When throttle kickdown is not set at 100%

Graph show what happens when the Throttle Kickdown tables are not set at flat 100%...

( 4-3 Kickdown curve has been axis-swapped to match axes of 3-4 PT Upshift and 4-3 PT Downshift curves )

Above red line = upshift into 4th
Below green line = downshift into 3rd
To right of blue line = throttle kickdown into 3rd

The blue region shows a conflict (PT upshift table wants 4th, throttle kickdown table wants 3rd).

PCM may or may not follow the kickdown table... it won't shift when you think it should, and vice-versa.

http://img249.imageshack.us/img249/4...ickdownty3.png

I noticed some of my tables were not all 100% so I set them at 100%.

What about 4-2 kickdowns - that has been my PITA (literally) since 2000!

MRK,

What are you seeing...?

For 4->2 kickdowns the PCM iteratively uses the 4->3 and 3->2 before commanding the downshift.

OK - that makes sense.

I have been trying to get that kickdown to require MORE throttle input before it happens. Messed with it a year or so but only seemed to confuse thing in the tranny.

As a most typical application instance, a 40 to 60 MPH accelleration at (SOTP) 70% throttle does a 4-2. I'd like to see that changed to a 4-3 and save the 4-2 for 95% WOT -

I know it's possible - I jsut haven't spent the time to play and dig.

The simplest way to adjust what you're saying is to set the kickdown tables to 100% flat and then adjust the PT downshift tables such that at 40-60 mph 70% TP 4->3 is "in the region" and 3->2 is not (i.e. operating point falls below the 4->3 PT downshift curve and above the 3->2 PT downshift curve).

Is this the reason there is a 1-3 second delay on WOT downshifs, or is that a mechanical limitation or something?

I don't know if the delay electronic or mechanical or what...?

The PCM should be able to do it very quick (my stock TA jumps quick-smart, spins tires upto ~35 mph)...

I am wondering if your trans calibration has some delay parameter that has not been discovered/published...?

I'm looking for the spreadsheet that has makes the color graph. Is it posted somewhere?

SSpeedDemon has the spreadsheet you are looking for. (I Think)

Jeff

Quote:

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Originally Posted by FeetDry

I'm looking for the spreadsheet that has makes the color graph. Is it posted somewhere?

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I copied the PT/kickdown tables into a program called DPlot, and then played with the shading feature... attached is the .grf file if you're interested.

Digging up old but helpful thread, have a hanging 1>2 shift that sometimes requires me to lift in order for it to shift, usually when I am peddling it out of the hole or starting from a roll and on and off the gas to get the tires under control. 100% across the board on the next tune and we'll see if it cleans it up. I like my valvetrain intact...

Hi JM, if you get it working, post the before/after tunes.

No Such Luck, did it again last night but didnt catch it in the act. I have a log a couple weeks old, not the same tune as posted but basically the same. here is a log of it doing a full throttle shift good and then missing the shift.

Note, my set-up is a turbo blow through carb 99 c1500. The TPS I use only goes to 88% when it is at wide open throttle. 30% throttle is very light cruise, 50% throttle is a good hard pulling out into traffic type of acceleration, 85-88ish is wot. I currently have my kickdowns at 100% which should be unattainable but it still acted up last night.

Problem seems to be rolling hard acceleration or when tires spin out (raising mph on the vss) most likely doing a 1-2-1 shift when I pedal it and get it back to wot. Oddly I noticed delivered engine torque drop to 0 at 5600 rpm, though it should never have been there in the first place (should figure that out for when I raise my shift rpm).

Any suggestions would be appreciated.

Hi JM,

the problem is this:

your WOT downshift speeds are above the WOT upshift speeds... they should be below (at least 5 mph lower)...



set D0925-7 below D0910-2,
set D0930-2 below D0915-7,
set D0935-7 below D0920-2.


Attachment 13762


Same applies to the part throttle downshift/upshift tables (the downshift should be below the upshift at each corresponding throttle position) .

BTW those WOT upshift speeds are quite low...

Awesome, easy to fix! I didnt even notice the wot downshift speeds, I did make the upshift speeds low so it would always be satisfied easily and use the rpm for the shift point. Need to sit down and fix a bunch of this stuff, I rushed the trans in and kept changing stuff on the truck and never took the time to hone the trans tune.

Is it easy to figure out why my torque number drops to zero at 5600, it sent shift pressure down to 43 which will not be good when I start shifting this thing higher...

Thank you so much for figuring this out for me!

I see you have all the fuel cut offs set to 5600.

ahhh-Ha! Awesome again man, that would have taken me days to figure out (if I ever did...). Thank you!!!!!

Quote:

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Originally Posted by joecar

Hi JM,

the problem is this:

your WOT downshift speeds are above the WOT upshift speeds... they should be below (at least 5 mph lower)...



set D0925-7 below D0910-2,
set D0930-2 below D0915-7,
set D0935-7 below D0920-2.


Attachment 13762


Same applies to the part throttle downshift/upshift tables (the downshift should be below the upshift at each corresponding throttle position) .

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Quote:

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Originally Posted by joecar

BTW those WOT upshift speeds are quite low...

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Joe you know I'm in no way trying to step on your toes as you are the master with this stuff but those shift tables he posted are stock. And every truck based 4L80E tune I've ever seen have the downshift speeds higher than the upshift speeds so I wouldn't say that is the issue. Suppose it makes sense too. It can't downshift unless it already upshifted first, correct?:redface:

could also have been how far they were from the corresponding part throttle shift points, either way I needed to fix a bunch of stuff now that I have driven the truck and am getting a feel for what it wants. here is my new shift map, noy much stock about that trans tune, maybe the downshift wot values...

Quote:

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Originally Posted by Big Mike

Joe you know I'm in no way trying to step on your toes as you are the master with this stuff but those shift tables he posted are stock. And every truck based 4L80E tune I've ever seen have the downshift speeds higher than the upshift speeds so I wouldn't say that is the issue. Suppose it makes sense too. It can't downshift unless it already upshifted first, correct?:redface:

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Hi Mike,

No worries, I welcome all comments, I'm open to learning new stuff...

hmmm, so trucks have the WOT downshift set higher than the WOT upshift (along with Throttle Kickdown tables not set to 100%TP).

when WOT downshift is above the WOT upshift, then when the operating point is between these there is a conflict, and this is further compounded by the Throttle Kickdown not being 100%TP...

I suppose then that WOT shifting is accomplished by the operating point crossing the non-100%-curve on the Throttle Kickdown tables... in the colored graph in post #1 imagine that the WOT shift points are where the red and green curves hit the right-hand-side vertical axis (100% on the horizontal axis), and that the green point was above the red point... so the blue curve would command the WOT upshift when the MPH crosses from below the blue curve to above it (moving upwards along the RHS vertical axis)... interesting way to control WOT up/downshifts, I didn't think of the Throttle Kickdown table being used to command an upshift.

Now I am really stumped, Still doing it with my latest changes, Should be the shift curves as above but here are the log and tune from the latest run. Around frame 246 it does a 1-2 shift just rlling around then after some throttle it shifts back down and hits 6000 until I lifted. weird...Attachment 13802Attachment 13803

Hmmm, weird... I'll take a closer look tomorrow.

Gracias!

Quote:

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Originally Posted by johnmaster

Now I am really stumped, Still doing it with my latest changes, Should be the shift curves as above but here are the log and tune from the latest run. Around frame 246 it does a 1-2 shift just rlling around then after some throttle it shifts back down and hits 6000 until I lifted. weird...Attachment 13802Attachment 13803

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Hmmm...

Try setting D1206 to 95% and 85% and D1207 to 95%.

When you changed any of the speedo parameters (Hxxxx) did you apply the shift point correction...? [ I'm grasping at straws here ]

Click on any of the MPH cells in any PT shift table, and look at the bottom of the tunetool, it shows the RPM that that MPH corresponds to in each gear...

is the correct RPM shown for each MPH...?


manually calculate this and see if it agrees with the tunetool:

RPM = MPH * 336 * GR / TD

where:
GR = overall gear ratio = transmission ratio * axle ratio
TD = tire diameter in inches


If it does not agree, then that is the problem.

No problem, I'm out of straws to grasp here so I'll see what yours turn up. When i did the axle swap i changed the ratio and the rev/mile so it should be good and when I manually calculate it checks out, comparing to my log it's 200 rpm higher which would account for slippage.

My tps only goes to ~90% pegged wot, It is the wrong type for this vehicle and it is mounted on a carburetor baseplate so the range is a bit off. I figure I have adjusted for it but maybe not. Thinking about it now, Why do I even need WOT throttle settings? I can figure out where my rpm is at for each mph per the log and just put that into the part throttle tables at 90% throttle right? Then do as you say and set throttle % for WOT above my wot tps and it will be unattainable and never be used.

Any flaws in my logic? I have a feeling the issue is moving from the pt tables to the wot settings and back again but not sure why from the way i have my tune. Maybe I will try adjusting my pt tables and setting 1206 and 1207 to unattainable and see if it keeps acting up in pt mode.

Do wot shift speeds need to be above part throttle highest value? IE if my high end part throttle 1>2 shift speed is 50 but my wot shift mph is 40 and 5300 rpm could that be my problem?

That shouldn't be the problem because the WOT are enabled when D1206 is met (and D1207 is below D1206)...

but try making them the same anyway (this is how I always set mine).

Regardless the source of the problem, I solved it by calculating what I wanted my shifts to be at and set the mph at the high end of the part throttle tables, set 1206 and 1207 so they were unattainable and after one test so far it is working, clicking off nice 5500rpm shifts... will report back if its still acting up or if i learn anything more. now after I go to the track i can finally start tc tuning:) Thank you for the insanity check!

Ok, that's a good way to do it.