Garrett, I think we are all using different terminology in shift points. For my description, I meant that Higher Shift points means shifting up at higher RPM's. A lower shift point to me, is forcing the transmission into a taller gear early in the torque curve which reduces power going to the wheels.
Overall, I think the TR system was designed as you describe. Particularly in Snow. Quoting from the same document Umberto cited:
One other aspect that TR program does that hasn't really been discussed or explained is how it changes the throttle response. It is significant.
As for manual control....yes, sort of. I agree with Gordon that you can mimic manual mode, but as Tami states, there is no way to lock the rear diff manually. However, I think engaging Low Range pretty much does lock the center diff?
Overall, I think the TR system was designed as you describe. Particularly in Snow. Quoting from the same document Umberto cited:
"In this setting the individual systems revert to control software which optimises the sub-system, and thus the vehicle traction, handling and driveability, for low μ conditions. When driving on ice or wet grass it is particularly important to avoid wheel spin when driving off, because any wheel spin will change the surface, and reduce traction below the original low level.
The Program was specifically tested under low ( conditions in Northern Sweden, both on frozen lakes as well as on inclines. Particular emphasis in this Program is on modifying the powertrain torque delivery and avoiding wheel spin, by applying torque to the wheels gradually and by sensitising the traction systems. In addition to Northern Sweden this Program was also tested on gravel surfaces in both the UK and Belgium and on grass."
One other aspect that TR program does that hasn't really been discussed or explained is how it changes the throttle response. It is significant.
"The basic requirement for the engine management with regard to T.R. is to offer pedal progression maps which are specifically adapted for each Special Program. For each different Program there is a different relationship between throttle pedal position and the amount of engine torque produced. Additionally the rate of torque build up (or reduction), following pedal movement, depends on the active T.R. Program.
An additional requirement is that Program changes can take place under as many circumstances as possible, including whilst the throttle pedal is applied. Having to release the throttle, or not, can make the difference between maintaining momentum, or getting stuck off road. When changing from one Special Program to another, whilst the throttle pedal is applied, there needs to be a change in engine torque, even with the throttle pedal not being moved. This function is referred to as 'blending'.
Blending means that an engine torque change will occur, even when the throttle pedal is kept stationary.
As for manual control....yes, sort of. I agree with Gordon that you can mimic manual mode, but as Tami states, there is no way to lock the rear diff manually. However, I think engaging Low Range pretty much does lock the center diff?
"Terrain Response sub-systems on L319/L320 exist of:
? Engine management
? Gearbox Control (where automatic gearbox is fitted)
? Driveline Control (electronically controlled centre and optional rear differentials)
? Stability Control System (ABS, Traction Control, HDC, DSC)
? Air suspension
? Instrument pack message centre (LCD)
Specific functionality for these systems has been developed for the Terrain Response system. The fundamental philosophy here is that each system is optimised in its calibration or functionality, and is switched to a condition which is most likely to be of benefit to the driver, i.e. it is most likely to be of benefit to have HDC switched on when driving in mud and ruts. However, the system offers the flexibility of switching sub-systems manually, overriding the automatic choice. It is always possible to manually control the air suspension, or to switch HDC or DSC on/off.
Of course it is not mandatory to use the T.R. system. The vehicle will still perform admirably well in severe off road conditions, even when used in the T.R. General Program. It will just not perform as well as in the appropriate Program because it will have to respond to the prevailing conditions, rather than being able to anticipate them. Furthermore, some systems, such as the engine and gearbox, will be optimised for on-road driving, when in the General Program,. It will be possible to drive off road using those settings but this will require more driver skill. In particular a very careful modulation of the throttle pedal and manual shifting of the automatic gearbox (using CommandShift) will be required."