Thread: D4 Cruise Control

Originally Posted by Disco4SE

They suggested that there is no control on the downhill, in other words, the vehicle will not slow on a downhill slope on cruise,

I find that odd as the throttle should close when overspeeding and as certainly the torque converter should be locked the car should slow back to the set speed. Lower speeds might be different but at "cruising sppeds the torque converter should be locked. However with my RRS you have to ride the brakes to keep the speed in check on overrun.

Garry

I'm certain mine does slow down (or it appears to) when it overspeeds but it can be well over the speed limit when it does.

I have a scangauge 2 on my D3. This gives a fuel consumption update every 2 seconds & according to it fuel use drops to 0 when over-speeding down hill. If I set it to litres per hour it still uses a little fuel, I don't remember the figures.
Every other car with C/C I have owned mentions in the manual that C/C will not apply brakes & to be aware that the car may increase speed down hill, makes sense to me. If you are doing (or trying to do) 100kph at the top of a steep hill you will be speeding by the bottom if you don't use the brakes or drop a gear. Try it without C/C, you will still be speeding.
Also I have never heard of a C/C that uses the brakes though the gear box etc is pretty clever, you wonder why it doesn't drop a gear or 2 to slow you down a bit?
Jonesfam

Originally Posted by Celtoid

I'm certain mine does slow down (or it appears to) when it overspeeds but it can be well over the speed limit when it does.

My D4 does the same.
Generally, CC maintains +- 2km/hr from the set speed, but this can vary as much as +-10km/hr at the crest or bottom of a hill in undulating topography.
Also, the CC does runaway down large hills.
Overall, given the fact that the speedo is inaccurate (displays 106 at a true/correct 100km/hr), I'm not suprised the CC also is inaccurate.

Originally Posted by jonesfam

Also I have never heard of a C/C that uses the brakes though the gear box etc is pretty clever, you wonder why it doesn't drop a gear or 2 to slow you down a bit?
Jonesfam

My R51 Pathie's auto is particularly good at dropping gears to maintain the CC setting when travelling down hill. I wish the D4 did this...

Originally Posted by Duck's Guts

Overall, given the fact that the speedo is inaccurate (displays 106 at a true/correct 100km/hr)

That is not an inaccurate speedo - well within specs - must not read slow and can over read by up to 10%.

Garry

Originally Posted by garrycol

That is not an inaccurate speedo - well within specs - must not read slow and can over read by up to 10%.
Garry

Yes the speedo operation IS within specification....but that doesn't mean it is accurate.

I'm very pleased to report that since my 3.0 D4 had some software updates applied yesterday, CC now works properly (IMO). Overrun now totally cuts fuel (as shown by the instantaneous consumption display), it only looses about 2kph uphill, it very quickly reduces power as hills are crested (I didn't have to cancel CC once in the 500 km trip home) and holding the speed decrease button causes CC to be suspended until the button is released whereupon the setspeed is set to the current speed. It is now very useful in quite hilly terrain - permagrin for CC at last!

Originally Posted by Graeme

I'm very pleased to report that since my 3.0 D4 had some software updates applied yesterday

Was this done by a dealer Graeme. I had a service recently and they told me that I had the latest updates installed, yet my cruise is still all over the place????
Cheers, Craig