Slide Potentiometer --> Variable Throttle Position Sensor
 

Hey y'all, I just wanted to shoot an idea your way. I did some research online and couldn't find anyone who has done this or considered it in a post, I don't know which one worries me more.
First of all, I have not built this yet but I am considering it greatly. I am at the point in the MegaSquirt build where I have all the sensors hooked up beside the vTPS. I was doing a little shopping around the junk yards in my area and a little online to find a vTPS that would give my MS the useful information it needs for AE. While in the midst of my research I thought to myself, "If all a TPS is, essentially, is a glorified potentiometer then why don't I just hook up a damn potentiometer to something that moves mechanically in correspondence to the throttle." Conveniently enough, we have a throttle cable in the engine bay that moves linearly in correspondence to throttle position so why don't we simply just hook up the sliding part to the throttle cable? The first thing that comes to mind is accuracy and consistency of this $2 potentiometer. I mean there has to be some reason some of these glorified potentiometers cost 2,000% more than my $2 counterpart, right? Secondly, if the voltage readout isn't completely linear on my $2 pot then this could potentially give the ECU bad information at various throttle positions. Lastly, we would have to do something about that moisture. It seems like a sound and practical idea which would work universally across all makes and models if all of the aforementioned problems weren't problems at all. If anyone is wondering how exactly this circuit would be wired please check out this .


Could someone explain to me why thing won't work or why it is a bad idea?

Because a potentiometer from radio shack doesn't have thousands of hours of oem testing and in millions if cars. It's not a bad idea, but i'd rather grab a real tps out of a junkyard.

The linear pots I use at work start at about $350 and go up as they get longer, the last one I ordered was $900. Even then they have a service life because it's a contact sensor.

With that aside, yes it would work to put a pot on the pedal. You'd likely have to mount it hanging from the steering column area, because the pot will a little longer than the stroke when it's fully retracted. So if you wanted it hidden behind the pedal, it would protrude into the firewall. Linear pots are very weak and cannot take side load. So watch out for your foot! We order spares of all linear pots we use, because it's just a matter of time before someone tries to do a spring change without disconnecting the ride height sensor, or kicks a pot on a hydraulic actuator.

You already have a throttle body that has a straight forward way to put a variable TPS on it, so I don't see any reason to reinvent the wheel when there's already a robust and cheap solution.