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[Frank Parker]

>      Hello,
>      I am building a simple MAP controlled system for a 2litre turbo.  It 
>      is micro-controlled and basically fires each injector with the spark 
>      signal, and the duration is based linearly on the MAP output.  There 
>      is also a 3d correction table which gives a correction factor for RPM 
>      and MAP (to adjust mixture, and to compensate for changes in 
>      volumentric efficiency with rpm & boost).  This works quite well, but 
>      I dont know what mixtures should be used theoretically at boost.  I 
>      have assumed a 14:1 mixture at light loads (about 1/2 bar absolute) 
>      and 12:1 at 1 bar (absolute).  Presumably I should keep enrichening 
>      the mixture as boost increases, but what to!!!  (I am ignoring 
>      volumetric efficiency changes with rpm at the moment)  My aim is 1 bar 
>      boost pressure, so does anyone know approx. what mixtures you should 
>      use at this level with an intercooled motor.  It must level off at 
>      some point (maybe 8 or 9:1). I have heard that turbo motors like very 
>      rich mixtures under boost.
>      Any help appreciated.
>      Mark.
> 
I think it depends on whether you have good intercooler now. If so and inlet
temp is within 20 deg or so of air temp, then you do not have to use fuel
as an intercooler as some mfr have done. They also do for warrenty reasons.
I do believe 12 to 12.5 a/f is best for power and can run down to about 
10 to 1 for cooling. Below that, I believe more fuel can actually make
detonation worse.
Also a good knock control system like an J&S helps you be able to run
closer to best power a/f

frank parker