Rolling road results

[spanner]

Now i picked up of those 'tuning and styling' magazines in Smiths, only to read it as they were doing a rolling road session and i was interested in just what an effect some of the engine mods actually do to the performance. But what surprised me is at the beginning it states,
"power measured at flywheel".
Now that seems rediculus to me. You can only measure it at the road wheels, and stating flywheel power will only be an estimate on the transmission losses.Why dont they just say its measured at the wheels and leave it at that?

[Bluebottle]

Because it's a smaller number and therefore less impressive

[woodyracing]

actually, the flywheel horse power is what is quoted by the manufacturers too.
and engine mods do make a difference, its not too difficult to double the power on most turbo cars.

[garcon]

As you'd imagine, there's lots of talk about rolling road figures and such on the Scooby bulletin boards. Many of them harp on about the figures their pride and joy now returns.

But the more pragmatic of them, including Pete Croney who runs Scoobysport and is the current SIDC chairman, pointed out that the absolute figures aren't actually all that accurate and the only real use of it is to measure relative outputs, i.e. your car before and after mods, or say a std UK Impreza against a Prodrive car against a 3rd party modded car.

[woodyracing]

the Powerzone rolling road that my car went on actually measures break horse power at the wheels and the guy, with his experience can work out how much power will be at the flywheel.
We compared before and after (at the wheels), and got 90 before and 120 after. Thats with about £400 of goodies

[carrera]

So before you had 108? bhp at the flywheel and after you had 140? bhp. What did you change?

[graham bahr]

if you want to compare different cars on a set of rollers the only true way to get the power figure is to meassure the run down losses to arrive at a flywheel figure, as this will take out differences caused by tyre pressures and compounds different gearing etc, on the rollers my race car has more power at the wheels on slicks than on my wets but the engine is still making the same amount of power.

but if you are only tuning the same car it doesn't matter which you use as long as you keep everything the same we once saw a 10 brake difference on my car by blowing up the tyres!

[woodyracing]

Originally posted by carrera
So before you had 108? bhp at the flywheel and after you had 140? bhp. What did you change?

well at the flywheel, 120 before 150 after.
mods where ss exhaust (from the cat back), Pipercross air induction, Superchips ECU unit (+10bhp), performance HT leads and Splitfire spark plugs.
i saw it myself, 120bhp at the wheels on the meter.