I'm a newbie at this, so I've probably made some incorrect assumptions here. Please set me straight!
I'm working on tuning my new engine. It's an LS3 with ported heads and a custom cam. I've also added headers and a larger intake tract. The LS3 has a 24x reluctor and all the appropriate LS1 sensors, and I'm running it with the stock P01/0411 PCM from my '02 LS1 F-body.
I am just using my narrowband O2 sensors so far; still need to wire in the wideband (planning on wiring it into the EGR circuit so I can datalog it directly from the PCM). I don't expect to be able to dial in a perfect tune like this, but I'm thinking I can get close-ish.
Initially, when I first had all the hardware hooked up, I started the engine on the completely-stock LS1 tune. It sounded like a normal cam+headers setup and idled fine; I only wanted to confirm fuel and oil pressure, and then shut it down. I didn't datalog this at all, but I assume it was running very rich since the it was driving 42# injectors with 24# injector data. Here's a quick video.
I then took my factory LS1 tune, updated the displacement, supplied MAF and injector data, and applied the RTT OS, then flashed that to the PCM, leaving the LS1's factory VE/PE/idle/etc tables as a starting point.
The engine won't even idle; I have to hold the throttle open a bit when starting, and then continue to hold it there for it to run continuously. Even after doing that for several minutes so that it's warmed up and I can start to see fuel trim values in VCM Scanner, it dies immediately when I let off the pedal. I assume this is an IAC issue due to the upgraded throttle body, but haven't looked into that yet because I was advised to tune VE before idle. This situation has me thinking I should probably do idle tuning first. Or, maybe: does the PCM need IAC calibration data like it does for the MAF? Another possibility: I went with a relatively inexpensive Speed Engineering 92mm throttle body before learning that most tuners won't even bother with those and insist that people use one of the more expensive TBs. Could this refusal to idle be a manifestation of my cheap TB? (I'm prepared to replace it; just hadn't heard about the cheap ones causing this specific problem.)
But, I digress; that's not what I came here to ask:
I had assumed that my stock VE numbers would be close-ish to right, and that for the most part I would be increasing some cells, primarily in the mid-RPM range, to account for the fact that the modified LS3 can flow so much more air.
However, on first start, I'm seeing O2 sensor data indicating a very rich condition. Steady ~0.9v from all four narrowband O2 sensors, with no fluctuation shown on the graph, plus a strong unburned fuel smell. If I understand VE tuning correctly, then a rich condition means that the VE number for the relevant cell(s) is too high. Do I have this right?
Running with that understanding, I focused on the 4-6 cells where I could hold the RPM steady just above idle. 1200-1600rpm, 40-50kPa. Using the RTT VE table, I slowly reduced the numbers from mid 60s all the way down to mid 30s, at which point I started seeing the expected fluctuating signal from the narrowbands -- cycling quickly and steadily between 0.2v and 0.8v.
I'll obviously confirm all of this once I have the wideband hooked up, but it's going to be a while before I have time for that, and I'm hoping to refine my understanding of the situation in the meantime.
So, to get out of that rich condition, I took out what feels like a TON of fuel. It feels weird to me that the volumetric efficiency of my new engine would be lower than my old one -- especially by so much! Is this a valid feeling?
It's possible I have the wrong MAF or injector calibration data. I'm 98% sure I got the injector data right; less sure about the MAF. Is there a definitive way to test this stuff for correctness?
I used OEM LS3 injectors, and copied the data from a 2014 Camaro SS tune (had to translate from gen4->gen3). The MAF is the 100mm from Hawks, which purportedly uses the "OEM GM LS3/LS7 MAF SENSOR," so I got the MAF calibrations from the same tune as the injectors.
I imagine it's also possible that the throttle body is a factor here, but I can't think of how.
I'm sorry, this is long. I'll stop rambling now. Thanks for reading! Any/all advice and feedback is much appreciated!