[ANSWERED] Can 'Performance Shift Active' be Explained in Detail
05-13-2016, 07:14 AM
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[ANSWERED] Can 'Performance Shift Active' be Explained in Detail
Original question is here.
AllFlash asked:
Under certain conditions, accelerating ones Corvette will trigger 'Performance Shift Active' on Corvettes and a number of changes are observed, least of which is a delayed changing of gears in the A8 while acceleration or deceleration is present. Can Tadge and GM explain exactly what changes the car experiences, whether it be engine, transmission or suspension while 'Performance Shift Activated'...is active.
Under certain conditions, accelerating ones Corvette will trigger 'Performance Shift Active' on Corvettes and a number of changes are observed, least of which is a delayed changing of gears in the A8 while acceleration or deceleration is present. Can Tadge and GM explain exactly what changes the car experiences, whether it be engine, transmission or suspension while 'Performance Shift Activated'...is active.
Tadge answered:
When you see the 'Performance Shift Active' message that means you have engaged a set of features we call PAS/PAL. PAS stands for Performance Algorithm Shift. PAL refers to Performance Algorithm Lift-foot. We, like many manufactures, try to have the car adapt to the way it is being driven. Sensors on the car detect things like the rate of steering wheel rotation, rate of change of throttle position and vehicle lateral acceleration. PAS/PAL are just a couple of features that fall into this category and they only affect how the transmission shifts gears.
The performance shift algorithm is an 8-speed paddle shift automatic feature that operates in Sport and Track mode with the shifter in “D”. Sport mode enables the lift-foot algorithm, Track mode additionally enables PAS which brings lateral acceleration into the equation. PAS is the more aggressive level of performance shift, it will force the lowest possible gear for a given speed range. Lateral acceleration plays a role in activating the feature and is also used to negotiate gear state, for example: Downshifts are not allowed above a certain lateral acceleration (don't want to have any abrupt torque changes that might disturb the chassis).
During an acceleration PAL is activated during a lift-foot throttle maneuver which is calibrated above a threshold pedal position and a calibrated pedal rate of return. These calibration values are set to prevent the algorithm from activating during normal driving conditions. Unlike PAS which selects the lowest available gear, the lift-foot algorithm will hold the gear the transmission is currently in until it times out (then normal shifting will begin).
There is a bit more to these features than I am sharing here and you can tell I'm not disclosing any specifics around the calibration for our algorithms. That is intentional. I always want to share as much as I can when answering these questions, but I have to balance customer's desire for specific information and spoon-feeding our competitors’ valuable proprietary information that would be expensive and difficult for them to obtain through other means.
When you see the 'Performance Shift Active' message that means you have engaged a set of features we call PAS/PAL. PAS stands for Performance Algorithm Shift. PAL refers to Performance Algorithm Lift-foot. We, like many manufactures, try to have the car adapt to the way it is being driven. Sensors on the car detect things like the rate of steering wheel rotation, rate of change of throttle position and vehicle lateral acceleration. PAS/PAL are just a couple of features that fall into this category and they only affect how the transmission shifts gears.
The performance shift algorithm is an 8-speed paddle shift automatic feature that operates in Sport and Track mode with the shifter in “D”. Sport mode enables the lift-foot algorithm, Track mode additionally enables PAS which brings lateral acceleration into the equation. PAS is the more aggressive level of performance shift, it will force the lowest possible gear for a given speed range. Lateral acceleration plays a role in activating the feature and is also used to negotiate gear state, for example: Downshifts are not allowed above a certain lateral acceleration (don't want to have any abrupt torque changes that might disturb the chassis).
During an acceleration PAL is activated during a lift-foot throttle maneuver which is calibrated above a threshold pedal position and a calibrated pedal rate of return. These calibration values are set to prevent the algorithm from activating during normal driving conditions. Unlike PAS which selects the lowest available gear, the lift-foot algorithm will hold the gear the transmission is currently in until it times out (then normal shifting will begin).
There is a bit more to these features than I am sharing here and you can tell I'm not disclosing any specifics around the calibration for our algorithms. That is intentional. I always want to share as much as I can when answering these questions, but I have to balance customer's desire for specific information and spoon-feeding our competitors’ valuable proprietary information that would be expensive and difficult for them to obtain through other means.
The following 18 users liked this post by jvp:
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and 13 others liked this post.
The following users liked this post:
Mike Campbell (01-30-2019)
05-14-2016, 10:46 PM
#4
Pro
I know I like it!! Performance shift mode is awesome! 
05-20-2016, 11:02 PM
#5
Le Mans Master
I love this feature for the roll racing I be doing in the mean streets and highways of Mexico