Thread: Hill decent and slippery stuff

Originally Posted by gghaggis

Basically from downloading and studying the GTR docs. The D4/RRS 2010 uses the Bosch DF11 ABS module - it has 7 or 8 sub-modules. One of those is dedicated to HDC. One to ETC etc.

We also had a car whose HDC was faulty, however the ABS (at speed) worked just fine.

Cheers,

Gordon

HDC would certainly have its own module, and HDC failing wouldn't knock out ABS but it would vice-versa. I suspect the HDC module is a controlling module for ABS like ETC and ESC. Question is whether it controls it in a different way or not relative to the driver. Must try and squeeze an answer out of LR. They do love questions like that ;-)

Anyway this has been an most interesting discussion so thank you for that.

It's actually more like the diagram below (taken from one of my seminar slides). Programatically there is an ABS module, under which there are algorithmic sub-sections and sub-sub-sections, one of which is the ABS sub-system (ie the actual ABS algorithmic section is a sub-class under the ABS module - they're two different things).

Cheers,

Gordon

Originally Posted by brad72

After my 1st dabble into 4wd'ing the other day I have a question regarding the HDC. For the following i was in low range and rock crawl mode. In forward, everything worked fine,descent was controlled, i could vary the speed with the cruise etc. When I went up a steep section forward I got stuck so i eased on the brake, put the car in reverse, let off the brake but even with HDC the car just seemed to be too fast to be safe and HDC didn't seem the same as forward. Was i doing something wrong, was rock crawl the wrong program when the ground was a bit loose, or is reverse just that bit faster.

Thanks

Can anyone tell me if I am dreaming, but recently took my new D3 on it's first outing and up a considerably steep climb on smooth clay (std road tyres) the vehicle slowed to a crawl at the crest of a run off, revs slowed, even though I engaged more gas peddle pressure. Then she just took off, like it regained lost traction. I thought afterward, "well that's what it's designed to do" but it was a little disconcerting at the time. Having been used to driving a vehicle and now this thing knows better than me?

Smooth clay climb, your DSC was probably activating (even if you had turned it 'off') as the car struggled to find grip and slewed side to side. In this scenario, the DSC will reduce torque to the engine (to prevent you spinning the car sideways), almost to the point of stall if necessary. As soon as it finds grip however, the DSC cuts out and torque is resumed!

Cheers,

Gordon

Originally Posted by gghaggis

Smooth clay climb, your DSC was probably activating (even if you had turned it 'off') as the car struggled to find grip and slewed side to side. In this scenario, the DSC will reduce torque to the engine (to prevent you spinning the car sideways), almost to the point of stall if necessary. As soon as it finds grip however, the DSC cuts out and torque is resumed!

Cheers,

Gordon

Thanks Gordon, yes I did have DSC turned off (thanks to the useful tips on this forum) but I didn't get any sideways movement, more so when approaching the crest of each section. But it worked a treat, just a bit nerve wracking for the first time. Cheers,
Neil.

That initially sounded like DSC but I doubt it for two reasons:

1. You had it deactivated and while the off switch doesn't truly turn it off it does significantly desensitive it and you have to do something pretty dramatic to kick it in

2. From what you describe I can't see the parameters being met for a DSC intervention anyway -- slow speed, no turning, no slide

So, I suspect it's a more prosaic case of the D3 just being a little slow on the uptake with a gearchange or response to throttle rather than being clever.

Originally Posted by gghaggis

It's actually more like the diagram below (taken from one of my seminar slides). Programatically there is an ABS module, under which there are algorithmic sub-sections and sub-sub-sections, one of which is the ABS sub-system (ie the actual ABS algorithmic section is a sub-class under the ABS module - they're two different things).

Cheers,

Gordon

Interesting...going off that model it may be different, assuming the ABS module is merely a control system and has no activation logic or at least not the type in question. Who's to know, I'd like to look at the functional specs for the system ;-)

I would suggest adding the steering wheel angle sensor and pitch sensor as these are also important inputs to stability control. I don't know what EBS is -- a collective term for EBD/EBA? TSC would presumably be another module next to DTC/EBS.

Originally Posted by rmp

I don't know what EBS is -- a collective term for EBD/EBA? TSC would presumably be another module next to DTC/EBS.

Robert,

EBS is the 'Emergency Braking System' - this is a cut-down diagram of the full system, so I haven't included all inputs/outputs.

Cheers,

Gordon