Not 100% healthy N55?

[NonoxX]

Hi!
Lately I’ve been doing pulls to compare MHD Stage 2+ against various fuels available here.
During that, I noticed that whatever I do, I get significant amount of timing pulled.
Here’s an example running Aral 102 (probably the best quality gas here) with the 102 map: https://datazap.me/u/nonoxx/log-1687...?log=0&data=11
Another one with RON 95 (and the right map used): https://datazap.me/u/nonoxx/log-1686...?log=0&data=11

I know cylinder timing 5 pulls are a thing on our cars, here I also have a significant amount of cylinder 6 corrections all along the RPM range, and various (but small) corrections in high RPM.

I’ve used those logs in virtual dyno and I get 317whp on 95 and 300whp on 102, which makes no sense to me…

Do you think I should investigate on my car?
Any idea of what commonly triggers that?

FYI: Car is FBO. HPFP, injectors, plugs and coils have a bit less than 30000km (changed last year).

Thanks a lot for your support crazy people!

[NonoxX]

Some more news... Bad ones.

TLDR; I get pretty strong misfires now on WOT, with blinking CEL. On the diag I mostly get cylinder 6 misfire codes (2EF4 / 2F04) and "several cylinder" misfire. I saw once cylinder 3 in addition to cylinder 6.

Let me tell you the whole story since last time.

Our Aral RON 102 is normally good stuff, so I wanted to make extra sure, so I chose a not too warm morning (about 25°C), warmed up the car an went for 3 pulls with a tank full of 102, and 3 different MHD maps: RON 95, RON 98 and RON 102.

https://datazap.me/u/nonoxx/fuel-comparison

95 is 100% clean. I only get corrections before the pull, which is supposed to happen.

98 just has some amount of correction on cylinder 6, so this cylinder is definitely a bit more sensitive, but nothing I'd worry about, I still call that a quite clean log.

102 shows corrections everywhere. It is obviously fuel related, I should just keep the 98 map with this fuel, or maybe add a touch of ethanol.

Still I wasn't reassured and as I told you I had suspicion on cylinder 6 before, so I have done a swap:
Spark plugs 1 <=> 5, 2 <=> 6 and coils 3 <=> 5; 4 <=> 6.

https://datazap.me/u/nonoxx/log-1687549422

Still pulls timing everywhere, and I realize now I was still on 102 map, so this test doesn't reveal anything... Comparison with 98 map would have been smarter... Anyway!

Problem doesn't seem to move the issue. All 6 injectors are pretty new (last year), I am not really suspecting them.

I wanted to give E30 a try, using the appropriate map, just to see how it behaves: and it went perfectly.
https://datazap.me/u/nonoxx/log-1687...21-22-23-24-25

Just a little timing correction on cylinder 3 at the highest RPMs, everything else being super clean, plus the car pulls hard and feels smooth. OK, I'll keep driving that mix for a while.

One or two days after, while I was on the highway, driving moderately but accelerating quite strong (say 80%) after a construction zone, the car shuttered and got blinking CEL. I stopped and read diagnostics, it was "just" misfires on cylinder 6. Bad news is that it now happens every time I as for heavy load (80% to WOT), whatever the RPM. I could catch it on a log:

https://datazap.me/u/nonoxx/misfires...2.5&tmax=595.5

You can see on my log that cylinder 6 gets 7.2° pulled, and the DME maintains that pull, until it really fail (see the throttle cut at 4100RPM).
If I compare AFR to the "good" E30 pull, I can see that it was a bit lower during this pull, and it kept going down as the RPM increased. On the failed pull, I can see it climb to 15.5 when the DME starts pulling timing, and it never really goes below 14.

Rail pressure is always above 180 bar (2500 psi) during the pull, so my HPFP / LPFP pair have no trouble to keep up.

I'm pretty lost with that... Could it just be an injector again? Do you have experience with that?

[wheela]

I'd check to make sure the coil is still seated well on the plug for 6, and also make sure plug 6 is properly torqued.

I developed a misfire on 5 that was similar, where just driving around was okay, but getting on the gas triggered misfire and injector disable and I'd have to pull over to restart the car. I assumed bad coils and bought a new set. I went to swap them in, and saw that somehow the coil for 5 had popped up slightly, so it could arc across and run the car at normal conditions, but couldn't handle higher loads. Also noticed that plug was loose, so I suspect maybe some combustion gas leaked past the plug and popped the coil loose. Since I had new coils I went ahead and swapped them out anyway, but I bet I would have been fine just re-torquing the plug and re-seating the coil.

[NonoxX]

Hi, wheela and thanks for your reply.

I made another test today, so I am sure the coil sits correctly on the plug, as I've been extra careful really pushing on it and pushing the connector into it (those are easy to get slightly wrong). What I didn't test though is the spark plug is properly torqued, although I always torque my plugs with a calibrated wrench, which I dit when I swapped them less than a week ago (23Nm), so there's no apparent reason for it to fail.

I started to blame injector 6. So just in case I made the test to swap injector 5-6 with injectors 1-2, and code the calibrations accordingly. The problem stayed on cylinder 6, and as I suspected my injectors are probably good.

This weekend I'll change the spark plugs, just to make sure as it doesn't cost much, and perform a compression test. I'm afraid of one thing is to fall into that case:
https://www.1addicts.com/forums/show...&postcount=124
That guy had a loose head bolt, and although it is pretty rare, it also seemed to happen to another guy. On of them had build date 01/2010, the other one 04/2010... Mine is a 03/2010....
Another sign is that my car has been burning coolant without any apparent reason for some time. The car doesn't give off white smoke of whatever, but if it only happens under heavy load, I could just not see it.
I also had the coolant tank replaced (because it cracked) and hose also gave up at some point... Could it be linked to overpressure due to loose head bolts? Or a slightly leaky head gasket?
I can't see any trace of water in the oil though.

[NonoxX]

OK I got it!
Plug on cylinder 6 had a carbon track on the ceramic due to arcing.


I'm not sure how is it possible that I missed it first time, and also that this problem didn't move while swapping plugs and coils... Still here we are.

I got a brand new set of NGK 97506, gapped them to 0.022" and called it a day. Car runs perfectly fine now!

[wheela]

Glad you got it sorted, thanks for following up with the cause!

Question - in addition to fixing the misfires, new plugs also fixed the timing corrections you were seeing? I can understand misfires, but was always a bit skeptical regarding timing corrections. I'm not happy with my corrections - currently running fresh (<5000 miles) on oem plugs, with MHD stage 2+ 93oct map. I have a new set of 97506 collecting dust, perhaps I should just gap them and throw them now and see if I notice a difference...

[NonoxX]

No it did not solve the initial problem that I have more corrections on cylinder 6 than on others.

There's only reason I could see spark plugs would lead to correction: pre-ignition due to too hot plugs. That's why I took the opportunity to switch to NGK 97506 (1 step colder) instead of stock ones.

https://datazap.me/u/nonoxx/log-1688...27-28-29-30-31

Here's a pull I've done since the spark plugs were changed. i'm purposely starting in low RPM to trigger potential issues. You can see that only cylinder 6 has timing corrections, and those are pretty high (up to -6.4).

The temperature was 18C so there's no reason the car pulls timing, provided that the fuel was obviously good quality (other cylinders are fine).

I can see that my log has quit a bit difference between the boost target and the actual boost (1.15 bar vs 1.35 bar at 5000RPM), but after converting to PSI... It is 19 PSI target, does MHD really expect the turbo to hold 19 PSI to 5000RPM? I can't believe it.

[NonoxX]

Hi guys,

Just a quick follow-up on the assertion that my car isn't healthy. My car had to go through inspection so I had to make it compliant for emissions test, and installed the stock cat back on it with stock map. I made pulls with virtual dyno, so no absolute figures but it gives a good idea, only thing is that my weight is accurate as I used the value measured during the tests.

On stock map I get 273whp and 400Nm estimated, which is pretty close to what I should expect.

On Stage 2+ map I get 340whp (+25%) and 571Nm (+42%) which is a more than nice increase, not that far from what MHD advertises.

Only thing I don't like (and never did) on stage 2+ is the "low" torque at high RPM... Plan is to fix that with PS2 or Pure 500, can't decide which one is for me yet...