Board logo

TPS orientation
contaminated - 20/5/09 at 11:07 PM

When the TPS is sat on the end of the shaft at the end of the throttle spindle should it be fully rotated anti-clockwise? If so i think I may have found my timing issue. In my case you slide the TPS onto the shaft and then have to rotate it clockwise about 30degrees (therefore the internal part of the TPS rotates anti-clockwise) to get the mounting holes to line up. I'm gussing this is not right and that the ECU thinks the throttle is open at idle?

NS Dev - 21/5/09 at 06:28 AM

no idea what the throttle pot is talking to in the way of ecu etc but regardless, an essential part of setting up and engine with management is zeroing the throttle pot correctly, and to do this you really need to know either what voltage the ecu expects to see at idle, or be able to look at the tps load sites on a laptop plugged into the ecu!

contaminated - 21/5/09 at 06:51 AM

hmmm. I take your point, and i think that's another good reason I'm going to go over to a megajolt (because I can't get into my GEMS ECU to have a look at or change any settings), but are you saying then that the TPS may (subject to it's relationship with the ECU) sit part-turned on the spindle at idle?

will121 - 21/5/09 at 07:20 AM

some TPS have the potential to rotate more the 90degrees although they will only sweep through 90degrees when installed to the butterflys, the principal of setting up the ECU is to set the throttle closed position of the TPS and then the 100% open, so as long as the TPS sweeps through the full 90degrees with continuous chenge in resistance the actual start value is not that critical (i think)

dinosaurjuice - 21/5/09 at 07:59 AM

quote:
Originally posted by will121
some TPS have the potential to rotate more the 90degrees although they will only sweep through 90degrees when installed to the butterflys, the principal of setting up the ECU is to set the throttle closed position of the TPS and then the 100% open, so as long as the TPS sweeps through the full 90degrees with continuous chenge in resistance the actual start value is not that critical (i think)


100% correct. its actually bad practise to use the full range of a potentiometer because unless there very expensive ones the first and last 5 degrees are rarely linear.

MikeRJ - 21/5/09 at 09:23 AM

quote:
Originally posted by contaminated
When the TPS is sat on the end of the shaft at the end of the throttle spindle should it be fully rotated anti-clockwise? If so i think I may have found my timing issue. In my case you slide the TPS onto the shaft and then have to rotate it clockwise about 30degrees (therefore the internal part of the TPS rotates anti-clockwise) to get the mounting holes to line up. I'm gussing this is not right and that the ECU thinks the throttle is open at idle?


Are you using the original throttle body and ECU for the engine?

For most OEM systems the TPS should have a specific voltage on the wiper with the throttle fully closed, the workshop manual may show this if you have one.

Aftermarket ECU's usually allow you to calibrate the end points of the TPS so you don't have to make it adjustable.

[Edited on 21/5/09 by MikeRJ]

BenB - 21/5/09 at 10:42 AM

It's best to have a little "spare" in the pot movement so that if you ever reduce the idle you won't put a twisting force on the pot and break it.

Most ECUs have a calibration mode where the ECU learns the min / max values for TPS value vs throttle throw.

contaminated - 21/5/09 at 02:28 PM

Thanks all - very helpful. On the basis that I've run out of talent I have today bought a megajolt. I don't have the software for the GEMS and going forward the MJ route will be easier given how many people I know using it.