GSX RC 750cc Fuel Injector upgrade





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Published on Apr 21, 2011

I bought a set of RC PL4-750 injectors. I needed 'em. I had RC 550cc's in this thing and managed to crank out 357awhp pretty consistently. But I've restarted my tuning from scratch in preparation for something interesting coming soon.

I know the tune on the car right now is balled. I started over. No point in re-tuning for the same hardware. If you want to read more about the theory behind these preliminary stages, I've included it below. I'll make a video about it later.

Right now the status is... my MAF is calibrated... I have yet to check for boost leaks... and as for how the injectors turned out?.... You'll have to watch what's next.

Tuning poop:
All of my tuning adjustments have been made to the airflow tables by calibrating the BoostEstimate value in DSMlink against actual logged boost from an AEM 3.5bar MAP sensor. A stock MAF sensor has a temperature sensor in it. A GM MAF sensor does not. Using a GM MAF clamps the intake temperature at 80° no matter what they really are, this makes air mass calculations a little more difficult. Without the intake air temperature sensor, the GM part is never calibrated correctly for use on a DSM. GM cars have a separate IAT sensor so they don't have this kind of issue. Their ECU will correct for the sensor's behavior based on air temperature. My configure relies alternatively on an air pressure value.

By calibrating airflow tables (maf correction) to bring boostEst (an ECU estimated value) and actual logged boost pressures dead-on... The air mass is being accurately metered, and as a result, it brings all the STFT and LTFT fuel trims to within 1% or less. That's the short explanation. It was tuned after achieving zero boost leaks and a steady idle.

I will be doing this again with the 750cc injectors after a healthy round of boost leak testing, but some other things need to change first.


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