GTR Injector Tuning

John from Akuma Motorsports put up some good information that will help out some people tuning R35 GT-R’s.  Larger injectors change two important parameters, theoretical pulse width and base fuel schedule, if the car is not tuned for the larger injectors correctly, the car will not respond well in AUTO mode, as the transmission uses these values as an input for shifting.

Fuel injector inputs GT-R

To scale injectors correctly, and subsequently, keep the trans running correctly, he must do the following.
1. Set the Target AFR table to the appropriate values...11.1..11.2...10.9 what ever you want the AFR to target.
2. The tuner must first adjust the FUEL MULTIPLIER(lower the number for a leaner response)...800cc approx -15 -20%
3. The tuner must then watch the AF Trims to see where the AFR Learning values are. We want a lean...115%. At idle and about 95-105% under cruise and under load the fuel curve is close to the BASE FUEL TABLE values. No need to go crazy with boost, just see that it does not drop below the desired target AFR.
4. If you upgraded to a larger MAF, I have seen about a 5%increase through the entire MAF curve is a good start. Keep in mind there is a MAX value at 4.91 Volts that you can not exceed is a physical limit of the ECU. Keep in mind the stock MAF curves vary for each bank. You may find keeping them a little closer to one another keeps the variation in each bank(AFR) will have to find out what the intakes/intercooler set up work best with.
5. Start the car and open the FUEL VE Table. In the beginning you will want to use the Trace feature to get a sense of where you are. You will use this table to smooth out the AFR Learning and the Fuel Curve. Cruise is in the 30 -60's, idle 16- 24s', and WOT is in the upper few columns172+. try not to do a Cell by Cell smoothing, rather keep the table rather smooth, 'V' and 'H' are your friends...LOL
6. Do a few VERY light load/boost need to go to redline here. See what your AFR and Load-Theor Pulsewidth are doing. If your injectors are bigger than 750cc, your Theo PW will be off.
7. If the AF Learning and the THEO PW are too far off, look out trans and P0700! smile.gif This is where the last step comes in. manipulate the BASE FUEL SCHEDULE value to gain proper resolution in the tables. Reducing the value too far will put you in a worse situation(you would only raise it for smaller injectors than stock). Start with a 10% reduction for 750cc, 15% for 850cc or bigger. See what works best for the car.
Rinse and repeat. ;)
This is how to Properly scale injectors and load. Do not manipulate the Target AFR table to make large changes in the AFR curve. This will take time, but it will work. If you are having trouble, let me know and I will do what I can to help out.

Transmission shifting


No comments:

Item Reviewed: GTR Injector Tuning Rating: 5 Reviewed By: Sean Morris