TPS switch

im trying to hook-up a relay to power up a water injection pump on my car.  i need a throttle switch like a nitrous setup but instead of wide open throttle, i need one that closes at part throttle.  my TPS sensor puts out about .5 volts closed and about 4.9 at WOT, i need it to power up a relay at about 1.0 to 1.5 volts and stay on all the way to WOT. any ideas?

Didn't you get the memo about your TPS sensor?  You need to use a different cover sheet with those from now on.  I'll get you another copy of the memo.

huh?

Mmm hey galantin. Whatsup?? Mmm yea, did you get that memo this morning about using the new cover on the TPS report?? "Yes I got the memo" WEll you didn't use the new cover sheet for the TPS report. Did you get that memo?? I'll make sure you get it. Mmm bye. Oh, by. the. way. I'm gonna have to ask you to come on in on Saturday. Yea. And on Sunday too. Greeeeeeat. Bill Lumberg

It sounds like you want to run a single-stage setup, with no modulation on your water injection.  Most injection kits use a digital controller that operates off of mass-air flow or TPS.  This is for a modulated application,though.  Is there a relay (adjustable perhaps?) that will activate at 1.5 volts?  1.5 volts is on the low end of your TPS voltage spec, so you may just want to flip a switch to activate the injection.

What you can do is connect a potentiometer in series with the coil of your relay.  Keep adjusting it until the relay activates where you need it to.  Then, take a resistance reading of the pot where it's set, and replace it with a resistor of that same value.My ex once told me I have a perfect face for radio.

that also is a good idea but still i would need a relay that could activate at a very low voltage, the only relays i know about(and can get) are the 12 volt kind.  i found an output on the tps (4 wire) that is grounded when the throttle is shut (closed throttle switch)so  i might just wire a relay to that and connect the pump to the normally closed 87a  terminal so that the pump only activates above closed throttle.