RwKw vs FwKw.

Gary57 · Post by **Gary57** » Thu Nov 23, 2006 3:02 pm

Does anyone know how much power the sx looses in the drivetrain. One of my mates put his std sx on the dyno here at the coast and it was 90RwKw, thats nearly a 30% loss

.

As far as I know his motor was in good nic.

widowmaker · Post by **widowmaker** » Thu Nov 23, 2006 3:43 pm

it must have been a red one then

Gary57 · Post by **Gary57** » Thu Nov 23, 2006 3:55 pm

Why a red one?? I think white is the prettiest by far, no offence guys.

widowmaker · Post by **widowmaker** » Thu Nov 23, 2006 4:01 pm

read my statement again

(btw, i have a white one too)

Draco · Post by **Draco** » Thu Nov 23, 2006 4:20 pm

ROOOOI IS MOOOOI

Toby · Post by **Toby** » Thu Nov 23, 2006 4:26 pm

ROOI IS FOKKEN MOOI

ChemCool · Post by **ChemCool** » Thu Nov 23, 2006 4:37 pm

On the second of December we will know if it is red or white

ChemCool · Post by **ChemCool** » Thu Nov 23, 2006 4:44 pm

Gary , I go for the 30% loss. Me sx was dyno tuned up here 122Kw Rw. Tuner worked out 183 Kwrw at coast with his formulae ad calculators.We up here can have a BHP loss of plus minus 30 Horses. I also read from various articles on net that this figure is not a fixed one though. Varies from motor to motor. Fot time being I will use that percentage to be on the conservative side.Will be good to get the exact science on this one.

The Calibrator · Post by **The Calibrator** » Thu Nov 23, 2006 8:01 pm

I wish this would be made sticky. You CANNOT use percentages to work out gearbox loss.

Heres why.
Take your sx it made 90wkw? and you say a 30% loss through the gearbox I get 27kw.
Now add some boost and take the power to 150wkw and work out your 30%. What happened how is it possible that on the same engine and gearbox your losses went up to 45kw?

If you want to know what your gearbox losses are remove your motor fit an electric motor and work out how much power its takes to turn the drivetrain at speed.
Other wise put your motor on an engine dyno and get an accurate figure of what it makes at the flywheel.

If you cant do this then dont bother working it out because at best you have a good thumbsuck and at worst you will be miles out.

ChemCool · Post by **ChemCool** » Thu Nov 23, 2006 9:43 pm

OK, I got the percentage thing now. I follow that. But what do you mean engine dyno? The engine alone on a dyno I would say?
How practical is this for me common outjie? All dyno's I know is with the engine in the car, and my rear wheels on the rollers?I dont know what I miss here? May be if you can explain more.Thank you.

Charl · Post by **Charl** » Thu Nov 23, 2006 10:00 pm

i understand... its just the method of measuring the engine power and not the "wheel power" some of us dont understand. i would say that the loss varies on different cars aswell and that a front wheel drive car has less loss from the engine to the wheels...

The Calibrator · Post by **The Calibrator** » Fri Nov 24, 2006 6:13 am

An engine dyno is what the manufacturers use to measure the ouput of their engines. All the top racing teams use them however it is time consuming and costly to change them for different engines never mind the mission of removing your motor.

We are stuck with its poor cousin the chassis dyno they can give us us accurate information however they give wheels power accurately and an approximation of engine power.
You will never have a accurate measure of engine power while using a chassis dyno.

Sokar · Post by **Sokar** » Fri Nov 24, 2006 6:33 am

Myself personally, I'd be looking for my output on the wheels, I like to know the figure I'm putting down on the black top.

Engine output = Indication of how good your engine is/has been tuned.
Wheel output = Indication of how good your car as a whole is.

I dunno if anyone else feels that way???

Toby · Post by **Toby** » Fri Nov 24, 2006 7:12 am

The only reason I'd be interested in the engine output, is to compare it to what the manufacturer claims, and know that my engine is either running optimally, or not.

But I am more interested in the car as a whole, which is why I am so interested in the G-Tec Pro http://www.mrturbo.co.za/GTech-Pro%20Model%20SS.htm

Gary57 · Post by **Gary57** » Fri Nov 24, 2006 8:25 am

Sorry calibrator your calculation is incorrect

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.

*Nissan 200SX Club - South Africa

RwKw vs FwKw.

RwKw vs FwKw.

ooohhhhh