SSCoulter

iTrader: (4)

Ok guys, I'm sober this time so flame away. I posted a thread about this and got some good info and had a little fun along the way but I still have one question. Whatever the real number is, and let's just say 15% for the sake of this argument, why would that number stay constant when the engine is making more horsepower? What I mean is, if the drivetrain loss is due to friction through the tranny and rear ect, wouldn't that stay a constant drag even though the engine is making more horse power? If you continued to use the 15% number than a 600hp motor is losing 90hp vs a 400hp motor is losing only 60hp. If nothing else has changed in the drivetrain except the engine power, how is this accurate?

SCamaroS

It's like taxes... u pay 1 buck you pay 6 cents taxes... you pay 10 bucks you pay 60 cents for it.

ActionJack

Interesting read here:

http://www.eng-tips.com/viewthread.cfm?qid=81815&page=3

SSCoulter

iTrader: (4)

Thanks action, I think I just blew a fuse in my brain.

Blue Hawk

Think about it this way: If it was a constant number (say 60hp) and if you swap your 400hp engine for a 60hp engine, than by this theory, the final output to the wheels would be 0hp and the car would not move at all. But it's obvious that it's false and even a 60hp engine would still move a f-body to highway speed.

Friction is not the only contributing factor to hp loss. Inertia play a much bigger role in this too. The combined mass of all the drivetrain components is a resistance for an engine trying to go from 1000rpm to 6000rpm. And when you replace those components (axles, driveshaft, ring, pinion, etc...) with stronger (and heavier) ones, you just add to the resistance (inertia) against the engine.

Another silly example: If the total weight of all the drivetrain was 0, then there would be no difference between reeving the engine in neutral and reeving it in gear (with the rear wheels off the ground of course, say the car is lifted). Now replace that fantasy drivetrain with a real one and the engine will reach its redline slower as there is much more mass to twist.

Power loss is not a constant, and it's not a percentage too. It's something between the two (close to a percentage since inertia play a bigger role than friction in power loss). If inertia was the only factor, then it would be a pure percentage. If friction was the only factor, then it would be more of a fixed number.

Hope this help.

LiquidFire350

iTrader: (8)

all i want to know is can i punch ricers in the face every time they say that manuals MAKE more horsepower

luvmeZ28

iTrader: (3)

im pretty sure it isnt a constant number. if you are naming 15% as the percentage, just for arguments sake, i dont think that 15% is going to remain constant as HP production increases. and its like was said the other thread, its gonna be different on every car anyway. youre just gonna have to suck it up and guestimate unless you wanna pull your motor and have it dynoed that way, EVERYTIME YOU DO A MOD.

luvmeZ28

iTrader: (3)

yes , yes you can.

SSCoulter

iTrader: (4)

Thanks for all the posts. I'm feeling much better now. I shall never ask this question again.

SSCoulter

iTrader: (4)

It does help, and thanks for your time.

ZR2877

Since were on the topic of drivetrain and power I'll ask this here. Why don't 4.10 gears actuallly add power to the wheels on the dyno? You would think it would since the tires are spinning faster it would get the rollers spining faster. I was told once to think of it like leverage. You are trying to loosen a bolt but can't so you put a long bar on the wrench for leverage and it turns easier. You are not any stronger but you are turing it easier. Is there another way to explain it? Just curious.