Kilowatt at the wheels

[slydar]

yeah, they told so they didnt have to go through the whole explanation i did.

[Frak]

after performing around 2000 runs on our dyno and doing comparisons, I find that the losses on our dyno(mainline) are between 18%-22%

[slydar]

ok a chance for some relevent discussion. do you find say, (not sure if you even work on these cars) a 1 tonner with a 308. trimatic box, and 31" mts has more estimated drive line loss, than your average rwd corolla?

[af300e]

29.2% is absolutely a farce. Any technician stating such a figure in this context obviously has no clues. Oil viscosity will have enough effect to make such an "accurate" figure irrelevant. I actually thought it was posted here as a joke.

Slydar, I agree, the comparison issue is an important one. Hence, to compare a commodore to a corolla is prebably less informative than comparing a low output corolla to a high output corolla. Naturally a transmission designed to handle a higher load will zap more energy than a lighter duty one, the question is really how much more energy will a given drivetrain convert to heat when the input energy is doubled.

The issue in my mind is where the extra 30kw parasitic loss goes when the power is doubled. It can only be converted from kinetic energy to heat, sound or both in the driveline. Noise is going to be insignificant, so, if at 100kw the trans (and diff) oil is sitting on say 70 degrees centigrade (random figure), will it run close 140 degrees when 200kw? 210 degrees at 300kw?
I think not.

Anyhow, although engine KW may be largely irrelevant, parasitic loss remains an interesting issue.

[fixeruperer]

engine dyno's are for engine horsepower and rolling dynos are for wheel horsepower.
theres to many variables from the flywheel to the wheels to give a true actule figure, you can have a good guess tho.

[slydar]

my point was to try to convey as obviously as possible, 29.2 or whatever random percentage is clearly not applicable to all situations, and demonstrate that it is a slightly more complex issue.

and actually the wrong way to be looking at things. if you want to guess at your engine power level based on a chassis dyno figure, so you can be happy/sad about the power your engine makes compared to a quoted PS figure in a japanese magazine, then cool. but talk about it in general chat or something.

this isnt a tech article.

[driftke70]

did you talk to a technician, on a friday arvo, after had 16 beers,

were they laughing?


EDIT typo

[Sam-Q]

now I dont have any sort of experience that others on have had but I still think theres some factors that are clearly overlooked. For starters dynos vary heaps, they are all meant to be regually calibrated with a known power source but really who does it. The dyno that the guys at EFI hardware use gets a constant 75kw for tuned 20v engines with an intake and an exhuast, most others get 90kw and there was some guy on the old ae86dc that got 125kw with the exact same setup. So without even knowing a proper figure at the wheels this chart is tottaly useless.

Another point is that apart from how much tires affect the power figure the gear that the car is in at the time makes a huge difference. Fourth gear (or fifth for a 6 speed) should have a less loss than any of the others.

I have personally seen a 4ac motor with about 30% more power than stock pull 39rwkw, and normally a 20v on a stock ecu will get around 75rwkw. If this engine is meant to be 110kw or so in reality then thats a 46% loss. WRX's make 150kw or so and are known to commonly have 95kw at the wheel through their AWD system.

I right now have a 20v with porting from the valves to the throttles, higher compression, a wolf ecu and my exhuast system and I have a dyno sheet showing 101rwkw, theres no way I could have a 195hp engine.