anile8-zn said:
Why is the power dropping off after 7500.
OMG! Is that a real question? Are you genuinely interested in knowing?
Ok I'll give you the benefit of the doubt. Do you have experience with dyno's with M cars? In Johannesburg? What about Cape Town?
Well The S54 does not peak anywhere near 8000rpm on the dyno. Up at altitude it peaks around 6900 stock and sea-level around 7200.
Why you may ask? Because a small dyno fan can not in a million years replicate the air flow one gets on the road. The cooling air flowing through the grille, spoilers, ducts and dams at 170km/h at the top of 3rd flows over all the fins of your radiators, oil coolers, etc and keeps all the fluids cool and the ECu happy. A 40km/h fan directed at a small part of your grille (and totally away from the intake scoop in the brake duct) will never keep the fluids cool and the car will peak early.
But you knew that right? You have never seen an M car peak early on the dyno right?
Just to illustrate how unhappy the cars are on a dyno, here's another E46 that we did this week. I will post the dyno run also from KAR (sorry for the cellphone pic from the owner, I wasn't there) so that you can see the sorry state of the stock run. Look at the bottom run, it peaked at 6900. And the car was stock. The ECu definitely wasn't happy with the airflow on the rollers.