MS6 Shift Stutter Fix - How To w/Cobb Tuning AccessTuner

[ms3blackmica]

As most of you may know, @Cobb Tuning; has recently released access to some BETA tables in AccessTuner build 1.9.1.0-9908 (Build Date March 3, 2015).

Of these tables, there is one in particular which relates to a Shift Timer based on actual Engine RPM and the Currently Driven Gear.

You can find access to this table by opening the "Beta Tables" Folder ---> "Shift Timer".



*Notice I
These tables are BETA for a reason. Although the MS6 vehicles have the same ROM between the years, variations in the operating system between various production dates can exist. This means that what has worked for me, might not work for you, and in that case you must alter the table data accordingly. MS6's have a different shift logic algorithm than the MS3 vehicles.

*Notice II
Do not edit this table if your MS6 vehicle does not experience any sort of post shift stutter unless you have fully tested the effects of your changes to ensure a better shift experience/response.

"If it ain't broke, don't fix it."




Below is a snapshot of this table in OEM form with stock data.




I have been doing quite a bit of BETA testing on this table in every way possible on a select few MS6 vehicles that I have access to. One of these test vehicles is plagued by the "MS6 Shift Stutter" while the other has no issue at all.

The Shift Timer is exactly as it's name suggests, a timer. This timer is a down counter or "delay" to which normal engine operation will be resumed. Based on my experience through testing and analyzing the data, I believe these values to be in units of milliseconds (ms).

Reducing the amount of time that the timer is allowed to count reduces the severity of the stutter. Increasing the amount of time that the timer is allowed to count results in an even greater delay between gear changes yielding a very undesirable driving experience.

I was able to create a severe stutter on an MS6 vehicle that had no issues at all by increasing the timer units significantly.



After testing multiple vehicles, I have found that the table structure below is best suited for entirely removing the "Shift Stutter". I would not set the entire table to 0 especially in the lower RPM range unless you have confirmed that ill effects or unwanted response between low RPM gear changes do not occur.





If you want to better understand how the timer affects the shift logic, set the table to 60 or 80 units all the way to 7000 RPM in every gear and you will discover a very massive (not harmful) stutter in between gear changes.

This will help you better understand how the timer affects engine operation during a shift event.

[Rich990]

Thanks Nishan, and thanks Cobb!

[mrmonk7663]

Nice work sir.

[udntknw]

Very awesome!

[El Beaner]

@texas_wizard I think this was the isue for the stutter you had during our runs.

[Lex]

Good writeup on this. What I find quite interesting is that as you mentioned some cars experience this and some don't. Most Gen1 MS3s don't and the tables in the ROMs available from COBB have the same values.

It looks like other areas of the tune (such as the fuelling and timing) during shifting as well as modifications and driving style can exacerbate the condition or make it less noticeable.

[Dizzy Turbo]

@f15ms6;

[f15ms6]

Originally Posted by Dizzy Turbo @f15ms6;

Thanks for the heads up, I am using the ots stage 1 right now, so I am going to pay attention to this numbers once I start tuning

[ItsNox]

OH MY GOD THANK YOU @ms3blackmica; & @Cobb Tuning;

Sent via Tapafail

[Caldazar]

nice to see Cobb still actively working on this program. Hadn't seen an update(non beta) in a year so I figured it was not being developed anymore.

[udntknw]

This was the last, for a long while.