Posted this on HPtuners too, but thought I'd throw this here too for more traffic.

It's been quite a while since a tune had me stumped, but here we are. I am tuning a customers 2010 SS Camaro LS3 and everything on the MAF air model is absolutely great almost everywhere. I have the idle at 750, no bucking, no issues. Under slow throttle acceleration the AFR stays right about -2% in most places. The VE table I tuned in most light cruise and under some hard acceleration, but I also ran into the SAME problem that seems intermittent. Sometimes it leans out, sometimes it doesn't.

I felt that the VE was "close enough" to go back to the MAF, so I added about 20% to the WOT area before returning to the MAF cal assuming that if anything, any transients coming from VE calcs would end up being richer, and I'm cool with that.

So today, as I drove this thing to work, I had the problem reoccur a few more times, so I took some more time to adjust the VE while at work. I basically added another 30% in the bottom corner. It literally changed NOTHING. Spike still persists, and intermittently.

Mods are:

TSP 235/239 .627/.624 on a 112 LSA
Cold Air Intake
Headers
15% underdrive balancer

The fuel pressure was dipping as I saw in earlier logs, so I flat lined the fuel pressure to 58.5 in the FSCM. It helped with the fuel pressure drops, but the spike is still there.

Now this seems to only occur in 2nd and 3rd from a roll. The other concerning part, is that even though PE conditions are met, sometimes it still commands stoich. I guess I need another set of eyes on this to get this ironed out. It's literally the ONLY issue I have to solve before giving this thing back to the customer. I'm not too cool with allowing a 40% rich spike that occurs "randomly" under hard 2nd and 3rd pulls, while commanding stoich (why not right GM? Where's that cold table for PE anyway?)....

Oh and for the PE numbers, yes it's active at idle as I'm anticipating issues with trims at idle.

My thoughts right now are:

Is it torque management of some kind chopping fuel? It falls on it's face during some of these "episodes" but it's tough to see in the log.

Is it transient? I think the error is more than a transient would normally cause. The VE right now is set so rich I'd expect the opposite. I can't even really tune those areas on the VE table because the spike keeps happening and the changes don't affect it at all.

Yes it's a stock pump. Yes they are stock injectors. But I don't think the mods here are enough to warrant new hardware considering the IDC is only 65% under max loads, and the pressure drop isn't enough to make a 40% lean condition. It may still be some sort of FSCM setting I am unaware of that could help, but I am new to tuning those things and not sure if I want to test my luck there.

Here is the log and tune. Note that the issue occurs at the first RPM peak (as I was getting on the highway lol), but if you take a look at the second one, it's a 4th gear pull through 120 and the AFR is pretty damn good on that one, which rules out the air calibration, at least on the MAF.

I will say gen 4's aren't my specialty, so hopefully one of you fine folks could help me out a bit on this one. I'm really starting to think it may be the pump...

 

Man, I don't know, but it's not consistent. I don't think it is anything int he airflows, because at time 04:55:38.197, you're at 606 g/sec and 1.79 g/cyl and 5088 rpm and 14.8 ms. Then at 04:53:31.123, you're at 5085 rpm, 615 g/sec, 1.81 g/cyl, but only 10 ms on the injectors. Several other times in the log, and it's always right near 10.5 MS. Plus, you don't have that huge rich tip out that typically would be associated with transient. I wish I could see the tune, but your version is newer than mine, and I'm on a work computer, so I cannot open it or install the newer version without going through IT.

I don't know that I would suspect the pump, as the injector pulse width is actually being commanded to 10.5 vs 14 ms under different pulls. Are your injector timing tables still stock? Perhaps some settings in there under the right conditions have "boxed" the pulse width in where it cannot go as wide or as long as it needs to?

Possibly you need to scale the tune to get under the 512 g/sec VE limitation on the ECU? note that VE airflow is only reading 512 when dynamic airflow is reading 600+. Perhaps this discrepancy is causing the ECU to "bounce" back and forth between the dynamic and VE settings? Such as an intermittent maf failure?

Kinda reaching, I know, but I also know your tuning skills, so it's hard for me to think there is something obviously wrong in the tune.

 

You didn't display the throttle position PID in the log.....turn it on and take another look at the different WOT pulls and I think you'll see what's going on

 

Why is the injector gain enabled?

 

Yeah it started out pretty normal, on the first runs under lighter accel it worked great. Got everything going pretty good. I took the car home to work on the dreaded "bucking" the cam was causing. Solved that on the timing and air tables. It still bucks some with the DFCO off, but that will be re-enabled upon return, mostly so it will crackle and pop like a monster... which it does with DFCO on lol.

I played with some transient settings today, and some of the injector tables. I also noticed the injector gain was on for some reason as Smokeshow pointed out. Maybe I accidentally enabled that when scrolling through the settings. I know for a fact I didn't enable that on purpose. Oof. lol. Maybe that was the problem hahaha.

I will say that the last log was a lot better. More to follow as I couldn't push it hard due to the MAF AFR being lean.

I will probably end up scaling it down some once I get the numbers more dialed in.

I also returned the EOIT to stock just to rule that out. As expected it got leaner almost everywhere which is why I couldn't push it hard.

I'll post another log when I get home, and the tune fixes, provided it goes well. I really appreciate the responses.

 

Probably because my dumbass accidentally scrolled it "on" as I was going through the tune. I know it wasn't intentional by any means. I was surprised it was on when I went and looked lol. Thanks for pointing that out.

 

Throttle position is definitely in there. Not sure what you mean brother. All of the throttle PID's are being logged, actually. After I posted this I reorganized my channels into groups like I usually do. It's in that mess somewhere lol. I am logging a bunch of extra stuff too because later I like to do math and play with formulas. Someday maybe I'll crack a way to tune various things like fuel transients using data and math. I figured throttle has something to do with this too and I save all my old logs for reference. Hence the mess o'crap being logged lol.

 

Some of the pulls aren't actually going WOT even though you're revving it out. I can't open the tune file but if you don't hit the min TPS limit to enter PE you'll still command stoich when trying to make a pull. It's a typical reason for lean tip in, especially if there is any type of throttle blade or tps sensor issues.

 

Done that before lol. I don't even know why air pump nonsense is still in GM software... And I don't remember if the air pump fuel control overrides power enrichment or the other way around...but no sense risking that either way.

 

It appears to be using the PID "Relative Throttle Position" when PE activates. It's roughly half of the other values. I went ahead and made the adjustment to the PE table tapering it down to 10% at the higher RPM's. Hopefully that solves that issue. From the run this morning, the spikes are a lot less after playing with the transients and the Inj flow rate vs MAP multiplier. Definitely feeling better now about stabbing it. Once I get it figured I'll go ahead and redo the VE and call it a day on this thing.

 

The pid I was using was Throttle Position [Sensor] and it goes from 0-100, but it isn't going to 100 or even close on some of the pulls. That's why I was suspecting a TPS/TB issue. It sounds like youre close. Always feels good to wrap up a tune and see the persons face when they go for the 1st ride.

 

Is that high cylinder air mass because you were previously trying to make sure it was getting enough fuel? That's 800hp worth of air lol

 

Yes, I was trying to compensate for the lean condition, which is why I stopped to investigate other issues with it because there is no freaking way it should be hitting that lol. The last log got to about half as much, so it came down some already. I am certain it's whacky, but I figured if I solve the issue then it should return to normal. The MAF curve is getting steep af at higher RPM. So like I said, once the lean spike and injector issue is solved I assume the MAF will follow and return to more sane numbers lol.

 

I assumed that was being done diagnostically, because the pedal position was also in the 50-75% range - at least where I saw it.

 

There is definitely a pull in there that looked like a full pull attempt, but the throttle pedal looked like it was capped and constant through multiple gears so I assumed that was not intentional.

 

Yes I was trying to be cautious knowing this issue was occurring. After I made some changes to the injector data, transient, and of course turned off the Injector Gain, things are looking much more normal. Airmass came back down, but it also put me in a different place on the spark map, so I got some pretty bad knock the other day when testing. I have since reduced the main spark, but then weather hit us and I can't do anything until the roads dry back up.

There was only one spot where I think I got it all the way to the floor. In one of the pulls I see the mismatch in pedal and TPS that I assume you are talking about. This was also one of those places where it lean spiked, and I am really thinking it had to be that Injector Gain causing it to go all screwy. Still can't believe I had that on by accident lol.

Upping the Impact factor in the warm areas definitely helped with the lean tip in. I also reduced the Flowrate vs MAP Multiplier in the low MAP areas to help with the rich tip out. Not that I'm all that concerned with that lol. DFCO will be back on when I'm finished so that won't matter at all haha.

I'm actually trying to finish a few videos right now, since I haven't posted anything in forever. Time to finish up my scaling series and also share my new derivative formula for use when filtering MAF data. I don't have a ton of gen IV use with it, but the theory is sound. Basically it filters TPS or Accel pedal changes greater than say 10% or whatever you choose in order to get more accurate steady state data. I figured it would be useful in this case with a manual car, since the pedal is all over the place throughout the log. It's not actually a new formula, it's the same one as accel rate, but repurposed for use as a filter.

 

Since it came up, what exactly does injector gain do for it against the tune?

 

It is part of what controls fueling during secondary air injection. Rarely used, so it is likely other associated calibrations were not set right and just enabling it alone caused problems.

 

I’m pretty positive this was indeed the problem. Unfortunately I haven’t been able to finish the tune because of snow everywhere right now. Could be awhile.