Feature suggestion for MShift

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
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Philip Lochner
Posts: 34
Joined: Thu Mar 08, 2012 9:00 am

Feature suggestion for MShift

Post by Philip Lochner » Wed Jul 01, 2015 10:48 pm

Just a suggestion:

I live in an area with many "traffic calming speed bumps". This requires frequent reduction in speed after obtaining Vmax from the previous speed bump. My daughter's S40 Volvo is most frustrating in this area as it only initiates a shift to the correct gear AFTER crossing over the speed bump. My wife's VW DSG based car gets into the right gear BEFORE the speed bump - awesome. I want it the same in my 4L60e implementation - BEFORE the speed bump.

One method of achieving this is to bring the downshift point earlier (at a higher speed than required by the gear map) based on the derivative of the vehicle speed, VssDot. The faster you decelerate (the more negative VssDot), the earlier it downshifts, all tuneable of course. This would also result in the box behaving more sporty the sportier you drive - without map switching.
Best regards
Philip
'80 Jaguar XJS 5.3L V12 = MS-2
'74 Jensen Interceptor Mk3 440 V8 = MS-2 + GPIO (GM 4L60e)

Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Feature suggestion for MShift

Post by Bernard Fife » Thu Jul 02, 2015 6:22 am

Philip,

This is an interesting idea. It should be 'doable', but will have to be carefully implemented so that it doesn't screw other things up. I'll try to come up with a plan for this.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw

Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Feature suggestion for MShift

Post by Bernard Fife » Thu Jul 02, 2015 6:45 am

Philip,

One thing I forgot to mention is that this desired behavior is contrary to the 'decel mode' behavior that is the default for the code. The decel mode prevents downshifts when decelerating.

Decel mode wasn't originally in the code, and isn't something I would ever use, but other users wanted it so that the trans downshifts would be more 'OEM-like'. But decel mode makes the trans much less responsive and less 'sporty'.

So one thing you might do, if you haven't already, is disable decel mode under 'Throttle and Load Factors'. Setting the 'Max. sLoad' to zero (0) disables decel mode completely. There is more on this here: http://www.msgpio.com/manuals/mshift/V5tune.html#gh (you have to scroll down a bit).

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw

Philip Lochner
Posts: 34
Joined: Thu Mar 08, 2012 9:00 am

Re: Feature suggestion for MShift

Post by Philip Lochner » Thu Jul 02, 2015 10:31 am

Thanks Lance

I appreciate the tip :D

May I point out that this idea of VssDot could possibly tie in very nicely with the suggestion I present this thread: viewtopic.php?f=4&t=1021

A simple VssDot graph could then adjust the downshift speed bin value upwards for the shift bin which is being moved to.
Best regards
Philip
'80 Jaguar XJS 5.3L V12 = MS-2
'74 Jensen Interceptor Mk3 440 V8 = MS-2 + GPIO (GM 4L60e)

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