Downshifting

[Jackpine]

OK, here's my first "dumb" question. It may apply to all vehicles, but I'll start it here.

I'm cruising down the highway at around 75mph with the speed control set and in overdrive. The rpms are in the neighborhood of 1800-1900. I come to a hill, not a big hill, but one that's maybe 2-3% grade and one I'll be on for about 20-30 seconds. Partway up the hill, the rpms increase to maybe 2300-2400 (I really need to document this more closely and I'm going off the vehicle's tach, not the one in the Gryphon). Anyway, the speed is maintained without problem to the crest of the hill and then the rpms drop again as I get over the top. Here's the question(s):

1. Is the rpm increase caused by the truck dropping out of overdrive, or is it because the torque converter is unlocking? Or, is it both?

2. There really doesn't seem to be that much load on the engine prior to the rpm increase and there is a lot of potential throttle increase remaining. If the truck had a manual transmission, I would never even consider downshifting in this situation, I'd just open the throttle a bit more. In fact, my Honda Accord (also an automatic) would go over this hill, maintaining speed, without the rpms increasing, and it's only a 4-cyl. Is there any way to delay this rpm surge until it's really needed?

It really bugs me that this truck, with its great big engine, wants to up the rpms for added torque so quickly.

Is there any "user" setting on the Gryphon (such as 4-3 downshift or 4-3 torque converter unlock) that might "calm things down" a bit? Or, is this something that has to be "programmed" into the tune? Or finally, is this just something I have to live with?

I guess I really think that this truck seems too "eager" to "downshift" at any speed, when the throttle is depressed a bit. And, I'm not talking about moving the accelerator halfway (or more) down to pass someone here. But I'd just as soon see less activity out of the transmission for "ordinary" cruising.

Hope what I'm asking makes sense!

- Jack

[bangingd]

Hey Jack, I would set the PID for your trans gear to display and watch it. It sounds like the torque converter is unlocking for the grade then locking back up after. You will see a little lock appear when converter locks up. You will also be able to see if it's down shifting but that would be pretty obvious.

[Jackpine]

Originally Posted by bangingd

Hey Jack, I would set the PID for your trans gear to display and watch it. It sounds like the torque converter is unlocking for the grade then locking back up after. You will see a little lock appear when converter locks up. You will also be able to see if it's down shifting but that would be pretty obvious.

Thanks, bangingd. I feel it's probably the torque converter too. I suspect the transmission downshifting from 4th to 3rd would be a much bigger rpm change. I like your suggestion, but I can't figure out which PID to display. The only ones I know of that directly relate to transmission gearing are the OSS and TSS (Output and Turbine Shaft Speeds). I used to monitor these when I first got the programmer, but decided they weren't telling me a whole lot. Is it one (or both) of these? (And if so, I don't ever remember seeing a "lock" but this could be another of my "senior moments").

- Jack

[Power Hungry]

Jack,

I rebuilt the latest files I had for you and set up a target update so you can have all the latest goodies. This will give you the new datalogging features as well as the new "Metric" display capabilities (not the Metric is very useful in the US).

To monitor gear and lockup, go to [Menu], [Setup], [Display Settings], [4 Segment Digital], and then select which segment you want to change. Scroll down to "GEAR" and press [Enter]. Select [Set as Display] and then return to the main display. It should now display what gear you are in and also display a little "lock" symbol when the converter is locked.

As for the issue, I agree that it is most likely the converter strategy causing the problems. If you were to go into the Custom Options and lower the 4th Gear Converter Unlock a couple miles an hour, it may improve or even completely resolve the issue. If it improves but doesn't go away completely, I can further refine the strategy to eliminate it.

Hope this helps.

[Jackpine]

Originally Posted by Power Hungry

Jack,

I rebuilt the latest files I had for you and set up a target update so you can have all the latest goodies. This will give you the new datalogging features as well as the new "Metric" display capabilities (not the Metric is very useful in the US).

To monitor gear and lockup, go to [Menu], [Setup], [Display Settings], [4 Segment Digital], and then select which segment you want to change. Scroll down to "GEAR" and press [Enter]. Select [Set as Display] and then return to the main display. It should now display what gear you are in and also display a little "lock" symbol when the converter is locked.

As for the issue, I agree that it is most likely the converter strategy causing the problems. If you were to go into the Custom Options and lower the 4th Gear Converter Unlock a couple miles an hour, it may improve or even completely resolve the issue. If it improves but doesn't go away completely, I can further refine the strategy to eliminate it.

Hope this helps.

Aw, Bill - you're just TOO good to me! (In a "manly" sort of way)!

I'll run right out and pull my Gryphon (after setting it back to stock of course) to download the updates.

bangingd had PM'd me about these changes and I was going to ask about it in an email with a "no hurry" caveat, but here you are before I can even think of what I was going to ask for!

Thanks bunches!

- Jack

[Jackpine]

OK - think I've got it! When you said "Gear", that means "Comm Gear", right? I see it shows "1" with the engine off. And, I see you relabeled Inst MPG as "Inst Economy" and Avg MPG as "Avg Economy" too (just to keep us on our toes, I bet).

It's too late now for us 's, so I'll take it out for a test drive tomorrow.

Bill, I DO appreciate the support you give us. I think I join with everyone in this sentiment.

- Jack