Cruise control engine braking

[Downsizer]

Living in east Anglia, I rarely drive on fast long downhill roads.  However, this week I was driving west on the A55 dual carriageway in N.Wales with cruise control set at 68 mph.  When we came to a long downhill stretch, I was surprised to find the revs rise to 3500-4000 and the speed was held at 68 all the way down, after which they dropped back to 2200.  No braking was needed, and of course touching the brake would have cancelled cruise control.  There seems to be no mention of this feature in the handbook.

[Jocko]

Someone else has mentioned that here, but without adaptive cruise control I don't see how. My old automatic Volvo (conventional auto, not CVT), had cruise control, and on a steep down grade it would shut the throttle, but if the hill was steep enough, and the set speed low enough, the speed would continue to rise above that set on the cruise control.

[trebor1652]

Yes Downsizer
I have had the same happen with my ex.
But it only seems to work above 50mph.
Or is that just me and my car ?!?!?

Sent from my moto g(6) using Tapatalk

[John A]

I'd guess that if the engine braking is effective enough then it will hold the speed, and at higher speeds air resistance helps the "braking" effect. But, it won't always do it, eg on a relatively steep incline in a 30mph limit, the cruise control can't keep it at 30mph. Can help it by selecting a lower "gear" using the paddles, which doesn't deselect the cruise control.

[Jocko]

Yes, but why would the revs go up? Unless it is just something the CVT does on the overrun at higher speeds. You would have to try the same descent, at the same speed, but without cruise control.

[Downsizer]

Yes, but why would the revs go up? Unless it is just something the CVT does on the overrun at higher speeds. You would have to try the same descent, at the same speed, but without cruise control.

There's no doubt that on that stretch of road, the car would have run away without this restraint.  It's a long hill, with a crawler lane in the reverse direction.  I would guess about 1 in 12.

[Jocko]

Yes, but would it have got that restraint from the CVT without cruise control. Unless Honda are secretly fitting adaptive cruise control to CVT equipped cars it must be a characteristic of the CVT transmission itself.

[Downsizer]

Yes, but would it have got that restraint from the CVT without cruise control. Unless Honda are secretly fitting adaptive cruise control to CVT equipped cars it must be a characteristic of the CVT transmission itself.

How would cvt alone provide downhill restraint without using the paddles?
Answering my own question, I see from a map that the descent was as I crossed the line of Offa's Dyke. Make of that what you will......!

[Jocko]

How would cvt alone provide downhill restraint without using the paddles?

No idea, as I don't have a CVT.

[VicW]

My CVT provides engine braking on steepish downhill roads without using cruise control.
If you throttle back to avoid the speed increasing downhill the revs rise and the car holds its speed.
The increase in revs is the same effect as you would get if you were in a manual gearbox car and changed down to hold the cars speed.

Vic.

[richardfrost]

My CVT provides engine braking on steepish downhill roads without using cruise control.
If you throttle back to avoid the speed increasing downhill the revs rise and the car holds its speed.
The increase in revs is the same effect as you would get if you were in a manual gearbox car and changed down to hold the cars speed.

Vic.

Yep, this is what I would have suggested. I don't have a CVT so could not be certain.

In my Hybrid RAV4 you can 'engine brake' by flipping the gear lever to 'manual' and selecting a lower gear, it simply increases the amount of charge flowing back into the batteries from the brakes and lowers the nominal gear ratio. On the new Corolla I had on loan when my car was being serviced, it has a B option on the gear lever to achieve the same effect (no 'manual' gear select on this car). I put manual in quotes as the hybrid cars don't have manual gears either, it is very much like a CVT in that respect.

[Downsizer]

My CVT provides engine braking on steepish downhill roads without using cruise control.
If you throttle back to avoid the speed increasing downhill the revs rise and the car holds its speed.
The increase in revs is the same effect as you would get if you were in a manual gearbox car and changed down to hold the cars speed.

Vic.

I don't recall ever experiencing this, but as I said above, I live in a flat part of the country.  I shall look for a suitable hill to experiment.

[peteo48]

Yes - I've noticed this on my car - not often but the first time I noticed it, curiously enough, was on a long downward stretch on the A55!

I think Vic has nailed it. It's just like changing down in a manual.

[Rory]

Someone else has mentioned that here, but without adaptive cruise control I don't see how. My old automatic Volvo (conventional auto, not CVT), had cruise control, and on a steep down grade it would shut the throttle, but if the hill was steep enough, and the set speed low enough, the speed would continue to rise above that set on the cruise control.

Both my old conventional torque converter Mercedes and wife's DSG Tiguan shift down to hold the speed.  The Merc will still speed up a little but the Tiguan will really whack the gears down and its engine braking is more positive than the Merc.