Kilowatt at the wheels

[AE86R]

From old dc, posted by jonny rochester

The loss is generally about 30%. So...

If your motor has 80kw (107hp), you would get 56kw (75hp) at the wheels.
If your motor has 90kw (120hp), you would get 63kw (84hp) at the wheels.
If your motor has 100kw (134hp), you would get 70kw (94hp) at the wheels.
If your motor has 110kw (147hp), you would get 77kw (103hp) at the wheels.
If your motor has 120kw (161hp), you would get 84kw (113hp) at the wheels.
If your motor has 130kw (174hp), you would get 91kw (122hp) at the wheels.
If your motor has 140kw (188hp), you would get 98kw (131hp) at the wheels.
If your motor has 150kw (201hp), you would get 105kw (141hp) at the wheels.
If your motor has 160kw (214hp), you would get 112kw (150hp) at the wheels.
If your motor has 170kw (228hp), you would get 119kw (160hp) at the wheels.
If your motor has 180kw (241hp), you would get 126kw (169hp) at the wheels.
If your motor has 190kw (255hp), you would get 133kw (178hp) at the wheels.
If your motor has 200kw (268hp), you would get 140kw (188hp) at the wheels.
If your motor has 210kw (282hp), you would get 147kw (197hp) at the wheels.

This chart only applys if the loss is 30%, and that we can never be sure off. Also, the 30% loss is not a constant with all amounts of power. It is used here as a rule of thumb.

[Wally]

I thought it was closer to 25%?

[AE86R]

i have also read around 30% or to be exact 29.2%

[Wally]

So a stock bigport should have 64rwkw according to that?

[YAZE]

Johnny Rochester knows everthing. Also, I belive one killowatt is approx 1.41 horsepower. That might be of some use in this thread.

YAZE

[Wally]

Doubt I'll get my 100rwkw then from my engine :(

[AE86R]

1 kw = 1.34102 hp

1 hp = 0.7457 kw

[Wally]

1 kilowatt = 1.3410220924 horsepower

[AE86R]

like i said

[YAZE]

I stand corrected. haha

[Wally]

depends. there is alot of different types of horsepower :P

[AE86R]

haha what are u smoking now??

[Wally]

Horsepower from a horse
Mechanical horsepower
Metric horsepower
PS
CV
Boiler horsepower
Electrical horsepower

:P

[klusio]

you have forgotten the KillerWaps lol

[klusio]

Johnny Rochester knows everthing. Also, I belive one killowatt is approx 1.41 horsepower. That might be of some use in this thread.

YAZE

hahah have to have a talk to him about everything when I see him next:hehe:

[Frak]

on our dyno(mainline) bigports get in the 62kw-67kw at the wheels depending on stock or with aftermarket exhaust fitted, my bt gets 100.35kw at the wheels :jdmsmile:

[AE86R]

yeah sounds right.

[Wally]

didn't you get like 79 damo?

that was a smallport though correct?

[Delazy]

you have forgotten the KillerWaps lol

those killerwasps are the ones u want...massive power those

[Jonny Rochester]

But if I knew everything, I would have a doctrite of engineering x2 just like Jeremy Clarkson.

[AE86R]

lol jonny u the mannn

[af300e]

Why is it 30%?
100fwkw, 30kw to parasitic loss.
Same drivetrain, 200fwkw, 60kw parasitic loss?

Doesn't make sense. There is a small increase in energy converted to heat in the transmission/diff when more power is put through it, but it's nowhere near double the loss as these low power levels, the loss does not increase linearly.

I'd suggest the loss for t50/w5* boxes and t-g series diff is closer to a constant 20kw. Dyno results for stock motors seem to suggest this.

I spoke to a dyno engineer about this subject in length as the percentage thing has always had me stumped. He agreed, for most vehicles the loss is closer to a constant 20-30kw.

[Wally]

Mmm interesting point raised.

[AE86R]

jonny needs to answer that or sam q

[Wally]

I'd be keen to see the answer back to this.

As I used to always read about ~25% but this throws a spanner in the works... It makes some sense and could be pretty close right

[AE86R]

25% and 29.2% or 30% is fuck all really

[Wally]

Settle down tiger. We are all friends here.

[AE86R]

lol not taking any stabs just saying 4.2% is fuck all really

[slydar]

a dyno is a machined used for tuning and comparative testing. trying to work out your engine power level from a chassis dyno is pointless, as it is irrelevant.

there is no point in even knowing what HP your engine makes. taking your car to a dyno to check that it is making similar numbers to what other similar engines make on that same dyno has some relevance, as you will be able to determine if your engine/driveline ect is in good condition/performing correctly, and therefore make a better decisions on your next repairs/improvements.

i just dont understand why you even posted the thread? also these figures, be they percentage or rule of thumb kw figures for specific drivetrain loss are just every rough guides.

things like, tire type and condition and even pressure, diff ratio/condition/oil type, tailshaft uni condition and configuration/angle, transmission type and condition/oil used/oil level, ambient temperature, will all effect the reading. these are just a few of the variables..

stating that it is 29.2% is getting very close to being just plain un intelligent.

[AE86R]

i think every one likes to know hp - atw. there is no rough thumb rule on the whole interwebs and jonny took his time to write that up so i think it should be a basic guide..

29.2% is what is stated on many sites, and a few technicians have told me its that..

[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.