Originally Posted by
matt5112
OP: My suggestion for your car is switch back to the factory injectors, TB, MAF, and tune. See how that works with the 3.4. If it doesn't, get a larger pulley.
Ramblings:
Tuning injectors is apparently voodo magic in the 3800 world.
Some injector companies will give you someone else's data to shut you up.
Some injector companies test their product and give you that data.
Some tuners care, some don't.
Some tuners suggest adjusting the IFR and leaving the MAF as is.
Some suggest finding out your fuel pressure, making sure your fuel pressure doesn't bleed off, then putting in a constant value for IFR, as it should be if your FPR is working correctly and the fuel pump can keep up. This is because the FPR is boost/vacuum referenced 1:1, meaning the delta pressure across the injector should never change. Unlike the LSx stuff where the FPR is fixed. In other words, do not use LSx injector values as is, you need to find the delta 3.5 BAR value and use that across the board. That is only if your fuel pressure actually changes as it should. Once you figure all of that out, tune your MAF to get your trims back in line. I presume you have an intake or elbow right in front of the sensor. They'll all change the calibration of the MAF. Yes, you can tune around it by changing the IFRs, or you can change the MAF.
The issue lies in only having one unknown constant. If you change your intake/MAF and injectors, then you have nothing to compare against. Making all changes just guesses. If your tune changes from season to season and your fuel isn't changing, then something is off. E85 is an entirely different battle. The fuel changes all the time.
There is no known manufacturer data for offsets for your injectors if you have the Lucas 42s. Any data anyone promises you, was found experimentally. As a result, it will have error associated with it. If you choose to use it, then expect to have to dial it in further. Make sure you consider both the voltage offset and the injection time offset tables.
As for the O2 placement, I ran my upstream narrow in the crossover, and the WB in front of the cat. I never had much of a problem with it. Arguably, running a WB that you do not calibrate regularly will cause your values to drift as the sensor wears and buildup on the tip occurs. If you can't trust your WB explicitly, then what was the point?
To argue you need to monitor the rear bank as well as front actually introduces more error. If the rear bank is running lean causing your WB to read 12, you richen it up until the WB reads 11. Now the front bank is running 10 and the rear at 12 which might magically average out to 11. So yes, monitoring everything is ideal. However, making blind changes to your AFR without first looking to see if you don't have a mechanical issue first is dangerous.
I ran everything from 10's to 12.0 for an AFR. I found the car to be fastest when running 15-16* of timing, 11.0 AFR, and the smallest pulley that wouldn't cause knock. I was also top swapped, so I have no experience tuning an L67 bottom end. They may like more timing due to the lower compression. But I have a sneaking suspicion, as long as you're still running a dinner plate on the M90, smaller pulley is where it's at.
As a side note, I did not find that rockers helped with the amount of timing I was able to run in the slightest. They did add some top end. Nowhere near worth the cost though. Consider saving for an intercooler instead. Much better investment.
