it in anotherway...how much horsepower would you need to make a car do 15.4sec at 93mph assuming total car weight of 3800lbs

[markbotv3]

anyway my whole point is mopar specifically underated this motor for insurance purposes. they said it produced 180hp and 260lb of torque. but anyone who ever drove one would tell you it is way higher than that. on their hottest motors they only advertised at lower rpms to get a lower number. example 340 six pack was rated at 290hp but realisticly it was making 330. 440tnt was rated at 375 but was making 420. you say it takes 591 torque i say it only needs 290 lb/ft 30 more than advertised

[MoPar7055]

If it is turning at 1600 rpm it DOES need 591 torque to make 180 HP. This is like quantum physics for you to comprehend. If it's turning at a higher RPM then it doesn't need nearly that much torque but you specifically said it makes 180 HP at 1600 RPM therefore you were wrong!

[markbotv3]

ok apply your formula to this...two 1979 318s only differance is the carb...2bbl 140hp at 4000rpm 245torque at 1600 rpm...4bbl 155hp at 4000 245 torque at 1600 rpm...peak horsepower and torque are at the same for both engines so according to you they should produce the same horsepower...but they dont. my source is allpar volore specs

[MoPar7055]

I can't apply the formula to that, You listed to different RPMs. You're peak torque is at a different RPM than your peak horsepower. If you wanted to you could apply the formula to figure out what your torque is when you're at your peak HP and vice versa.

[markbotv3]

a 591 torque engine would prolly produce 300horse at 1600

[MoPar7055]

Wrong

[MoPar7055]

I'm telling you, go look at a picture of a dyno graph on the internet and you will see how much higher the torque is at low RPMs compared to HP and vice versa.

[markbotv3]

ok i see your point though if peak hp is only 1600rpm than it would need 500 some torque...like a diesel engine or somin. im just saying you cant quantify a specific torque at a specific rpm the world just doesnt go by mathmatics there are way too many variables...like the above said engine didnt need anywhere near 600 torque to produce 241hp at 3000 and torque dropped at lower rpm albeit not much

[MoPar7055]

I can tell you why you think that increasing VE improves HP but doesn't effect torque. It's because increases in VE generally occur in the higher RPM ranges, this will increase the HP as well as the torque but since you rarely have peak torque in the high RPMs the peak torque number will actually remain unaffected, what you don't realize is that torque has actually gone up with HP just not at the RPM where the peak torque is measured.

[markbotv3]

what about the two 318s both maxed horse power at 4000 and both maxed torque at 1600 both had the same torque but different horsepower ratings...the VE was increased by the 4bbl

[MoPar7055]

Give me the torque and RPM and I'll tell you the HP. Or even better yet give me the TQ and HP and I'll tell you what RPM the engine is at.

[markbotv3]

asuming this lil red engine makes 230hp at 4700rpm and 260 torque at 1600...say theoreticlly its raising from idle to 4700 at what rpm would it be at when it makes 180 horsepower?

[MoPar7055]

This may be hard for you to comprehend but that can't be calculated with the information you have given me. If engines had a linear horsepower increase with the RPMs it could theoretically be calculated but for all I know the Horsepower may spike up at a certain RPM then slowly rise or even begin falling again before it reaches 4700RPM.

[markbotv3]

lol then how can you say defacto that it needs 591 torque to make 180 hp at 1600. that other engine was makeing far less peak torque and when it passed the 180 mark it had to be less than 3000 rpm...prolly less than 2000

[MoPar7055]

I explained that already. I can say defacto that it needs 591 torque at 1600 rpm to make 180 hp but if you give me a HP and RPM value at X RPM I can't tell you the torque value at Y RPM.

[MoPar7055]

I you say it makes 180 HP at 1600 RPM I can tell you the torque at 1600 RPM but I can't tell you the torque at 3000 RPM. Make sense?

[MoPar7055]

Actually it would be possible to estimate that by assuming the horsepower gradually rose and then interpolating. Ofcourse it would just be an estimate though.

[KamalaManring]

Man, I cried when I saw this. I miss my Formula S car SO MUCH!

[partyguy420]

dude thats so sweet... you guys have the 60 ford f-100 which is the same as my 63 f-100...

and the 66 barracuda which is the same as my dads 65