I have read posts on injection timing until dizzy, and it seems there is a consensus that GM attempts to inject on a closed intake valve to aid in vaporization, though there are some other thoughts out there as well. I am working with a completely stock 6.2L L94 with a Whipple, 72 lb injectors, 8 psi, and have played around with injection timing some but recently it seems that I may be getting fuel dilution in the oil, which made me revisit these settings.
I'm plugging numbers into the wonderful spreadsheet that some generous genius created, and looking at the stock cal, it appears GM was NOT injecting before the intake opens, but just AFTER opening, at low rpm. I would think this is the time you would want to inject early? Beyond that, they start really advancing the timing (lower boundary numbers) in the higher rpm, to the point that injection is fully completed BEFORE the intake even opens? Kind of a pain to put each rpm possible into the spreadsheet, as the variable cam begins retarding around 2400 rpm. But it is definitely an early injection timing at high rpm, even taking into account the stock cam retard. Does this sound right? Seems backwards.
I am boosted so I know that changes things, but have delayed injection time accordingly, trying to get the full injection amount in the cylinders 30+ degrees before IVC. I am also leaving the stock cam in the locked position. Stock cam is 195/201 - 115 @ 0.050". So I don't have any overlap to be concerned about as most others do.
Attached is the stock boundary chart, the one I used most recently, and a couple of snapshots taken from the spreadsheet graph. For the recent injection timing, I added in 100 to the RPM Boundary chart, up to 1000 rpm, thinking that it would help to fully inject on the closed intake. Above that rpm, the RPM Boundary is zero'd so injection is targeted more towards the open intake.
0 512 1,024 1,536 2,048 2,560 3,072 3,584 4,096 4,608 5,120 5,632 6,144 6,656 7,168 7,680 8,192
Stock
Boundary 506 506 506 506 506 506 499 468 418 382 363 347 336 328 328 328 328
Normal RPM zero'd
Latest cal
Boundary 500 500 500 550 550 550 550 560 570 570 570 570 570 570 570 570 570
Normal RPM 100 100 (through 896 rpm)
The ECT chart was left stock, decreasing from 245 cold, ending at 110 when fully warm.
Makeup ECT left stock at 30
Makeup RPM left stock at 0
Just wanting to make sure I am not way off base here? Right now I think I will zero out the Normal RPM again, and leave the Boundary as it is, unless someone tells me I'm not just off base, I'm not even in the right ballpark, lol