HDC - Hill Descent Control questions

[irondoc]

Hi guys, a couple of questions re HDC on my 2011 D4 2.7:

-is the switch illuminated when HDC is on or the headlights are on? Mine is dark with both.
-what speed does it limit you to when it is on? The manual talks about different speeds for different gears, adjusted with the cruise control buttons, but I've had a play with it and it just doesn't seem to work as advertised.

Cheers
Lucas

[NavyDiver]

jump on a hill. Put it in low range 1st or 2nd. foot off brake and accelerator. You should see HDC indicated on your dash. You should hear the brakes engaging and disengaging on one or two wheels at a time- if is rather freaky the first time you feel and hear it!

Use the speed up/down control on your cruise control to increase/decrease speed.

How fast? Not sure- I only use it on very very steep slippery stuff at a snails pace if possible:D

HDC will automatically engage when you select some traction modes. Have a look at the FAQ. Play with it before you really need it.

[CaverD3]

The traction control sign comes up on the dash no light on the switch.

[WhiteD3]

HDC is enabled in some TR modes in high range and all modes (I think) in low range. You will see the green HDC lamp (downhill car symbol) on the dash. There is no lamp in the switch.

[Redback]

HDC is enabled in some TR modes in high range and all modes (I think) in low range. You will see the green HDC lamp (downhill car symbol) on the dash. There is no lamp in the switch.

Yeah, start the car and just put the car into Rock Crawl or Mud Ruts and the green symbol(car shape) will come up on the dash.

Baz.

[JamesH]

Speaking generally about off-road settings, you'll find the booklet put out by Green Oval Experience (gghaggis) very useful.

[connock]

In my opinion
Try putting it in 1st /2nd low and let the engine braking do its thing so you know you will have a set of nice cool brakes at the bottom if needed


connock

[rodjam]

I agree with Connick.
I regularly do a very steep and windy descent into a valley.
With my Kimberley Kamper attached, weighing 1.8 t with water etc.
The first few times with hill descent, the brakes lit up after 10 mins and had to wait some time to cool sufficiently.
That's even with the electric brakes turned up.
After about 10 descents trying various settings tried manual low and engine braking...
Works much better IMO!
Without the van, hill des is fine.
Just my experience!

[101RRS]

Speaking generally about off-road settings, you'll find the booklet put out by Green Oval Experience (gghaggis) very useful.

So is the car Handbook that outlines all of this.

Garry

[camel_landy]

Hi guys, a couple of questions re HDC on my 2011 D4 2.7:

-is the switch illuminated when HDC is on or the headlights are on? Mine is dark with both.
-what speed does it limit you to when it is on? The manual talks about different speeds for different gears, adjusted with the cruise control buttons, but I've had a play with it and it just doesn't seem to work as advertised.

Cheers
Lucas

OK... Testing HDC on the D4.

Firstly, give the HDC button a firm press and make sure the system is coming on (the green icon on the dash should come on). If it comes on, turn it off and go find yourself a long, straight slope (black top will be fine).

Position the car at the top of the slope, so it can start rolling down the hill. As HDC will work in Neutral on the D4, turn on HDC, slip it into Neutral, FEET OFF ALL PEDALS and let the car start to roll GENTLY down the hill.

If HDC is working, your speed shouldn't get more than approx 10km/h, with the rumbling of the ABS system working in the background. You can increase or decrease your speed by using the +/- buttons on the cruise control.

Once you've confirmed it's working OK, read up on 'HDC', 'target speeds' and 'engine braking'.

NOTE: The important thing is to not touch any of the pedals. Also, don't operate in Neutral for too long as the ABS pump will eventually overheat.

HTH

M

[joel0407]

I agree with Connick.
I regularly do a very steep and windy descent into a valley.
With my Kimberley Kamper attached, weighing 1.8 t with water etc.
The first few times with hill descent, the brakes lit up after 10 mins and had to wait some time to cool sufficiently.
That's even with the electric brakes turned up.
After about 10 descents trying various settings tried manual low and engine braking...
Works much better IMO!
Without the van, hill des is fine.
Just my experience!

Is your trailer braking electric?

If so, is it proportional or time delay. If it's time delay, it might not be doing anything.

Most (I know nothing about yours) time delay units are connected to the brake light. Once the brake light comes on the brakes are applied at a set rate. The set rate is usually a dial on the side of the unit. While these units work well most of the time they are next to useless in an emergency as they dont know you are stopping faster and still come on at the same rate. Basicly once the brake light comes on the start applying and continue to full brake in the set time. The set time could be 10 seconds by which time you have already crashed in an emergency.

Also I dont know about LR but my Skoda doesn't activate the brake lights when HDC is working so I would have no trailer brakes with a time delay brake cotroller.

Most of what I have seen in Australia are time delay units. I suspect mainly due to the cost here. Hayman Reese want $250+ for their cheapest proportional unit compared to less than $170 for a time delay unit. Proportional units are far, far cheap OS and where mine (now my brothers) came from.

Proportional brake controllers have an accelerometer that monitors the rate of deaccelertation and applys the brakes accordingly. If you jump on the brakes hard in an emergency, the controller will apply full brakes as fast as possible. Like wise if you use a lower gear for engine braking down a hill the controller will apply a small amount of trailer brakes. These are irrelevant of if the vehicle brakes are applied or not. The aim is to have the controller set so as to not apply anymore vehicle brakes than as if no trailer was attached. All the extra weight of the trailer is braked by the trailer itself.

I did some research about electric brake controllers as my Skoda has a different stability program for when towing to the vehicle on it's own. I suspect LR has a similar thing in the D4 with the "Anit trailer sway". It's a requirement for any trailer over a certain weight in the UK to have break away trailer brakes, including electric so they have a battery mounted in thier trailers/caravans with a proportional brake controller which runs the trailer brakes. The whole system operates seperate to the to vehicle. If the vehicle breaks away the trailer will start to slow and the deaccelaration will cause the brakes to be applied which will cause it to slow faster which will cause more braking. I think it's a great system and something we should see more of here. All trailers over 750kgs in Australia require to be braked. If the brake controller is part of the trailer, any vehicle can tow it without the need for the tow vehicle to have a brake controller. Makes sense to me and it works far better than the time delay controllers the majority of people currently use.

Happy Days.

[gghaggis]

The LR HDC works in any gear (including reverse). It activates the brake lights, so will also activate your trailer brakes (if electric).

HDC has a certain amount of "intelligence", in that it controls each wheel independently. So whilst engine braking is an effective way to control downhill speed, and saves wear and tear on the braking system, on a very slippery downhill HDC will provide better braking whilst also keeping the vehicle on line.

Use it only when you need to.

Cheers,

Gordon

[joel0407]

If the situation is bad enough, just using engine breaking can be useless. With an open diff, when one wheel is on a very slippery surface like mud and the opposing wheel has traction, the wheel on the slippery surface will spin in reverse while the other roles forward. Once it goes, it's much harder to stop.

I have used it in the Yeti and it's fantastic when you are on a very steep decline.

I know the Yeti brake lights aren't activated because I had a mate following and he commented that I didn't touch the brake pedal.

Happy Days.