Throttle position sensor question
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Joined: Jun 2003
Posts: 66
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From: Salt Lake Utah
Throttle position sensor question
Have an Accufab four barrel style throttle body with a CTS Corp 825 series throttle position sensor. Using a FAST "Classic" ECU, and the TPS does not travel (rotate) far enough. Consequently the ECU registers 20% at idle and only 55% at full throttle, and the range is not adjustable in the ECU.
CTS Corp has a 581 series TPS with a shorter sweep range (90 degrees instead of 110 degrees on the 825) and would work but I'm unable to find what kind of car they are used on. Does anybody have a suggestion to correct the problem or know where to find a 581 series TPS ???
Thanks
CTS Corp has a 581 series TPS with a shorter sweep range (90 degrees instead of 110 degrees on the 825) and would work but I'm unable to find what kind of car they are used on. Does anybody have a suggestion to correct the problem or know where to find a 581 series TPS ???
Thanks
Pro
Joined: Jun 2008
Posts: 610
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Interesting problem. For the thing to work correctly you not only need the two extremes to be correct but also every position in between. Potentiometers come with different "tapers" - log, linear, purpose built, which will give you different output voltage vs. position which is what the ECU is looking at. I would assume the TPS has to be matched with the ECU as well as the throttle body if in fact the programming cannot be changed. As you positive about that?
Thread Starter
Advanced
Joined: Jun 2003
Posts: 66
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From: Salt Lake Utah
Interesting problem. For the thing to work correctly you not only need the two extremes to be correct but also every position in between. Potentiometers come with different "tapers" - log, linear, purpose built, which will give you different output voltage vs. position which is what the ECU is looking at. I would assume the TPS has to be matched with the ECU as well as the throttle body if in fact the programming cannot be changed. As you positive about that?
FAST advised me today the programming can not be modifed, the limited range can be tuned around and that acceleration enrichment is all that's affected by throttle position. Seemed odd to me but assume I should believe them. The ECU is a speed density type. Your thoughts sir?
Pro
Joined: Jun 2008
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Jim, my experience in this area is more theoretical than hands on. From what you relate I would agree that you need to find a position sensor with the correct range of motion. Perhaps another member will have more information.
Race Director
Joined: Sep 2000
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From: The Top of Utah
It is hard to comment effectively without seeing it, but it seems the TPS could be activated differently, so the TPS will have full travel to match the throttle travel. It is a little like some replacement TBs that won't attain full throttle unless the throttle cable attachment point is altered. That is what I refer to as doing a "re-ratio" of the throttle linkage. Does Accufab not offer a compatible TPS? If not you may have to fab your own activation linkage.
RACE ON!!!
RACE ON!!!
Thread Starter
Advanced
Joined: Jun 2003
Posts: 66
Likes: 0
From: Salt Lake Utah
It is hard to comment effectively without seeing it, but it seems the TPS could be activated differently, so the TPS will have full travel to match the throttle travel. It is a little like some replacement TBs that won't attain full throttle unless the throttle cable attachment point is altered. That is what I refer to as doing a "re-ratio" of the throttle linkage. Does Accufab not offer a compatible TPS? If not you may have to fab your own activation linkage.
RACE ON!!!
RACE ON!!!
I think I can tune around this limitation via changes to acceleration enrichment. We'll see.
Thanks for your help guys and Happy New Year!!
