The saga of fitting a MOTEC M600 ECU to my Audi UrS4

A 1994 UrS4, right-hand drive, living happily in Australia. The car has 59,000 miles on the odome- ter (94,000 km), and has the following modifications: RS2 Exhaust manifold RS2 Turbo Lucas Delphi injectors Waste gate screw initially turned down 3.5 turns (Dec. ’05), back to original position (Feb. ’06) Samco hoses 3 inch locally made exhaust system with cat, 3 resonators and a lightly baffled rear muffler.

The Symptoms
Not enough power. Unsatisfactory drivability. For more than a year I have been trying to find appropriate chips, but without success. The chips I tried never seemed to suit the car, and, on dyno testing, always had excessively rich AFR ratios and excessively low power. I concluded that it is not possible to chip tune my car without someone locally doing some hands-on programming, and there is no-one I know in Australia with that expertise. Given that there are, I believe, 18 UrS4s in the country, this is perhaps not surprising.

The Treatment
Fit a MOTEC M600 ECU in place of the Motronic ECU. MOTEC’s are made here in Australia, and there is local expertise in setting them up.

The Doctor
Neil Trama, of Queanbeyan, NSW has a long history of MOTEC installations, including a number of rally and race cars, as well as his own concourse winning Audi 90 quattro. He is a qualified engineer, and loves this sort of challenge

The path to robust health
I travelled to Canada and left the car with Neil to work on. Neil’s aim was to make the conversion readily backwards compatible, so step one was to buy a cheap BMW 318i ECU which had the same plug as the S4 Motronic ECU. This was gutted to provide a chassis and plug for the MOTEC.

The aluminium cover was deliberately left off the chassis to aid cooling of the MOTEC ECU. The 3 bar sensor is the black blob atop the ECU. It can be replaced by a 5 bar sensor by the brave (or foolish) who seek such levels of boost. Next, the oxygen sensor was replaced by a wide-band OXS that works with the MOTEC.

(The green wire goes to an exhaust gas temperature probe, used in earlier testing, and since removed). Finally, the MAF was removed, and replaced with a tube of the same external shape that Neil turned from a solid block of industrial strength Nylon.

source