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TPS Wiring Trickery


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#1 Dundaberg

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Posted 31 March 2014 - 7:43 AM

So I'm wanting to use the intake manifold off my wrecked GTB on my RS. Just wondering if anyone knows of a way or if it's even possible to wire in the 3 wire TPS using the 4 wire BC5 loom?

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#2 boostin

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Posted 31 March 2014 - 7:58 AM

The 4th wire is for the idle switch. You'll have a permanent fault without it. Why do you want to use that manifold?
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#3 Dundaberg

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Posted 31 March 2014 - 8:22 AM

Oh yes, I want to run straight pipe through from turbo and into GC8 or GTB factory air box to match and get rid of the 90 degree bend off the turbo.

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#4 Drunkenmonkey

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Posted 31 March 2014 - 4:16 PM

Could you put a switch on the pedal to replace it?
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#5 Dundaberg

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Posted 31 March 2014 - 5:17 PM

There is already a switch under the pedal lol have no idea what I'd does though

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#6 boostin

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Posted 31 March 2014 - 10:13 PM

Can you bolt the RS throttle body up to the GTB manifold?
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#7 Dundaberg

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Posted 31 March 2014 - 10:26 PM

Naa tried that, it needs to be flipped, but even the the RS TPS fowls on the manifold

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#8 Dundaberg

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Posted 31 March 2014 - 10:28 PM

I might try and see if I can swap out the shafts from the throttle body's and make is mixed and matched to make it work

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#9 Drunkenmonkey

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Posted 31 March 2014 - 11:11 PM

There is already a switch under the pedal lol have no idea what I'd does though

Don't see why not just use a relay off it so it doesn't interfere with what ever that uses
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#10 Speedfreak

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Posted 04 April 2014 - 8:08 AM

3 wire TPS on 4 wire loom, i have done this personally on the new rally car and works :) look down the bottom at the colored pic explains it well :)

http://www.clubsub.o...ic,17075.0.html

#11 Dundaberg

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Posted 04 April 2014 - 7:38 PM

Oh sweet, that's got to know, do you have any idle issues seeing the brown wire not used?

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#12 Speedfreak

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Posted 07 April 2014 - 5:34 AM

nope no issues really, its a rally car so doesn't spend much time at idle so prob not the best test but i haven't had any drama, even after a sprint get to the end and idles away happily.

not really sure why it doesn't need the extra wire, but it works for me so i'm happy

#13 boostin

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Posted 07 April 2014 - 8:30 AM

But they're not on factory ECU's.
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#14 Reuben

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Posted 09 April 2014 - 11:22 PM

What about wiring up an actual micro switch, aftermarket. Isn't that all it is anyway? I'm facing the same issue with blighter, now that we've gone with a bf-gt loom, and I'm using the ej20k manifold with the larger throttle body.

I'm going to have a look tonight and see if the switch inside the 4-wire is normally open, or closed type...
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<Shale>: Blighter doesn't really have an accelerator pedal, it's more just a loudness pedal. You can change volume, but you won't go any faster.


<mjlqtown>: (Southern US accent) I'v excised the demon! This car is now clear!


<Reuben>: I feel like when you stomp the throttle in Blighter, it's like you've startled an old man!

#15 Dundaberg

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Posted 09 April 2014 - 11:40 PM

Oh yea, nice. Will be interesting to know what you find out

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#16 Reuben

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Posted 09 April 2014 - 11:58 PM

Just had an idea. An accelerator switch, cruise control cars have em on the pedal box, but any universal one will do the trick. Just gotta figure if it's normally open or closed.
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<Shale>: Blighter doesn't really have an accelerator pedal, it's more just a loudness pedal. You can change volume, but you won't go any faster.


<mjlqtown>: (Southern US accent) I'v excised the demon! This car is now clear!


<Reuben>: I feel like when you stomp the throttle in Blighter, it's like you've startled an old man!

#17 Reuben

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Posted 10 April 2014 - 9:35 PM

Going to post up some quick excerpts from the manuals

For how the ECU handles the CEL's, and the fail safe for idle switch.

Fail-Safe Function: For the part which has been judged faulty in the self diagnosis, the ECU generates the associated pseudo signal (only when convertible to electric signal) and carries out the computational processing. In this fashion, the fail-safe function is performed

42; Idle Switch. Diagnosis: Abnormal voltage input entered from idle switch. Fail-safe operation: Judges ON or OFF operation according to the throttle position sensors signal


In other words, with no idle switch the ECU chucks up a CEL, and then proceeds to guess when to idle based on the TPS signal. Smart.

About the BC/BF TPS:
Posted Image
TPS-about by Reuben Horsley, on Flickr

BC/BF Turbo Pinout:
Posted Image
4-plug-pinout-1 by Reuben Horsley, on Flickr

Posted Image
4-plug-pinout-2 by Reuben Horsley, on Flickr

Trouble Check for Idle Switch:
Posted Image
TPS-trouble-check-1 by Reuben Horsley, on Flickr

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TPS-trouble-check-2 by Reuben Horsley, on Flickr

And from the trouble code page for idle switch, the switch is closed (read completes a circuit, and sends a voltage to the ECU) when the throttle is closed, It is open when the throttle is open, and no signal will be sent to the ECU.

So for us to used an accelerator switch on the pedal box, we need a nomally OPEN type switch. This means, that when there is nothing touching the switch (the accelerator is depressed), we need the circuit to be open, and no voltage sent to the ECU. When we let off the gas, and the accelerator pedal touches the switch, it needs to close the circuit, which will send a voltage to the ECU. Which has to be 5v, not 12v, according to the pinout. To get this voltage, we can can tap into pin 1 on the TPS, that's the wire that would normally be sending the voltage though the TPS. This wire will be coming from the ECU (pin C6 on the ECU), so we can tap into this wire at the ECU, and just run it down to the pedal box, and plug it into an normaly open pedal switch, then on the other pin of the pedal switch, we can plump back into ECU pin D1.

What confuses me is that D1 appears to be a common ground for the TPS, Idle Switch, and TPS sensor shielding wire. So I don't know HOW it works, I just know the idle switch is a switch between C6 and D1.
Posted Image


<Shale>: Blighter doesn't really have an accelerator pedal, it's more just a loudness pedal. You can change volume, but you won't go any faster.


<mjlqtown>: (Southern US accent) I'v excised the demon! This car is now clear!


<Reuben>: I feel like when you stomp the throttle in Blighter, it's like you've startled an old man!

#18 DacerX

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Posted 10 April 2014 - 9:40 PM

brain hurts
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#19 Reuben

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Posted 10 April 2014 - 10:16 PM

And now regarding the 3-wire TPS... Because it's a little bit backwards compared.


3-plug Pinouts:

Posted Image
3-plug-pinout-1 by Reuben Horsley, on Flickr

Posted Image
3-plug-pinout-2 by Reuben Horsley, on Flickr

Posted Image
TPS-3wire-wiring by Reuben Horsley, on Flickr

As we can see, the 3 wire reads 0.5v at fully closed, and 4.3v at fully open, where the 4 wire reads 4.7 fully closed, and 0.9v fully open. Both 4-plug and 3-plug ECU's supply a constant 5V to their TPS's

And the wiring for the 3-wire tps, sadly the later manual is less detailed. But one may be able to read though the lines and pick that pin 1 and 3 are a supplied voltage, and ground, and pin 2 is relaying a sensed voltage to the ECU, leading to reasoning that if we reverse the polarity of pine 1 and 3, we will get a signal close to what the 4-plug ECU wants to see...

Edit, the wiring diagram tells us what we want to hear, B136-14 is the 5V power supply, B136-13 is ground, B136-16 is sensed voltage across those two pins via the TPS. So we should be able to reverse them. B136-14 is pin 1 on the TPS, so we would wire the 5V into pin 3 to reverse the polarity, meaning that pin 1 becomes common ground on the TPS, and we keep 2 unchanged, and send that signal to the 4-plug ECU

Practically, when wiring up the 3-wire TPS into the 4-plug loom, we just need to make sure that the power and grounds are supplied over pin 1 and 3 on the TPS in a mannor that gives us about 4.7v on pin 2 with the throttle closed, and 0.9 with the throttle fully open. Looking at the trouble code stuff on the TPS for the 4-wire, a 4-plug ECU is happy if the voltage is anywhere between 4.4v and 4.8v close, and 0.7v and 1.6v fully open. If we can adjust the 3-wire to get close to these numbers, at least within range of what the 4-plug ECU want's, then we're all hunky dory.
Posted Image


<Shale>: Blighter doesn't really have an accelerator pedal, it's more just a loudness pedal. You can change volume, but you won't go any faster.


<mjlqtown>: (Southern US accent) I'v excised the demon! This car is now clear!


<Reuben>: I feel like when you stomp the throttle in Blighter, it's like you've startled an old man!

#20 DacerX

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Posted 10 April 2014 - 10:35 PM

Sci fi shows have always showen that reversing the polarity solves all problem and kills bad guys
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