[ReeseGia]

Hello,

Want to get another set of opinions on a issue:
I have a 2016 435i and have full bolt ons and just installed dorche hpfp stage 2 and precision race works stage 3 lpfp (safe for ekp). The sensor and fuel pumps work great, and the power added by running ethanol blends is insane. However for some reason, the car seems to be stuttering around high rpms (5k) right before a shift or at the end of the pull. It went away after a few days when I was on e62 blend, but now I'm on e75 after a fill up and it's doing it again. I've heard some people call this stuttering breaking up? I have a few logs I'm gonna send over as well, looks like throttle closure from overboost too.

Could this just be like an adaptation period each time the e blend changes? Or do I need to change the spark plug gap or look at other things on the car? (they were changed not long ago.) or maybe the stock turbo is maxed out?

PTF said it looks like the car leans out and the stft are bad at 1? They said unplug the MAF sensor or look into the injectors or o2 sensor being the culprit? The plugs were replaced not long ago and gapped to .022. This only seems to happen on high ethanol blends, but I see a lot of others having overboost problems with these new multimaps. I attached a few logs where the car breaks up in the high rpm's. Wanna make sure this isn't a problem when I put in my upgraded turbo 🥴

E62 blend

https://www.bootmod3.net/log?id=6343...0b43afee4ba088

https://www.bootmod3.net/log?id=6343...0b43afee4ba089

https://www.bootmod3.net/log?id=6343...729bae68633691

E75 blend

https://www.bootmod3.net/log?id=6345...90c6e0a56a1dd2

https://www.bootmod3.net/log?id=6345...729bae68634283

[thejeremyman9]

You can try unplugging MAF and relogging. You dont have LTFTs in your logs so you can't see if there's a LTFT issue.

It is odd that your STFT goes to 1 a few times - for some reason the car is going back into open loop, which could in theory be from a bad O2. Aside from that there's nothing that really shows why it could be breaking up after 5k. Fuel pressure is fine so its possible its the plugs, did you ever try stock plugs and stock gap at high E%?

The throttle closure in the one 75% log is from overboost

[ReeseGia]

Originally Posted by thejeremyman9

You can try unplugging MAF and relogging. You dont have LTFTs in your logs so you can't see if there's a LTFT issue.

It is odd that your STFT goes to 1 a few times - for some reason the car is going back into open loop, which could in theory be from a bad O2. Aside from that there's nothing that really shows why it could be breaking up after 5k. Fuel pressure is fine so its possible its the plugs, did you ever try stock plugs and stock gap at high E%?

The throttle closure in the one 75% log is from overboost

I haven't tried stock gap or anything because bm3 says to do .022, but I might check the gap myself. After unplugging the MAF then plugging it back in while running its still breaking up at high rpm's. I can feel the overboost throttle closure as well, sometimes it just cuts my power lol

Edit: also don't see LTFT as a log option in bm3
Also saw that some run .020 when using e85?

[thejeremyman9]

Originally Posted by ReeseGia

I haven't tried stock gap or anything because bm3 says to do .022, but I might check the gap myself. After unplugging the MAF then plugging it back in while running its still breaking up at high rpm's. I can feel the overboost throttle closure as well, sometimes it just cuts my power lol

Edit: also don't see LTFT as a log option in bm3
Also saw that some run .020 when using e85?

You don't unplug the MAF and plug it back in, you leave the MAF unplugged and drive/log with it unplugged. It's basically to test if your MAF is messing with your fuel trims.

LTFT should be there, ive seen it in other people's logs.

You want the largest gap possible. Yes we all know thats the BM3 recommendation and most people blindly follow it even when its not needed and potentially even detrimental. It may be that in your case with high boost and ethanol you need an even smaller gap but generally speaking i would try stock plugs stock gap and only go down from there if necessary.

[ReeseGia]

Originally Posted by thejeremyman9

You don't unplug the MAF and plug it back in, you leave the MAF unplugged and drive/log with it unplugged. It's basically to test if your MAF is messing with your fuel trims.

LTFT should be there, ive seen it in other people's logs.

You want the largest gap possible. Yes we all know thats the BM3 recommendation and most people blindly follow it even when its not needed and potentially even detrimental. It may be that in your case with high boost and ethanol you need an even smaller gap but generally speaking i would try stock plugs stock gap and only go down from there if necessary.

I just did 2 data logs with the MAF unplugged. Still was breaking up in high rpm's on the gear 3 one. I also don't see LTFT anywhere on bm3, not even in the advanced channels or when searching it. Weird

Thanks for helping me with this

3
https://www.bootmod3.net/log?id=6349...0b43a0ea848ff0
4
https://www.bootmod3.net/log?id=6349...729b87653e1e4c

[thejeremyman9]

Could just be misfires from plugs or coils. As BM3 said, it does look like it gets some lean spikes in AFR up top and STFTs start adding more fuel all the sudden. If you have a misfire, the unburnt O2 in the exhaust shows increases the AFR. Not sure what else you can try in terms of datalogging before just trying different plugs/gap

[ReeseGia]

Originally Posted by thejeremyman9

Could just be misfires from plugs or coils. As BM3 said, it does look like it gets some lean spikes in AFR up top and STFTs start adding more fuel all the sudden. If you have a misfire, the unburnt O2 in the exhaust shows increases the AFR. Not sure what else you can try in terms of datalogging before just trying different plugs/gap

I'll test different gaps and try that out. Might have to ease off the ethanol a bit until I get the turbo and a custom tune. Didn't do this on e50 as much

Thanks !

[thejeremyman9]

Originally Posted by ReeseGia

I'll test different gaps and try that out. Might have to ease off the ethanol a bit until I get the turbo and a custom tune. Didn't do this on e50 as much

Thanks !

You could start by going down to 0.020 with your current ones. IF going smaller doesnt work, i would go the other direction and replace all plugs with new bosch at stock gap

[ReeseGia]

Originally Posted by thejeremyman9

You could start by going down to 0.020 with your current ones. IF going smaller doesnt work, i would go the other direction and replace all plugs with new bosch at stock gap

I just found LTFT in bm3 on my PC. Was under other channels. I'm gonna gap them to .020 and log with LTFT on this time

[714BMW]

Originally Posted by ReeseGia

I haven't tried stock gap or anything because bm3 says to do .022, but I might check the gap myself. After unplugging the MAF then plugging it back in while running its still breaking up at high rpm's. I can feel the overboost throttle closure as well, sometimes it just cuts my power lol

Edit: also don't see LTFT as a log option in bm3
Also saw that some run .020 when using e85?

I tried 0.022 on full E85 but ran into misfires in boost towards higher RPM. Gapped down to 0.018 and it's been solid for a few months now.

Seems everyone's car reacts a little different but, yeah I would just follow Jeremy's advice. If gapping down doesn't work go the other way. Hopefully it'll solve your issue like it did mine

[LA1Z24]

Just an FYI, We are all fairly positive the PR stage 3 pump IS NOT safe for the stock EKP. The stage 2.5 pulls enough amperage to melt the ground pin on the EKP.

[ReeseGia]

Originally Posted by thejeremyman9

You could start by going down to 0.020 with your current ones. IF going smaller doesnt work, i would go the other direction and replace all plugs with new bosch at stock gap

So I gapped down to .020 and put in my stock intake for this log (just in case the aftermarket one was throwing off the mixture that bad) and it actually stuttered way worse this time.

Gear 3

https://www.bootmod3.net/log?id=634b...0b439dc6593fcf

Edit like 20 mins later:

I just reflashed the car and went down to e59 blend and it's not breaking up anymore. Maybe these multimaps stink idek

[ReeseGia]

Originally Posted by LA1Z24

Just an FYI, We are all fairly positive the PR stage 3 pump IS NOT safe for the stock EKP. The stage 2.5 pulls enough amperage to melt the ground pin on the EKP.

Stage 3 from PR is two walbro 450 fuel pumps (one for ekp and one connected to battery via relay and Hobbs switch at 7psi) not one huge pump (walbro 535) like found in the stage 2.5.

We will see what happens 🥴

[thejeremyman9]

Originally Posted by ReeseGia

So I gapped down to .020 and put in my stock intake for this log (just in case the aftermarket one was throwing off the mixture that bad) and it actually stuttered way worse this time.

Gear 3

https://www.bootmod3.net/log?id=634b...0b439dc6593fcf

Edit like 20 mins later:

I just reflashed the car and went down to e59 blend and it's not breaking up anymore. Maybe these multimaps stink idek

I wouldnt have changed 2 things at once, but anyways, if smaller gap made it worse i would go to stock plugs stock gap