30% Drive train losses is a rule of thumb that was out dated 20 years ago. It probably worked then, but not now.

In the last 20 years, the power output per litre of engine capacity has increased. A 4.0L engine 20 years ago might have put out 120kW.

Also, drive trains have become more efficient in the last 20 years aswell, so less losses through the drive train. 20 years ago, that 4.0L engine might have lost, for the sake of example, 40kW through the drive train giving you a 33% loss and 80kW @ the rear wheels.

Now, with a more modern Falcon, you're producing approx 160kW but you might only lose 30kW through the drive train. So you lose 18.75% and get 130kW @ the wheels.

If you want more info, read this link Of particular interest is this paragraph

"The worst scenario case for a rear drive setup is on the order of 12.5% in 4th gear, not the 20 -25% often published. If 25% was being lost in the drive train, the oil would boil in the differential housing in short order and aluminum transmission cases would fatigue and break from the temperatures generated. On a 200 hp engine, something on the order of 37,000 watts would have to be dissipated out of the transmission and differential housings. Obviously, this is not the case."

The main reason why the 30% loss calculation is so commonly used is because men have C**k. And to calculate your engine power by dividing rear wheel power by 0.7, you get a calculated power output that is higher than reality which makes all our C**k feel bigger and more masculine. I hate to say it, but it's the truth.

Also, the power output of 157kW that Ford quote us is wrong. It's different now, but for decades, car companies have been quoting power figures higher than what the typical engine actually puts out. If you get over 150kW out of a brand new, stock standard I6, you're doing good. Tack on 250,000km onto that engine and you'll get nowhere near that 157kW that you think you have. This is another reason why people calculate larger that actual power train losses. If your XR6 puts out 130kW @ the wheels, then based on a 12.5% power loss, you've only got 149kW @ the flywheel. It'd be nice to factor in a 33% loss which gives you 194kW, but the reality is, no factory EF/EL XR6 has EVER put out 194 FWKW!

So boys and girls, (well, not really girls) it's time to look down at your penis' and realise that it's not responsible for 15kW more fly wheel power than you actually have. Instead of talking up your engine for more than it is, put your money where your mouth is so that when you say "I have 200 flywheel kW" you actually mean it.

How the f**k is there even an argument here? Theres no definite way to convert rwkw to fwkw.

Chassis dynos are too inaccurate, and cars vary too much. There are too many variables.

FPV_GTp I can't even understand what your saying, a little bit of spelling and grammar wouldn't go astray.

i know a standard version of my model makes 145 rw kw, that car is rated at 210 kw so that is 70 kw loss
so i beleieve my driveline is 70 kw loss
the driveline i have is
zf 6 speed, heavier than standard flywheel
b/warner 3.45 gears
235/45/17's on alloy wheels.

FYI the ba 220 kw engine auto made 175 rw kw on a brand new DD dyno

How the f**k is there even an argument here? Theres no definite way to convert rwkw to fwkw.

Chassis dynos are too inaccurate, and cars vary too much. There are too many variables.

FPV_GTp I can't even understand what your saying, a little bit of spelling and grammar wouldn't go astray.

I agree with you on the spelling/grammar.

FPV_GTp - There is no reason what so ever to post in big, bold, caps all the time. It's rude and unneccessary and I for one don't even read posts that are formatted like that.

145 divided by 2 = 72.5

145 plus 72.5 = 217.5 kwatts

100 - (145 divided by 217.5 multiplied by 100 ) = 33 % LOSS

am i wrong or am i right


cheers

and remember the guy who started the thread was just asking a simple question a conversion factor

cheers guys

You're right! But you're making the assumption that the published power figure of an engine is accurate.The only way to get a true drive train loss figure is to dyno the engine, then dyno the car and compare.

Add to this the fact that a chassis dyno is innacurate and it throws the whole 33% loss into question. I know my previous car pulled 85kW on one dyno and 92kW on another. That's a big difference. If you work on the 85kW figure, this translates to 126kW @ the fly with 33% loss, but if you use 126kW @ the fly to calculate the losses on the dyno that gave me 92 kW, you get only 27% loss.

I know for a fact that the published figure of the engine was 106kW and the only mod this car had was a K&N air filter which was 'supposed' to give 10 kW more power over the standard paper one. So, taking that as gospel, 116kW, you get drive train losses of 27% and 21% on different dynos.

Now, if V8capri's engine isn't actually putting out 210kW, let's say 200kW, and the dyno reading was under-reading by 10 kW, you get a drive train loss of 22.5%. Vastly different from your 33% and it is entirely reasonable for an engine to put out 5% less power than published and a dyno to read 7% out... see above exapmle.... approx 8% difference between dynos.

now lets boost the car higher say 14psi and the tune is done and now the car produces 220 kwatts at the rear wheels !!!! follow !!!!! why have the lossses increased ????