Downshifting
 

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

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"). :geezer:

- Jack

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! :love: (In a "manly" sort of way)! :evillol:

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

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). :evillol:

It's too late now for us :geezer:'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. :bow:

- Jack

OK - a little followup: I like being able to see the current gear and the TC status in the Gryphon. I'll probably keep monitoring that as well as the TFT and Battery. I was interested in how the TC unlocks as soon as you come off the gas pedal a bit - I had not expected that behavior.

I've only driven it on the country roads around where we live so far. The nearest interstate is about 14 miles away. I seem to be getting a more "locked" state in the TC so far by having the 4th gear lock set at -5 and the 4th gear unlock set at -7.

I was also fascinated at how quickly the truck would shift all the way up to 4th on light acceleration from a standstill. I think that's part of how you tuned it Bill, and it "feels" right! Before I had the PID to confirm things, I thought it was shifting that way, but since the shifts are so "light" at these throttle pressures (just the standard, "keep up with traffic" acceleration), I wasn't really sure.

I'll probably experiment more with the lock and unlock settings, for all the gears now as well as, possibly the part throttle shift points.

Anyway, thanks again! I think, Bill, your modifications to the Gryphon are really adding to its value.

- Jack

Thanks, Jack. I'm glad those help.

Yeah, I had to change MPG to Economy for those crazy guys up north! :D All that metric stuff is SOOO confusing. :huh:

Anyway, keep us posted and if we need to make any more revisions, let me know.

I've noticed too how the tq conv unlocks easily when slightly letting of the gas to coast down a small slope. Then when you slightly press the gas pedal, the rpms are too high for the current speed for a few seconds. I find this strange too.

I think the TC unlocking and locking with the gas pedal being let up is a Ford thing I believe.Pretty sure I read a thing once that Bill posted about it.Its real noticable with my PSD.

It's irritating, isn't it? Feels to me like the transmission's doing way too much work and that can't be good for its overall life. I wonder if this is the "funny" torque control Bill has talked about previously? I don't remember other posts along this line, chappy, so maybe that's what you're referring to.

- Jack

The TC unlocking when letting off the throttle is a means to thy to help improve fuel economy by letting the engine RPM drop down during coasting. I know it may seem a little "busy", but it's actually better in the long run because it takes negative load off the engine and transmission. The only thing it's not good for is if you need engine braking, although a gasser isn't going to be good for that anyway.

For what it's worth, we've reduced the amount of time for the converter to relock and all that we ended up with was the infamous "shudder" on tip-in on certain vehicles. What's irritating is it doesn't do it on every vehicle. :shrug:

One thing that has been requested was to allow more throttle/load before the converter unlocks, particularly in those situation where you're going across an overpass or up a slight grade. I am addressing those requests and as soon we get something that we feel comfortable with, we can get include that in the tuning. It's tricky getting the right combination of converter hold going up a small hill versus quick release for passing or accelerating.

Let me know if you have any other questions. :D

Take care.

Interesting that unlocking on coast is easier on the transmission. Having grown up in mountain areas, I'm a big fan of engine braking and will do it anytime I'm coming down a mountain. So far, haven't had any transmission failures.

Good to know though that you are still looking into the throttle/load to unlock point though.

- Jack

Hey, I drive these things, too! It's a little frustrating getting around Chattanooga and having the converter unlock going up a measly 4% grade. Sat and watched my mileage going down the tubes for like 5 miles. :cursin: Even a sizable overpass is annoying.

Don't worry, we'll get that nonsense straightened out. :D

Cool! I know you're talking about exactly what I'm complaining about! Glad to know I'm not the only one who doesn't like this and that I'm not :crazy: or :dunce:

- Jack

x2
Mark

Hate to drag up an old thread, but I was watching my lockup the other day, running canned tune #2 and it seems to be too early, speed wise. Can I change it to lockup at a higher speed?

I was wondering why this little mummy was resurrected. :giggle:

You can used the custom options menu to raise it.

9th question:
http://forum.gopowerhungry.com/faqs-...ions-menu.html

OK, I found it..