This beautiful E28 M5 came to us recently for a little touch-up tuning.
The S38 engine in this beast was built with a stroker crank and Mahle pistons to 3.8L and 12:1 compression. The head was ported and fitted with custom cams.
The MAF kit fits neatly and looks like it belongs there. Note that the inlet to the stock air box is opened up and fed through a 4 inch round tube.
We started by disconnecting the battery for 10 minutes to clear adaptation in the ECU. We disconnected the stock O2 sensor to keep the ECU in open loop.
Tuning began with setting the idle mixture and moved on to a light throttle cruise condition. Air/fuel ratio was set to 14.7:1 up until about ½ throttle. We were then ready to start on wide open throttle pulls. The tune came in nicely and netted 292 hp and 280 ft-lbs. Pretty sweet.