Drivetrain Loss calculation. question

[Drifte]

If I have 600 engine hp and a 25% drive train loss what equation is correct for determining WHP?

I believe 600 x .75

Tballer believes 600 / 1.25


Tell me which method you believe is correct, and why.

[Drifte]

Loser has to admit they are wrong!

[TbTalon94]

The question was you have a car that makes let's say 450hp on a DYNO, like a mustang dyno....what would be their calculated Crank horsepower.

MY formula says 562.5 crank hp
Drifte's Formula says 600hp

Matter of opinion I guess. We argue for hours and we both know there will never be one difinitive answer.

[Ricky]

I got 562.5


You have 450 WHP and a 25% drive train loss.

450*1.25= 562.5

*Edit* I was wrong. I over thought it. :banghead:

[qoncept]

TBaller is backwards. If you knew you had 450whp and had a 25% drivetrain loss, then you divide.

450 / .75 = 600

[AutoMods]

I'm in the boat that drivetrain loss is loss from engine horsepower. So if using 25%, you take that away from engine, not adding 25% to whp

so if you have 25% drivetrain loss that is .25

So if 600 engine horsepower . you take 600 * (1-.25) which is 600*.75 = 450whp

To go backwards from wheel to engine it would be 450/.75 = 600

[Ricky]

i am wrong.

I was taking 25% of 450 and that is wrong.

Colton and qoncept are correct.

I was backwards too. the 450/.75 shows you that 450/.75 is saying 450 is 75% of what you know and you want to find what makes the other 25% (your loss)

150+150+150= 450 or 75%
add another 150 or 25% and you have your 600

[Ricky]

450=75%
600-450= 150
150+150+150= 450
450(75%)+150(25%)= 600


Case closed. Trevor say "Colton Krumm you are my hero"

[JustinS]

Isn't math awesome?

[69gt4speed]

Kinda off subject though similar.. What ticks me off is every damn dyno unless maybe same brand reads a lot different. It then boils down to seeing only gains and losses and a/f ratio if it has a wideband. You would think w all the tech we have it would be within 1 or 2 whp if tires aren't spinning. The Tq formula of accel a known weight to xxxx speed/rpms in xx time is fixed. What is so hard about that?

[AutoMods]

Here is a fun calculation for Rob,

Driveline loss for a solid axle-equipped car like the Mustang is typically 11-13%. This is a bit less than the usual 15-18% you'd expect on an IRS car, as solid axles have fewer power-sapping U-joints in their driveline. http://www.mercurymarauder.net/forums/s ... hp?t=61383 (http://www.mercurymarauder.net/forums/showthread.php?t=61383)

Moral of the story: new mustang has about 20whp over the camaro just due to the rear. not fair. ls3 ftw

[TbTalon94]

Ok he didn't give info on how the convo started. He said he was calculating the CrankHP from wheelHP numbers on say Brent's car, then my Evo. I thought his numbers were kind of high and he said he was using 25% drivetrain loss. I did exactly what Eric did at first and multiplied 25% of the given wheel HP numbers. Mathematically this is wrong, you were right Colton, BUT it really depends on the dyno. Colton's numbers were inflated and are not correct if you use the general consesus of ~25% drivetrain loss most AWD owners agree on.

So either he was wrong on the drivetrain loss, or the dyno comes into play when reading out the Wheel horsepower numbers and you cannot just simply say that the displayed wheelHP from the dyno is 75% of what the actual engine is making. I stand by the fact that the dyno makes the difference and saying that the wheelHP given is 75% is wrong.

Example here:
http://img141.imageshack.us/img141/2551/gtxawhpvsps1bar.jpg

In that graph it has Wheel (axle) horsepower on the left and Crank (power ps) horsepower on the right. If you use my formula for 25% drivetrain loss (it's an Evo dyno) then the numbers match. If you use Colton's formula for 25% drivetrain loss the numbers do not. If you use 20% drivetrain loss Colton's numbers match and mine do not. Again we go to dyno's play a difference BUT if you look around 23-25% is what most AWD guys say the drivetrain loss is.

I believe the read out of wheel horsepower is not exactly 75% of what the engine is making. There are many factors to be played in there and just simply assuming that it is will give you an inflated crankHP number.

So to conclude, Colton IS CORRECT in mathematic terms how to calculate the crank/wheel numbers...BUT my method I believe works better for real world results because of the dyno factors. The only REAL reason to know is if someone put their motor on an engine dyno, then put it in the car and put it on a roller dyno...measured both levels of power and then calculated the drivetrain loss. There really is no sure fire way of calculating the wheel/crank HP level if you do not know 100% sure what the drivetrain loss is. Both of our formulas get you close and you really can't say which one is right because you do not difinitively know the drivetrain loss.

[Scott]

Dyno's suck anyway!!

[Drifte]

The drive train loss is always going to be a variable, every car is different. I only wanted to use the correct equation when calculating off the estimated drive train loss.

Annnnd, I didn't need to know I was right, I just wanted YOU to say you were wrong!

[TbTalon94]

Maybe I need to start a new thread about turbos huh?

I concluded that you were going about the math the right way...but it was still wrong lol. Like I said we can go on for hours with no difinitive answer.

If you look online all of the calculators vary. Some matching me, some matching colton, others way off. Again no difinitive answer lol.

You cannot just assume you are getting 25% loss on a particular dyno. But you can take that number and multiply it to get close to a real world result. Not assume that the number you got on that particular dyno was actually 75% of what the engine is making. It goes round and round....

[Ricky]

You cannot just assume you are getting 25% loss on a particular dyno. But you can take that number and multiply it to get close to a real world result. Not assume that the number you got on that particular dyno was actually 75% of what the engine is making. It goes round and round....


you would make a good politician, you like diverting from the answer colton wants with a example on how you could be right.... :cop:

[sparkles]

A very common formula used for calculating wire size needs on continuous loads in electrical work.

And fwiw Rob, a dyno is a tuning tool first, number maker second. That's probably why the manufacturers haven't unified readings. That and they all probably think that THEIR way should be the way to measure WHP.

[AutoMods]

I concluded that you were going about the math the right way...but it was still wrong lol. Like I said we can go on for hours with no difinitive answer.

If you look online all of the calculators vary. Some matching me, some matching colton, others way off. Again no difinitive answer lol.

You cannot just assume you are getting 25% loss on a particular dyno. But you can take that number and multiply it to get close to a real world result. Not assume that the number you got on that particular dyno was actually 75% of what the engine is making. It goes round and round....

There was nothing wrong with his answer it was 100% correct. Doesn't matter what real world % loss is. He never claimed all awd cars have 25% loss. That was just the scenerio that both you guys were calculating off of. And you argued with him on the messenger for an hour and a half why he tried to explain it to you and you wouldn't listen and basically you said he was an idiot.

Given 25% loss that is how you calculate it. If online calculators vary they are using a different loss % . Its a simple equation and there can only be one correct answer.

He deserves an apology and 1.75*90/1.75 minutes of his life back

[Jappbox]

here is the real kicker, autos take more, manuals take less, AWD takes more away, and RWD and FWD takes less away, Also note that the more WHP you make, the % ratio goes less, so if you lose 25% with 600hp you only loss say 20% with 900, 15% with 1200, and so on. These are all guesses inless you dyno with a chassis dyno then take it out and dyno it on a engine dyno.

[Ricky]

here is the real kicker, autos take more, manuals take less, AWD takes more away, and RWD and FWD takes less away, Also note that the more WHP you make, the % ratio goes less, so if you lose 25% with 600hp you only loss say 20% with 900, 15% with 1200, and so on. These are all guesses inless you dyno with a chassis dyno then take it out and dyno it on a engine dyno.


^ :offtopic:

Your looking too much into the question.

Here is the known:

600 crank hp
25% loss


Nothing about if it was RWD or FWD or AWD or how much more power you make. That has nothing to do with the original question.


If I have 600 engine hp and a 25% drive train loss what equation is correct for determining WHP?

anything else other then the answer is irrelevant and holds no water.

[Drifte]

here is the real kicker, autos take more, manuals take less, AWD takes more away, and RWD and FWD takes less away, Also note that the more WHP you make, the % ratio goes less, so if you lose 25% with 600hp you only loss say 20% with 900, 15% with 1200, and so on. These are all guesses inless you dyno with a chassis dyno then take it out and dyno it on a engine dyno.

Different argument, but.

Well I've heard a lot of different things, it's a given different platforms are more efficient. But the % changing with more power is somewhat arguable. A gearbox with 90% efficiency is still 90% with 10 or 200hp. Then I look at it like a speaker. Take a driver at 89db 1w1m and give it 500w. Now at 500w 1m how many db is it?

[Domestic Disturbance]

Reminds me of a good arguement some of my friends had awhile ago whether drivetrain loss stayed linear or dropped as power increased. Say x trans gives 20% loss to a 300hp engine, would it still lose 20% power if it the engine made 600hp? We tried to argue that the trans wouldn't add increased resistance as power increased, so the power loss would be a lower % on a 600hp engine. Kind of off topic, but the main 2 people arguing it are both on here from time to time :biggrin:

[TbTalon94]

There was nothing wrong with his answer it was 100% correct. Doesn't matter what real world % loss is. He never claimed all awd cars have 25% loss. That was just the scenerio that both you guys were calculating off of. And you argued with him on the messenger for an hour and a half why he tried to explain it to you and you wouldn't listen and basically you said he was an idiot.

Given 25% loss that is how you calculate it. If online calculators vary they are using a different loss % . Its a simple equation and there can only be one correct answer.

He deserves an apology and 1.75*90/1.75 minutes of his life back

The convo started with the 25% number. Period. Don't back-peddle.

I never once said he was an idiot, i told him we could argue for hours because there really is no difinitive answer.

He does not deserve an apology it was a friendly debate, him and I do this all the time.

If you think that's the case then I deserve an apology and time of my life back when you tried to argue with me that a bigger turbo at the same boost level won't make more power then a smaller turbo at the same boost pressure. Tell me i'm wrong on that one, or should we start another thread about that too?

[Scott]

here is the real kicker, autos take more, manuals take less, AWD takes more away, and RWD and FWD takes less away, Also note that the more WHP you make, the % ratio goes less, so if you lose 25% with 600hp you only loss say 20% with 900, 15% with 1200, and so on. These are all guesses inless you dyno with a chassis dyno then take it out and dyno it on a engine dyno.

Different argument, but.

Well I've heard a lot of different things, it's a given different platforms are more efficient. But the % changing with more power is somewhat arguable. A gearbox with 90% efficiency is still 90% with 10 or 200hp. Then I look at it like a speaker. Take a driver at 89db 1w1m and give it 500w. Now at 500w 1m how many db is it?

Not sure I agree with that one, take a huge trans out of a piece of construction equipment and theres probably some small passenger car engines out there that will take 50-75% of its power just to turn the transmission, put the proper engine in front of it and it will probably only draw 10% or less of its power. I know this is a out there wierd example but its still a example

[AutoMods]

The convo started with the 25% number. Period. Don't back-peddle.

Yes the convo did start with 25% and it was to stay that way. What part of me is back peddling?


I never once said he was an idiot, i told him we could argue for hours because there really is no difinitive answer.

sorry...stupid was the actual word you used. yes the equation has a definitive answer. maybe he could post the whole conversation if you want


I do this all the time.

yea thats the problem. that and your often rude when your trying to prove a point


If you think that's the case then I deserve an apology and time of my life back when you tried to argue with me that a bigger turbo at the same boost level won't make more power then a smaller turbo at the same boost pressure. Tell me i'm wrong on that one, or should we start another thread about that too?

that topic was similar in your attitude and close mindedness on the topic and you also called us stupid on that topic. it started when you suggested putting an OVERSIZED turbo on a car so it could make more power at lower boost. In that scenerio I still stand by you would not see much of a change in hp per psi. There is plenty of scenerios will power per psi will change but not if backpressure and intake air temp are the same. That topic was 500x more complicated then this equation was so I am not willing to donate that much time to argue with you about that. Go back to that thread with an open mind an re-read it.

[TbTalon94]

First of all Ryan it was a friendly debate between colton and I. I like how you left out "him and I" in that little quote of yours.

I was not being rude to him, and he knows it. It was a heated debate between us and I didn't call HIM stupid. I probably said the argument was stupid right after I said we could go on forever.

Second of all I always have an open mind in a debate. I even told colton that the math he is doing is right but it's not arriving at the right answer because of the factors at play. I also told him and you with the debate of turbo's that if you oversize the turbo it obviously would have a negative effect...but you also sat there and argued that a 35r wouldn't make more power over a 20g at the same psi. It will and you know it and neither turbo are out of efficiency ranges in the real world.

[Ricky]

:misterlock:

[qoncept]

In the end it doesn't matter much anyway. The estimates for drivetrain loss on different setups are just that, estimates. And in the end all that really counts is how much power you're putting down at the wheels. This was a conversation about the math, not cars.

Which reminds me... the Prosport AFR gauge I have wired to my LC-1 is reading wrong. Who can tell me how to fix it?

I know 14.7AFR is 2.331v and 11.3AFR is 1.578v. I've got 2 sheets of notebook paper full equations that give me the wrong answer. Even drew a graph because apparently it's been too long since I've taken algebra. (I think the right answer is send the gauge back)

[sparkles]

I guess some people just can't admit they're wrong. That's the awesome thing about math. You're either right or your not. In this case...you're not.