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View Full Version : Why does changing VVT settings affect Shifting of an A6?


MN C5
September 1st, 2009, 01:16 PM
Like the title says after swapping to a TVS blower intake I was having issues with the trans shifting early and having it stack shifts together. At times it would be in 4th gear before I cleared an intersection at light throttle. To eliminate the issues I had to zero the VVT tables.

My guess is that it has something to do with MAP but the TCM has no provisions for MAP vs. anything that would vary shifting.

Does anyone have any ideas on this?


Thanks

Dennis
RonC
September 1st, 2009, 04:58 PM
The stock VVT tables have a lot of cam retard at light throttle that might do that. That can't be good for performance.

By zeroing out the tables, do you mean making them all zero? Or just taking out the hi-retard "blob" area and filling it in with "normal" numbers like the rest in the rows, which is what I did? That worked well for me but I don't have boost.
MN C5
September 3rd, 2009, 04:57 PM
I had some issues prior to boosting it too. With a large cam it would not shift correctly either. But since supercharging I'm convinced that MAP must have some influence over shifting. It may not be a direct relationship to MAP but something affects shifting with cam retard.

The peaks at part throttle are for gas mileage I think....
GMPX
September 3rd, 2009, 05:00 PM
It is probably affecting the calculated torque figure the ECM sends to the TCM.
MN C5
September 3rd, 2009, 08:00 PM
Humm.... I'll have to think of a work around as I've shut all TQ control off. And set other variables to their Max values... :doh2: Some times it isn't easy but its always fun:grin:
CalEditor
September 10th, 2009, 11:02 AM
is the MAF xfer calibrated?
MN C5
September 10th, 2009, 01:30 PM
is the MAF xfer calibrated?

I don't know for sure what is the "MAF xfer"?
Redline Motorsports
September 10th, 2009, 04:32 PM
It is probably affecting the calculated torque figure the ECM sends to the TCM.

Thats exactly the problem. The A6 looks at engine load (dyn/cyl air) and uses that data to calculate estimated torque valves. These values are then weighed into the T43's calculation for shift characteristics.

The tables effected by dyn/cyl air need to be scaled much the sames as you would do for larger injectors.

Howard
MN C5
September 16th, 2009, 03:00 PM
Thats exactly the problem. The A6 looks at engine load (dyn/cyl air) and uses that data to calculate estimated torque valves. These values are then weighed into the T43's calculation for shift characteristics.

The tables effected by dyn/cyl air need to be scaled much the sames as you would do for larger injectors.

Howard

Which TCM tables are affected by dyn/cyl air? You lost me, did I miss an update with more tables..

Thanks