TPS Function

Neil_E. · Oct 16, 2007

The specific function of the TPS seems like "smoke in mirrors". All I can find is that it advances the timing at low RPMs and has reduced effect as the revs climb.

Has anyone found any graphs or charts to indicate how much the TPS shifts the timing?

I unplugged mine and immediately noticed a lean bog. The engine did not run as well as before, but came on stronger at half throttle. When I checked the TPS values originally, they were in the range specified by the manual. I am looking at this since Sparks mentioned the possibility of extra bearing wear from advanced timing at low RPM.

Chas · Oct 16, 2007

The TPS functions much like the vacuum advance in older auto distributors, i.e. to aid in part throttle running and fuel economy. The TPS adds maximal advance during part throttle low to mid RPM conditions and tapers off as the throttle is opened up. With my TPS disconnected, I could discern little if any 'seat of the pants' difference in the way the engine ran or in engine response.

It might be informative to compare the advance with a strobe light with and without the TPS. I'll bet that Dale Lineaweaver has access to TPS advance info.

Neil_E. · Oct 17, 2007

Chas,
I have emailed Dale, but he is still buried in his big OEM project. I just checked my notes and realized that I put in the 150 MJ at the same time I disconnected the TPS. This is wrong as I should only make one change at a time. The lean bog is probably a result of not changing the needle position to accomodate the change in main jet. I am still interested in knowing how much the TPS shifts the timing. Dale probably has some info on this.
Neil

chilledspode · Oct 17, 2007

Hi Neil,

Yes it is in a thread somewhere - I have read it but can't find it now...

I'll PM you my recollection of the number so I don't start anything bad here...

Cheers

Mark

Neil_E. · Oct 18, 2007

Well I tried the bike without the TPS, then with TPS set at 800 ohms and set at 1200 ohms and I can't tell any difference.

steve · Oct 18, 2007

When I disconnected the TPS on my 650 I noticed I slight improvement in initial throttle response, a slight hesitation was gone, so it worked for me, subtle, but better. If you can't telll the difference, then leave it connected. When disconnecting, protect the connector ends so it can be reconnected sometine if necessary.

Steve

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