LSJ Injectors 101. Your basic how-to.
First, let me state that I am in no way trying to step on anyones toes here. I am simply trying to educate the LSJ world about injectors. I do not want to see people deal with the frustration I went through.
There seems to be a ton of misinformation floating around about injectors in general, let alone in the LSJ world. There is a couple injector offset tables floating around for our cars, and I have done the math and improved upon them.
I bought some Bosch EV14 630cc injectors to use with my car. The advertised offset at 14v was just over 1ms, according to the Bosch spec sheet. I even received GM offset charts with them in the normal LS1-E40-E67 formats. My IFR tables were setup correctly. I interpolated the data into the LSJ charts and started the car. It was pig rich. I could not remove enough fuel from the MAF and VE tables to make it even close.
I know you are thinking I did not set something up right, but I assure you it was. I even tuned my car when it was stock so I have a solid reference to fall back on. I scaled my tune by 50%, just like the LS guys do for big injectors and for hitting the 1.36 G/cyl wall. Nothing changed. On paper you should be able to swap injectors, and as long as your injector data is correct, you should not have to change any trims. In reality nothing is perfect and at max you should not see more than a 2-3% change in fueling if nothing else was changed but injectors.
What I have discovered is the LSJ computer(P12) has a parameter that HP Tuners has not mapped out that needs to be changed. This parameter is available on about every other PCM/ECM they support. There is a way around it by cutting the offsets in half, and it tunes in well. Only issue here is on coastdown and at idle the engine will RPM hunt due to wide AFR swings, and some pretty crazy temp related AFR swings.
The other way is to pretty much cut 60% off the MAF/VE tables around idle. This causes a basket case of other problems too, like MAF HZ out of test range code.
You can scale the tune just like the V8's, and you still have to pull a ton of fuel at idle, and there are even more problems that come out of this. Also, HP Tuners has not mapped out everything you need to change to properly scale a tune, like Airflow Mode, Max Torque timing, Knock retard tables, Transient fuel multipliers, Complex cylinder charge bias tables, and so on. And you can forget ever trying to run an automatic....all the torque tables are airflow based.
Another way is to half the IFR table then double the stoich value. This method seems to work pretty good so far for me, but I am only a few days into playing with it. Only downside so far is the computer keeps going open loop everytime I come to idle due to the IVT calculated temps......which we cant modify because its not mapped out.
I have also verified the IFR voltage multiplier table DOES NOT WORK above 63.5....no matter what. The computer will only go up to 63.5....and the multiplier does not take it any farther.