WOT odd shifting behaviors

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

Re: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

The target gear is based on the average load ("avload" in the datalog) rather than the instantaneous load ("load"). Average load is crucial with MAP signals (which can bounce around a fair bit) but TPS tends to be more stable.

There are a number of factors that affect the load averaging. If you want the target gear to follow the instant load more closely (i.e. drop quickly when you let off the throttle), you have to reduce the averaging (aka. "smoothing").

These factors are 'load smoothing factors" (under 'General Settings -> Throttle and Load Factors') and you can read about them here: http://www.msgpio.com/manuals/mshift/V5tune.html#gh (I realize they are a fairly complex set of parameters, but users have found them necessary). I would start by changing the:

Load Smoothing Factor from 1000 to 250,
Load Smoothing w/ Braking too 'Usual Rate while Braking'

and then look at experimenting some of the other load parameters on that menu.

You can also use 'decel mode' to prevent unwanted downshifts on coast-down, there's more on the same link: http://www.msgpio.com/manuals/mshift/V5tune.html#gh (scroll down a bit). (Decel mode has changed in the latest test code so that it shuts off at slow speeds to allow the trans to come to back to 1st gear when stopping. The minimum speed for decel mode is 5mph in this code, but I will make it a user variable for the next version.)

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
mill3833
Posts: 72
Joined: Mon Jan 27, 2014 3:33 pm

Re: WOT odd shifting behaviors

Post by mill3833 »

Lance,

I just tried 5103iii and it never makes it out of 1st gear.

Attached is data log from the 5102iii drive (crawl), and the tune.

Dave
Attachments
MShift_CurrentTune.msq
(57.81 KiB) Downloaded 325 times
2015-10-18_16.51.57 Sun Drv1.msl
(3.62 MiB) Downloaded 319 times
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

Okay, thanks for trying that, I must have buggered something up something simple in the code. It shifts fine if the rpm checking is disabled, but of course that defeats the purpose of the recent changes!

I will fix this and post back here soon.

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: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

I can't find anything obviously wrong in the code, but I did find something messing around on my bench.

The lower rev limit will prevent an upshift if that shift would result in the rpm being below the lower RPM limit. In your datalog, the current gear is 1st, and the RPM is 1400 RPM or less. The lower rev limit is 1500 RPM by default. Obviously a shift to 2nd would result in an RPM of quite a bit less than 1500 RPM (since it is <1400 in first gear) so the shift to second isn't happening. In other spots, you get up as high as 3200 RPM, but that still may not be enough to get over 1500 RPM after the shift, depending on your ratios.

So you need to either work on your shift table to make sure the target gear doesn't drive the RPMs too low, or change the lower rev limits to a lower value. You can set it as low as zero RPM (if it was mine I would try 100, though).

Reducing the lower limits worked well on my bench and the shits worked as expected once I did that.

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: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

I looked a little further in your log, and in other spots, you get up as high as 3200 RPM. To get over 1500 RPM after the shift, with your ratios you would need 2.840/1.550 * 1500 = 2750 RPM. And there are spots where you have achieved that.

However, by the time you do that, you have switched to table 2. However, the target gear doesn't adjust. Since your table is all 4's the target should be 4th, something is preventing this.

I suspect it has to do with a flag not being cleared. I will look in the code and make sure all the flags are cleared when switching tables.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
mill3833
Posts: 72
Joined: Mon Jan 27, 2014 3:33 pm

Re: WOT odd shifting behaviors

Post by mill3833 »

Thanks for looking into this. On that test drive, I made the mistake of pulling out onto a busy road, figuring it would eventually shift out of 1st.

The 2nd test drive with the 5101 code worked as expected. I continue to hone in on the proper shift table.

I'll await any updates to 5102iii. -Dave
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

I assume you are not using the shift buttons to shift manually, you are exclusively using the shift lever instead? I ask because the down shift button is always "ON" in your log. That's also why it wouldn't upshift (at least that's exactly what does it on my bench).

In theory, you should tie the shift button inputs to Vref if you aren't using them.

But enough people have had this issue that in the next release I will put an option in to not act on the shift buttons at all, just log them. That may take a several days, as I am traveling as of tomorrow (I might get it out before I go, if I am lucky).

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: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

Attached is new 5.102iv test code:
Monitor_5102iv.abs.s19
(84.31 KiB) Downloaded 330 times
GPIO_MShift_5102iv.ini
(297.11 KiB) Downloaded 329 times
This code:
  1. Implements a minimum speed for decel mode (the default is 10 mph) under 'General Settings -> Throttle and Load Factors -> Minimum Decel Mode Speed',
  2. Has an option to ignore the shift buttons (under 'Shift Input Patterns -> Lever and Shift Button Configuration -> Shift Button Mode' now has option to 'Do not use - log only'),
  3. Clears all shift and hysteresis flags when changing from one shift table to the other.
While this works on my bench, it may not work on your car (as you have seen). So please use great caution if you choose to test this untried cod.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
mill3833
Posts: 72
Joined: Mon Jan 27, 2014 3:33 pm

Re: WOT odd shifting behaviors

Post by mill3833 »

Lance,
I do not see the "Min Decel Mode Speed" option, as you mentioned.
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: WOT odd shifting behaviors

Post by Bernard Fife »

Dave,

It is here in the added red box:
Capture.JPG
Capture.JPG (49.33 KiB) Viewed 7091 times
Funny thing is that I missed it too the first time I looked for it, I thought I forgot to add it...

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