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Thread: Throttle Position Sensors - ridiculous price!!!!

  1. #1
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    Throttle Position Sensors - ridiculous price!!!!

    Every FInj RRC or Disco needs these replaced eventually but hello - $320 locally for a $10 potentiometer is ridiculous.
    Ok, cheaper via the ebay route but still annoying at $120+ + on costs + hassle

    I don't have access to rumage through a parts bin - but a Ford falcon EH unit looks the go.

    Anyone done a conversion or research on this?

    ta
    Chris

  2. #2
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    Ordered one from RS components as a spare around 40GBP, only need 90deg swing but this gives 130 deg swing.

    A lot of the guys in the TVR forums use this, as you rightly put it, stupid price for something so simple.

  3. #3
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    And to make things worse, alot of them are faulty even when new. I'm on my third replacement now. The first they didn't even bother fitting.
    98 Harvey the tractor - 300 tdi Defender Wagon
    84 Alfetta GTV

  4. #4
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    Ordered one from RS components as a spare around 40GBP, only need 90deg swing but this gives 130 deg swing.

    Are you sure that would work?
    You are still going to need the same resistance/voltage outputs over the 90* range. Otherwise it's going to cause more greif than a broken one.

    I would think you would have more chance getting a Falcon one to work. It's the amount of modification it would require to get it to fit - mounting points, pin outs, connector fitting, and throttle shaft fitting, etc - that's the question. But you never know.

    HTH
    Andrew

  5. #5
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    Ordered one from RS components as a spare around 40GBP, only need 90deg swing but this gives 130 deg swing.

    Seeing the throttle only opens 90degrees , and the TPS swings between 0.3 volts or so at idle to near 5 at WOT, then IMHO it will not work. The ECU needs to see 4.7 or so for full throttle enrichment and 90/130 = 70% then you will not more than about 3.5 volts..
    Why go for a bodgy set up? surely there are many options from other cars that could be jury rigged.
    Regards Philip A

  6. #6
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    Ok,
    Looked into this in some detail and may have some viable options - bear with me!!

    Firstly, I found that disconnecting the TPS resulted in a much smoother idle (albeit when warm); no "shunting on acceleration"; and actually couldn't notice a difference at WOT. I borrowed an oscilloscope and confirmed that the Lucas TPS was producing a very noisy output - overall linear yes, but big drop outs in places. The ecu reads the TPS output to adjust injector pulse width based on rate of change as well as rest positions (idle/WOT) and I think these drop outs are simply confusing it...ie you accelerate and the TPS output momentarily drops out to 0V and it cuts the injectors hence lumpy etc.

    This problem is well known to the TVR/Ginetta/Morgan crowd where the issue is more noticeable on lighter vehicles.

    The obvious solution is to just fork out the $320 for a new one, which is fine - except it really annoys me! At the end of the day it's a 5Kohm linear pot in a nylon housing and three times the cost of a GM or Ford part. Also, new ones aren't as guy said, necessarily good out of the box.

    As I said they are simply a 5k linear pot. The input to the pot is 5V.It' s important to note that the mechanical range is not important. The electrical range over 90 deg is as Phillip said - roughly 0.3V> 4.7V with that 5V input. The issue is finding one that mechanically mates to the throttle body without painful modification.

    There's a few contenders from the Motorsport world. Jenvey http://www.jenvey.co.uk/home/accesso...ttle-position- a UK company have a range of TPS. Cheapest is the Colvern or Wabash units at 52 pounds which are simple pots - or more interestingly, the Penny & Giles Hall Effect TPS which is a contactless unit that will provide the analog .3V to 4.7 volt we need. Both units are available via the Australian distributor Competition Systems - Motorsport Electronics at a reasonable cost
    The P&G unit can be ordered in a multitude of configs, Haltech/Megasquirt users can order with a PWM output. Both units have std 32mm mounts - sorting the mechanical/seal possibly a bit more challenging...

    At the end of the day probably way too much effort to save a $0! but it's the principle and it's more fun than gardening!!!!

    I'm going to have a go just for kicks....

  7. #7
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    What about the 100 degree unit???
    Factory one is 100 also.

    Using Capitals, the difference between helping your Uncle Jack off a horse or helping your uncle jack off a horse...

    Bonnie - MY03 D2a TD5 Auto (One Bourbon)
    Clyde - MY93 RRC 3.9 Classic (One Scotch)
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  8. #8
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    At the end of the day probably way too much effort to save a $0! but it's the principle and it's more fun than gardening!!!!

    I'm going to have a go just for kicks....

    Let us know how you go. I have repaired electronic throttle bodies with $10 parts from JayCar when to send away for repair was a couple of hundred.

    I borrowed an oscilloscope and confirmed that the Lucas TPS was producing a very noisy output - overall linear yes, but big drop outs in places.


    Yep. Test don't guess. The scope is just as good as your scan tool.
    Colin can I get a scope option added please.

    As you probably know, usually with TPS drop out you get hesistation and stumbling at certain speeds.

  9. #9
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    Quote Originally Posted by LOVEMYRANGIE View Post
    What about the 100 degree unit???
    Factory one is 100 also.
    Yup - spot on. Basically all potentiometers have a mechanical range and an electrical range. The mech rang will always be wider by a few degrees. Most throttle plates have a mech range slightly less than 90 degrees as the plate rests at a slight angle at close to prevent sticking.

    The flapper ecu's required that the pot is mechanically set to give a range between .3>4.7V. However, Hot wire ecu's are adaptive - hence the fixing screw are fixed not slotted. This is (for once) useful as the ECU learns the range (albeit within limits). As long as idle is <0.1V and runs to <4.7V all is good. It would be quite fine to bodge say a 15k ohm audio pot with 270 deg travel and just use the first 3rd of travel.

    However, the goal here is to get a reliable plug 'n play alternate, The Penny & Giles contactless pot is probably the worlds best TPS but not much cheaper than OEM- the others cheaper but still very good.

    As previous the challenge is not electical but duplicating the "D" drive and mechanical mounting to the RRC plenum .
    Planning to pull my TPS off this sunday to measure up accurately then CAD draw- unless anyone has that already????

    ta
    Chris

  10. #10
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    As long as idle is <0.1V and runs to <4.7V all is good
    I would double check that. That is probably in self check territory and will log a short to ground code (in most cases).
    I would of expected around 0.5V
    Last edited by nobbyclrk; 7th October 2011 at 10:39 PM. Reason: Added info

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