RwKw vs FwKw.

"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

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??

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.

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

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.

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deleted. dont ask

deleted pls dont ask

Deleted, Dammit I told you not to ask

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.

After reading all of this, the G-force meter must make a lot of assumptions to give you all that data from an accelerometer.... 🙄

But I would still like 1 for christmas.... even if it can tell me a guestemate of my cars real performance.

I find with powerfull engine it sometimes takes a bit longer before you pick up that something is wrong with the power delivery. With a 1300cc you know right away if something is wrong. Guess the G-force meter will help to indicate this sooner... 😕

The G Force meter has it easy it measures accell forces over time I cant remember exactly how it works out distance but its all maths. The Power figures it gives are derived from the forumulas you can find and it works out power from speed over distance. These have been refined by emperical testing and are pretty accurate.

I have drag software that if you punch in lots of data on a car will spit out a number within .2s and 2 or 3 mph.
I have tested this on 2 cars I have personally run at a dragstrip and it is remarkably accurate.

However no amount of maths will work out your drivetrain losses accurately.

Thanks for the input. Seems like I will have to get a G-force meter for christmas, from dad to dad. 😉

Interesting post...

I guess what it boils down to if you do find out the true loss through the drive train is how to lesson it? :?:

Well on our SX's its not too expensive to gain some slight power to the wheels, our cars have a 2 piece prop shaft with a center bearing... top drifters drop this for a one piece prop shaft, one can even buy them off the shelf... This will give you a slight gain.

Then the weight of it all also plays a roll, you can get aluminum prop shafts that are light but they twist more, and you get steel ones that weighs more but twists less... Google it and do some research

The other good news is, since SA is Nissan 1 Tonner bakkie heaven, there is plentura of places to source a prop shaft and have a custom one piece made, cost is ±R2500-R3500 depending on where you go...