We took the cats out of our car with no ill effects. For a while we ran on a standard map, and it graually improved the performance as the ecu learned and evened out the mixture, Basically, from what I can gather, the ecu measures the post-cat lambda, compares it to known parameters and adjusts the mixture automatically. I'm sure its a lot more complex than that, but thats how my dyno chap explained it!
Where are you based Robert? If you're within reasonable distance of the South West, take the car to Circuit Motors at Castle Combe and get Paul to remap it. He has done all the engine setup work on every race car we've ever run, and also happens to know a lot about BMWs in general.
Failing that, we have just bought an S50B32 to transplant into ours, so have a 2.8 with a remapped ECU going spare if you want a good starting point!
Sorry, just saw the part about the ABS.
We removed the entire module and plumbed in new brake lines. The ABS *can* be mapped out of the ECU, but its not easy on the standard setup. The car ran fine on the track without the ABS, as all the wheel speed sensors returned values the ECU was happy with, but as soon as we put it on a dyno, it would only rev to 5250 and sit in limp mode. Eventually, with no other option, we connected a wire into the cam sensor in the ecu, and connected it up to the input for the front wheel speed sensors. That way, it always got a reading within parameters, and therefore didnt limit the car when the back wheels turned and the fronts were stationary. It had absolutely no ill effects on circuit.
We're looking into stand-alone ECU options at the moment, as the BMW ones have limitations. If you are building a serious race machine, I would consider this for the long term, but if you get someone who knows what they're doing (cant recommend Paul at Circuit Motors highly enough) then you will get by on whats already in the car.
