Cruise control downhill?

[MrJames]

So I was using the cruise control the other day, set it at 30mph going though an area with a thousand speed camera signs and realised the car was holding the speed even going downhill ( My C70 never did that it just sped up! )

The weird part is it didn't feel like engine braking, I could feel a gentle pulsing more like the brakes were being applied, I didn't think the car had anything like that though? Does anyone know how it works? I'm curious now...

The car is a 2004 S60 Diesel with the Geartronic box.

[tykesi]

I've noticed this on my V70 (2004) on long downhills with cruise on. I'm pretty sure it's just the car feathering the throttle to keep the speed steady. I've not looked into it but I'd be pretty certain these don't have the ability to regulate speed with the brakes.

[Georgeandkira]

I don't believe there's a brake activation system in our old cars either.

I've chalked up the small rpm adjustments I feel in "near constant speed" operation to the valve adjustment hardware + software.

My usual highway run features long rolling hills. I'm quite steady with the foot but use cruise sometimes. Whether I'm using cruise or not seems to make no difference.
Downhills produce way fewer of the slight "surge feelings".
The small surges made me wonder if the little screen on the cam phaser gasket is clogged a bit.

Again, mine's a petrol with only the one cam phaser.

[richard]

The geartronic has torque convertor lock up.
And gives a surpising amount of engine brake I found.

[stuart bowes]

mine is not geartronic, going downhill I definitely feel the cc cut out, the revs drop and it picks up speed a bit (or a lot depending on the hill obviously)

[V8XCV]

Engine braking on a D5 should be sufficient to hold speed on most inclines, that's what the cruise control uses.