Wheel Kw = Engine Kw?

[Bruce Lee]

Hi just wondering how I can figure out what engine kw my T has.

Is there a simple calculation?

My T has 287.2rwkw

Ive heared people say that you loose 30% of your engine kw, but the numbers justt seem too high.

Edited 28/05/07 09:22 AM by Bruce Lee

[galconn]

As a rule of thumb somewhere between 18-22% power loss would be a reasonable estimate.

[Guest bluprinturbo]

I remember when the rule of thumb used to be flywheel kilowatts was approximate rwhp.I guess drivelines are more efficient now than they were 10-15 yrs ago.

[Turbo6man]

An efficient manual gearbox which is correctly matched to your car's torque and weight will see a loss of about 12%. Through the remainder of the driveline you will see cumulative losses of up to 5%. So a good manual will yield about 17% loss from flywheel to rears. An auto generally adds up to 5% more than a manual but modern autos are very nearly as efficient - a good one will be down around 15%. So this would yield a cumulative total of 20%. An older style auto will yield total losses of around 25%.

There will always be some exceptions and examples that fall outside these figures, however as a general rule of thumb this is what you get ...

manual, about 17%;

modern auto, around 20%;

older auto, around 25%.

[shnaped_second]

I remember when the rule of thumb used to be flywheel kilowatts was approximate rwhp.I guess drivelines are more efficient now than they were 10-15 yrs ago.

I was familiar with this rule aswell, my 34 puts out 206kw standard and atw it made 213hp with a aftermarket pod filter, so I think this would be your best bet

287.2kw = 385.14hp

Therefore that should mean

flywheel kw = 385 or round abouts which is a loss of 25%

[DAFEY]

Totally off topic but I gotta say I like the lateral thinking with the xr8 wheels on the skyline, that's gold!

I was familiar with this rule aswell, my 34 puts out 206kw standard and atw it made 213hp with a aftermarket pod filter, so I think this would be your best bet

287.2kw = 385.14hp

Therefore that should mean

flywheel kw = 385 or round abouts which is a loss of 25%

[Bruce Lee]

Thanks for the help!

[Blonk]

I am quite certain that percentage loss through drivetrain is bad maths.

Say a 50 kw loss through drivetrain (IE 240 fw - 190 rw)

This drive train loss should be static with amendment for friction as power increases.

Same motor with Mods -

therefore drivetrain loss at 500 fwkw's would still only be around the 50 kw +/- overcoming friction, heat and noise

As we increase the reliability of gearboxes and diffs we add to that drivetrain loss, but no-where near as significant as 25%.

I believe a percentage is is the wrong application in this instance,,....

[Felix]

So you could use a percentage to work out un modded power, then use that number to work out modded power.

If your car stock made 100kw at the fly and 70 at the wheels, that's 30kw loss,

Dyno the same car after mods and it makes 170kw at the wheels,

Then you can say it has 200kw at the fly.

so rough example 287rwkw would be (standard zf auto loss of say 35kw) 287+35 = 322 fwkw or 431rwhp or 437 cheval vapeur-atw

But keep in mind that I failed maths B.

Felix

[Blonk]

I think the curve loss would be parabolic through maximum friction, heat and noise, but potentially a variable could show adjustment to base figure