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Millisecond fuel map and MAP corrections for Alpha N

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Getting ready to help a friend tune his 2ZZ Lotus after an engine swap from a 1ZZ already equipped with a Syvecs ECU.

It’s my first time tuning a Syvecs ECU and also the first time tuning a system that uses a millisecond fuel map. The original tune in the ECU uses TPS for engine load (which is the default for Syvecs) and I thought it would be a good chance to experiment with Alpha N and have not converted the map to speed density.

After watching various webinars on Alpha N (webinar 89 and 163), I noted all the examples used ECUs with VE or “VE like” (Link Traditional) fueling which is an actual fuel model and will account for variations in MAP, meaning most work have been done for you other than some scaling at high boost like in the GTR R32 example.

With a pure old school millisecond fuel system however, it doesn’t account for any of that. The Syvecs ECU does not even have a MAP input setup. (Actually the previous tuner did install a separate MAP sensor and wired it up to the Syvecs ECU but for some reason, he did not enable the I/O calibration so it basically does nothing.)

For my existing case with the 2ZZ, it should be "ok" without any MAP corrections it should mostly be consistent under the same RPM/TPS (although I still prefer some MAP correction if possible) but having worked on a RB26 previously also make me wonder how to tune turbocharged engines with a millisecond based Alpha N.

I do see a Simple Manifold Pressure Multiplier table and a Load Multiplier table in the Syvecs calibrations which should allow adjustments. Looks like the “simplest” way to account for MAP in turbo applications would be to make a linear 1:1 table for the Manifold Pressure Multiplier table and retune the main fuelling with the multiplier applied and afterwards, crank up the boost and fine tune the multiplier for the upper MAP values in the Manifold Pressure Multiplier table. Would this approach work? Also is there a simpler way for NA engines if I wanted to account for the slight variations in MAP?

I have search everywhere and could not find much additional information for MAP corrections for Alpha N other than you should apply corrections even for an NA engine but none of those posts explained how.

We always just set the map compensation for the linear "double the air, double the fuel" or "half the air, half the fuel", even for Normally Aspirated engines. Then tune your Alpha-N fuel map. Now when the load (Manifold Pressure) changes at a fixed throttle position (like going up a slight incline). This will cause the fuel map to look a little flatter.

Good Luck with your tuning.

Thank you David. Yes that was the approach I had in mind. It's good to have confirmation and know that I am on the right track since I can't find any information anywhere.

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