How Much Is 250rwkw In Engine Kw?

[BaysideBlue]

I have always wondered how much power my engine is actually producing after it made 250rwkw on the dyno.

A factory standard GTT with 206kw at the engine usually makes 145-150kw at the wheels.

If everything else stays constant: tyres, wheels, drivetrain, dyno setting, temperature and etc.

How much would the same car produce at the engine with 250rwkw? In other words: How much is 250rwkw in engine kw?

Do you add the 56kw drivetrain loss (as from 206kw - 150rwkw = 56kw) which give you 306kw at the engine?

or do you calculate in percentage power loss (206 divide by 150 = 1.37), then you times 250rwkw by 1.37 which give you 343kw at the engine?

Applying whichever the correct method, what is 300rwkw equals at the engine? and 330rwkw?

I understand that unless you put the engine on a engine dyno you can't get a definite power figure at the fly. But whats the general rule of thumb method to calculate engine kw from power at wheels?

Thanks

Edited May 26, 2007 by BaysideBlue

[cheez]

it stays about the same as long as the drive train hasnt changed. but if a car is putting down 250rwkw, then your looking at almost 320kw at the flywheel.

could be less than 320 as with 250rwkw, u would have a new clutch/pressure plate and i would assume pump would be diff too. but you could expect close to 320 at teh fly.

[MBS206]

If a car makes 250RWKW legitimately at the back wheels, you're looking at probably 251RWKW at the engine.

Drivetrains don't soak up much power at all.

[fEkuaR]

What have you been smoking? a 1kw loss through your drive train? Your dreaming mate. You will be looking at a significant amount to be lost through your drive train by the time power has been transfered through your gearbox, diff ect. What do you think these things dont absorb power?

If a car makes 250RWKW legitimately at the back wheels, you're looking at probably 251RWKW at the engine.

Drivetrains don't soak up much power at all.

[sinistaGTR]

ummmm....standard r33gtst

engine 184kw

wheels 137kw

yes there is about a 50kw loss

[teazn_r33]

http://www.mr2ownersclub.com/converter.htm

[BaysideBlue]

you're looking at probably 251RWKW at the engine.

Drivetrains don't soak up much power at all.

what are you talking about? 251RWKW means 251kw at the rear wheels. you don't normally say 251 rear wheel kw at the engine, do you?

[BaysideBlue]

ummmm....standard r33gtst

engine 184kw

wheels 137kw

yes there is about a 50kw loss

yeah but does that mean if the car has

wheels 300kw + 50kw loss = 350 engine kw?

[fEkuaR]

yeah but does that mean if the car has

wheels 300kw + 50kw loss = 350 engine kw?

Drivetrain loss will remain the same unless things are changed.

[32vspecII]

percentage loss

[fEkuaR]

percentage loss

Are you saying that for example on a standard gts-t that is looking at a 50rwkw power loss which is close to 25% loss. That on a 1000kw car you are looking at a 25% loss also resulting in a 250rwkw loss through the driveline? Why would it absorb more power the more power you make?

Edited May 20, 2007 by fEkuaR

[Adriano]

Definately less than percentage loss, but definately more than no increase. Just think, losses due to oil drag in g/box & diff will be the same, but frictional losses will increase proportionally. The only way to know for sure is to pout it on a engine dyno and then a chassis dyno. I would say 250RWKW=about 320FWKW, and 300 RWKW=about 380FWKW

[2rismo]

percentage loss

Simply the dumbest statement in this thread.

A given drive train will convert (not absorb, not remove, not hide) the same amount of hp/kW regardless of the engine power. Some of this energy is converted into noise but most of it is turned into heat energy and dissipated through the drive train components including everything from the flywheel to the tyres.

To say that a drive train will somehow magically absorb triple what it does from the factory just because the engine horsepower increases by that amount is laughable. Imagine 50kW of heat coming off of your drive train in total and then imagine what 150kW of energy would do to those components. Ever stood next to a 2kW heater?

[R33GOD]

250rwk would equal an approximate of 325 kilowatt at the fly.

ive been told by mechanics just plus 30 percent on top of what kw you made at the wheels

[Cubes]

R33Gods calc is what I would expect.

--

Clint32 many moons ago had his rb25 on an engine dyno. Made 580hp

On a DD Dyno it made 338rwkw. Thats close to 95rwkw drivetrain loss.

I believe as power output increases the amount of power absorbed by the drive train is also increased *SLIGHTLY*.

As more load is placed upon gears and bearings more friction occurs. This has to equate to an increase in drivetrain loss.

The old LS1 V8 manual commodore for example... GTS ~300kw at the fly = 225rwkw,

The run of the mill SS's back then... 225kw at the fly = ~165rwkw.

All approx values as dyno's can vary 5-10rwkw depending on how its strapped down, air temp etc etc.

[Forged]

http://www.mr2ownersclub.com/converter.htm

I dont see anything in the link that convertes rwkw into engine kw.

Btw to say "just plus 30 percent on top of what kw you made at the wheels" is too general. maybe true up to a certain power level. but would result in big discrepancy say for between a car with 100rwkw and a car with 400rwkw.

[Cubes]

At light throttle cruising along.... Your motor may be making 30kw at the fly.

IF the drivetrain loss were a fixed value you'd have to drive around with half throttle everywhere.

So a percentage it is. Rough enough is good enough

Its most likely a fixed value + percentage to take in to account increased friction and load upon bearings/gears. BUT too difficult to determine.

[R32 Driver]

250rWkW = 325rw @ engine = 250 * 1.3 = engine power

kw @ engine is same as hp @ wheels

300rwkw = 390rwhp or 390kw @ engine

330rwkw = 430rwhp or 430kw @ engine

this would be a more realistic percentage loss through the drive train

and may god blow up all over reading dynos

ps these are rough calculations, if you want exact get it on a dyno

Edited May 20, 2007 by R32 Driver

[Cubes]

R32 Driver,

Interesting way to look at it.

[andz]

If a car makes 250RWKW legitimately at the back wheels, you're looking at probably 251RWKW at the engine.

Drivetrains don't soak up much power at all.

Edited May 20, 2007 by andz