Disco 3 Cruise control

[broennum]

Does anybody have experience with Disco 3 (automatic) cruise control?
The cc doesn't maintain speed downhill in drive- and sportdrive-mode, but only when in fixed gear.
On my old '93 Volvo automatic the gearbox downshifts when needed when in cc.

 

[richpike]

Hmmm - ours seems to do a fantastic job (within physics). Of course it isn't going to hold your speed going down a steep mountain pass, but ours will downshift ~1 gear and hold the speed reasonably well. If I really need some engine compression for braking it probably isn't safe to use CC anyway, so I guess I've never noticed an issue.

It looks like you may be outside the US - do you have a TD? Is the transmission different on those? Perhaps they are less likely to downshift because of the lower redline on diesels. I'm also not totally familiar with diesels, but perhaps there is lower engine compression for braking in them (although that seems counterintuitive since they have such high compression to facilitate burning of the fuel).

-Rich

 

[broennum]

To Rich

Hi Rich,

Thank u for a very competent reply. Yes, I'm outside US, Denmark actually, and right, it's the 2,7 tdi.

But I have the same notion as you - it isn't right.

The LR-people are starting to talk about "adaptive memory" in the gearbox, sounds sophisticated (to put it gently) to me...

 

[mustbeaudi]

Sorry, but are you saying that the Volvo downshifted automatically with cruise engaged in order to slow the vehicle? You describe maintaining speed Downhill - I'm envisioning gravity pulling the vehicle ahead of the programmed speed while downhill. Maybe I'm reading too much into it, but why else would downshifting be required to maintain speed on the downward slope?

 

[broennum]

Right, the downshift happens to maintain (i.e to not increase) speed downhill by engine-brake. My point is, it is not happening on the Land Rover

 

[mustbeaudi]

Okay, then. I have never had that happen on any of my cars before. I found it unusual that the 93 Volvo did it. My later Volvos, Audis and all other manner of domestic and foreign cars never downshifted automatically to engine brake in an attempt to hold speed down on a sloping grade where gravity increases velocity.
As for my LR3, I have not had it long enough to find such a grade and so, sorry, I am of no help here. But, I appreciate your explanation and I am interested to see if others' cars downshift too.
BTW, the transmission's adaptive shift logic relates to the TCU becoming familiar with your foot's driving style and "learning" how to best respond or anticipate your intent. On recent Audis, at least, the ZF trans TCU can be de-programmed or set back to factory default settings so it can learn fresh by using a certain sequence of simple throttle/ignition key steps. I don't know about our LR3s.

 

[Houm_WA]

I'm pretty sure I've felt a downshift while using CC on a downhill slope plenty of times...in this vehicle and in others.

 

[mustbeaudi]

A few months later, now I verify that our LR3 downshifts to induce engine braking to slow the vehicle while coasting down a grade where mass and gravity otherwise conspire to accelerate the vehicle, but I still don't know about with cruise control on. (It's very flat around these suburbs, and it's primarily the wife's ride.)

 

[dantheman1]

Mine will indeed downshift gears to maintain cruise control speed via engine braking. I live in Austin, TX with plenty of hilly highways and it maintains my cruise control speed pretty well.