[Steve W]

Those of you with '84 to '89 Motronic equipped Carreras may have wondered what the differences in fuel mapping between some of the different popular chips for our cars are. I pulled it off three different chips I have with a eprom reader/programmer and used a program to disassemble the code and map the fuel values shown here.

The first graph is that off the original Porsche chip from my '84 non-California equipped Carrera. California cars were even more conservatively mapped and so are a 1/2 sec. slower, however I don't own my '84 California Targa anymore so I can't map it. There is also a mapping for full throttle. Full throttle is when the throttle switch of the Motronic is tripped closed, when past 75%-80% open, and a fixed fuel map is engaged. In this situation, the O2 sensor is ignored and a fixed fuel quantity is injected. If your car has been modified via intake or exhaust modifications, and this timing is not increased, you will not notice a significant increase in power, for the amount of power you generate is generally proportional to the fuel you burn.

The second is that of an Autothority chip. Its rev limiter is set at 7040. The third is that of a Weltmeister chip with a 6840 limit. What is interesting about the Weltmeister chip is that it was originally a Dinan Engineering chip, as evidenced by the letters 'Dinan Engineering' I found in parts of its hexadecimal code.

Quick code examination reveals that Autothority is actually coded a bit more aggressively (richer) at the top end while the Weltmeister is coded a bit richer on the low end.