I have had this idea for a while of modifying a cruise control into a throttle lock. My best gas mileage comes not from holding a steady speed, but from holding a steady throttle. I use my ScanGauge to find my TPS (throttle position). If I want to got about 35, I hold it at about a TPS of 13. If I want to g0 40, then TPS is 14. 45-55 mph, I use a TPS is 15 or 16. I will try to just hold my pedal at that position, which is not easy. I love the ease of cruise control, but gas mileage can be better.

My idea is to modify a cruise control to hold the throttle at a fixed position, instead having it adjust the throttle to maintain speed. I think the cruise control receives pulses from the speed sensor, and it uses those to tell speed. If the frequency of the pulses increases, the speed has increased, so it lets out the throttle a bit. If the frequency drops, it increases the throttle. What if I made a small add on to send a fixed freqency to the cruise control. I could get the throttle adjusted to where I want it, say at a TPS of 15 by the ScanGauge. Then I would activate the cruise control. It would read the frequency from the speed sensor, which is now the output from my add-on device. It would read a certain frequency of pulses. Since the pulses would neither increase, or decrease, it would hold the throttle at that postion. It seems like it would work. I could also have a switch that would switch between the speed sensor input and the fixed frequency input. That way I could use it as either a cruise control or a throttle lock.

Another option is to buy a used cruise control, and gut the circuitry from it and make my own. I am guessing it is basically stepper motor of some sort. Of course, I haven’t done any electronics work like that for years, and it goes a bit beyond anything I ever did. I would still want to be able to hit the brakes, and have it release the cruise control. But I would no longer have it as a cruise control.

Too bad someone didn’t already make something like this.

Posted by Rob in My Car on May 23rd, 2009 | No Comments