ECU pulling lots of timing in cylinder 5

[Cpt_Rum-bo]

Hey,

I've tried multiple tunes on this car (cobb OTS Stage 2 93, Cobb OTS E30 and my own custom E30 tune starting with Cobb's OTS E30 as a base) and they all result in the same issue. Lots of timing pulls in cylinder 5. Every other cylinder usually has very minor or 0 corrections.

Car has BMS DCI and Chargepipe, Mech Tuning 5" IC, VRSF catless DP and a custom catback.

I already swapped injectors, ignition coils and spark plugs with cylinder 1 which never had any corrections and it still stayed in cylinder 5.

Logs attached.

Any help is much appreciated.

[Pig Farmer]

I seem to recall someone mentioning that you are more likely to see timing pulled on cylinder 5 do to the location of the where the PCV valve dumps into the intake manifold. The theory being that the oil vapors coming from the crank case lowers the octane in cylinder 5. I can't confirm this, but it may give you a place to start looking. In other words, you may have a bad PCV valve?

[Cpt_Rum-bo]

Thanks a lot, will check it out.

[spxxx]

Originally Posted by Cpt_Rum-bo

Thanks a lot, will check it out.

This is well documented on n54tech... No one really knows is the answer lol. It's so sad because some people are seeing this with low timing maps (7* max) and even with 100% E85. It may be related to false knock or overly sensitive knock sensors. My guess is also PCV recirculation occurring above cyl5. Have you gotten walnut blasted?

[Cpt_Rum-bo]

Originally Posted by spxxx

This is well documented on n54tech... No one really knows is the answer lol. It's so sad because some people are seeing this with low timing maps (7* max) and even with 100% E85. It may be related to false knock or overly sensitive knock sensors. My guess is also PCV recirculation occurring above cyl5. Have you gotten walnut blasted?

Yeah, i've read so many threads with no conclusive results. I'm going to do each one and see which fixes it so hopefully we can have something concrete.

1st replace plugs
2nd replace pcv
3rd walnut blast

[spxxx]

Consider swapping coils and possibly replacing valve cover as PCV channels may be clogged.

[Cpt_Rum-bo]

Originally Posted by spxxx

Consider swapping coils and possibly replacing valve cover as PCV channels may be clogged.

I already swapped coils and injectors.

[mike@x-ph.com]

As mentioned above cylinder 5 is very sensitive to timing drops and unfortunately there is no fix to it at the moment. you either ignore it at your own risk or run a more conservative map.
Im having problems seeing your log so i cannot tell how bad these drops are.
It would be very helpful if you can post it on datazap

[Cpt_Rum-bo]

Just to keep this updated, in the event I find a fix. Didn't change anything with the car and decided to do a couple logs over the weekend. Only difference is it's much warmer than the previous days I logged.

In terms of the results,h alf of the logs were completely clean and half had -3 degrees of timing in cylinder 5 from ~5300RPMS with it tapering of to 0 by redline. So it's much better for no reason besides the warmer temps .... sigh!!!!

I'm installing upgraded PCV tomorrow.

[Cpt_Rum-bo]

Installed PCV valve and timing corrections in cylinder 5 are not happening anymore after multiple logs.

[Mike@N54Tuning.com]

Originally Posted by Cpt_Rum-bo

Installed PCV valve and timing corrections in cylinder 5 are not happening anymore after multiple logs.

Thanks for reporting back. Thats a useful piece of data. Maybe log again in a few days / week to see if it stays clean.

Mike

[Cpt_Rum-bo]

Originally Posted by Mike@N54Tuning.com

Thanks for reporting back. Thats a useful piece of data. Maybe log again in a few days / week to see if it stays clean.

Mike

Yeah, I'm going to. I've done 2 sessions already and so far so good. Will definitely keep this updated.

[Cpt_Rum-bo]

Changed valve cover gasket and went back to E30. Logged and no corrections in cylinder 5. I tune myself, so started increasing load. Went to log and there are corrections in cylinder 5 again .. sighhhhhhhh

[135Pats]

My *guess* has always been that's it's the cylinder which sees the most direct airflow from the manifold. The stock intake mani is awful, i'd love to see flow distribution by cylinder but a quick once over shows that it's far from optimal. Cyl 5 is almost always the noisiest on these motors.

What do the other cylinders look like? What does the global timing curve look like? Some corrections across a single cylinder are not at all uncommon, and don't mean anything is "wrong" automatically.

[Cpt_Rum-bo]

Originally Posted by 135Pats

My *guess* has always been that's it's the cylinder which sees the most direct airflow from the manifold. The stock intake mani is awful, i'd love to see flow distribution by cylinder but a quick once over shows that it's far from optimal. Cyl 5 is almost always the noisiest on these motors.

What do the other cylinders look like? What does the global timing curve look like? Some corrections across a single cylinder are not at all uncommon, and don't mean anything is "wrong" automatically.

So you're saying it's getting more air than the others which triggers a lean condition?

The other cylinders have 0 corrections.

[135Pats]

Originally Posted by Cpt_Rum-bo

So you're saying it's getting more air than the others which triggers a lean condition?

The other cylinders have 0 corrections.

The DME does an outstanding job of monitoring and adjusting AFR by bank - it has no ability to see or understand AFR by cylinder. I'm not sure as to whether Cyl. 5 runs a touch lean, bank 2 has never shown consistently leaner conditions but the DME's behavior would be to simply richen up Cyls. 4 and 6 in the event that 5 went lean. So far as it's concerned all is well, even though Cyl. 5 is not happy the bank is hitting lambda.

That's speculation on my part, to be clear.

If you are only seeing corrections on Cyl. 5 and global timing looks good, you are probably just fine. A log with 0 corrections at any point across any cylinder is tough to pull off on the street.

[Cpt_Rum-bo]

Originally Posted by 135Pats

The DME does an outstanding job of monitoring and adjusting AFR by bank - it has no ability to see or understand AFR by cylinder. I'm not sure as to whether Cyl. 5 runs a touch lean, bank 2 has never shown consistently leaner conditions but the DME's behavior would be to simply richen up Cyls. 4 and 6 in the event that 5 went lean. So far as it's concerned all is well, even though Cyl. 5 is not happy the bank is hitting lambda.

That's speculation on my part, to be clear.

If you are only seeing corrections on Cyl. 5 and global timing looks good, you are probably just fine. A log with 0 corrections at any point across any cylinder is tough to pull off on the street.

Ok. I have a couple things I want to try. Will post results after I've tried them.

[Cpt_Rum-bo]

Update:

I changed valve cover gasket and still had the same problems. After some reading, I decided to make some VANOS Intake and Exhaust changes which so far is yielding positive results. Logs attached.

[Cpt_Rum-bo]

Corrections are now gone with the changes to Intake Vanos and going back to the stock values for Torque Eff Divisor (Fuel).

[Rob.K]

What sort of changes did you make Cpt?

[135Pats]

Originally Posted by Cpt_Rum-bo

Corrections are now gone with the changes to Intake Vanos and going back to the stock values for Torque Eff Divisor (Fuel).

Did you lessen the duration?

Again going back to my theory (it's not "mine", just what I believe to be the root cause), i'd imagine it's an airflow issue. CYL. 5 gets fed the most direct charge relative to the other cylinders. So curious what you did on the VANOS side.

[Cpt_Rum-bo]

What works best for me was advancing the intake degrees so that it opens earlier and reduces the Intake/Exhaust overlap. Pic of my changes attached.