How does it work the Cruise Control?
Thread Starter
Junior Member
Joined: Apr 2009
Posts: 35
Likes: 2
From: Costa Rica
2005 E500
How does it work the Cruise Control?
I know, I know, the question seems a bit silly at first but I would like to know how the cruise control really works behind the scenes, I do not mean how to set, increase, decrease or unset it but rather how the computer does it work. When I have set a given speed and drive down hill the car maintains the speed, I noticed the revs are not specially higher as when I am not using the cruise control and use the engine compression to hold a bit on the speed. A few days back I happened to noticed a car driving behind me close enough to see the reflection of the break lights on while going downhill and having set the Cruise Control, which led me to think the computer was pressing the brakes. I naively thought since the very beginning it was something in the computer telling the engine to hold, but now I am realizing it is actually using the breaks. Am I totally lost on this presumption or do any one agrees/know who can explain in more detail? Thanks in advanced!!!
MBWorld Fanatic!
Joined: Jan 2009
Posts: 9,225
Likes: 1,798
From: V E G A S
1922 Ford Model T / no OBD
This is called "controlled descent" if I remember it right.
When on CC cars rolls down faster than set speed, computer will apply engine brakes (turbo fins on diesels) or it will downshift the gears for better braking. Maybe in critical situation will push the brakes as well, but not sure about it. That triggers brake lights as warning to drivers behind you.
When on CC cars rolls down faster than set speed, computer will apply engine brakes (turbo fins on diesels) or it will downshift the gears for better braking. Maybe in critical situation will push the brakes as well, but not sure about it. That triggers brake lights as warning to drivers behind you.
Super Member
Joined: Apr 2007
Posts: 633
Likes: 48
From: USA
2006 E320 CDI
This is called "controlled descent" if I remember it right.
When on CC cars rolls down faster than set speed, computer will apply engine brakes (turbo fins on diesels) or it will downshift the gears for better braking. Maybe in critical situation will push the brakes as well, but not sure about it. That triggers brake lights as warning to drivers behind you.
When on CC cars rolls down faster than set speed, computer will apply engine brakes (turbo fins on diesels) or it will downshift the gears for better braking. Maybe in critical situation will push the brakes as well, but not sure about it. That triggers brake lights as warning to drivers behind you.
