Quote:
Originally Posted by AleroB888
The GM 36 lb injectors had been in the car for about 2 months now with fair to good drivability, so I installed the 35 lb RC injectors:
................I must mention here that there has been a problem with misfires on cylinder #1 since the last time I raced back in November, pretty severe when the engine is cold, and confined to low rpm. So far, it disappears at WOT. But there is definitely a mechanical problem with cylinder 1.
Base fuel pressure used is about 44, with a 2001 year model PCM program file. I had the IFR set to 33 for the GMs, and installed the RCs without resetting it. Between that and uneven flow at start up, the first run at idle was pretty shaky, fuel trims went way too far negative. After resetting the IFR twice, I wound up leaving it at 35 lb/hr, the manufacturer's rating. With ambient temps in the low 80s today, Long Term Fuel Trims (LTFT) scanned between (+5) and (-5), close to zero average.
So this means that the RC 35's have a higher flow than the GM 36's for the same psi. The Injector Duty Cycle is 8-10 percent less than the GMs at WOT.
There appears to be more random misfires with the RC 35 compared to GM 36 lb, until the engine warms up. The 28 lb Envoy/ 'Blazer injectors did much better in that respect. After only one day of use, my impression is these RC injectors will be usable as far as drivablity, but time will tell. I would really like to have them in for the next trip to the track, as they are closely flow matched, and it would be interesting to see how the single-hole design does under boost.  |
After a few days of testing, I found the drivability of the RC Engineering injectors not acceptable, so the GM 36s were reinstalled. Nothing other than Injector Flow Rate (IFR) was recalibrated for these tests, and it's still possible that the RCs can be made to work. But since the GMs are less problematic, I'll keep them in for now.
I settled on an IFR of 31 and did some scans yesterday, with (much lower than normal) ambient temperature in the 60s. Just a few days before, the temps hit 100 degrees. Setup was in street trim, 1/4 tank of gas. On the first scan, the Injector Duty Cycle (IDC) hit a maximum of 94%, with decent Long Term Fuel Trims, (+2,-7 %) and no Knock Retard (KR). That was much better than I'd seen in the last few months, and don't expect it to be typical, but seems to be moving in the right direction.
IAT (intake manifold) at start of run = 75 degrees, end of run = 93 degrees. Boost peaked at 11 psi