RwKw vs FwKw.

Draco · Post by **Draco** » Fri Nov 24, 2006 8:59 am

What does it all matter, we want our cars a bit stronger on the road so if we can get a deasent RWKW figure we should be happy that the engin performs better and therefore you have a stronger car.

What is more, I want to proove my car puts 200kw(I wish

) on the road and it is proven on paper(dyno). You get so many people saying but at the end it is just talk.

Gary57 · Post by **Gary57** » Fri Nov 24, 2006 9:13 am

I just want to know because they say the STD CA18DET motor is good for 250FwKw. If there is a drivetrain loss of 30% then I am at 210FwKw so then I still have some room to go

.

Anyway lets try not make this an arguement, just a descusion. So if anyone has some figures, let us know.

ChemCool · Post by **ChemCool** » Fri Nov 24, 2006 9:16 am

And again I am confused

Draco · Post by **Draco** » Fri Nov 24, 2006 9:36 am

Confushes, The Hoff and Chuck says, it's okay to be confused Freddy, it comes with age. The point is we don't know so stick with what the dyno says and thats where it stoppes, hopefully.

ChemCool · Post by **ChemCool** » Fri Nov 24, 2006 10:01 am

Oh man. Beatifully said. I feel so much better.

Phinx · Post by **Phinx** » Fri Nov 24, 2006 10:35 am

"Sorry calibrator your calculation is incorrect Exclamation

If you take the 128FwKw minus the 30% loss you get 88.9RwKw, thats a loss of 39.1Kw. You cannot use 30% of the Rwkw because its already down to 70% of the orginal power. So what you would do is take the 90RwKw divide by 70 (the percentage of the orginal power) then multiply by 100, that will leave you with 128Kw. How I got the 70% is simple, just take the FwKw (which we know is 128Kw) divide by how much is on the wheels and you get 70.3%.

Drivetrains loose percentages of power not actual power. ALL drivetrains have efficences which is measured in % not Kw. I work with gearboxes all day and even in the calalogues it gives the % power loss."

Not to be rude but this will only work-out if you know the fly-wheel KW.
30% power lose is insane maybe on a 4WD car but on a RWD you are seriously joking.

there is no way any stock 13 year old CA18det will put out anywhere close to the stock 128 KW at the flywheel

Gary57 · Post by **Gary57** » Fri Nov 24, 2006 11:00 am

Thats what I thought, 30% is MASSIVE. But this guys car was neat hey only had 162000Km on the clock with full service history from agents. He showed me the sheet and it was 90Kw on the wheels. I could only assume that the power was as good as STD so thats where I got the 30% loss asumption from.

What do most RWD car loose through the drive?? What does a M3 have on the wheels??

WooHaa · Post by **WooHaa** » Fri Nov 24, 2006 11:59 am

3 Litre E36 M3 will have about 155KW on da wheels.
A buddy of mine as the 3.2 litre four door with a RG Stage 1. He gets 168KW on the wheels.

Pretty impressive, but if you push about 130KW on the 200SX, you could eat an M...slowly.

The wieght of the car & frontale resistamce is alot less.

Gary57 · Post by **Gary57** » Fri Nov 24, 2006 12:01 pm

What does the E36 have on the fly?? I think its 210Kw, thats about a 30% loss.

Daniel · Post by **Daniel** » Fri Nov 24, 2006 10:49 pm

I remeber reading somewhere about a guy that wanted to find out the answer to that. and i think he found it to be a 16-20% loss. But otherwise i wouldnt know, always heard that rwd cars loose up to 30% and 4wd is like 45%. but i dunno.

The Calibrator · Post by **The Calibrator** » Sat Nov 25, 2006 6:06 pm

deleted

The Calibrator · Post by **The Calibrator** » Sat Nov 25, 2006 6:06 pm

deleted. dont ask

The Calibrator · Post by **The Calibrator** » Sat Nov 25, 2006 6:06 pm

deleted pls dont ask

The Calibrator · Post by **The Calibrator** » Sat Nov 25, 2006 6:07 pm

Deleted, Dammit I told you not to ask

The Calibrator · Post by **The Calibrator** » Sat Nov 25, 2006 6:08 pm

Litre E36 M3 will have about 155KW on da wheels.

On who's dyno? When was the last time it was calibrated and what was the atmospheric correction factor on the day of the test?

I ask these questions to emphasise the point that no two dyno's read alike. Take your wheels figure before your mods compare it yto what you have after your mods and leave it at that.

Spinx in a perfect world every gearbox would have the same losses however in the real world the losses will depend on the make, size and pressure of the tyre. Mileage on the drivetrain, condition of the cv and u joints as well as condition of the gearbox and diff. Even what oil is used and the temperature of the drivetrain will have an effect.

The bottom line is you CANNOT work out drivetrain losses with any degree of accuracy all you end up with is a thumbsuck.

Which brings me back to the point I am beating on. Use 1 dyno preferably one that has barometric compensation and use the values for what they are and stop trying to invent power figures.