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TPS alternatives any ideas ?

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As you all know I have made a few changes. Along with all changes comes headaches.

The majority of these have been overcome, but a few little niggles remain.

The most troublesome and recurring is the throttle pot accuracy.. !!!! 

This does not stop me enjoying the performance and is only noticeable from the lap top

when driving.  You can not really feel anything , but it will need to be sorted to ensure the

best possible results.


When the engine is first started the values are spot on at 28 at tick over. as the engine

runs over time this value moves to as much as 32 at tick over, This change the fuel values 

slightly as the ECU thinks the throttle is in a different position.

As it is we can dial in a tolerance to tell the ECU the throttle is shut anywhere between

these values, this relieves the tick over from variations.

However it does not change the fact that the standard TPS fluctuates with engine temp.

I have tried several standard units now and some are worse than others, all from various

sources inc OEM. A veriation of 4 is the best of the bunch.

For me to get the best results i think i will need to move to a more up to date contact-less


Has anyone changed theirs or know of a suitable alternative i could try before i go blindly

fishing in the markets....?

Any ideas on this will be greatly appreciated...




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This is probably dumb, but reading the post I started to think about valve clearances, and possible variations between hot and cold.

Would a leaking valve not produce the same symptom ?

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I think you have miss understood or i have not explained clearly enough Roger.

The throttle potentiometer is supposed to indicate the position of the actual throttle

at any given time. It value should remain constant at any set point and is not... The

signal sent to the ECU is then inconsistent. Only when the values are identical to

the mapping program as dyno'd will the tuning be its best. 

I do realise that the error is only very slight and not enough for great concern , but

it could be better and i would prefer it that way..

What i need is a more accurate TPS which is not influenced by externals such as heat.

Any idea's ?    

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OK, I thought the  throttle potentiometer indicated the volume of air passing, rather than the physical position of the butterfly. My mistake.

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You don’t mention what the change by 4 units is equivalent to in percentage terms (or should that be in perhexage?), but if the closed to wide open scale is nominally 28 to 255 then that represents an unacceptably large drift.


I’ve previously used the standard “rotary position sensor” that RS sell for about £25 and that is more stable than you’re


Have you considered that the throttle pot may be the victim and not the cause, and measured the Vref that it receives,
and the pot’s Vout to see whether they vary similarly? (Sorry if teaching you to suck eggs…..)


If you’re adamant that it is the pot that’s at fault then the next step is to use a Penny & Giles TPS280DP which is a
contactless device that contains some pretty trick electronics which is claimed to have a stability of ±30ppm/°C. From memory the cost is somewhere around £120.


So far I haven’t used a P&G myself but I’m currently in the process of fitting an injection system to a 1972 Porsche 911
for a friend and the P&G device is what we’ve settled on….

... and apparently P&G deal with the great unwashed directly without having dealers as such.




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Thanks for your input

So It seems I am not alone in the TPS change market. .. I was starting to feel lonely..


I think you are correct to assume the TPS units may be the victim and compatibility

with the new ECU may be the influencing factor. The closed to open scale you refer

to is tighter than what you stated, the exact i would have to check, but  tighter makes it 

even less acceptable for drift... So you will understand my desire to change.

I also think the tolerances on the standard TPS are too wide for what i am using. They

seem to work well but when you study the data it tells a different story, especially when

heat soaks into them... 


Over the last two days i have been trawling the markets and talking to all my m/sport

contacts for ideas and recommendations..

I have looked into and received details on the 'Rotary position sensors' also linear. 

They have potential but the fitting could cause problems.


However and coincidently... I have decided to try the Penny and Giles contact-less

unit , The spec is superb and fitting should only require slight engineering..

More important I found out it is approved by Omex (my ECU supplier) and a preferable

unit to use with the 710.

I have an appointment to visit the suppliers and have been asked to take the Esprit down 

so they can see to discus all points.

​Should be interesting ..






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​I sourced a penny and Giles unit on Monday and spent a couple of days

manufacturing the conversion mounting..and fitting.

I set the parameters on the lap top and took it for a test drive. There was an

instant difference with the light throttle response and It felt very positive..

Today I went back to N'hampton motorsport to have the lineage checked.

Although the extremes were the same the centre section was slightly different.

After a little fiddling with the fuel map it is now spot on...

The open closed scale on the standard TPS was 28--197 which drifted a min

of 4 points during use...

The new scale is 29---222 with P&G unit  with no drift at all with use.

I can not explain such a change in the smoothness ,but I will say with

confidence that it is now as good as I could of ever hoped for...Me is well happy  :thumbup:

I know some think this was a bit fussy to be concerned with but as i have said

many times its all the little points added together that make the difference...

Pic's of kit and fitment..





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Hi Dave


Always satisfying to resolve a niggle. However reading your first message I would countenance against using a lap top whilst driving. 

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Im sure what was meant was that the data was gained on the laptop whilst driving...and then analyzed later...not analyzed whilst driving....

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I know this is a 4 month old thread, but I do have a question or two.

Has anyone tried this new TPS using the standard GM ecu? With the programmability of the TPS regarding output range, is there really a problem on considering it for replacing the stock TPS (other than mechanically adapting it)? The ranges shown above seem to be pretty close, maybe 10% difference on the top end, but I would even expect that in different stock TPS's.

It would certainly appear that fueling would be more accurate, by removing the thermal drift of the stock unit. And would also appear it would have longer life, and as you have eluded to, better low end drivability.



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After getting a part number from gixxer, and chasing down what info I could, it would appear most replacements for the stock TPS these days are hall effect based, and no longer have temp sensitivity.  I am ordering a Delphi SS10425 (that crosses from the gm 17106681 tps). It is plug and play, and are quite inexpensive (25-35 dollars US).  Following is the description from Jegs....


"Delphi speed and position sensors are designed for use with any control module that accepts a digital input. Our sensors use the Hall Effect or magneto resistive (MR) principles for accurate and clean signal input to the electronic control module (ECM). The result is more design flexibility to address unique applications requiring high-temperature operation and extremely stable switch point repeatability and/or high air gap capability. Our speed and position sensors also maintain optimal performance during drastic temperature changes for robust, long-lasting sensor protection thanks to a single-element design. Delphi speed and position sensors undergo certified electrical testing with industry EMI protection against noise interference and other sensor output, and feature enhanced sensing functionality that delivers reduced emissions, improved reliability and superior driveability."


It should be better than the 18 year old one it has now.





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