Turbocharging the 4G64

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Turbocharging the 4G64
Page 4

First Startup & Tuning

Once everything is installed, refill all your fluids, and give it a last look. If you installed 450cc injectors in place of the stock 275cc ones, you'll need to lean out your SAFC considerably (if you still have the stock ECU). Start with the low throttle settings at someplace around -35% all the way across the RPM range. Also, since boost can come on at very low throttle position, you'll want to set your low throttle position at somewhere around 20%, and the high throttle position at somewhere around 70%. At this point, you can leave the high-throttle correction settings at -25% for later tuning.

Plug in your OBDII datalogger, and start the engine. Hopefully, the car will start up right off the bat. With everything you changed, however, you may have to do some diagnosis. Hopefully, not too much. With the car idling, check for leaks. You'll want to dial in your low-throttle correction settings on the AFC. Watch your OBDII datalogger. Keep the STFT (short term fuel trim) at around +5%, while making sure the o2 sensor readings are cycling up and down, and the system is in closed loop operation. For me, this was at around -37% across the RPM range.

Take the car out for a short ride. Come back and check for leaks AGAIN. Make sure everything is running properly. Now you're ready to make some higher speed runs.

CAUTION: If you kept the stock Spyder ECU, It is very important that you keep a POSITIVE STFT and LTFT (Short Term Fuel Trim and Long Term Fuel Trim). The 4G64 Spyder ECU is somewhat unique in this matter. If you have a NEGATIVE fuel trim (even STFT of -5%, with LTFT at ZERO), the ECU will lean out your Air/Fuel mixture badly at WOT (wide open throttle). I'm sure the Mitsubishi engineers did this for emissions reasons, but it caused all kinds of problems when I first started tuning my car. No matter what I did to the SAFC (even added +50% air), I could not get my engine to run the proper rich A/F ratio. Thus, I leaned out the car furthur, so that in closed loop operation it was adding fuel to compensate (i.e. POSITIVE STFT AND LTFT), and all my tuning problems were fixed. This is why you MUST have an OBDII datalogger. It's the only way to see the STFT and LTFT readings.

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