ZFR LNF Cobalt Acting Badly Cannot Figure this One Out.

[Terminator2]

Here is a screenshot showing the issue. It looks like a misfire or some other fault but none are recorded when this occurs. Plugs are OEM one month old. We tried stock gap and 0.028" gap, tried unplugging the purge valve, cleaning the MAF, Rotating the filter (K&N intake) no change. I tired an older tune revision before this issue popped up and no change seen. This is rare but I think I need help with this one. No codes pending either. Some pulls in this same log the car seems fine no issues. Even with the issue the last log the car ran a 4.0 60-100 time on 93 octane. MAF sensor bad maybe? MAP sensor bad (has 3 bar MAPs tried disabling P0106 just to see if that was the issue but no change) Injection window misfire comes to mind but no misfires recorded so?




Same log Pull from 70 ish no issue at all (Ignore the tiny bit of KR never tune version has none seen. What the Heck?

[Iam Broke]

I can't open any of my old LNF logs, but as I recall IWM did not set a code. No blinking CEL light or any indication of misfire.

[Terminator2]

I can't open any of my old LNF logs, but as I recall IWM did not set a code. No blinking CEL light or any indication of misfire.

That is my thought unless anyone has any other ideas. Up until this point never seen an injection window misfire on gasoline before. This car must make a lot more torque than normal right there at 3700. I backed the WG DC back down some and I might need to decrease the MALT a bit although it is very smooth already. Car pulls hard even with the hiccups. Car is boosting 284 kpa (26 psi at his altitude) flat.

[Iam Broke]

Does it feel like a miss & pop a bit in the intake? I wish I could remember what the ms were when I hit it on E70, but it was around 7ms I *think*. Sux getting old.

You might be running into it due to the HP fuel pressure tanking in the midrange. You could raise the commanded pressure a bit and see.

[cobaltssoverbooster]

i see so far:
your at 7.1 ms on the injectors and they blow the spark out at values as low as 6.4 ms so most likely this is one of your issues.
your rail pressure didnt really drop so its not a supply issue yet.

i would still double check boost control sources for weak springs or leaks just to be sure i have nothing messing the boost up which causes wavy load and boost lo res sensor signal returns.
already found 2 tial wg springs improperly coded for the value the owner thought he was getting. little mix ups between the old 50 and the new q

[Terminator2]

Does it feel like a miss & pop a bit in the intake? I wish I could remember what the ms were when I hit it on E70, but it was around 7ms I *think*. Sux getting old.

You might be running into it due to the HP fuel pressure tanking in the midrange. You could raise the commanded pressure a bit and see.

I believe the rail pressure is tanking right there due to the miss. It holds as commanded otherwise. It gets to 10ms at 3800-4000 which is pretty long but I did have a LNF on E-85 hit 11 ms at 3700-4000 without this issue though.

[Terminator2]

i see so far:
your at 7.1 ms on the injectors and they blow the spark out at values as low as 6.4 ms so most likely this is one of your issues.
your rail pressure didnt really drop so its not a supply issue yet.

i would still double check boost control sources for weak springs or leaks just to be sure i have nothing messing the boost up which causes wavy load and boost lo res sensor signal returns.
already found 2 tial wg springs improperly coded for the value the owner thought he was getting. little mix ups between the old 50 and the new q

Could be but of course the max injection time depends on RPM. I have a lot more than 6.4 ms at 3700 RPMs due to slower piston speeds and a lot less than 6.4 ms at 7000 RPMs.

[cobaltssoverbooster]

True it's rpm dependent if I could only find the calculation for it that was here we could compare as a double check.

[Terminator2]

True it's rpm dependent if I could only find the calculation for it that was here we could compare as a double check.

Well this car still has the issue even getting the injector pulse width down from 10 ms max in that screen shot down to 7.1-7.4 ms at 3900. I have tuned BNR2871 LNFs on E-47 and had them seeing 8.3-8.4 MS at 3900 and they had no such misfires or anything although I had more midrange injection angle on those cars. I now have the injection angle maxed out and the fuel pressure cranked up in the midrange now. I hope it fixes the issue if not I have no idea what the heck the issue is. Car pulls really hard even with these hiccups it ran a best of 3.9 seconds 60-100 on 93.

[cobaltssoverbooster]

Your a thorough guy... We're the insulators inspected for cracks. Whats was the Color at the base of the insulator if u did check?

I'm not there so I gotta ask

[Terminator2]

Your a thorough guy... We're the insulators inspected for cracks. Whats was the Color at the base of the insulator if u did check?

I'm not there so I gotta ask

Not doing the car in person. He is PA I am in Florida. Plugs are only a month old and I had him pull them and close them down from 0.035" to 0.028" gap no change seen. I believe the plugs are fine but if this persists I am going to ask him to swap them out. Need to eliminate some possibilities.

[Iam Broke]

He might have some inj seals crapping out. Ask him if he smells fuel on a hot shutdown. If he's been flogging it on the old white seals they might be cooked out.

If they are leaking and causing an issue it'll sound like popcorn popping by his feet when it gets bad enough.

[cobaltssoverbooster]

i hear that man. i have that sound on my lnf but i have a new motor so you know that means i dont give two cookies about it.

where in floridas roughly. im in destin area

[Terminator2]

I figured it out. It was injection window misfire due to it needing a lot more injection angle in the midrange vs normal and more fuel pressure (seeing 2600 psi as commanded with no drops anywhere). I have the IPW down to 6.1-6.3 ms max now and with how advanced the injection start angle is I see no problems pushing this thing a bit harder now. MAF still looks off though it still has a bit of a sine wave sometimes so I think he needs a new sensor or it has some turbulence at the MAF which was exacerbating the issue but at least the popping is gone.

[cobaltssoverbooster]

Sweet! Thanks for sharing the problem and diagnosis. I'm going to add this thread as a link so members can refer to it as a problem that may occur with aftermarket turbochargers.
Injector window change came to mind when i started questioning injection blowouts. How did the sensor signals react to your changes on the window time? (ex: did small window changes see some sensor improvement or did it only see gains after a big change)

[Terminator2]

Sweet! Thanks for sharing the problem and diagnosis. I'm going to add this thread as a link so members can refer to it as a problem that may occur with aftermarket turbochargers.
Injector window change came to mind when i started questioning injection blowouts. How did the sensor signals react to your changes on the window time? (ex: did small window changes see some sensor improvement or did it only see gains after a big change)

You know me I am a go big or go home kind of guy. I advanced the injection window out as far as possible in the midrange so I have more room to play with torque output wise, and I gave it as much rail pressure as I thought it could take which was 2600 psi and it holds 2600 like a champ and now has at least another 2-3 ms of available injection window now from my calculations.

[cobaltssoverbooster]

Problem fixed... Optimized window time--- close enough lol

[Knightwolf]

Is that all you did was up to 2600psi on the fuel pressures and it fixed the issue?
Also.. I'm new to this, but I'd like to know.. what do you mean by?

I advanced the injection window out as far as possible in the midrange so I have more room to play with torque output wise

And where in the table? I have the occasional injection misfire, but it's quite rare.. seems to be only when I upload a tune initially and then it "learns" it away. Pops maybe once and only in a higher gear(3rd or 4th) high load WoT situation.
I have my fuel pressure at 2200 psi currently above the 2176 factory setting.. not much I know.. but I didn't want to get carried away; for the most part it works fine on my stock turbo. I will need to increase it most likely once the ZFR goes in.. hopefully August I'll have enough cash for a clutch kit and I can finish her off.

[Knightwolf]

Wow... 6 yrs later and I didn't get a reply. But here I am looking for clues for dropping rail pressures and this thread comes up Lol
4200 rpm approximately and she swings way lean when pressure drops below 1200psi. Upgrade lpfp or hpfp or both? Mid 400whp at 4200rpm and 517wtq around same rpm... potential still unknown but guess mid 500whp/tq

[T-Man]

Wow... 6 yrs later and I didn't get a reply. But here I am looking for clues for dropping rail pressures and this thread comes up Lol
4200 rpm approximately and she swings way lean when pressure drops below 1200psi. Upgrade lpfp or hpfp or both? Mid 400whp at 4200rpm and 517wtq around same rpm... potential still unknown but guess mid 500whp/tq

Look into your advancing your injection timing and also look into how your boost is being brought in. 517wtq at 4200RPM is quite a bit of torque I'd imagine and your HPFP simply cannot keep up. It's a bandaid but based on what you're saying, you're out of HPFP. The in-tank pump usually shows itself in the higher RPMs from what I can recall.

I've run into the FP drop on both a modified K04 and a 6758 EFR. My solution was to reduce ethanol content, slow down mid-range spool, lean it out and increase my injection timing.