Started up my new crate motor for the first time and am getting fairly bad back-firing (~3 backfires per second).
https://photos.app.goo.gl/zn3X4ZhXeVt2AkG98
Details:
Engine: New Crate motor from Blueprint, LS3 427ci, EFI w/ full wiring harness and GM LS327/480 ECU
Intake: Harrop ITB setup, w/ custom intake manifold that joins both Left & Right banks into a common 4" intake tube so that I can use the MAF. Harrop integrates the OEM Electronic Trottle body into the ITB set-up, so that's what drives the ITBs.
Fuel pressure:confirmed to be ~60psi, as expected
My thoughts:
-Data says the ECU thinks TPS (Throttle position) is 30% open...but that's at idle. I can see the ITB throttles and they are all closed. Maybe it's dumping in extra fuel b/c it thinks the throttle is at 30%? (I blipped the throttle a few times, which shows up in the TPS data,...so I know it works).
-Intake: Maybe I have a leak, and it's running lean?
-ITBs: maybe it's un-even (should be all pre-set & flow confirmed from Harrop)...I measured the temp at each exhaust runner and most were at 120F, but a few ~85F. Not a big difference, but I didn't let it run very long.
-Fuel Injector wiring harness: I had to lengthen all of the wires...fairly confident that I did it correctly and confirmed good crimps. Each exhaust runner is hot, so I assume that IF I get fuel, it won't be intermittent...so this seems like a lower likelihood.
-Spark Plug wires: I had to make custom length spark plug wires and had to be much more firm when installing the boots. Each exhaust runner is hot, so I assume that IF I get spark, it won't be intermittent...so this seems like a lower likelihood.
Any help would be greatly appreciated...I've done some tuning before (not a lot), but this is my first time w/ HP Tuners. Thanks!!
Link to video: https://photos.app.goo.gl/zn3X4ZhXeVt2AkG98