uh oh.... does it look like plug 2 is getting too hot? (maybe an issue with injector 2?)

plug 1 is towards front of the car on bank 1.

Plugs are DENSO 4511 with stock 1mm gap. bought new and have been run for 500km tops since the swap.


UPDATE: I noticed my VE table was still as the corvette 5.7 I copied over, so thats probably why my MAF was maxing out (my cam is very similar to the Z06, so copying it over was a "cheat"), so I increased 5.26% (equivalent to 5.7 to 6.0) everywhere and used the base MAF values from the corvette +5.26% as well. This seems to have improved AFR alot as it hovers around 14.7 right away while before I had to adjust 10%+ to get it even close. However, the idle is quite choppy now, which I will have to fix as I want it as smooth as possible.

 

Hopefully someone who knows what they are talking about when reading plugs will chime in here. That 2nd plug definitely looks different, but beyond that, I could not say much with any confidence. It is possible that an exhaust leak before the o2 sensor is causing a false lean reading, but I don't know what to make of that plug looking so different.

 

I built a custom LQ9 which sounds somewhat similar to a few of your changes...

It maybe you're tacking too much here. You probably already know this... but need to mention if you don't... There's two aspects, MAP (aka Speed Density) and MAF the PCM uses to calculate fuel mass. MAF is easiest to tackle... but not sure with your cam if you need to be running a speed density only tune? Also I assume you know how to setup a calibration for the controller to calculate fuel mass from MAF only or MAP only as they need to be logged separately. The OEM calibration uses dynamic airflow which is a blend of the two.

Does your cam have a lot of lope? If it has too much reversion (air that travels wrong way / back out intake) the MAF cannot discern that and will mess fueling up. I don't have such a cam so I only know in theory. I digress...

You need to focus on idle and startup first. Is the setup a throttle by wire or cable? You have need to calibrate your base idle airflow as well as the throttle body blade angle when closed (it never fully closes to allow some air for idle then the IAC makes very fine adjustments). Once you have it starting well and idling well you can move onto cruise / stoich calibration.

Closed loop, using the wideband ONLY to make sure you're in the ball park. Note, wideband will likely report 3% lean once your long term trims have settled out. It will take an hour or so of driving for the idle and cruise trims to settle out in light city and highway driving (NO WOT and light throttle only).

This can get tricky as many people turn off the long term trims if the cam is too aggressive. In which case you have to tune with your wideband... or possibly an average of the short term trims.

You'll adjust your MAF and VE tables accordingly... Once you've got idle and cruise working then you can dig into the Wideband for non stoich regions of operation aka PE.

Another question, did you update your injector characterization? It sounds like you're using a 4+ bar regulator as you reported 60PSI? Flex injectors are rated at 3 bar so in the least they flow needs scaled for 4 bar.

I also read your fuel pressure never changes under load? If you see that then there's an issue with your regulator. It should dip... it's referenced to the manifold pressure as intake manifold pressure changes you should see some change in fuel pressure.

Hope some of this helps. Likely you knew most of it already...

PS. I went down the plug rabbit hole when I built my engine and started tuning. They can tell you a LOT... That said I think they look fine. If you need to buy a new one and hold it next to yours. I don't think they look fuel washed, nor carbon built up, the electrode doesn't look burnt out either.

 

UPDATE: I replaced the injector #2 and there was a significant improvement in the o2 reading (doesnt stay stuck on lean anymore), I also replaced the #4 for good measure but didn't make much difference. I guess its time to take these injectors to do a flow test, since I have about 3 sets now and the ones I had originally in the car sat in a box for about a year, it seems that even after cleaning them with decarb and an amazon kit didn't actually help much.

I ran the car after it was warm and also ran disabling cylinder by cylinder trying to see which one would make the most difference, but couldn't pin point anything further. Also ran lowering the idle to 700, 600 and it chops, and I think this cam shouldn't be chopping at all. ( I dont want chop, I want as smooth as possible)

It has a pretty tame cam, Elgin 1838P, specs very similar to the Corvette Z06 for 2004. I have tuned MAF in idle and all. Haven't made any changes to anything other than MAF ( and of course using a table from a Z06 +5.23% to compensate for engine volume). Its a drive by wire setup, it seems to idle fine, not sure how to improve this further other than adjusting the MAF/VE.

Yes, I updated the injector information on the PCM, it has the correct flow. Im using a evilenergy adjustable fuel regulator and I set it for 60psi measured at the fuel rail. Its a non referenced fuel regulator, I dont have the vacuum hooked up leaving it to be constant pressure, should I? Isn't the engine vacuum already being compensated by the VAC x Flow table? (my table is not all the same values, it varies depending on engine vac).


The issue I started was going lean at higher rpms exponentially, to the point it would go out of table at the near end, these changes I made seemed to help reduce this a lot, but I didnt have the chance to drive much, starting to snow around here. Another thing I noticed is a hiss when I rev it 3000krpm+, I thought it could be a vacuum leak but wouldnt that be present at lower rpms as well? Maybe its just induction noise?