EG6SiR

Newbie question: how do cruise control systems work? I can't imagine it's from a cable directly activating the throttle butterfly...

naishou

It is. Why wouldn't it be? On most modern cars there is a place to mount a second throttle cable specifically for this purpose. There's usually a vacuum operated actuator though some are now electric.

AusS2000

The thing to remember is that the cruise control disengages the second you touch the brakes or throttle (and in a manual car also the clutch). So it keeps you at a constant speed until you make an input to change the speed. Oh, and they also have a 'Resume' function so if you are on the freeway at 110 but have to brake in traffic once it's clear agan you just get in the right gear and press Resume.

Austblue

If it is operated by means of the throttle how does it brake when going down hill?

naishou

It doesn't. It will release the throttle completely but on a steep hill engine braking might not be enough to stop you picking up speed.

AusS2000

The misapprehension about cruise control is that it does all the driving for you. It doesn't.

All it does is help you maintain a given speed in stable conditions. This is even more true in a manual because if you come across a steep incline you may need to engage a lower gear and of course that requires you to manually change and then resume cruise control.

In reality cruise is for the M2 or the M5 on your way to Wakefield.

Austblue

I like the function on my old man's CLK that allows you to set a maximum limit. This allows you to maintain control but eliminates the need to monitor your speed. Especially good when exiting freeways.