Seems I have one of the rare XK8's without cruise control and it's really the only flaw on the whole car. So today (on a long journey with the people mover enjoying the CC very much) I decided to create some sort of CC for the XK8. Browsing through the Forum I think I learned that the accellerator pedal contains just a variable resistor (aka the position indicator) that gives a signal to the computer to take care of business.

So if this is true, my plan is to attach some simple electronics to the pedal output and have it mirrored. When I hit a switch the electronics will simply maintain the output from the pedal while I take my foot off the pedal to take a rest. As soon as the brake is activated, the system is reset and the output from the pedal is leading again.

I know it's not a true cruise control but rather a 'fix the pedal' gadget, but won't it do 90% of the job at 10% complexity?


Curious to learn what the Forum thinks about this wild idea; Anyone able to build the electronics...?

 

The CC is overridden by applying the brake.

In normal driving you would have the time to switch off your 'constant velocity' device and brake. In an emergency? Braking hard and the engine still held at fixed revs. That could get you into a lot of trouble very quickly.

Graham

 

There are a couple of companies that make after market automotive cruise controls. They are relatively inexpensive, work very well and are reasonably easy to install. This seems like the way to go, to me, at least. Check out amazon and ebay.

 

Been wondering about that... Not where you want to be. Hope you don't speak from experience... My 'design' caters for it: " As soon as the brake is activated, the system is reset and the output from the pedal is leading again"

@Friarshuck: Indeed more affordable then I thought. Anyone have a specific experience with such a device in an XK8?

 

The accelerator pedal arrangement isn't quite as simple as you suggest! As far as I recall, there are three potentiometers; two of them operate in the way you surmise, but while one is increasing its resistance, the other is reducing - both of these feed the ECM at the same time. The third pot feeds the Mechanical Guard on the Throttle Body in a way that, as a 4.2 litre man, I don't need to know!! If you want to persist with your idea, you'll need to research that bit as well!

 

No - in the UK we're rarely out of traffic jams long enough to be able to switch to CC.

Graham

 

Triggered by the responses I took out my multimeter only to discover I HAVE A CABLE,,,, (June '97) So back to square 1, and I will probably fix a 30 Euro semi mechanical solution, straight on the pedal. Will post a picture when done.

Thanks everybody for your thoughts!