This is the IAT compensation table I used with N.A. and now with F.I.
Ambient temps in NZ are typically between 10 and 20degC, maybe up to
25degC on a good day
So the amount of compensation applied on an N.A.
engine is relatively minor and positive.
With the F.I. engine the IAT is measured after the S/C and under light cruise
running the temp measured at the inlet manifold was 57degC. It is to be
expected that the S/C discharge temp will increase as the manifold pressure
increases. Using the above table this will result in more negative trim being
applied at a time when the ECU will be commanding a richer mixture.
The target AFR table requests more fuel according to boost, and as temp
varies with boost, it could be said that the AFR table calls for more fuel with
increasing temperatures. At the same time, the IAT compensation table is
reducing fuel with increasing temp. Which leads to these two possibilities...
1. Set the IAT compensation to zero and adjust fuel with the target AFR.
2. Allow the IAT table to apply corrections and adjust the target AFR richer
to compensate.
3. Leave the target AFR alone and let the IAT compensation trim the mixture
leaner as the manifold temp rises.
Seems that we are balancing two variables here, and I am wondering if we
can safely reduce this to one variable
EDIT: Thinking about this while I was out walking this evening; obviously the
IAT compensation will be useful when misting to lower the charge temp. So
option 3 looks good. And with this option I am going to assume that the AFR
target numbers are nominally based on (say) 20degC ambient temp, so that
fuel can legitimately be trimmed as the charge temp rises. Right/wrong ???
Cheers... jondee86