Dyno hack for M3 CSL - anyone know?

[phatgixer]

How do you get a CSL to Rev over 6,450 on a dyno.

My car managed to show a (STP corrected) figure of 361 bhp at the flywheel at AMD at 6,450, but it revs to 8k on the road...

I want to know if a re-map will get the best from my new exhaust, but no point unless I known the datum....

[john_p]

If you searched the forums on that other place you'd know! I even drew a diagram in MS Paint.

The limiter cuts in because the front wheels are stationary but the rear wheels are moving.

You need to bodge the wiring to the front ABS sensors so they actually feed off the sensors for the rear wheels and the car thinks all four wheels are doing the same thing. I'd guess the wiring for this is on the DSC unit near the brake cylinder.

Or link the front wheels to the rear ones with a long bar, similar to a train

[phatgixer]

Do AMD know this?

Sorry for not doing my homework John! Dog ate it ad nauseum.

[john_p]

I thought they did .. but it's worth asking.

[pentoman]

Or what about disconnecting the rear wheel ABS sensors - so the car thinks it's not moving? Should be easier.

Russ

[john_p]

It still limits the revs if the car is stationary and in neutral, so I assume it would if it was in gear as well.

If not I don't know how it would react to being in 4th gear at 8000rpm but doing 0mph. It would probably assume the clutch was slipping and go into a limp-home mode!

[burwoodman]

Couldn't you simply extrapolate the graph?

[900T-R]

burwoodman said:

Couldn't you simply extrapolate the graph?

The simple answer must be 'no'.

Say my car makes 281 hp @6,000 rpm before the power starts tailing off (totally hypothetic, this ) , but for some reason I cannot rev past 5,500 on the rollers, where it makes say 265. At 5,000 it makes 240. Redline on the road is 7,000. How do I know where it actually makes its peak hp, how steep the power graph will be towards that point and by how much it will tail off after that? It's easy to see the engine's VE will change over the rev range, otherwise all engines would be the same .

Extrapolate the power graph based on the 5,000 - 5,500 interval and I would get 5,000 - 240 hp, 5,500 - 265 hp, 6,000 - 290 hp, 6,500 - 315 hp, 7,000 - 340 hp.
Bingo! I've got a 340 hp engine, mate. Why, well, you see, I could not rev it beyond 5,500 on the rollers where it makes 265, but it revs to 7,000 so I've extrapolated the graph to 7,000. Cool. Pity is, in reality it's 'only' 281 as the torque curve is well on its way down after 5,500, so much so that from 6,000 on the power curve points slightly downwards, too.