BMW m20 off idle stumble

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BMW m20 off idle stumble

Postby Eskie » Tue Sep 19, 2017 6:38 pm

325iX_2017-09-19_20.51.39.msq
tune
(116.46 KiB) Downloaded 5 times
I'm having a hard time getting rid of a "stumble" that occurs when I throttle off of idle. It is most prevalent if I free rev the engine. It also happens when I take off in 1st gear. Its like a misfire for a second. When I first started tuning this car a couple months ago I figured I could just fix it without accel enrichment. The more and more accel enrichment I added it just seemed to make it worse. At this point I am wondering if I have a rich spot that I need to lean out. It feels like a misfire due to an over rich mixture. When looking at the log it shows lean spikes right when these stumbles occur though. It is definitely more prevalent when the car is in warm up enrichment but still happens when the car is fully warmed up. This again leads me to thing something is too rich.

This engine runs very well otherwise and has definitely picked up power over the stock Motronic.

Any suggestions? Thanks
Attachments
2017-09-18_14.10.33.msl.zip
datalog
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Eskie
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Re: BMW m20 off idle stumble

Postby Matt Cramer » Wed Sep 20, 2017 6:59 am

Looks like it's rolling through a lean spot on the VE table.
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Re: BMW m20 off idle stumble

Postby Eskie » Wed Sep 20, 2017 7:14 am

I just noticed that my tune file didnt upload..I will get that up shortly
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Re: BMW m20 off idle stumble

Postby Eskie » Wed Sep 20, 2017 10:55 am

Here is my tune .msq
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325iX_2017-09-19_20.51.39.msq
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Re: BMW m20 off idle stumble

Postby Tech85 » Mon Sep 25, 2017 10:03 pm

Hey, just wondering if you were able to work out the stumble by tweaking the VE table?

If not, any recent developments?
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Re: BMW m20 off idle stumble

Postby Eskie » Wed Sep 27, 2017 7:47 am

It turns out that it was in fact, too lean. I enriched the VE table directly above idle all the way up to 100kPa. This fixed the stumble when the engine is completely warm. I tried to increase the WUE thinking it would fix the stumble while the engine was cold but it ended up just making the entire map too rich. I then turned on AE TPS and increased the cold accel and so far the stumble has been gone. I did noticed that this morning there was a slight stumble when I did a free rev test right after starting, but it was a lot colder than the past couple of days. I'm going to try either enriching the cold enrichment in AE or increase the low TPSdot PW adder to fine tune things.
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