The Return Of The TCS Patch Issues

[swingtan]

Some time back I posted a thread on some timing issues that I believed were related to the TCS MAFless patches.

http://forum.efilive.com/showthread.php?t=7401

The solution in this case was to remove spark smoothing, which was causing some weired timing problems.

Over the past few weeks I've been battling with a rather strange issue that again seems to be TCS Patch related. It's still a stutter issue with leads me to think that spark smoothing was not the real cause of the original problem, but possibly how the patch was working. Here's the point form of what I've seen.

Vehicle is a VZ L76 M6 with 4>1 longs and a 2.5" twin system. the rest is stock apart from the tune.


When cresting a hill in a high gear ( 5th or 6th ) and I come off the throttle a bit so as not to start building speed, The car feels like it hits a wall for a split second and then continues on. Sometimes there is a very small amount of bucking involved, but normally it's a single hit. This is quite easy to reproduce by simply pressing on the throttle and releasing it, not quite all the way. See log Stutter_01.efi and Stutter_02.efi

When applying very light throttle, the car car start some serious bucking, to the point where you can hear the slack in the drive train being taken up as it goes from drive to overdrive and back again. this can also be invoked by turning of DFCO and applying a very small amount of throttle when coating down a hill. See log Stutter_03.efi


The similarities with the original thread are numerous,


Only occurs at light throttle.
Commanded spark is oscillating up to 12'.
Removing the TCS patches also removes the symptoms.
Changing the settings for spark smoothing has no effect at all.


I've tried a large number of things in an attempt to stop this.


Varied the high / low spark tables in the effected cells between 16' and 45'
Varied the idle spark table between 16' and 45'
Varied the coast down spark table between 16' and 45'
Varied the DFCO spark timings and entry timings
Varied the torque management settings
Varied the TCS settings including turning TCS off at the switch


All this had minimal if any effect on the problem. The only thing that has made a difference is to remove the TCS patches completely, which has completely removed the problem. So I still believe that there are issues with the TCS patches, at least for my OS - 12607218.

Comments anyone?

Simon.

EDIT: Sorry, I just realised I should have posted this in the E38 section. Mods, please move it if required.

[swingtan]

OK, I here by eat at least some of the words above.....

I did a fair bit more testing this afternoon and was able to get the stutter to reoccur with no TCS patches in place. However, it was much harder to achieve and the effects were not as severe as previous. My new thoughts on this are that the the ECM is dropping momentarily to the Base Idle table (B5104), due at least in part to the low RPM when the stutter occurs. I'm going to try and boost the idle spark table to see if that helps.

Given that the effects were much harder to reproduce, I still think that the TCS patches still had some effect. Perhaps they were amplifying the spark oscillation? I'm still interested in other opinions though.

Here's a log from todays test.

Simon

[gmh308]

OK, I here by eat at least some of the words above.....

I did a fair bit more testing this afternoon and was able to get the stutter to reoccur with no TCS patches in place. However, it was much harder to achieve and the effects were not as severe as previous. My new thoughts on this are that the the ECM is dropping momentarily to the Base Idle table (B5104), due at least in part to the low RPM when the stutter occurs. I'm going to try and boost the idle spark table to see if that helps.

Given that the effects were much harder to reproduce, I still think that the TCS patches still had some effect. Perhaps they were amplifying the spark oscillation? I'm still interested in other opinions though.

Here's a log from todays test.

Simon

Very interesing. I get very similar on an E38 which is largely "stock". Without TCS patch. Occurs between 1050-1250 rpm. Coasting throttle. Can be in CL or OL at the time, but is certainly around an OL <> CL transition point. i.e. on the edge of DFCO maybe. At times it appears to occur as it transitions out of CL and then OL is too lean (etc). Though clearly your events are MAF less.

Have been logging to try and get some focus on the right area before commencing any potential changes. Maybe not related, but certainly similr effects.

Cheers.

[swingtan]

Yes, it sounds very similar.


It's NOT the TCS patches though, at least not solely the TCS patches. I've removed them and tested and it's harder to make it happen, but it's still there. TCS patches back on simply makes it easier to achieve the issue.

I've tried mixtures, richer and leaner and no change was seen. I've tried main spark, higher and lower... no change. I've set the idle spark, coast down spark, higher and low table all to the same in those areas and no change!

I've come to the point where I want to put the MAF back in the loop to see if that changes it. But for this one issue, I'm really happy with how the car is running. I even got the lifters to quieten down after re-seating the rockers!

Simon.

[gmh308]

I even got the lifters to quieten down after re-seating the rockers!

Simon.

That's interesting!

[swingtan]

OK, a very quick update. I've finally found the problem and it's all related to PE exiting. For some reason, timing is pulled when exiting PE. It occurs 90% of the time and can pull as much as 15' of timing, making driving rather interesting. I've now removed PE entirely from the tune and am just running enrichment via B0148. This seems to be working very well.

I think there may be a PE exit spark table, or maybe it's got something to do with the ECM dropping into CL as it exits PE, then it fails the O2's and returns to OL, causing some timing issues on the transition. More work is needed.

I'll check back when I get 'Net access next.....

Simon