Think you're smart? Step in. My LS1 issue...

[Eagle]

Ok folks.

I'm having problems with my TA around 4900-5200 RPM. It feels like its blowing out the spark, but I don't think that's what it's really doing. Cooler weather has been running ~14psi.

So far I have:

1. new TR7 plugs gapped down to .022 from .027
2. replaced all 8 coil packs (THANKS TOM! :bowdown)
3. replaced all 8 wires w/MSD 8.5mm
4. adjusted the tune here and there... no change
5. taken the 2step out - no change
6. watched fuel pressure - stays steady no drop ~52-54psi (base is 38, total depends on boost psi w/1:1 FPR)


Something tells me its injector related. It would SEEM to me that it only happens when injector msec is >16.0. See below for an example:

You can see in the above image that RPM flattens out for a short bit while it works through the problem area, then inj msec values drop <16.1 and it comes back and pulls like a SOB again as if nothing is wrong.

I'm at a loss and Brandon has been booked up for days... so I'm looking for other ideas/suggestions on how to troubleshoot this.

Solve my problem. Please.

Click to read more...

 

[Eagle]

Don't worry about it being a bit leaner than commanded.. I'm not. It was cooling off to mid-low 60s when this was logged. It's tuned for about 75-80*.

 

[SRT41320]

hmmm - your ref line...is that where you think the problem is or before/after the stumble? were you tuned on tr7 or tr6 plug?

 

[SRT41320]

40 - 80 roll....is it a short burst of wheel spin? do you feel it or hear it?

 

[Eagle]

It was tuned on TR7s.

The marker line is right on the tail end of the stumble, right before it took off again like nothing was wrong.

If the wheels are spinning its minor. This was logged with the Mickeys on.

 

[Ron Vogel]

Sounds like a fuel issue to me, probably not enough pressure, I'd set base pressure at 45 or more, and go 1:1 with boost...what kind of injectors?

If they are a delphi style pintle with a disc, then that's part of the problem. If it's the squirter Lucas style, then it's kosher. I like the Delphi style for the streetability, but they aren't as good for boost when you get more than 10psi and if you don't crank out the FP then this can happen.

When I was running 15-16psi of boost, I'd see 65-70psi at the rail, 52-54 sounds kind of low to me? (stock injector bodies are pressure tested to 125psi)

I am not familiar with the tuning parameters in the f-body, but similar things can happen if Tq management is still on in a few cells. It's enough to drop 1-3 injectors if it hits set limits. Ususally it happens fast enough that it won't show up in a WB, and you won't see it unless yo are monitoring each injector iduvidually.

 

[SRT41320]

fuel psi does seem low but it really depends on the car and tuning...

you think it would be the injector if it only started happening recently (since cooler temps) ron?

 

[Eagle]

Thanks, Ron.

80# seimens injectors:

 

[Eagle]

The base fp was set low intentionally as to not push my luck with the fuel system running out of PSI on the top end.

If I bump base fuel pressure, all my injector offset tables and more will be off... track is tomorrow...

 

[TURBOC1]

i would try and pull alittle timing out of that spot. if it was spining the rpm would spike not go flat.

 

[hellraiser319]

IDK, random spew of thought... o2 sensors? I know they aren't gonna be perfectly uniform, that is impossible, but there are 2 random peaks, one small one kinda large, maybe one is fritzing out or its just seeing something we cant see or smell.... weird though because inj msec is dead in both banks... plus I don't remember if the pcm reads o2's at wot anyway..

IDK just some ramblings...

 

[Eagle]

Worthy attempt. If the car were in closed loop it might matter, but its in open loop. Therefore O2's don't matter to the PCM, fueling, etc.

However... those weird spikes correspond to the time when the thing stutters... so hell if I know.

 

[Eagle]

i would try and pull alittle timing out of that spot. if it was spining the rpm would spike not go flat.

But timing stays flat @ 15.5* when at full boost. Pull more?

 

[Mike K]

What is your plug gap at? You might try closing it a little. Did the car ever run without the lag or did this just appear?

 

[10sec]

My guess, it's spark blow-out man, when boost spikes aka when the injectors are way up there in the msec's is when the motor is in FULL load, full pissed off everything. This is always when spark blowout is experienced first, after that it's almost always valve springs or valve float, which you better not have especially with that build. Either way, i'm going with spark blowout, especially with the cool nights like this, it's the #1 thing people complain about on turbo cars.

 

[Eagle]

Gap is at .022

How the he'll am I gonna blow that out? That's what I described it as when I told Brandon about it. Spark blowout.

 

[10sec]

.022? How can you even gap .022? That's a tiny ass gap in that case the gap is too small, i'm surprised you aren't turning the ground-strap into a glowing hot glo-plug. That's too small man, i would go .030-.035, if you're blowing that out your ignition system blows ass.

 

[10sec]

And yes, pun was intended

 

[10sec]

it can't be a fueling issue if fuel pressure is constant, it's not an "air" issue because... well you can't have that in your case. It has to either be a spark issue or a valve float issue. It can't be anything else IMO.

 

[MikeyLikesIt]

It sounds like a problem we experienced in the SRT world when they started hitting real high horsepower. They referred to it as the 6xxx stumble.

It was a problem of too much oil pressure/volume in the head. It caused lifter pump up issues. They installed a valve in the head and it limited the oil pressure in the head. I'll have to google that to see if they have anything like that it in the lsx world.

 

[Pressure Ratio]

.022? How can you even gap .022? That's a tiny ass gap in that case the gap is too small, i'm surprised you aren't turning the ground-strap into a glowing hot glo-plug. That's too small man, i would go .030-.035, if you're blowing that out your ignition system blows ass.

Small gaps like that are not that un-common. With a MSD 6AL and coil I have run gaps as low as .22. But usually at 25#+ boost. I have seen a few Ford applications where a small gap was needed at lower boost levels. But they do not have a strong ignitions like the LS motors.

 

[02BlueGT]

Could the colder plug have an Effect, as in the small gap, and colder plug are not getting hot enough to cause good ignition? I know spark is spark, but if the porcelain is cold, and keeping the close air cold....Throw the TR6's back in there and see if it goes away

 

[Eagle]

It ran great with TR7s for a long time @.027 without issue.

And it was definitely blowing out spark on TR6s gapped at .050.

 

[02BlueGT]

It ran great with TR7s for a long time @.027 without issue.

And it was definitely blowing out spark on TR6s gapped at .050.

Did you try a gap Like .035?

 

[daturbosix]