Cruise control

[guest5079]

My fortnightly trip down the A30, last Monday was quite pleasurable as the traffic was light. So I thought I would use the cruise control. Set it up for 70mph and off we went, climbed up a hill and kept a pretty constant speed as would be expected but going down the other side, as the speed increased, there was a definite feeling of brakes being applied. So much so that my Wife commented on it. I think the speed climbed to about 72/3mph but that was all.  I was surprised that the brakes were applied, it was definitely not just the throttle causing the retardation.
On the Rover 45 V6 auto, that was fitted with cruise control, I used to curse going down hills because, on braking it over rode the setting and once the speed was were it was wanted, the cruise control had to be set again.

Is this yet another little gift Honda have given us?

[stiggysawdust]

Mine will change down a gear or three to stay a little over the set speed.
Never had the brakes apply.
I use my cruise as much as possible especially when cameras are about.

[Hobo]

As another person that uses the A30 frequently I use the cruise control regularly but have never known it apply any braking, as stiggysawdust says judging by the  engine note it appears to change down a gear and use engine braking on a steep downhill.

[guest5079]

I am grateful for the observations. I could well have imagined it but I am certain the engine note did not rise and for my Wife to notice it was surprising.  That is what made me notice, it might have been engine braking but the absence of any increase of engine revs was what made me think it was braking.
Whatever it was I was pleasantly surprised as the old Rover would run away.

[guest3521]

I've not noticed the phenomenon you describe, when using the cruise control on my Jazz, which I do regularly on my commute to/from work, although there are no serious hills to involved there is a longish sweeping downhill run towards the junction with the M40/M25 (1A), Junction 4 to 3 or 2 to 4 (M40) would be a better test?
Next time I do use it I'll try and note exactly what happens when there.

[applicationcen]

I have searched for advice in the manual and on the web - but I cant see anything that informs us that the brakes are applied as part of cruise control speed maintenance.

My observation is that the braking effect is limited to holding lower gears to induce engine breaking.

On the more expensive predictive braking system (radar and camera systems on more expensive or newer high end Hondas) a special system applies the breaks if it sees an accident in the offing. However even on these systems speed maintenance down hill is with engine breaking via selection of a lower gear.

I cant be certain but the effect you witnessed is likely to be the car changing down.

I find this to be less effective as the engine revs so freely. Coming down Telegraph Hill I have to be in third or second to inhibit the car from speeding up! That means I have to flapy paddle  down a couple or three notches.

However, once you place it back into auto (either in or out of cruise) it holds the gear you selected until you accelerate.

[guest5079]

Thanks for the input. I must admit I found hard to think that the cruise control would apply the brakes. It was such a surprise but there you go, forgive an old man for his musing.

The other day, I experienced the VSA momentarily.  Due to piggin road works the only alternative was some narrow lanes. Got one dear sole who was frightened of their paintwork, never mind mine. So into the hedge as close as possible, when a light flashed on the speedo. It was only a flash.
Decided to look it up, well It was the VSA. Evidently if one gets into a soft surface the VSA operates. I thought it was only for stability, well it seems it is also traction control. Thankfully, I always take it light on the throttle when in soft surfaces/snow etc but it is nice to know the Jazz has the bits to help.
So Mr Honda gives us traction control.

[applicationcen]

VSA very good for snow / ice.

I had a real wheel BMW 5 series and if you took a roundabout and floored the accelerator even with snow on the road it would keep the rear totally in line.

I can imagine the mess made if you disengaged the stability control.

There is slightly less concern with front wheel drive as it is inherently a more stable configuration for laying power on to the road surface.

[culzean]

So Mr Honda gives us traction control.

VSA will  detect when car is not following the correct track (sideways movement) and if steering wheels are not pointing in same direction as car is traveling (skids) also knows if a driving wheel is rotating faster than a non-driven wheel.  VSA will apply brakes / cut engine power to get car back on track.  Sometimes VSA is a help on snow,  sometimes not you will have to figure out when to disable it (press VSA button for a few seconds to turn it off, do the same to turn it back on) it will always default to the ON mode when you start the car.  I leave it on all the time but have had to turn it off sometimes on deeper snow / mud.  It is interesting to floor the accelerator when on a wet road island and feel the car just gently slide sideways and not totally lose it as would normally happen.

Front wheel drive is better on snow simply because engine weight is over driving wheels,  a rear engine rear drive car like old  VW Beetle is also good on snow.   Rear wheel drive is much better at putting power down under normal circumstances because the vehicles weight naturally transfers to rear of car when accelerating,  just like it transfers weight to front when braking and gives front wheels more grip.  A rear drive car like BMW will out-handle a front wheel drive car at the limits,  but we normal drivers don't have to worry about limits too much so front drive is adequate for what we require.  Rear drive lap time round Nurburgring is faster than front drive cars, there is a limit how much power can be put down through front wheels (bearing in mind torque steer and limits of CV joint power handling capability).

[Jazzdriver]

My observation is that the braking effect is limited to holding lower gears to induce engine breaking.

.................................

I cant be certain but the effect you witnessed is likely to be the car changing down.

This would mean that cruise control works differently from cruise control on a manual.

[guest5079]

I am not an automotive electrical engineer but if your Jazz is fitted with VSA, then I should think it works in exactly the same way I Shift/.Auto/CVT or Manual. After all it is merely the ABS telling the circuit that a particular wheel is either spinning faster or slower than the others which the computer would do by comparison. Traction control is I believe a system whereby either power is reduced to a particular wheel or there is some form of braking on that wheel.
The only car I can compare this to, did not have VSA nor traction control but it did have a snow button, which when pressed a) I believe selected and maintained a higher gear and b) applied braking to stop the wheel spinning ( the braking bit is purely guess work) The car was fitted with a Jatco 5 speed auto box and I found all this out when after heavy snow all around me were stuck on a slope and I just sailed up it.
Come on the brains, help us out here.

[culzean]

Trouble is with a standard diff as opposed to limited slip diff is that power is directed to the wheel that has least grip (hard to believe but true),  I believe that VSA / traction control applies braking to the wheel spinning the fastest because  braking that wheel will send  power to the other wheel. 

The old trick of lightly applying the handbrake in snow or ice on rear drive cars used to work by loading up both wheels so that the diff would distribute the power between the driving wheels a bit more evenly.

[chrisc]

Wife's Civic cruise control just reduces the throttle to zero when going downhill, even long steep ones but I have never felt braking.  Once a month we do a long trip (280km each way) which involves many long hills and I set the c/c to 110km/hour and it stays more or less like that.  There is one part where the downhill section is 3km long and it gets to 118km/hr in 5th

[guest5685]

I use cruise control quite a lot ( mainly to keep me to the speed limit - too many speed cameras down here)

But I do notice that the speed increases quite a lot when going downhill. Its very hilly in Devon too.

[guest4871]

I use cruise control quite a lot ( mainly to keep me to the speed limit - too many speed cameras down here)

But I do notice that the speed increases quite a lot when going downhill. Its very hilly in Devon too.

Me too! The trouble is that applying the brake knocks the cruise control out but I find changing down a gear or two at the beginning of the hill in cruise control (without braking) sorts the problem for me.