Found my huckleberry......

[cleatus12r]

It's been a while since I've given out any helpful information when it comes to tuning your own 7.3L so I figured I would describe a trick with the transmission operation.

About 7 months back I started playing with a lot of the parameters. One of the really useful things I came across works really well with a daily driving tune. Something that always bothered me about the shifting with some of the Super Duty trucks was the strategy dealing with the 2-3 shift and the torque converter clutch operation.

Under moderate acceleration (35-60%) the PCM would command a 2-3 shift at 35-40 MPH and the torque converter clutch would be applied as soon as the upshift occured. This usually resulted in a "double bump" kind of feeling and an unacceptable (to me) loss of RPM. There is a set of parameters that deal with a time delay between an upshift and the accompanying apply of the torque converter clutch. By simply changing the time between the 2-3 upshift and the torque conveter clutch apply from "0" to a value between "3" and "5" (salt to taste), the annoying shift and resultant TCC apply symptom can be alleviated. There is a catch, however, that if the TCC is already applied in 2nd gear (if you're above the APP/MPH threshold for an applied TCC), the torque converter will remain in a locked state after the shift to 3rd gear. Please see the last paragraph for another tip that works REALLY WELL with this modification.

This parameter also comes in really handy in racing programs when the effort doesn't want to be taken to fine tune the 2nd gear TCC apply speed. Leave the apply speed low but give yourself 2 seconds between the 1-2 shift and the 2nd gear TCC apply. This will keep the TCC from applying immediately after the 1-2 shift and snuffing out the turbocharger.

The first thing I did when I started tuning nearly 2 years ago (in late April) was changing the ridiculously early 3-4 upshift. If you change the upshift speed to a minimum of XX MPH and the APP to reflect a bit more resolution at low pedal positions, then you can command an upshift at any speed you desire. This setup works PERFECT (personal preference of course) with the delayed TCC apply mentioned above. Each shift is distinct. 1-2 at 12-15 MPH, 2-3 at 30-35 MPH, 3rd gear TCC apply at 42-45 MPH, and the 3-4 occurs at 55-65 MPH.

Here's an example of my PMT1 DD tune 3-4 shift schedule:






More to come soon!

[907DAVE]

Is this parameter you speak of the Delay Converter Lock?

It's a little late and I have had a few too many so bear with me for a second............






One thing I have yet to understand...............why is there only zero's in the first three positions (AD Counts)?

I understand there needs to be a closed throttle position, but why the next two? Seems like that space could be used to give the APP some more resolution.


Sorry, little off topic.

[cleatus12r]

Yes, you can easily change the "resolution" of the APP for shift points. I've spent many hours playing with different setups but in all actuality, it wasn't worth it. I couldn't really make heads or tails of any discernable difference since I am human and holding the accelerator pedal at the same exact spot every time for testing isn't possible. Oh, and 0 counts would be an open circuit. The voltage present on the APP is roughly half a volt (just slightly less on most trucks) which equates to just about 100 A/D counts.

The reason I changed the values as I did was because if I set the upshift speed to 52 (as I have in this case) without lowering the minimum APP value, I would STILL get a 45 MPH upshift. There is not enough leeway in the APP table to make up for less than 100 A/D counts. The values in this function are VERY different for each calibration I have made because of the accelerator pedal feel. The more "responsive" the pedal is, the more APP input it takes to shift later (if that makes sense). My super-stupid 30K heavy towing program for the automatics uses a strategy that causes upshifts at 2700 RPM when loaded. If there is any decent amount of accelerator pedal input, the engine WILL shift at 2700 RPM every time (except 3-4 which will hold 3rd gear until the accelerator pedal is lifted a little bit). The WOT Shift parameter is a little bit of a misnomer ( ) . I also alleviated the 4-3 downshift at any speed above 67 MPH since stock settings allow a 4-3 downshift at frickin' 74 MPH which is stupid. Interestingly enough, the ONLY way I could cause this to happen was with the 4-3 downshift (cruise) function. The standard 4-3 downshift function was useless in "fixing" that problem.

Just some more tricks.......

Here's a couple questions for Bill if he ever has time to respond :

Why do the shift functions not correlate to actual speeds. If the revs/mile and gear ratio are correct, then why do the speeds give a representation, but not an actual result?

Why does the anticipated shifting (even if the max. and min. speeds are altered) not seem to do anything regardless if the switch is on or off? This kind of goes along with me trying to get ACTUAL shift speeds out of the shift functions.

[Pocket]

Cody, thank you for those last few posts. You described perfectly what I've been working on lately, and you also pinpointed the exact issues I have had in regards to fine tuning my shifting.

I've really had to rethink my shift strategy after playing around with the new MFD table. But your explanation pretty much answered my questions. Nice job, dude

I think I might get this puppy licked before long.

[Pocket]

Originally Posted by cleatus12r

Here's a couple questions for Bill if he ever has time to respond :

Why do the shift functions not correlate to actual speeds. If the revs/mile and gear ratio are correct, then why do the speeds give a representation, but not an actual result?

Why does the anticipated shifting (even if the max. and min. speeds are altered) not seem to do anything regardless if the switch is on or off? This kind of goes along with me trying to get ACTUAL shift speeds out of the shift functions.

I came to the anticipated shifting switch and remembered you posted something about this. So it doesn't work to turn it off.... what about also turning off the switch for "Enable Adaptive Shift Strategy"? Has anyone tried that one yet? There's also switches for "Adaptive X-Y Shift Strategy Enable" (where X-Y is the gear shift for 1-2, 2-3, and 3-4). I didn't know if that would make a difference and give you the shift functions that correlate more with actual speeds. Thoughts?

I'm always a chicken to try new stuff myself, since I'm still so new at tuning.

[cleatus12r]

Actually, going a bit against what was originally thought, the SuperDuty PCMs are able to adapt for actual shift times (how long it takes the shift to actually occur when commanded). If you look a bit deeper into the parameters, you'll see that the shift pressure adaptive limits are +/- 20 PSI. By turning those off (which I always do), whatever shift characteristics you program into shift times/pressures will remain forever.....and the PCM will not alter the shift pressures by itself. That's what I LOVE about the OBS PCMs......they do exactly what you tell them to do every time.

The anticipated shifting switch that I was talking about in the quoted post SHOULD cause the PCM to command a shift at a consistent speed every time, but it still varies. I don't know if it's something that can be taken out or not.

Heck, you never learn anything if you don't try!!! I just alter all sorts of stuff and see what happens. Obviously I stay away from anything that isn't defined or sounds dangerous.

[Pocket]

Ahhh, so Adaptive Shift Strategy deals with shift pressures rather than shift times. I saw the shift pressure parameters in there, but I also saw some other related stuff and had absolutely no idea what it was.

I may try to turn off the anticipated shifting switch to see how it works on VDH2 tuning, and if I get a different result than what you got.

[907DAVE]

Originally Posted by cleatus12r

Under moderate acceleration (35-60%) the PCM would command a 2-3 shift at 35-40 MPH and the torque converter clutch would be applied as soon as the upshift occured. This usually resulted in a "double bump" kind of feeling and an unacceptable (to me) loss of RPM. There is a set of parameters that deal with a time delay between an upshift and the accompanying apply of the torque converter clutch. By simply changing the time between the 2-3 upshift and the torque conveter clutch apply from "0" to a value between "3" and "5" (salt to taste), the annoying shift and resultant TCC apply symptom can be alleviated.

This is EXACTLY what I was experiencing today while playing around with some shifting stuff. I was able to get the shifting perfect (low APP) in a new program I was working on, then when I stood on it a little I got this crap. To say the least I was disgusted, then I remember this post. Well after a few tries I was able to get rid of that stupid "double bumpin........ early lockin garbage".


Thanks for the tip.

[Tyson42]

What happend to the pictures?

[F-127]

I would guess that Cody(since he did most image posting) either re-organized his photobucket account (it would be a pretty big pain to go back and re-update a bunch of links in who knows how many threads), or just flat-out deleted them to prevent them from floating around the internet.