Since I don't know for a fact, how much hp is lost from the crank to the tires? I've got one guy telling me it could be 20+. I laughed but I would like to know in order to shut the kid up.

 

20+ what? Percent?

 

FWIW, a good swag is between 20-30 percent.

 

For automatic transmissions it's usually between 20-25%, manual 15-20%

 

^ 20+ hp lost

 

A Corvette C6 Z06 is rates at 505 HP, but dyno's at 440-450 HP. That's a loss of around 60 HP to the wheels w/ a manual tranny.

2006 Acura RL rated at 290 HP, neuronbob dyno'd his stock at 191 HP to all 4 wheels, that's a 99 HP loss. http://www.dragtimes.com/2006-Acura-...phs-11766.html

 

Dangerously close to an OP fail. As questioned above, 20 what? Also, are you laughing at the kid for being too low or two high on that undefined 20 number?

 

If you're talking percentages, most people feel 10-15 percent is the norm. Rear drivers tend to have slightly more loss than front drivers. Keep in mind that horsepower ratings from manufacturers have, at times, not always been entirely correct, resulting in wheel horsepower being either higher or lower than the expected frictional loss to the drive wheels.


Terry

 

If he was telling you it's 20+ percent then he's pretty much right.

If he was telling you it's 20+ HP, then he's still pretty much right depending on how much HP the engine is rated for.

As was mentioned above typically autos lose 20-25%, manuals 15-20%.

So, if you are driving a07 TL-S which I believe is rated for 286 hp you would be losing ~57hp on an auto, ~43hp on the manual from the crank to the wheels. And that's on the low end.

I also remember seeing dynos of the 01-03 and 02-03 CL-S/TL-S where people were getting just a tick over 200hp to the wheels meaning they were losing between 50 and 60hp since the engine was rated at 260hp.

So, I am thinking you may not want to say anything to the kid... b/c he is right.

 

As most have said ~20% is about right for a AT, MT's are lower typically ~15%. I'm guessing that SMG gearboxes maybe slightly higher than a pure manual.

Also a FWD has less losses than a RWD. A transverse FWD drivetrain typically has less losses than a longitudinal FWD drivetrain (it does not have 90o gearset). And 4WD has more losses than RWD and FWD.

 

One additional thing about FWD cars is that almost all of the power at the wheel is applied in the direction where you want to go. RWD cars lose power when the car isn't pointed in the exact direction of travel (i.e. when you turn the steering wheel).

 

He's right.

 

AWD loses even more.

 

Wow, I didn't think it would be that much being its front wheel drive. I would expect that 20% / 20hp loss to a rear wheel drive. Guess I will need a little salt and pepper with the crow I'll have to eat.

 

A drivetrain loss of only 20 HP on any car with more than 150 HP would be highly unlikely; 20% is much more likely.
Example: Various members on the 3G TL forum were dynoing at 210-220 hp at the front wheels with the auto trans, although the '04-'06 engines were rated 270 hp (changed to 258 HP per measurement standards for the '07-'08 3.2 TL).

 

This prolly doesn't help but:
I did dyno my RL, but not a baseline...
Factory claims 210hp /224 lb. ft. tq.
I dyno'd at 181whp/190 tq. with a crappy axleback and a shortram intake.