No Kickdown?

[DrX]

My PCM does not seem to be responding to the throttle kickdown tables. So when part throttle boost kicks in the engine just loads up, resulting in knock. In the screenshot below kickdown should have occurred at around 32% TPS but didn't happen until close to 70%. Did I screw up or is something else going on? I also tried playing with the TCC release vs TPS table to no avail. Factory values are all set to 100% in that table.

[joecar]

DrX,

Please post pics of your 3-4 upshift and 4-3 downshift tables.

Joe

[DrX]

Here ya go:

[joecar]

I'm looking at them and thinking about it. And plotting some graphs...

[joecar]

Ok...

If you transpose the 4-3 kickdown table and plot this along with the 3-4 PT upshift and 4-3 PT downshift tables ("Normal" columns), you get this...

http://img301.imageshack.us/img301/4766/43kickdowncn3.png


Look at the yellow region between the 3-4 PT upshift curve and the 4-3 kickdown curve:

the kickdown curve is saying "downshift", but the upshift curve is saying "upshift", and the upshift curve appears to win.

You have to move the kickdown curve so it lies to the right of and below the upshift curve.
.

[DrX]

Thanks for the graph. I'll play with those tables.

[DrX]

Looks like the factory tables are set up the same way. GM does not allow part throttle downshifts. Sucks for towing, uphill roads or moderate acceleration. The only way to initiate a 4-3 shift is to hit >75% TP. I may have to modify the upshift table to prevent any upshifts at over 40% throttle or so. Similar to a Z06 tune. Raising the TP values in the kickdown table would be counter productive.

[joecar]

What would happen if you set the kickdown table to 100% and then manipulated the other two tables
(being sure to keep the PT upshift curve above the the PT downshift curve)...?

i.e. control your downshifts purely from aggressive PT upshift/downshift curves
(raise up the higher TPS parts of both, but still allow it to shift to 4th when it runs out of 3rd;
181 km/h is 113 mph, should be able to go higher than that... what gear do you have...?).

or...
when you want performance, manually select 3rd (3/D) this will prevent upshifts to 4th;
and then when you want economy, manually select 4th (D/OD).

[DrX]

What would happen if you set the kickdown table to 100% and then manipulated the other two tables
(being sure to keep the PT upshift curve above the the PT downshift curve)...?

i.e. control your downshifts purely from aggressive PT upshift/downshift curves
(raise up the higher TPS parts of both, but still allow it to shift to 4th when it runs out of 3rd;
181 km/h is 113 mph, should be able to go higher than that... what gear do you have...?).


That is exactly what I have one. Seems to work quite smoothly. Still needs some tweaking but it is a 100% improvement. Might have to do the same thing with 2-3/3-2. Don't need any kickdown tables. The stock truck trans tune doesn't work well with FI. A quick 4-3 downshift is required to prevent loading up.

BTW 3:73 gears

[joecar]

In other words, set the Kickdown tables to 100% all across, and let the PT shift tables control PT shifting.

If the Kickdown tables are not 100% then you risk hitting the blue area in this example.