ECU Turbo Control

[Orin Eman]

>      I am trying to work out how the boost map works in a Subaru EJ20 
>      engine. I have the addresses of the boost maps (There is two for some 
>      reason). I have created some 3-D surface graphs of these maps, which 
>      yield nice smooth surfaces which indicate that I am on the right 
>      track, but I can't quite work out how they work. My only method of 
>      testing is to burn eproms and try new boost maps, but this is slow. I 
>      have altered the boost by altering these maps, but have not been able 
>      to successlfully get the boost I want yet. I suspect that the x and y 
>      axis of the maps might be combinations of engine load, revs, throttle 
>      postions, Map sensor output etc, but testing to work it out is slow. 
>      Does anyone have an idea of what these axis might be? Has anyone 

Engine load, MAP sensor output, current boost are all essentially the
same thing and probably aren't an input.  One axis is almost
undoubtably RPM.  I'd guess the other is intake air temperature,
though throttle position is a possibility.

>      modified boost maps in ECU maps in different cars, and has an idea of 
>      parameters might commonly be used for the boost map axis'? It is also 
>      possible that both maps alter the boost, or one controls overshoot, or 
>      anything!!

Yes, I have modified the Audi 5000 boost maps.  Boost is controlled by
a spring and the computer.  The computer only increases boost if
the throttle is more than 2/3 open and engine temperature is OK and
the engine isn't at the limits of the knock control.  The map is RPM
based only and is desired boost for a given RPM.

Are you sure those are boost maps and not ignition timing?  The Audi
computer has two ingition timing maps, one for premium fuel and one
for regular.  It switches between them depending on engine knock.
The axes for these maps are RPM and MAP.

Orin.