spark blowout?

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BoobieTrap

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	spark blowout? « on: December 13, 2017, 02:06:48 PM »

So I have this issue with stumble on full boost (26psi), the MAF signal shows huge dips (about 40g/s) and the AFR spikes lean.
Only happens on full boost and is very noticeable inside the car...
Definitely not TM as it's disabled at the moment.
Spark plugs are almost brand new iridiums gapped to 0.7mm (0.027-0.028).
Coils are bolt down Hitachi, also almost new.
Not TIP collapsing because it's aluminium with silicone couplers.
CFs are <7 degrees.
Throttle angle constant at 100% so not throttle cut.
GTX30, 1.8T, 5120 hack.

Spark plug gap too big? What's the recommended gap for 26psi+ on stock coils?
This only started to happen since i turned up the boost.
Don't think it's fueling as running inline Bosch 044 pump and 1000cc injectors.


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rnagy86

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	Re: spark blowout? « Reply #1 on: December 13, 2017, 03:01:17 PM »

it is probably compressor surge


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vwaudiguy

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	Re: spark blowout? « Reply #2 on: December 13, 2017, 03:06:03 PM »

- Logs would help
- Just because you have xyz fueling components does not mean it's not fueling related
- Gap them down and report
- <7 CF is too much in my opinion. Depends on the conditions somewhat, which we don't know because no logs
- What fuel matters. Didn't specify

Miss this?


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"If you have a chinese turbo, that you are worried is going to blow up when you floor it, then LOL."

BoobieTrap

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	Re: spark blowout? « Reply #3 on: December 13, 2017, 03:54:37 PM »

Quote from: vwaudiguy on December 13, 2017, 03:06:03 PM

Sorry, here you go:
https://drive.google.com/file/d/1ITVA2Yfd7Tp-dXRVvsDl29bpJsRZFgnJ/view

I left the log running for a while so you will need to filter it.
There is 2 full WOT runs; the first one didn't have misfire (although there was throttle cut due to slight overboost, which I'm sorting out), the second one has misfires all over and no throttle cut.

Fuel is 98RON.
The fueling system had no issues so far with up to 24PSI boost, the OE fuel pump is relatively new, stock FPR, inline 044 pump


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rnagy86

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	Re: spark blowout? « Reply #4 on: December 14, 2017, 02:59:20 AM »

Looking at the MAF values i am almost certain it is slight compressor surge. MAF signal jumping around will
fuck your fueling up for sure.


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BoobieTrap

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	Re: spark blowout? « Reply #5 on: December 14, 2017, 04:15:07 AM »

Compressor surge crossed my mind, but the graph I have seen on here for compressor surge show the MAF signal spiking up before dipping down and showing more of an oscillation.
I've reduced the spark plug gap to 0.6mm, will give it a go later and report back.


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THANAS

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Yes.

	Re: « Reply #6 on: December 14, 2017, 04:24:34 AM »

Surging manifests as a rapidly oscillating MAF curve, misfire manifests as a sharp negative spike in the MAF reading, from my experience.


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BoobieTrap

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	Re: spark blowout? « Reply #7 on: December 18, 2017, 11:21:59 AM »

Quick update: reducing the gap to 0.6mm has stopped the misfires, confirmed on a 200 mile round trip. However, I have already replaced the coils twice in the last 12 months so time for an upgrade.
Just ordered D585 LS2 coils + leads & connectors. Anyone has the dwell settings for these by any chance?


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