N54 N54 have I sabotaged my own tune?

[Maroon_e90]

Hey all,

For as long as I have owned my car I have battled a high RPM misfire. At first I thought it was due to my dual mass flywheel, well changed that and the problem stayed. Ive gone through at least 50 spark plugs and that doesnt seem to be it either. I decided to install b58 coils well that didnt fix it either. I have changed injectors, no dice. Rebuilt the motor and cleaned the head still got the same problem. Pretty much I am at my wits end, and it finally dawned on me that maybe I am messing my own tuning up.

So if it wouldnt be too much of a hassle could someone with more experience in this subject take a look through my bin file and maybe see if I have made a mistake anywhere? please see latest log below.

Also the tune is for 93 octane but I am running race gas in the log.

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[wheela]

Not sure if it's related to your misfire, but that timing value seems very low. Guessing at that boost with 93 you're at the edge of timing corrections. I wonder if you'd do better reducing boost a bit until you can run at least 4 degrees? What are your build details?

 

[Maroon_e90]

Not sure if it's related to your misfire, but that timing value seems very low. Guessing at that boost with 93 you're at the edge of timing corrections. I wonder if you'd do better reducing boost a bit until you can run at least 4 degrees? What are your build details?

I know what you mean I’ve tried to reduce boost and increase timing but that approach doesn’t work either. Seems anytime I go over 4-5 degrees of timing it has a ton of corrections at least this was the case when I ran like 18 psi or something. It’s also worth noting 100 octane race gas is correcting so much.

It’s a built bottom end, stock head, speed tech bottom mount single turbo. Charge pipe injection kit. New Stock hpfp. Motor build has maybe 3k miles.

 

[wheela]

Are you feeling the misfires or getting misfires codes? Out of curiosity, what turbo are you running?

 

[Maroon_e90]

I’m not feeling the misfires at all, and there is no misfire codes. It’s just like somewhere around 6000-7000 rpm it goes fuel mode 15 and deactivates some cylinder although I have no idea which one since there is not codes ever. The turbo is a tx6662 .84 ar

 

[Brule]

Your afr go to 13.9 while your still 100% throttle after 6000rpm.

Your lpfp spikes to much and when it spikes into the 60s-90s its hard for dme to keep up and is on edge of hitting limp mode multiple times.

Timing is very low even for even low bad fuel. Requiring it that low is masking a tuning or mechanical problem. Especiallu if your on 100 octane.

With built motor knock sensors maybe to sensitive.

IAT falls very quick when on boost do you have a shit ton of meth flowing?

 

[Brule]

Just read your post again and seen "chargepipe injection".
Thats one problem.
Uneven distrubution.

Your lpfp and hpfp can generally support around 20-22psi on smaller turbos like 6266 6466.

Above that all fuel is being used from your meth or whatever fuel your spraying in the charge pipe.

For example you make 550hp on 21psi boost your lpfp and hpfp then you put the boost up to 27psi and make 640hp.

Your fueling 6psi extra boost thats 90hp of fuel injected unevenly through your chargrpipe.

 

[Maroon_e90]

Thanks for pointing this out. I’d still love to get some tune verification, but I’ll disable the charge pipe injection and drop boost to 20 psi. Maybe dial in some timing or actually reach redline. This should also help resolve the LPFP oscillations.

Some questions though

With CPI, does the DME realize it can’t control AFR predictably across cylinders (due to uneven distribution) and then go into a fuel safety mode that deactivates a cylinder?

Or is this simply the result of a misfire threshold being exceeded because one or more cylinders are too lean or too rich due to uneven fuel distribution?

 

[Brule]

lpfp oscilations are normally from an afyermarket fuel pump through a stock regulator or a dead head fuel line.

Your dme can just average bank 1 and bank 2 cylinders. So cylinder 1 might not be getting 5% of cpi but cylinder 2 3 4 5 6 are getting 19% each but dme will just read afr of bank 1 is 10% lean and stft will add extra 10% on bank 1. (edited you only have single bank so you cant see if any cylinder is lean or rich)

Its a well known problem with spraying fuel in chargepipe.

From that log 6300 and up is going lean Not sure why ill look at map later.

 

[Brule]

Your knock factor is very high from 6240-7000.

The rest of the cells are same or a bit higher then a bms single turbo flash.

 

[carabuser]

The knock tables won't have much of an effect on the misfire detection, they are 2 separate functions in the DME. Misfire is primarily detected by crank rotation and O2 sensors. Also the knock tables do not alter the DME response to excessive knock, they just change the amount of correction applied, so if you get a ton on knock the DME will still go into a limp mode.

There is individual cylinder balancing in the DME. It has a per cylinder fuel adaptation value for injection amount. I doubt that would be able to handle an imbalance caused by external fuelling though, it's just designed to compensate for stock variances in the air and fuel.

 

[Maroon_e90]

This is good to know, a safe assumption that cpi is causing this.

So is my car going into fuel mode 15 because of repeated knock then? Which is why it’s not registering as a misfire?

 

[carabuser]

This is good to know, a safe assumption that cpi is causing this.

So is my car going into fuel mode 15 because of repeated knock then? Which is why it’s not registering as a misfire?

From memory, fuel mode 15 is emergency mode and has quite a few different triggers.

There's a few triggers for knock, they wouldn’t all create a code. Some are based of outright voltages of the knock sensors, some are a rolling total of noise, then you have pre and post ignition knock.

The DME only logs a code with misfire or knock when things get really bad. You can log all the different triggers of fuel mode 15, but looking at the chargepipe injection first is easier.

If I wanted to go past the stock fuel system limits, I'd first get one of those hydra HPFP overdrive kits and max the DI out before putting any port injection in.

 

[Maroon_e90]

I was able to get an hour to do some runs. This is the best I could get in about an hour of tuning. However I am very pleased to share the engine revs all the way up to 7200. no misfires or cyl shutdown. Its odd to me the stock hpfp cant even handle 19 psi of boost though. The rail pressure takes a nose dive at 6300 so I need to definitely upgrade hpfp. Thanks for all the help in finidng this.

Now any ideas why my car hates timing?

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[wheela]

Seems like your timing corrections get really bad at the point where your rail pressure tanks down to around 1100psi. Not sure if it's related or coincidence, but maybe corrections are from poorer fuel atomization from the lower rail pressure?

 

[Maroon_e90]

I 100% agree I will be ordering the hydra sprocket kit, install and follow up from there