N55 M2 bootmod3 weird power cut (feels like rev limiter)

AmuroRay · 03-02-2023, 09:06 AM

Quote:

Originally Posted by Westersund

Had this problem after my M2 was tuned last summer by a friend, got massive misfires after I collected the car but those went away after I changed to new BMW spark plugs. However the hesitation after 5K rpm remained. What I noticed while pushing the car without the engine insulation installed (after the spark plug change) I could literally hear the fuel rail getting sucked dry when the hesitation started. I strongly think that the stock LPFP, in some cases, can't even support a stage 1 tune if you beat on it. Pulling a couple of gears sure but not constantly. The HPFP can only supply sufficient pressure if the LPFP can deliver enough fuel, my belief is that the LPFP is the main restriction not the HPFP. If you stick to a stage 1/2 tune that is (Under 450 hp but with supporting mods).

I don’t think that’s the issue or correct.

You’ll likely need to clear the adaptations to remove that hesitation, as it’s ‘learned’ behavior. But the HPFP is a bigger restriction - if you look at your logs, you’ll likely see it doesn’t always keep up with demand.

It’s often rectified with an upgraded HPFP. We know the High pressure pump is a limitation because upgrading the LPFP by itself doesn’t really offer a lot of extra headroom.

Westersund · 03-02-2023, 10:03 AM

Quote:

Originally Posted by AmuroRay

I don’t think that’s the issue or correct.

You’ll likely need to clear the adaptations to remove that hesitation, as it’s ‘learned’ behavior. But the HPFP is a bigger restriction - if you look at your logs, you’ll likely see it doesn’t always keep up with demand.

It’s often rectified with an upgraded HPFP. We know the High pressure pump is a limitation because upgrading the LPFP by itself doesn’t really offer a lot of extra headroom.

I'll have to do some pulls and log the values. Does the logs distinguish the pressure before and after the HPFP? If not it's hard to tell if it's the LPFP or the HPFP that's the cause. I was only runing a stage 1 tune as I don't have any supporting mods yet so I was surprised by the outcome. The tune is custom and ran great in the dyno besides the high IAT after a couple of pulls.

What adaptions do you mean and what's the procedure to clear it?

AmuroRay · 03-02-2023, 10:30 AM

Quote:

Originally Posted by Westersund

I'll have to do some pulls and log the values. Does the logs distinguish the pressure before and after the HPFP? If not it's hard to tell if it's the LPFP or the HPFP that's the cause. I was only runing a stage 1 tune as I don't have any supporting mods yet so I was surprised by the outcome. The tune is custom and ran great in the dyno besides the high IAT after a couple of pulls.

What adaptions do you mean and what's the procedure to clear it?

The high IATs will cause that issue, as will poor quality plugs and coils. Can you post a log?

Westersund · 03-02-2023, 11:03 AM

Quote:

Originally Posted by AmuroRay

The high IATs will cause that issue, as will poor quality plugs and coils. Can you post a log?

Not yet. I don't have MHD or BM3 so I can't easily log pulls, need to have my brother in the car with the ECU flash program runing on the laptop. I'll look into it this summer but I guess a new IC is needed.

M2RAW · 03-04-2023, 12:02 PM

Quote:

Originally Posted by Big.Al

Any updates on this issue? On a similar boat, but on stage 2 91 map. Hpfp pressure drops around 5400 rpm way below target. However stock map car pulls fine and going to upgrade my hpfp soon as that seems to be the culprit.

Any updates? same with my car stock tuned it pulls normal but misfire on stage 2 bm3 tuned. just bought ngk plugs that bm3 recommends.

MikeF87LCI · 03-04-2023, 04:40 PM

I have also had an issue with my 2018 M2 shortly after going stage 2.

Slightly different to that of the OP, mine will only give misfires in 5th gear cruising at lower rpm say 1500-1750 ish.
Pulls sweet the rest of the time and can cruise in 6/7th no issue (dct)

I’ve been on to BM3 and have had map revisions sent, tried 2 sets of plugs (checked gap), tried different coils and also smoke tested to see if any boost leaks.

Big.Al · 03-05-2023, 09:38 PM

Quote:

Originally Posted by M2RAW

Any updates? same with my car stock tuned it pulls normal but misfire on stage 2 bm3 tuned. just bought ngk plugs that bm3 recommends.

No updates, currently enjoying the car on the stock map. Most likely will go dorch stage 2 hpfp to hopefully resolve my issue.

I'd take a log and see how your car is pulling on the tune to find your issue. From my logs that I sent in the thread, hpfp takes a fat dip but timing is all good which is leading me to a fueling issue aka stock hpfp is shit lol

calvin07 · 08-16-2023, 10:04 AM

Quote:

Originally Posted by thermal

n55 m2 with 20k miles, upgraded fmic,chargepipe,mst turboinlet,catless dp.

Was running bm3 stage 2 tune and on a 3rd gear pull around 5400rpm got a weird power cut, almost identical to hitting rev limiter. I pulled over and looked at the codes and got a:
152508 Super knocking cylinder 5: injection shutdown.

After looking up the code and finding out that it's pretty serious I got the car home and started researching the causes. There isn't one specific one but could range anywhere from bad spark plugs/bad gas/loose chargepipe/loose downpipe on the turbo side.

So got looking into all the parts installed, making sure chargepipe is good and downpipe is tight, I also replaced the spark plugs (oem+oem gap) Had less than quarter of a tank, so changed gas stations as well just in case. Flashed the car back to stock and logged some 3rd gear pulls:
https://www.bootmod3.net/log?id=635a...729b7bba2e6e31
https://www.bootmod3.net/log?id=635a...90c66de08d066e

Felt great, car pulled no hesitation I thought I fixed the issue (the spark plugs were 20k old), so I moved forward and flashed bm3 stage1(91octane with 93 in the tank):
https://www.bootmod3.net/log?id=635b...729b7bba2e6e89
Instead of a rev limit feeling, it now felt more like a hesitation which you can see it happen on the log. Checked codes and nothing came up and logged one more pull. Same thing happened again, not as aggressively as the first time on stg2(93octane) but more now as a form of a [...]

Hey OP did you ever figure out the problem? I’m having similar issues.

ericlr1225 · 08-18-2023, 11:41 PM

hmmmm Suggest you guys to check my older posts.
First thing first, try to do some logs with stock tune maybe stage 1 maximum when BM3/MHD ready.
Mainly pay attention on HPFP target/actual and give yourselves a break not to worry about ignition system too much.

Long story short, highly chance that stock hpfp is failing like mine.

03-04-2023, 04:40 PM	#28
MikeF87LCI Second Lieutenant 560 Rep 212 Posts Drives: BMW F87 M2C Join Date: Jan 2020 Location: UK iTrader: (0) Garage List 2019 BMW M2 Competi ... [9.50]	I have also had an issue with my 2018 M2 shortly after going stage 2. Slightly different to that of the OP, mine will only give misfires in 5th gear cruising at lower rpm say 1500-1750 ish. Pulls sweet the rest of the time and can cruise in 6/7th no issue (dct) I’ve been on to BM3 and have had map revisions sent, tried 2 sets of plugs (checked gap), tried different coils and also smoke tested to see if any boost leaks.
	Appreciate 0 Quote

08-18-2023, 11:41 PM	#31
ericlr1225 Second Lieutenant 135 Rep 248 Posts Drives: 2018 M2 LCI 6MT Join Date: Sep 2022 Location: Los Angeles iTrader: (0)	hmmmm Suggest you guys to check my older posts. First thing first, try to do some logs with stock tune maybe stage 1 maximum when BM3/MHD ready. Mainly pay attention on HPFP target/actual and give yourselves a break not to worry about ignition system too much. Long story short, highly chance that stock hpfp is failing like mine.
	Appreciate 0 Quote