Cruise Control

[guest5079]

Being a bit of a luddite, I freely confess to not understanding some of the 'electrics' on modern day cars... Some time back I raised a query over the Cruise Control as fitted to a Mk2 EX behaving as below.
Last Monday, on the A30 at a place called Palmers Bridge the east side of where Jamaica Inn is I had cruise control engaged and set at just below 70mph. This hill if not checked is steep enough for the Jazz to wind up to over 90mph with no throttle. It is not often I can use cruise control on the A30 due to lorry 'convoys'.
As the Jazz started the descent, I felt it holding back and then it changed down to 5th and a short while later changed down  again to 4th, holding the set speed . This has happened before on this hill with cruise control engaged.
 Honda could/would not answer this query.
I know the Jazz does not have reactive cruise control but I have recently read about a car having cruise control with speed limiter.  Is this causing the car to behave the way it does on steep hills on derestricted roads while in cruise control? I cannot remember reading about  this in the handbook.

[Jocko]

My Volvo had cruise control, and on a hill would change down when I wouldn't. The car will change down to the gear it feels is suitable. All the cruise control is doing is setting the throttle to maintain the speed you set.
You weren't inadvertently in S mode were you?

[culzean]

Being a bit of a luddite, I freely confess to not understanding some of the 'electrics' on modern day cars... Some time back I raised a query over the Cruise Control as fitted to a Mk2 EX behaving as below.
Last Monday, on the A30 at a place called Palmers Bridge the east side of where Jamaica Inn is I had cruise control engaged and set at just below 70mph. This hill if not checked is steep enough for the Jazz to wind up to over 90mph with no throttle. It is not often I can use cruise control on the A30 due to lorry 'convoys'.
As the Jazz started the descent, I felt it holding back and then it changed down to 5th and a short while later changed down  again to 4th, holding the set speed . This has happened before on this hill with cruise control engaged.
 Honda could/would not answer this query.
I know the Jazz does not have reactive cruise control but I have recently read about a car having cruise control with speed limiter.  Is this causing the car to behave the way it does on steep hills on derestricted roads while in cruise control? I cannot remember reading about  this in the handbook.

Maybe with an I-shift like yours or CVT /auto it will change down or up depending on engine load (or lack of it) but on a manual box it cannot do more on a downhill than fully close the throttle in the gear it is in (if you are in 5th and stay there you won't get much engine braking),  or on an uphill fully open the throttle in the gear it is in to try to maintain set road speed, and again if you are in 5th it may  struggle to maintain set speed.  If i-shift chooses to change to lower gears it will do so until it finds a gear that can maintain set speed on downhill stretches using engine braking.

[Jocko]

If i-shift chooses to change to lower gears it will do so until it finds a gear that can maintain set speed on downhill stretches using engine braking.

Cruise control, on an automatic, will not change down to give engine braking when descending. It will stick to the highest gear. Traditional automatics don't have a lot of engine braking at the best of time. Some high end cruise control systems will apply the brakes if the set speed is exceeded, and closing the throttle does not correct this overspeed. Adaptive cruise control is the future, with not only the speed being controlled but the maintenance of a safe gap also entrusted to the software.
Personally, I do not see a lot of benefit of cruise control on a manual transmission, but I loved it on the automatic.

[guest5079]

This is the mystery,  the Ishift is a manual box with an automated clutch and gear change, it will only change down and use engine braking at 70mph. It is quite definite in it's actions and 4th gear at 70mph not only buzzy but pretty good at retardation. Any other speed no matter how steep the hill and the car runs away. The Rover's auto box and cruise control always needed intervention by me with the brake.

[Jocko]

The Rover's auto box and cruise control always needed intervention by me with the brake.

That is what the Honda Jazz manual says you have to do. And that includes the iShift model. It says to brake, which automatically disengages CC then reengage it when you reach the required speed.

[guest5079]

Yes I do know that one has to brake to reduce speed and the Cruise control disengages BUT why at 70 mph does the Cruise Control do the speed reduction without me  braking. The cruise control remains engaged.  I purposely left my foot off the brake to see if what has happened in the past occurred again which it did.
I suppose it is one of lifes mysteries. However nothing mechanical nor electrical happens without an explanation.

[Hobo]

Cruise control, on an automatic, will not change down to give engine braking when descending.

Well like auntneddy both my CVT Jazz and my auto Civic change down and give engine braking when descending on a steep hill if the car picks up speed rapidly without me touching the brakes when the cruise control is set.

[Jocko]

Well like auntneddy both my CVT Jazz and my auto Civic change down and give engine braking when descending on a steep hill if the car picks up speed rapidly without me touching the brakes when the cruise control is set.

Must be a Honda thing.

[Pine]

Well like auntneddy both my CVT Jazz and my auto Civic change down and give engine braking when descending on a steep hill if the car picks up speed rapidly without me touching the brakes when the cruise control is set.

Must be a Honda thing.

My Ford Fiesta automatic (dual clutch) is the same i.e. changes down for engine braking if the speed increases above the set speed on cruise control when going downhill.

[Jocko]

Well maybe it's a CVT thing. I don't know. None of my Vauxhalls, or the Volvo, ever changed down. They all had hydraulic transmissions. Borg Warner I believe.

[Hobo]

Well maybe it's a CVT thing.

Erm, my present auto Civic is not CVT.   

[Jocko]

Well, its maybe just a me thing.