Findings and conclutions about misfires and ignition pulls

135boost

Sergeant
Oct 28, 2017
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Hi

I started this cause there seems to be numerous different approach about this stupid and very annoying issue of n54 misfires

I think half of those is just related to worn out parts like stock coil, plugs, faulty injector or just clogged intake runner, piston ring land, or something else very obvious.
But then there seems to be a bunch of misfire issues not covered by those common easy fix and owners has throwed and swapped every part in whole engine department and still struggle with this issue.

First this engine is still just a petrol burner, air, fuel, squeez, bang, exhaust dump..
I have struggled with these for few years now and still miss the root cause for them. Trebila has been awesome help and p33p33 even more awesome help to tune this but still there is to much on the dark side of this issue, and for sure, i'm not the only one with this. This seems to be stupidly sensitive to all what can cause misfires.

At the end of day, solutions should not be in a level of "edge where maybe it ignite every pulse", more like enough room for to be sure we aren't even close to misfires, damn, gtr's with these miniatyre plugs iginite even with 55psi and 2000 horsepower and propably 40% more cylinder pressure at the moment of ignition without issues.

What i have read from these forums, numerous injector swaps, numerous playing with different coil packs, spark gap, finetuning of software, different plugs, wichcraft, gremlings, different brand of fuels etc and still misfires even with big players like Tony @ vtt, Terry @ burgertuning and numerous others too.

Damn it, even 1970 made carburator engine turbocharged ignite mixture without issues so why is this so damn difficult.

First known real issue, miniatyre size spark plugs what for sure is more prone to run to issues cause of very thin layer of insulator and frame been close to electrode, that is somethinw what just is, caused on limited space in combustion chamber in di engines.

Then few things about di and plug relation what can trig issues, injector is very close to spark plug and with very high horsepower n54, on di, when injection window start (not sure about excact timing cause of missing map in xdf but some guess is that window is some 250 degree ) piston is close to tdc and maybe there is on big injection quantitys in that situation to some degree of risk to wet the plug.

First question, have there been any notices of difference in full di to the max with bigger di hfpf systems versus di plus pi cause on that occation, di plus pi should be less prone to this if that is the case

Second question, b58 style spark plug with much more protected center electrode could also provide some protection against that wet foul possibilities, some notices if that does any positive effect against misfires. Someone maybe even tryed pi only?

Seems that pr coils, b58 coils etc has for sure enough energy to ignite this kind of combustion so i think we all can be sure it's nothing to do with pure spark energy. Energy need is also reduced with spark gap reducing even if combustion pressure increase energy need and spark resistance at level of 1 to 1

What about mosfets or cabling to coils, i don't think cabling are too small to proper support coil charge even if they ain't ment to support more than stock coils but what about mosfets ability to disspatch heat with much longer dwell times in optimated dwell maps? I really think we have enough knowledge on those proper optimum coil dwell tables to rule out thatwrong chargetimes from issue causings list.

There has been one test what i have found from web where those was measured and conclution was that b58 coil is superior to allmost everything what can be throwed in in dumb coil markets. Has there been any taughts on temperature issue or is there real differences when used smart r8 coils on misfire front?

What about heat sink glued with thermal glue on top of all mosfets? Not so very difficult task to do.

On mechanical side there has been reported that some teflon tape wrap to injector has cured a small amount of misfire issues, sounds like bush fix, it may work but not caused of better sealing to combustion, it should worse out that sealing situation caused by many time bigger area to be sealed than that orginal 8mm but there is one thing what on my opinion has been totally missed and what that teflon tape could on short term cure.

What if the issue on that is not gas leakage, but jiggering of whole injector as a result of combustion chamber high pressure pulses?

Seems to be that issue is escalating with boost pressures over 25 psi and that teflon wrap fix has been when there has been complains about injector bore been out of shape or loose.

I came to stupid taught, what if that big cylinder pressure is starting to resonate the whole injector against the injector holding clip, that could easily explain wear out injector hole, that for sure could cause very erratic injector behavings caused on movements inside of injector and it's needle. Area of injector is in size of 0.5cm2 (8mm cross section ) at injector injecton nose where that teflon seal sits so if there is some 100bar cylinder pressure at highest point, the spring has to be hold some 50kg force and i'm sure it does not withstand that without some warping or small resonation. What if the injector locking spring is orginally designed to work as some kind of hydrolock protector to give up after example double orginal cylinder pressure and designed to protect pistons and stock rods in a case of injector fairlure and pump combustion chamber full of gasoline? And then when we reach that level with double absolute charge pressure, what is in a level of prox 40psi compared to stock some 20psi abs, 14,7psi plus some 7 or 8 psi boost? Just playing with idea...like valve float, difficult to show out as small amount until it's sewere issue an can be heard.

On these n54, that resonating frequency is in a rateof 2500 to 4000hz, half of engine rpm so monitoring should on my opinion be done with high speed videocamera in a dyno under full pulls to se if there is a issue. That spring type injector holder is not to be seen in any diesels, tfsi, n55, b58 or other engine models so what if this is the real issue in these n54's and was at the beginning a idea of bmw engineers to do it as that mentioned protector cause it was their first di engine?
I think movement level to mesh up injector is in a level of 1mm or something so movement does not have to be even visible to eye without slow motion diagnostic video.

Easy fix for sure is stack 2 springs to clamp that injectors, doubling it's clamping force. Has anyone even tryed that?
I have a spare of those and for sure will throw them in to do road test to it but i don't have easy access to chassis dyno or high speed camera equipments to do real investigatios other than road tests.

On afr side to solve this issue, it seems to be regardless of afr, for sure very rich mixture is causing misfires but even of correct best power level afr or little on lean side of it, it seems to be a issue still having mystery misfires.

Next question, if that is dme related, then all with syvecs s6 or s7 should be without any misfire issue at all, is that the situation? If it is, then dig again us in to dme mosfets.

In some occations, there seems to be claims that weak battery is causing these kind of issues but
That should stress more generator than trig misfires if dme feed voltage stays on decent level.

For sure i know this is a network of different bus in these so maybe there is some relations caused of some mystery module like lfpf but i think it's long shot.


My setup starts to run to misfires in a region of prox 23-25 psi, tested 3 different injector packs, 3 different coil packs, both pr and n58 coil packs, slight different afr's, diferent plug gaps, different dwell table values, even p33p33 knowledge, and misfire is popping up somewhere in 6000-7100rpm at every pull with at least one gear recovered after second or two to normal again and to the point of misfire everything seems to be totally normal except ignition pulls
Propably related to some torque limit table, 6at (testing at the moment on 29psi and target at the end is 33psi with 1:1 boost exhaust pressure) what i think is a totally other issue.

That ignition pulls has been reported that is more prone on xi models, and if so, it can be related to noise from dront diff ve rwd cars, more than diferent in calibrations or something else, faulty prop shaft or half shafts can bring noise to oil pan what can trig it but on mine, i tested few pulls with knock deactivated at over 3500rpm and still puls so it's not knock in my situation.

Known trigger increaser is forged internals, check, high lift cams, check, closed deck, check, xi, check, so i have them all.


Taughts?, suggestions to keep my mouth shot? Ideas ? And yes, again, i know my english is not perfect so gramma lections suggestions don't belong here eather or could it be better to write on my natives Finnish or Swedish 😛
 
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Solution
“We choose to tune bmw n54 in this insanity and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one ... so.. is it even technically possible to increase that 1389 value or is only path port injection

Jeffman

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Soo.. tests continue, had issues on vanos, 1 filter clogged, that is solved and seems that engine perform better thqn ever assumed on transmission clutch pack E issue.

I ordered parts for trans so i think i can solve thqt too with little mods in clutch pack.


I had 0notl_wert 15 issues when this kas knock issues, now i got once 0notl_wert 13, what is that 13, it was on pull with slipping trans so it can be related to it and now i has no possibility to test it before trans upgrade.
Curious about your vanos filter that was clogged. Was this the first time you cleaned it? How many miles on the engine or since you last cleaned it?
 

135boost

Sergeant
Oct 28, 2017
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Yes, it was the first time i cleaned them, surpriced about one of them as it was totally clogged by something looking part of oil filter element. Engine is now on 150 000km.

Stupid me, i didn't know they even exist when i did my head.....

I should recieve new clutch packs with extra friction plates today so i can start with clutch pack mods,
 
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Sergeant
Oct 28, 2017
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So, transmission swap going on at the moment.

I modified zf6hp21 to inhale different clutch quantity and now there is 7pc E, 5pc A, 7pc B, 5pc C and 6pc D frictions.

On my knowledge, in rwd 6hp19 there is only prox 19-21 frictions and in 21 there is 22-24 so that 30 could be just enough to keep trans alive.

Next upgrade if this does not hold is some 6hp21/ 6hp26 mix
 
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Sausage

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To my experience, the clutch capability of the 19/21 is built by ZF to slip before breaking shafts. You can guess what will happen when you upgrade the clutches.
 

135boost

Sergeant
Oct 28, 2017
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Yes, i'm well aware of risk to brake that input shaft and this was to narrow safety margin between clutc slippage to brake shaft, maybe even overpass slippage and blow that shaft.

Idea is that if trans slip at 800nm and shaft is designed to withstand 900nm, this is now with 900nm clutch too

There is quite big differences on clutch packs in 19/21 and with same input shaft so on lower torque level trans it even should be safe to increase friction disks.
 
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Sergeant
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... and one pov on eather burning frictions or blown input shaft, both mean same 10 hour workload to take trans off the car, open it, fix and throw it back in my 4x4 setup, even prox same part cost so it's useless to leave fewer frictions as fuses in the trans.

I think i can manage to fit 8pc E, 6pc A, 8pc B, 6pc C and 7pc D with custom steels.. and that is huge increace in torque ability of zf6hp19/21. This 9hp21x has from factory higher 600nm torque rating than 19
 
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wheela

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... and one pov on eather burning frictions or blown input shaft, both mean same 10 hour workload to take trans off the car, open it, fix and throw it back in my 4x4 setup, even prox same part cost so it's useless to leave fewer frictions as fuses in the trans.

I think i can manage to fit 8pc E, 6pc A, 8pc B, 6pc C and 7pc D with custom steels.. and that is huge increace in torque ability of zf6hp19/21. This 9hp21x has from factory higher 600nm torque rating than 19
Sorry for the dumb question, is there an easy way to find out if one has the 19 or the 21? Is there certain transmission p/n's for each that you can check on realoem? Or maybe model/year, or rear drive vs. X-drive?
 

135boost

Sergeant
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At the moment it seems that trans work and don't slip.
I did some mistake during clearance in one of friction packs, rule, if you increase frictions, increase clearance too.
From reverse to forward this had some 0.5sec squeek sound at the beginning, but it dissapeared in few days of usage.

Now i had tested with first few 3rd to 4th flatouts with 30+psi boost and no slipping issuea so far, this rip stupidly hard with shifts at 7600-8000rpm
 

nyt

Sergeant
Sep 15, 2019
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rofl, you're brave. I have the nizpro billet shafts in my build with additional upgraded (alto) frictions and steels. Shifts hard at 38psi or so but I still worry about snapping those shafts.
 

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Sergeant
Oct 28, 2017
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😀😀

I saw spikes to 34.5 psi during shifts and yes, waiting for input shaft snaps..
Seems othervice than turbos that we have quite similair setups, what kind of power and torque levels do you archieve with that setup and how high do you rev it? I wanted to move rews higher up to reduce torque max values below some 900-950nm with that rpm shift.
I assume you can have even 150nm more torq but because that tiny 🥰 turbo, assume your powercurve flat out some 1000rpm sooner than mine with max power in some 7600rpm
I wanted smaller turbo powerband but did not figure out the way to solve long powerband and keep torque levels without sacrifice top end.



I have differ from yours there double hfpf, double g25 660,those are only 54mm's and with .72 ar but then i don'tdon't have jb4 and instead of pr coils i use b58 coils and my have big valves on heads, assume it's same with you too.
 
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nyt

Sergeant
Sep 15, 2019
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😀😀

I saw spikes to 34.5 psi during shifts and yes, waiting for input shaft snaps..
Seems othervice than turbos that we have quite similair setups, what kind of power and torque levels do you archieve with that setup and how high do you rev it? I wanted to move rews higher up to reduce torque max values below some 900-950nm with that rpm shift.
I assume you can have even 150nm more torq but because that tiny 🥰 turbo, assume your powercurve flat out some 1000rpm sooner than mine with max power in some 7600rpm
I wanted smaller turbo powerband but did not figure out the way to solve long powerband and keep torque levels without sacrifice top end.



I have differ from yours there double hfpf, double g25 660,those are only 54mm's and with .72 ar but then i don'tdon't have jb4 and instead of pr coils i use b58 coils and my have big valves on heads, assume it's same with you too.

I have my rev limit set at 7800 rpm. I shift around 7600 in first and second and like 7400ish otherwise. The stock exhaust is choking off the power up top and limiting to around 800. From memory, torque peaks around 950 ftlbs at 4500 rpm at like 38psi, and the power just holds flat around 800 until shift. Boost curve tapers from 36psi down to 25 psi up top to avoid issues with too much boost for the exhaust :( I like it quiet, but losing out on power. Car is trapping 138 at 2400 da according to dragy.
 
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135boost

Sergeant
Oct 28, 2017
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Yes, you have stupidly much torque, and like assumed, rev range is much lower than mine.
I like too quiet and thats why i built my own exhaust.
My peak torque is somewhere close to 5500rpm

I try to shortshift 1-2 before 6000, 2-3 before 7000 and 3-4 close to 8000.
I taper upward boost from some 28psi at 5000 level to over 30 at 7500.

Because of tuning issues regarding what we have been gone trough here there is none 1/4 mile with this engine, on unopened stock internals i got only 135mph trap on quarter.

I try today or tomorrow get one or two clean dragy 1/4 to do estimations of true 1/4 traps
 

nyt

Sergeant
Sep 15, 2019
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2010 335xi
Yes, you have stupidly much torque, and like assumed, rev range is much lower than mine.
I like too quiet and thats why i built my own exhaust.
My peak torque is somewhere close to 5500rpm

I try to shortshift 1-2 before 6000, 2-3 before 7000 and 3-4 close to 8000.
I taper upward boost from some 28psi at 5000 level to over 30 at 7500.

Because of tuning issues regarding what we have been gone trough here there is none 1/4 mile with this engine, on unopened stock internals i got only 135mph trap on quarter.

I try today or tomorrow get one or two clean dragy 1/4 to do estimations of true 1/4 traps

I need to replace my driveshaft so I can actually launch the car. With a 1.95 60', it ran 10.8 @ 138 in high heat/humidity on an unprepped surface. I reckon the car has high 9s in it as is, likely mid if I put a new exhaust on it.. The issue is, there are no aftermarket systems that are as quiet as it is now, and I don't have a lift to work on my own for another 6 months :(
 

135boost

Sergeant
Oct 28, 2017
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Long time gone again and some updates.

I blew my engine few weeks ago on dyno, crank and main bearings gone.
Noticed issue in time so crank lived that without issue but it piled me some extra work.

Issue started with reduced oil pressure and vanos fails so we stopped dyno pulls and i started to do some
Diagnose work. It showed that oil pressure variate from 0.5 to 1.2bar so i opened the engine, 4x4 so it's not the easiest
And my turbo setups does it even more messy to do.

What i foudn was little disturbing, never taught it before but there is 3 small m6 bolt keeping oil and fuel pump chain guard back plate in place, those are weak and 8000 rewwing engine with very high fuel pressure put them in much more stress that intended with all kind of vibrations. Those was broke, back plate loose and both plastic guards fell to oil sump and chain was loose enough then to cause issues.

My strong advice, if you open oil sump, change those 3 small bolts to steel ones.
 
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Jeffman

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Thanks. It’s good to hear from you. Sorry about your motor, but thanks for the advice. I wish I had seen this 14 months ago when I did my oil pan gasket (also xi - what a pain).
Be well.