The maximum road speed that...
The maximum road speed that a manually forced down-shift (using the in-car shifter) can be evoked is tuneable.
It is the author's opinion that a building-block approach should be taken when dialing in the calibration. The part-throttle and light-load tuning should be done first, and then the vehicle should be driven in a more aggressive manner, extending the shift points out and experiencing higher engine power. Eventually, the WOT shift tables can then be tuned.
The part-throttle and light-load can be done very easily on the street, especially if you enlist someone to drive, while you make the changes. It is best to do the WOT tables either on a chassis dyno or at the dragstrip on a test-and-tune day. You don't want to break any laws or endanger anyone's life tuning your transmission.
When working with the calibration, don't forget that the way the transmission responds to downshifts is just as critical for proper driveability as the upshift logic. When cruising at a steady speed with the TCC engaged, any input into the throttle of more than a few degrees should first unlock the TCC; then, if aggressive enough, pull a downshift. Depending on the road speed and the amount of throttle input, the transmission may go down two gears instead of one.
The TCC control strategy allows...
The TCC control strategy allows for improved performance and fuel economy with a number of different calibration tables.
For example, when you're out cruising about 35 mph on a level road, in most applications the transmission would be in Overdrive with the TCC engaged. Imagine a fellow in a Brand X car pulls alongside and wants to embarrass your Pontiac. When you whack the throttle to the floor, depending on the engine and rearend combination, the transmission may be required to provide a Four-to-One gear change momentarily, and then a rapid upshift to Second gear. The transmission's job is to fully exploit the power the engine makes in every rpm range-not work against it. If the transmission in your Pontiac was only to downshift to Third, or possibly Second gear, the other guy may very well get a jump on you if he's a good driver and his transmission is calibrated properly.
To create the perfect transmission strategy, the SuperMatic controller provides 15 different tables that you can alter. You were introduced to them in the third installment of this series, and we will go over them in a little more detail now.
WOT up-shift rpm and the kick-down...
WOT up-shift rpm and the kick-down mph are set by changing the number in the appropriate box.
This needs to be in lock step with the transmission's mechanical ability to evoke a gear change. Ideal is without any electrical-induced delay over the inherent mechanical time. The time to create the shift should be precise with no lag.
Part Throttle Shift Time: The time required to complete the shift should be tuned to allow a seamless gear change with no confusion experienced by the transmission or engine.
Minimum TPS % for Idle: The TCU needs to assign a TPS voltage for closed throttle, so it can calculate the throttle opening as a transient value.
Maximum TPS % for WOT: Likewise the TCU needs to assign a maximum TPS value that coincides with full throttle.
This is the same dashboard...
This is the same dashboard screen seen in image 4, but we now have evoked the Performance Mode signified by "Flags1" reading "128" and a "1" in the Performance Mode box.
This will control the road speed during coast-down. The transmission will go down a gear until it is back in First. It should be set for seamless coast-down, with no perceived flash in engine rpm or jolting of the Pontiac.
Reverse LP Kick %: This table works off the line-pressure calibration that is required when shifting into Reverse. The gear change should be smooth, with no pressure surge that will cause the Pontiac to bang into Reverse or jolt the torque converter.
Economy/Performance Kick %: This transmission offers both an economy and performance setting that alters the amount of line pressure in each mode. The performance calibration will increase the line pressure over the economy setting.
WOT Parameters: This is where the upshift rpm (which should be about 100- to 200-rpm below peak power) is tuned, along with the road speed to allow a forced WOT downshift.