Climbing a snow packed hill

[nwoods]

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:

"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."

 

[umbertob]

I think engaging Low Range pretty much does lock the center diff?

Not really. Even in low range, and regardless of program used or DSC position, the center diff locks and unlocks electronically depending on terrain conditions, just like the rear one (if the car has one.) Only thing I can tell - by looking at the diff "status" on the touchscreen's GUI - is that the center diff locks more frequently than the rear.

 

[TheataSigma]

1st gear "lock out" means that a vehicle will not start in 1st, but rather 2nd gear. Many cars have a winter mode that does the same thing to minimize wheel spin. Toyotas had them in the FJ80s. It's a nice little button to have.

In sport shift mode, you can start in 2nd gear in High Range. Not sure what it allows in Low Range. I have found that in most cases I just leave the vehicle in normal mode and just drive. Because BMW helped design the DSC I usually shut it off in the winter as it is a major pain in the ass to deal with.

Winslow

 

[lionvt]

DSC off does the trick.

Thanks for all the input. Recent snowy weather finally allowed "field testing" some of these suggestions -- and turning the DSC off permits the wheels to spin and dig down to the gravel (when conditions warrant it). The "real world" problem climbing this hill is that the LR3, when left to its own devices, is so preoccupied with limiting wheel spin, that it will slow you right down to a halt on a snow packed hill. The slipperier it is, the quicker it slows each wheel down til you grind to a halt. Keeps you on the road I guess, but it won't get you up the hill. In impossibly slippery conditions -- this might still be warranted. And I can't say enough for the same electronic wizardry while going down this particular hill (aka my driveway) or along our ice packed road. Or backing down the hill.

I almost dumped my D1 in the woods last night because I got a little cavalier about a throttle blip along the road and it almost spun me off the road -- the LR3 can teach you bad habits by being so forgiving. But on a day like today, new snow, on a soft layer of ice, the LR3 won't climb the hill. The D1 and RRC will, but by barreling up the hill, and then grinding through the snow to the gravel when the going gets tough. But the LR3 will just slow down, slow down, and stop -- while you are standing on the throttle. Very maddening.

But turning the DSC off seems to have solved this. I must say, I have not had luck either in Low Range or some of the other options discussed here. I guess the DSC over rides everything in its quest for no wheel spin. Which does have its role. The LR3 is a very hard car to (even deliberately) spin. But it won't climb an icy hill worth a lick if you don't turn the DSC off.

Thanks for the thoughts.

 

[allodial]

dsc= devilish sissy control

i always turn that bad boy off and go with my driving skills versus the computer.

but at high speed offroading i will often leave it on for the hell of it.

just say no to the dsc.

 

[RVRSRVC]

Very similar circumstances for me yesterday. I dropped the trailer in the field and went to have a look around with the LR3.
Greasy sloppy mud and couldn't get out of a small climb in any setting until I turned of the DSC.
Admittedly road biased tires.
I've had trouble with the RRC on A/T's and the Disco with the Swampers in the same place, but the LR3 required more "effort".

 

[Jonty]

DSC must be turned off for soft sand, snow or mud. Tires make a huge difference too.

 

[lionvt]

I will say that the LR3 can be handful to control with the DSC off. Its torquey, very much acts like a front wheel drive car, and its icy road handling is dramatically different -- if you drive the way you do normally with the DSC on you can easily dump it off the road as the DSC has lulled you into bad habits because it was fixing all your mistakes. So I'll keep the DSC the rest of the time, its doing its job, but I will turn it off when hill climbing in the crud.