My TPS with a classic FAST is reading 30% under idle and 76% under WOT. Adjusting the TPS to the other end of its range I get 37 idle and 77 WOT. Does this sound like a bad TPS or is this just how the classic FAST is?

Thank you,
-Aaron

 

Not familiar with FAST but shouldn't there be a way to calibrate the TPS?

 

I would have to confirm my WOT % but I have a high idle % too. I slotted the TPS and the best I can do is 28. I set the max tps at idle = TPS plus 1 so for me I set it at 29. I also had to adjust the throttle follower. I'm just learning the system myself though...

 

My old classic went from 15% to a little more than 90% so you should be able to get that better. Slotting the tps is one way, I also know there are several different Ford TPS sensors too. Then there is stuff like Accufab who clocks their bolt holes a little different.

 

Brian,

I have an accufab TPS - I am going to go out tonight and unsure that the throttle is opening all the way, and then test the voltage. If things are not looking right I will order a new one from Accufab.

-Aaron

 

With Accufab's throttle body you will have to slot the tps to get the reading right. He drills his clocked different than everyone else.

 

Thanks Brian,

I ended up taking the TPS off and measured a range in the FAST from 0 to 80%. I bought a replacement and it only went from 0 to 84%. I haven't put them on a voltmeter yet but it seems like it will be near impossible to get the >80 flood clear and fan turnoff and still maintain a good throttle follower characteristics. Idle is ~37 with a WOT of 77 when the sensor is fully clocked. Drilling out the holes more will result in something like 40 idle and 80 WOT, whereas the throttle follower table maxes out at 40...

-Aaron

 

The problem isn't the sensor it's the throttle body. The way that Accufab drills the holes is clocked different than everyone else. My Wilson throttle body didn't have this problem. I have seen guys leave only one screw in them so they can twist it more and get it to go closer to 0 tps at an idle. If you could get something like 15% that would give you more towards the max side.

 

Thanks again Brian,

I will be purchasing a Wilson for the turbo build this winter anyway so I think I will leave this one be for now.

-Aaron

 

Yes, if you are going to change then just leave it.

 

Is this on a 4-hole? My 4-hole accufab did this too. You won't see 100%, just adjust the low side settings for idle . You will be fine.

 

To answer the question of "is it a problem" from a control perspective the answer is no... almost. It can be accounted for in almost every table. You'll need to set the max TPS for idle threshold appropriately, which you can do. As far as any steady-state stuff, the TPS has no effect on fueling or timing. The AE fueling curves will have to be tweaked, specifically the AE Fuel vs. TPS position graph. You'll want to have 80-90% settings near 40% and then have it taper downwards after that. The TPS rate of change fueling should be minimally impacted since it's based on change and not absolute position. Where you will lose control (as you mentioned) is with the throttle follower. If you are unable to make any mechanical mods to facilitate a wider range for the sensor, the lack of low percentage values to tune with in this table will be a problem.

The classic fast never had a TPS calibration method so this is a common occurrence, although a minimum of 37% is much higher than normal.

 

Thanks Craig,

I may also be moving to a FAST XFI at some point in the near future so I will have the TPS tunability there.

-Aaron