Drivetrain power loss,.,.,.IF a 100hp car....

[F1GT]

If a 100 hp engine loses 15hp(15%) from the flywheel to the drivewheels. Will it still be a 15%(30hp) loss if the engine was pumping out 200 horses going through the same tranny????

So, will it be 185 hp or 170 hp at the wheels for a 200 hp engine??
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[HAZ-Matt]

That's a pretty good question. I actually remember reading something about this one time on cz28 i believe. The idea was that it only took an exact number of hp to turn the tranny, and that when you upped the horsepower of the motor, the loss was the same. The point was that people were overestimating their horsepower at the crank when they added the 15% to their dyno numbers. At any rate, the overwhelming number of people responded that the loss is a percentage, no matter how much power you are putting down. I would suggest that neither is really true, but that the static percentage is nearer to reality. This is a question that is actually outside my field of expertiese, but I think it's likely that the loss is really a function of the power input, but I could be way off. In any case, just say that it is always 15% [img]smile.gif[/img]

[12secondv6]

Well, are we talking f body's?
Lets do that :D
I've always thought that our cars, auto with 2 piece steel d/s lose 21% power through the drive train.
Take that auto and replace the 2 pice steel d/s with a 1 piece aluminum and that power lost is now 20%
We know auto's rob more power than manuals.
For manuals I have always been told it is about 17%
So, 200 hp car:
Auto 2 pice d/s 42 hp lose 158 hp
Auto 1 pice d/s 40 hp lose 160 hp
Manual 1 pice d/s 34 hp lose 166 hp

Make sense?
Carbon fiber d/s free's up a bit more power.
Lighter pistons and crank free up more power, windage tray? or scraper on crank free's up power

[Backfire]

12Sec, I think those are the percentages that the two previous posts are questioning. They may very well be accurate, but it doesn't really answer the question about why is it a percentage of the input power and not a constant number ;) :D

I would guess that the reasoning behind the percentage, is that with greater power application, the drivetrain will experience greater loading and resistance. When transmitting greater power, the loading at the gear teeth would increase, which would result in greater friction between them. This increased gear loading would also increase the loading of the bearings, thus increasing friction there as well. I am sure there are many more areas where similar reactions occur. I am guessing that the power consumed by these resistances may turn out to stay fairly close to a certain percentage of the input power.

[F1GT]

Yes BackFire, I was just wondering if it's just a percentage and not a constant number, no matter how much of an increase you got from mods at the flywheel.
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[TheBlackSwordsMan]

if you lighten the flywheel does that have any affect on horse power loss?

[ravenp]

I would tend to agree with Backfire on this one. More power at the crank means more power through the drivetrain, causing more resistance, meaning it can't be a contant regardless of crank HP.

I dont' know that we can be that general though. Like you said there are so many factors...so many components offering resistance, and some of those depend on other factors such as weather, traction etc...

I would think that dropping an LT1 in our cars(auto for example), you would lose more hp at the wheels(a greater number) than with the 3800, but the percentage wouldn't necessarily be the same.

I'm just estimating though [img]smile.gif[/img]

[F1GT]

<blockquote>quote:</font><hr>Originally posted by ravenp:



I would think that dropping an LT1 in our cars(auto for example), you would lose more hp at the wheels(a greater number) than with the 3800, but the percentage wouldn't necessarily be the same.

I'm just estimating though [img]smile.gif[/img] <hr></blockquote>

Well, yeah, but we're just being general here :D and saying that the more power you make the more you lose through the drivetrain....
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[Camarorulz]

I've heard that drivetrain loss for an auto is anywhere from 15-20%, think that number of 21% is a bit too high..an f-body v6 auto should put about 165-170 to the wheels..Also, the percentage of horsepower lost through the drivetrain should be basically constant,regardless of hp, unless a modification is made to make the drivetrain more efficient.

[ September 24, 2002: Message edited by: Camarorulz ]</p>

[F1GT]

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