Turbo V6 Tuniing continued

["Jeff M" <tystorm@email.msn.com>]

Well, been enjoying tuning the 1990 Turbo Grand Prix with upgraded heads and
larger injectors.  After quite a bit of playing around with the tables, have
the engine running well enough that I don't believe it (yes!).  After the
last fuel tuning, Diacom runs show the INT making such small changes that
the BLM has not moved (it is enabled) for the past few days of driving, and
with 40 to 85 degree weather ranges, values still look as good (still need
to adjust the commanded /F ratio for 80 on up some as it looks a little lean
momentarily).  Now from comparing the Turbo Sunbird/Syclone/Typhoon chip
fueling approach, the one for the TGP is quite a bit different and I am not
sure the approach I used to modify it would be the same, or for other GM
ECMs.  The good news is the 29 lb injectors have no problem running lean
enough to fuel a 3.1L motor at idle (smooth idle with INTs anywhere I want
them to go from rich to leaner than needed).  I have added to the areas in
the main VE to accommodate the upgraded heads and the results are a V8 type
acceleration starting at about 4000 rpm that this engine never had even
with higher boost levels.  While doing a WOT run, O2 volts were now steady
at 946 to 986 (was 1016 before on some areas, no lack of fuel now with 13 to
15 psi) instead of falling off into the mid 800s with the stock injectors.
I would also like to add to those who have discussed knock sensors/knock
circuitry being over sensitive that this setup also exhibits false knocking.
The knock retard has a max of only 4 degrees and only with one knock count
when it occurs with a WOT run to about 90 mph.  I can take out timing
slowly to near nil, and/or add fuel till the o2 goes towards bog rich, and
still get knock resulting in 4 degrees of spark retard.  Now though I do not
recommend this, I know of another TGP owner who took it upon himself to
unplug his knock sensor wire and by doing this, was able to post better
quarter mile times (duplicate conditions, back to back runs) and to date has
not had a known engine problem.  For me I may just lower the area in the
chip for knock retard while in PE, but just enough to reduce the 4 degrees
to more like .8 to 1 to make sure not to get close to defeating at all the
protective benefits of this system.  I will also be checking the spark plugs
for any signs that detonation has occurred but if I am only changing things
a small amount, I don't expect there to be any problems.  That is it for
now, the results are finally rewarding me and my friend is quite pleased,
now time for that turbo upgrade ;-).

Jeff M





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