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Author Topic: Misfire, Wastegate duty cycle issues.  (Read 4175 times)
Bugman100
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« on: June 29, 2020, 06:11:07 AM »

I have an issue today with my 1.8t.

Background, i have been slowly upping the boost and making small changes, yesterday i upped the boost and changed some settings to limit overshoot on boost.
at the end of that i did a 30 mile run with no issues. The car ran great!

All logs for AFR,Boost,knock, EGT ect looked good with no issues and Zero misfires.

Today i decided to go out and take some more logs before i up the boost again. however in the 3000-4000RPM range the engine stutters. if you keep on the gas it will go away and then pull hard to high revs.

From the logs i can see that i do have a misfire but not always at the point the engine stutters. The other thing i noticed is that The WGDC drops to 5% when stuttering.

I replace the tune with a know good tune on with 1000 plus miles on it without issue and the stuttering is still there.

So the real question is when misfires occur does the ecu shut the wastegate to protect the engine? Or do i have two issues here ?  Misfire and wastegate issue.

I have already ordered new plugs (old ones have done 2k miles max gapped to 0.7mm). they will arrive later today.

I have included todays log file. I think i am logging the right stuff except up to this point i have just logged Total misfires as ive never seen a misfire todate. However if i need to log different stuff please educate me.
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Auriaka
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« Reply #1 on: June 29, 2020, 11:54:10 PM »

Looking at your log it looks like boost actual exceeded boost request at 2700ish rpm. Computer was trying to compensate for it.

Check your KFMIRL table and LDRXN.

Ideally get a log of a solid 1 gear pull, makes it easier to go through.

I would review your requests versus your filling however as a start.
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Bugman100
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« Reply #2 on: July 06, 2020, 08:12:37 AM »

Update.

The problem is now fixed, one coilpack was the issue.

However i still dont understand why missfire issue causes the waste gate duty cycle to goto 5% ish.

From the comment i do have an overboost issue, something i was trying to resolve when this issue came up. Overboost was far more severe at one point, i just havnt gone far enough with smoothing it out yet.

Also the map was asking to much load that the turbo could not supply at very low and very high rpm. These do need to be tweaked a bit. I was just trying to find the limits for the k03s turbo as i cant find a known good compressor map for it.
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nyet
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« Reply #3 on: July 06, 2020, 09:37:05 AM »

The answer is NEVER work on more than one problem at a time.

If you have a known issue, work on the obvious one first, in this case misfires, because yes, there are a ton of interactions between everything.

This is fundamental; if you go chasing boost problems while you are also having misfire issues, you're going to have to start all over again when you fix misfires.

This is by far the most common mistake noobs (and some "experts") make.

Fix one thing at a time, starting with the most obvious failure. Do NOT try to manage several at once, or even guessing why one is affecting the other, you're just wasting time (unless you are doing it for literally academic reasons).

Long story short: if you want help fixing your boost, post logs w/o misfires. Post logs that show ONLY the boost issue, and it is clear that there are no other problems.
« Last Edit: July 06, 2020, 10:27:52 AM by nyet » Logged

ME7.1 tuning guide
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Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
prj
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« Reply #4 on: July 06, 2020, 10:24:18 AM »

Looking at your log it looks like boost actual exceeded boost request at 2700ish rpm. Computer was trying to compensate for it.

Check your KFMIRL table and LDRXN.

If actual exceeds request, then these are NOT the tables that should be modified.
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nyet
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« Reply #5 on: July 06, 2020, 10:26:45 AM »

If actual exceeds request, then these are NOT the tables that should be modified.

Other than just increasing request to make things line up Smiley

But yes, obviously, I agree.
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ME7.1 tuning guide
ECUx Plot
ME7Sum checksum
Trim heatmap tool

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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