Unknown Misfire 2013 ZL1 408 LSA

[edcmat-l1]

Nothing in that log looks like a dead ringer for a miss.

At exactly 33.66 there is a pretty sharp negative spike on bank 1. At exactly 35.02 the same thing happens on bank 2. But neither look like a real miss. In addition, it doesn't look like it's missing anywhere else in the log.

Also, in both situations it looks like you're either in decel or steady throttle light load. Both of those scenarios are not likely to produce a miss, make a miss show up, antagonize a miss, anything like that.

[drewbo]

Understood, this is why I am having problems understanding.

Car is definitely missing at those RPMs/spots. Physically shakes back and forth/doesnt accelerate, AFR Spikes to 20-22.

[L1FTD]

Understood, this is why I am having problems understanding.

Car is definitely missing at those RPMs/spots. Physically shakes back and forth/doesnt accelerate, AFR Spikes to 20-22.

You're running the HPT 2bar OS, and boost enrichment hasn't been changed from 1.00.

Boost enrich is set to enable at 110kPa MAP, and it's still commanding stoich.

I made some changes to PE and BE.

PE will enable early, at half enrichment, and then BE at your full enrichment.

current tune v2 zl1 PE-BE.hpt

[drewbo]

You're running the HPT 2bar OS, and boost enrichment hasn't been changed from 1.00.

Boost enrich is set to enable at 110kPa MAP, and it's still commanding stoich.

I made some changes to PE and BE.

PE will enable early, at half enrichment, and then BE at your full enrichment.

current tune v2 zl1 PE-BE.hpt

Thanks for the input, will try tomorrow.

Wondering why you changed the power enrichment EQ Ratio to 13.0? That's a lot leaner than my actual target of 11.8.

Thanks.

[L1FTD]

Thanks for the input, will try tomorrow.

Wondering why you changed the power enrichment EQ Ratio to 13.0? That's a lot leaner than my actual target of 11.8.

Thanks.

Edited my previous post, but I'll put it here instead:

EDIT: Separate issue, but you most likely have the same lean problem a lot of us have. Your trims are adding up to +14% in the 2500-2800rpm.

You're running at stoich in boost, and hitting these lean spots, sending you really lean.

You'll need to add a lot of fuel to bring AFR inline.

Are you trying to run in SD?

The tune is a bit conflicting. Dynamic maxed to stay in SD, but no MAF codes set. Need to choose blended or SD, and set appropriately.

To your question: I set it up to use PE as a 'stepping stone' to full enrichment.

If you're going to use boost enrichment, that will take over from PE at 90kPa (it can be a bit slow, so it's set just before boost). Your original target is now in the BE table.

If you don't want boost enrichment, set it to enable 255kPa, and put your original EQ back into PE (have BE and PE tables the same, for safety).

[L1FTD]

I think the root cause is just your PE throttle enable is too high. The value used isn't a direct correlation to TPS, it's throttle area.

You're not at enough throttle to enter PE, and then BE enables at 110kPa and commands stoich anyway.

When you're above 110kPa and in BE, you lose your trims. Those trims were correcting the big lean area through 2500-3000rpm.

If you were at 70% throttle, you'd go into PE and get your commanded fuel. The ECM would choose the PE table as it's richer than the BE.

Previous post still stands, if you want to use the boost enrich function. Helps to smooth transition, instead of stoich to full enrichment.

[edcmat-l1]

If the occurrences in the data log are when it misses PE has nothing to do with it. It's in decel mode or very light load steady state at the worst. There's no load on it. No boost, no PE.

Fuel trims are pretty far off in general.

[L1FTD]

If the occurrences in the data log are when it misses PE has nothing to do with it. It's in decel mode or very light load steady state at the worst. There's no load on it. No boost, no PE.

Fuel trims are pretty far off in general.

I'm going off the latest log posted, screenshots attached.

Can see it's holding a few pounds of boost until it gets above 2500rpm, then boost starts climbing and spiking. No enrichment.

Just after 110kPa, the trims stop. 110kPa is the enable for boost enrich, and that was set to 1.00.

Boost-noPE.png TrimsStop.png

[edcmat-l1]

I'm going off the latest log posted, screenshots attached.

Can see it's holding a few pounds of boost until it gets above 2500rpm, then boost starts climbing and spiking. No enrichment.

Just after 110kPa, the trims stop. 110kPa is the enable for boost enrich, and that was set to 1.00.

Boost-noPE.png TrimsStop.png

I'm going by what he said in the post where he posted the last data log. He said 35 seconds. See the screen shot at 35 seconds.

35 seconds.jpg

I do understand what you're saying. In that log the car never went into PE ever even with a touch of boost. All I'm saying is, if the occurrence at 35 seconds is when it does its thing, PE is not involved.

[Alvin]

Update,

Boost a pump, aux pump, both unplugged. Fuel pressure no longer dropping, misfire is still happening. See the attached log.

Attachment 144975

See around 35 seconds. Can't figure this out for the life of me, any input is appreciated.

Please re read the reply I had early on. This thing is still very lean in boost and not commanding PE. That is a major problem that is simple to fix.

[L1FTD]

I'm going by what he said in the post where he posted the last data log. He said 35 seconds. See the screen shot at 35 seconds.

35 seconds.jpg

I do understand what you're saying. In that log the car never went into PE ever even with a touch of boost. All I'm saying is, if the occurrence at 35 seconds is when it does its thing, PE is not involved.

All good. Yeah not much happening at 35 seconds on the dot.

Either way, airflow models are definitely lean around there.

There would only be a small window for this to happen. Not enough throttle to enter PE, but MAP over 110kPa.

A bit more throttle and PE would provide enough to smooth it over, or staying under 110kPa and the trims would correct the leanness.

In the small window, trims stop, stoich is commanded, and airflow models are lean to top it off.

[edcmat-l1]

I agree with both y'all. The cal is all over the place in general and a lot of it looks like simple dial-it-in kinda stuff.

[drewbo]

I think the root cause is just your PE throttle enable is too high. The value used isn't a direct correlation to TPS, it's throttle area.

You're not at enough throttle to enter PE, and then BE enables at 110kPa and commands stoich anyway.

When you're above 110kPa and in BE, you lose your trims. Those trims were correcting the big lean area through 2500-3000rpm.

If you were at 70% throttle, you'd go into PE and get your commanded fuel. The ECM would choose the PE table as it's richer than the BE.

Previous post still stands, if you want to use the boost enrich function. Helps to smooth transition, instead of stoich to full enrichment.

Question, my PE Throttle enable was at about 15% (0 -> 3500) and 5% (4000 -> 7000), how is that too high? Aren't those values low?

Please re read the reply I had early on. This thing is still very lean in boost and not commanding PE. That is a major problem that is simple to fix.

Honestly, I totally forgot about this. I was more chasing down mechanical issues, thanks for the reminder.

I agree with both y'all. The cal is all over the place in general and a lot of it looks like simple dial-it-in kinda stuff.

Besides the airflow models being off, what else is wrong?

Thank you all, still new to this.

Thanks

[L1FTD]

Question, my PE Throttle enable was at about 15% (0 -> 3500) and 5% (4000 -> 7000), how is that too high? Aren't those values low?



Honestly, I totally forgot about this. I was more chasing down mechanical issues, thanks for the reminder.



Besides the airflow models being off, what else is wrong?

Thank you all, still new to this.

Thanks

The values in the PE throttle table arent direct pedal percentages.

15% PE is around 47% pedal, and 5% PE is around 30% pedal.

You need to be in PE earlier. Either put the whole table to 5%, or change the MAP enable to 90kPa and pedal table to 1%.

That should already be in the tune I posted back to you.

Sorry dont have much time right now, but theres a few things you could fix up

[smokeshow]

I can see what probably feels like a misfire. Two things...the PE delay is likely bringing out the injector spray angle issue in a bad way. When you lug it at low rpm getting into moderate boost, a lean mix is prone to intake backfires...especially with a bigger cam and those injectors. They'll leave a lot of fuel on the port, and the lean mix makes it real easy for too much heat to jump out the intake valve with that relatively long time window and ignite the incoming charge in the intake ports. I've seen it with a stock camshaft, but if you've got a bigger cam with more overlap, it'll be worse. I'm betting that's exactly what's driving the MAP spikes when you lug it out of enrichment. Jumping into enrichment sooner can help to keep that heat from backing up into the intake, but probably not going to be a total solution. Avoiding that low speed lug scenario is gonna be the best bet, so long as you have to use injectors that spray on-axis instead of offset like LSAs. The other thing is the ramp into aggressive spark at lower loads, and conversely the hanging out at high spark on a tip-out. I have to assume the 408 is higher compression than the LSA...so you're likely flirting with MBT and oscillating torque when the spark crests 45? and you're under 3000rpm. Ease up the ramp into spark on mild tip-ins and pull it out sooner on tip-outs as it transitions from main spark to coastdown. I think that should help a lot.