E38 in Turbo Denali 6.2 L9H All of the Sudden Decided to Disobey Fueling Commands

So I have had my turbo on my truck for a couple months now probably. I already went through the issues trying to run speed density, and then I decided to go back to MAF and I put a LS7 style MAF in the charge tube right before the throttle body.

I also upgraded the stock L9H injectors to FIC 850CC ones a week or two ago and seemed to be no issues. Lately I have been trying to get the MAF dialed in better, but, similar to VE/VVE tuning, it seems like I get nowhere, and the moment you think you are getting somewhere, then the next log file you get double the error you go back to the error you started with.

So the first thing I noticed was trying to do a boosted launch it felt like it had no power until second gear, so the logs were showing the EQ from the wideband slowly diverging and leaning out until second gear. So I started trying to mess with the MAF curve again with no luck. Now today randomly I am getting extreme lean out under half to full throttle but its completely random when it will be normal and when it will lean out. It seems to more consistently do it when I roll into about half or so throttle, but its done it to just going WOT all of the sudden.

You can see in this log the weirdness. To me discontinuities should never exist in logged data, or in calibration files for that matter as well, but circled in red you can see the boost curve ramping up and then the air mass per cylinder seems to diverge from it. It doesn't rise with the manifold pressure (boost) increase, then all of the sudden it does with a sharp discontinuity. You can also see below in light green the wideband showing it leaning out.
Attachment 119678

So I am back to full stock with a functioning MAF, so I don't' think I can blame the famous E38 speed density issues and weirdness. I am just baffled that the ECM is just blatently ignoring airmass and just deciding it doesn't want to fuel appropriately and disregard increasing airmass.

Does anyone have any ideas?

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That fuel pump looks like it's maxed out.

Yeah I am working on that, but it has been working ok before this especially at lower ethanol content. I just don't think this has anything to do with the fuel system since you can see the ECM cuts airmass when it leans out.

I can see its doing it even at zero accelerator pedal also here:
Attachment 119692

Its like it starts freaking out and goes extremely lean, and I don't know what in the airmass calculation could cause such a unstable and discontinuous calculation. And it just all of the sudden started this yesterday and I haven't changed anything at all.
I wonder if I should reapply the available patches even if I am running MAF?

I have a new appreciation for how fast responding the wideband is now, it will read the lean pikes and some of them look as short as 10 ms.

At this point after thinking of everything I can think of and trying to rule out as much as I can, the only logical explanation to me is there is something wrong with my new injectors. A part of me still thinks there is some quirkiness going on in the airmass calculation just because its done so much weird stuff before and the discontinuities and divergence between the boost curve and airmass curve just don't make sense to me.

So yes I did buy them used and I know injector companies say that ethanol is supposedly bad for them and you have to run a tank of regular gas every 3-4 tanks. I asked FIC about this directly and they said I shouldn't have any issues and they only saw E85 was a problem when it was allowed to sit up in an injector and the engine not run in a long time which doesn't happen with me. I don't know if fuel injector companies use OEM flex fuel cores or not, you would think they would given how popular E85 is as a race fuel. But I know my stock flex fuel injectors have zero issues and I have been running E85 over 95% of the time for years.

Maybe since I just bought the injectors and me immediately running E85 (about 60-75%) though them has caused the alcohol to dissolve some of the varnish and deposits from the dried up gas in the injectors, so maybe I just need to pull them off and try to run some brake cleaner and air pressure through them.

So after almost convincing myself it was the FIC injectors, since nothing else made logical sense, I put my stock L9H injectors back in and its doing the exact same thing:
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The commanded pulsewidth dosen't seem to change when it goes lean either, but then again the PID says it takes an "average" pulsewidth on each back and its only sampling at 200ms and the lean spikes are way shorter than that.

Along with the lean spikes it will also just gradually lean out over a couple seconds, then suddenly go back to normal.

So not seeing the ECM reduce pulsewidth, fuel pressure, or throttle position, or record any misfiring, this make absolutely no sense why it is spiking so lean and doing it so fast. Only other thing I could think of is there is a restriction past the fuel pump before the injectors in the rail, but a restriction wouldn't behave like what I am seeing on this log.

Is there anyway to see the instantaneous commanded pulsewidth?

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It definitely freaks out when it shifts which then causes boost to rise and spike (yes my wastegate is undersized but if I can get everything working correctly I can run a more normal amount of boost instead of a small 5-8psi and then should have more consistent and stable boost). You can see the boost rises hear and the cylinder airmass for whatever reason just diverges opposite direction and leans everything out:
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This really started out of nowhere, I haven't changed anything except for slight adjustments trying to get the MAF calibrated a little better based on wideband feedback. I probably should go back and redo the MAF in the non PE regions with the stock narrowband feedback.

Sorry I keep posting replies but I keep forgetting things.

I put it back in MAF only (zeroing out dynamic airflow enable RPM) and it still does the instantaneous lean spikes, but it hasn't done the gradually lean out over a second or so because manifold pressure (boost) is rising but airmass per cylinder calculation is not rising thing. So when in MAF mode I can actually go half throttle and let it roll into boost and runs fine without leaning out and sputtering.

I know there has been the infamous E38 lean out in PE after 2 seconds thing, but I don't think that is my issue since I am not showing the exact signs of it. Unfortunately all the threads about this look like they just hit a dead end with no solution ever found.

*Virtual* flex fuel? Man, I'd turn that shit off even if it wasn't acting strange. Desoot mode is also still on. Not saying either will cause what you're seeing, but those two are known to cause weirdness.

Quote:

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Originally Posted by blindsquirrel

*Virtual* flex fuel? Man, I'd turn that shit off even if it wasn't acting strange. Desoot mode is also still on. Not saying either will cause what you're seeing, but those two are known to cause weirdness.

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I tried telling him that. And a bunch of other things. Think we're getting trolled lol

Enrichment rate = 0.050 isn't ideal either. Hell, it's not ideal for stock much less for a FI hot rod.

I promise I tried haha, but I used one of those stupid racetronix fittings to use to connect to the stock fuel line and it left me stranded on the road and almost started a fire because the aluminum nut vibrated off and the other side fell off, which yes I should have remembered to put loctite on the nut from the fuel line vibration. So I am trying to hook it on another way now and I'm still waiting on some more fittings and parts.

I also disabled flex fuel entirely and changed the stoich target with the same result. But of course we know even when you think you turn off the master switch on a lot of these functions it still dosent 100% disable them.

This is how mine is stock and I verified it with some other stock tunes, but I will change it to go faster.

I've also tried turning off desoot mode and different combinations of the enable temp.

I just usually change stuff back to stock if I don't see a difference since I worry it might effect something else.

So I finally got my flex fuel sensor installed, I couldn't get it to fit and made a convoluted mess of fittings and hoses but its in there and wired and and virtual flex fuel is now disabled.

Unfortunately, its still doing the exact same thing.

With MAF enabled and stock 3800/4000 RPM dynamic airflow enable, it is still severely leaning out, but its only when you roll into the throttle. If you immediately go WOT it will go, but not always sometimes it will do it even when you go WOT instantly.

When in SD with the MAF failed, airflow calc mode will bounce back between "Normal" and "Unknown". From Chris's explanation I take "Normal" is the usual blend of SD and MAF and "Hi-Speed" is pure MAF operation. Somehow it runs in SD under "Normal" with the MAF supposedly failed.

Now with the MAF unplugged I get other issues, so I have to leave the MAF plugged in and let it generate a valid looking signal.

I have also I think been fighting MAF turbulence issues, since I am using a LS7 style MAF under pressure in my charge tube right before the TB. I redid all the charge tubing and added in about a 3 foot and about a .5 foot straight section of charge tube before and after the MAF to try to get rid of the jaggedy MAF signal. It seems to only get Jaggedy once the boost gets up there where the MAF signal appears to be maxing out.

Under pure MAF I believe my airflow is greatly exxagerated and it will make the transmission shift so hard it will complete the shift in almost .1 seconds and I feel like its going to explode next time it happends.

Under SD it will shift like stock at WOT at the commanded .325 second shift time.

But then I get all kinds of clunking and clanging under SD mode also.

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So I have been able to work around the lean out, by setting the dynamic airflow enable to around 2000 rpms, it will slightly lean out but goes above 2000 rpms quick enough for it not to lean out enough to make any difference in how it runs. I think having it at 2000 rpms also keeps it high enough you can have the more accurate airmass calculation benefits below 2000rpms to avoid clunks and clangs and jerks and stuff.

Another thing I could never figure out is if the GMT-900s have a separate barometric pressure sensor or not. I know they have a pressure sensor at the brake booster, but not sure if its used for anything else besides diagnostics for the braking system.

Key on engine off my MAP reads correct barometric pressure at about 14.1 psi, my barometric pressure PID reads 13.05 psi, the barometric pressure sensor reads 0 volts, I would assume it doesn't have one and maybe infers it based on the MAP sensor reading at engine off, but then not sure what would happen if you turned your engine on and then drove 5000ft up a mountain without ever cutting it off?

I adjusted the barometric sensor offset value (14.1-13.05)=1.05 psi but it didn't change the barometric pressure PID value.

Does anyone know how barometric pressure works on GMT-900s?

I am not sure the small 1 psi of difference is enough to throw everything off as much as I am seeing but maybe it is.