legacycentral bbs

Just curious if anyone has used the MRT FCD? I just got one from a friend for $50. It has an adjustment pot and an indicator light to tell you when it is working.

I haven't installed it yet. I'm waiting to do a couple of other things to my car.

The only thing I don't have a good feeling about so far is the setup instructions. It tells you to go out and run your car up to fuel cut and then keep backing down the pot until the fuel cut disappears. (The procedure is a bit more involved, but I'm not going to cover it all).

Would it make sense to you guys (vrg3?) to just apply 12.5psi or so to the map with a hand pump and adjust the pot on the fcd to clamp at that voltage?

Anyone know what the trigger voltage is for fuel cut from the MAP?

Thanks,

Kyle

http://www.graphics.cornell.edu/~v/fcd/

You'll want to clamp around 4.3 volts. If the MRT FCD doesn't allow you to turn the pot to a calibrated position, then you could try the hand pump method, or use any other supply of approximately 4.3 volts (you might be able to use the TPS; you'll probably need to block the throttle open a little to get its reading to be what you want).

Cool. 4.3V is what I needed to know.

Its an adjustable voltage clamp with a 25-turn pot. It lets the signal pass through until the trigger voltage and then clamps steady from there. Very similar to your design, from what I can tell.

Correct me if I'm wrong though, doesn't yours depress the curve as well, i.e. you're clamping the high voltage, but you're flattening the slope too.

Its actually a nice unit, meant to be under the hood. I would just rather clamp at a specific voltage rather than running the car into the fuel cut a few times and turning the pot until it goes away.

Thanks again.

Kyle

The design I described on that web page doesn't do anything with the slope. The signal passes through unchanged until it reaches the threshold voltage.

Mmm... 25-turn pot...