Cruise Control n00b questions

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Kloofvreter

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I was driving out to Gouda this morning, and for the first time in my life decided to use cruise control. Now this is on a manual car (Volvo S40). At first I locked it at about 100km/h, and it works flawlessly, in complete control of the engine. The speedo almost does not move at all, uphill AND downhill. So my question is, 1) What happens when I hit an uphill too steep for 5th gear? Will it just disengage cruise control? 2) Does it use the car's brake system to regulate speed downhill? It seems just a bit too precise for engine back pressure.
 
1) Your car will just start going slower until it flattens out again. The car should then accelerate back to 100km/h.
2) Your car will not apply the brakes, so you might find that the car will rely only on engine braking to slow down as much as possible, but if that is not enough the car will accelerate down the downhill. The when you reach the bottom of the descent, the speed will go back down to 100km/h.

My VW, Audi and Alfas all worked like this, but perhaps Volvo's is different?

I would just test it and find out?
 
Last edited:
It depends on the car, I can't speak for the Volvo. Some cars do use the breaks on downhills to regulate it for you, for cheaper cruise control models they don't (so beware of speed traps)

On a manual it should disengage when you press your clutch slightly or turn it off yourself. I've never had it disengage on me on a steep hill when at speed.

It's a bitch resuming your speed when you're in 2nd and 3rd etc. I drove the Audi RS4 the other day, automatic (first proper automatic/trip tronic) and it was beautiful just resuming your previous speed and listening to it change gears and go crazy :)
 
gifs said:
1) Your car will just start going slower until it flattens out again. The car should then accelerate back to 100km/h.
2) Your car will not apply the brakes, so you might find that the car will rely only on engine braking to slow down as much as possible, but if that is not enough the car will accelerate down the downhill. The when you reach the bottom of the descent, the speed will go back down to 100km/h
Click to expand...

With regard to 2, are you speaking in general or just with regard to OP's car?
 
gifs said:
1) Your car will just start going slower until it flattens out again. The car should then accelerate back to 100km/h.
2) Your car will not apply the brakes, so you might find that the car will rely only on engine braking to slow down as much as possible, but if that is not enough the car will accelerate down the downhill. The when you reach the bottom of the descent, the speed will go back down to 100km/h
Click to expand...

Thanks!

1) Perhaps I was not clear, or I am misunderstanding you. I mean what if I'm going too slow and the hill is too steep meaning there is not enough power to maintain that speed up the hill?

2) This is not what I am noticing. I'm cruising 100 on a fairly flat stretch of road, and hit a downhill, the car stays on 100, doesn't go slower or faster.

Meh, perhaps I should do a more in-depth test when I get time :D
 
efitol said:
With regard to 2, are you speaking in general or just with regard to OP's car?
Click to expand...

I was speaking in general out of experience with my previous cars. Edted my post to reflect this.
 
AcidRaZor said:
On a manual it should disengage when you press your clutch slightly or turn it off yourself. I've never had it disengage on me on a steep hill when at speed.
Click to expand...

This I know. What I meant was, what if I'm trying to go up a very steep incline and there is not enough power in 5th gear to maintain my set cruising speed? It's not an automatic, it cannot automatically downshift.
 
Slootvreter said:
Thanks!

1) Perhaps I was not clear, or I am misunderstanding you. I mean what if I'm going too slow and the hill is too steep meaning there is not enough power to maintain that speed up the hill?

2) This is not what I am noticing. I'm cruising 100 on a fairly flat stretch of road, and hit a downhill, the car stays on 100, doesn't go slower or faster.

Meh, perhaps I should do a more in-depth test when I get time :D
Click to expand...

1) If the hill is too steep for the engine to maintain the speed in that particular gear, the car will lose speed.

2) Perhaps Volvos do apply the car's brakes. But you need quite a steep downhill to requires additional braking.

So go test it on a mountain pass. I generally find that cruise control works great and only in limited situations like mountain passes do they need some manaul intervention.
 
Slootvreter said:
This I know. What I meant was, what if I'm trying to go up a very steep incline and there is not enough power in 5th gear to maintain my set cruising speed? It's not an automatic, it cannot automatically downshift.
Click to expand...

The cruise control will try its damnedest to maintain speed by the only means it can - by burying the throttle. If the gradient's too steep it'll either a) keep trying until it eventually stalls, or it might b) disengage at the first pre-stall hiccup thus allowing you to stall the car yourself.

As for the brakes - it varies from car to car. Many newer and more upmarket cars will actively engage the brakes to maintain set speed.
 
gifs said:
1) If the hill is too steep for the engine to maintain the speed in that particular gear, the car will lose speed.

2) Perhaps Volvos do apply the car's brakes. But you need quite a steep downhill to requires additional braking.

So go test it on a mountain pass. I generally find that cruise control works great and only in limited situations like mountain passes do they need some manaul intervention.
Click to expand...

I must admit, I was most impressed with this. It also seems to greatly improve fuel consumption.
 
AcidRaZor said:
It depends on the car, I can't speak for the Volvo. Some cars do use the breaks on downhills to regulate it for you, for cheaper cruise control models they don't (so beware of speed traps)

On a manual it should disengage when you press your clutch slightly or turn it off yourself. I've never had it disengage on me on a steep hill when at speed.

It's a bitch resuming your speed when you're in 2nd and 3rd etc. I drove the Audi RS4 the other day, automatic (first proper automatic/trip tronic) and it was beautiful just resuming your previous speed and listening to it change gears and go crazy :)
Click to expand...

I can change gears on speed control. I have a manual A4 2.0 TDi. I can set the speed at say 120km/h when I am driving at say 40kmph and then gear up like normal. I have yet to drive a steep enough uphill to lose enough speed for the cruise control to cut out, but then again, I can gear down manually if required without cruise control disengaging. The car will brake on downhills to maintain the max speed set on cruise control
 
OGroteKoning said:
I can change gears on speed control. I have a manual A4 2.0 TDi. I can set the speed at say 120km/h when I am driving at say 40kmph and then gear up like normal. I have yet to drive a steep enough uphill to lose enough speed for the cruise control to cut out, but then again, I can gear down manually if required without cruise control disengaging. The car will brake on downhills to maintain the max speed set on cruise control
Click to expand...

That is interesting.

I had manual VW Jetta 2.0 TDi with cruise control. When you press the clutch the cruise control will just disengage.

I had DSG Audi A3 2.0T. Down van Reenen's pass it could not stick to the set speed without me dropping to 3rd gear using the paddle shifts.

Neither of theses cars ever had an issue on uphills though.
 
Slootvreter said:
I was driving out to Gouda this morning, and for the first time in my life decided to use cruise control. Now this is on a manual car (Volvo S40). At first I locked it at about 100km/h, and it works flawlessly, in complete control of the engine. The speedo almost does not move at all, uphill AND downhill. So my question is, 1) What happens when I hit an uphill too steep for 5th gear? Will it just disengage cruise control? 2) Does it use the car's brake system to regulate speed downhill? It seems just a bit too precise for engine back pressure.
Click to expand...


the cruise control on my Audi applies brakes when the speed exceeds the speed i set it at, feels quiet freaky
 
gifs said:
That is interesting.

I had manual VW Jetta 2.0 TDi with cruise control. When you press the clutch the cruise control will just disengage.

I had DSG Audi A3 2.0T. Down van Reenen's pass it could not stick to the set speed without me dropping to 3rd gear using the paddle shifts.

Neither of theses cars ever had an issue on uphills though.
Click to expand...

My previous Audi wasn't like that though. The moment you touched the clutch, CC would disengage and it didn't brake on downhills.
 
ijacobs3 said:
the cruise control on my Audi applies brakes when the speed exceeds the speed i set it at, feels quiet freaky
Click to expand...

Next time you feel it braking by itself, press the brake pedal ... the applied braking is much more than you would expect.
 
On some vehicles (like my manual Kia Cerato) if the cruise control cannot maintain speed up a steep hill it will disarm itself.
On the Cerato the threshold is about 20km/h below the set speed.
i.e. If I set it to 100km/h and the speed falls to 80km/h the cruise control will disarm itself.

Some vehicles have "speed limiting" cruise control which will down gear (on automatics only) and/or apply brakes to limit the speed.
Most cheaper cruise control systems are not speed limiting.
 
The Volvo cruise control will also turn off if the wheels spin for whatever reason (eg aquaplaning)
 
HapticSimian said:
The cruise control will try its damnedest to maintain speed by the only means it can - by burying the throttle. If the gradient's too steep it'll either a) keep trying until it eventually stalls, or it might b) disengage at the first pre-stall hiccup thus allowing you to stall the car yourself.

As for the brakes - it varies from car to car. Many newer and more upmarket cars will actively engage the brakes to maintain set speed.
Click to expand...

Yes, BMW has a certain minimum speed for CC so if it falls below that it will simply disengage CC.
 
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