TPS Adjustment Experiment

[SledTheRockies]

This is my first post ever but I really wanted to share my findings with the community. I happened to have access to DW this week and was able to test some of the various theories about this subject.

Here's my experiment:
* First I set my TPS Baseline to .700 using the old school tool with 9V battery approach. The reference wire read 4.99 on the TPS when I was doing this.
* Second I hooked up a fresh 12V battery to the ECM power plug and checked the voltages on both wires with a back probe. The reference wire read 5.03 and the signal was now reading 0.708(.008 higher then what I set it to)
* Third I hooked up DW to the same sled and was surprised to find that DW was only showing 0.698 (which was even lower than when I was using the 9V battery tool)

I am a software engineer who works at hardware electrical levels so I know a couple things about low voltage electricity and this type of sensors. I have also worked as a mechanic in snowmobile shops and still do side jobs out of my garage for Polaris only. The only way I can explain these discrepancies is that the formula for what DW shows(and uses to adjust fuel) is actually something like this.

DW value = Signal wire voltage * (5 / Reference Voltage) * (temp compensation)

My biggest takeaway from all this is that you should NOT use the 12V battery approach unless you plan to compensate for the high reference voltage. If you set your TPS to .700 with a high reference voltage you will make it lean and will have a bad time eventually.

The reason a formula like this is necessary is because during actual operation the reference voltage will change constantly because of the way our sleds generate electricity. They are not large changes but enough to mess with the computer. If you don't believe me insert a backprobe into the reference wire, start your sled and rev it a few times. You will see the voltage change.

If people find this research interesting let me know and I will update this post once I run some more experiments regarding temperature compensation.

If anyone knows a software/electrical engineer at Polaris and can find out what the formula is in their code that would greatly help all of us.

 

[Wintertime]

I'm interested in what you find. Keep this updated many have had some trouble with this in the past. Would be good information and may help some with troubles.

 

[TRS]

Great find.
There are also other variables we found a couple years ago that may need answered.
Does the ECU read TPS voltage or resistance?
Temp also changes the reading, testing at freezing conditions and then hit with a heat gun changed readings.
Any magnetic source also changes the reading, hold a magnetic screw driver next to the TPS and watch what happens to voltage.
If you use a comparable BoschTPS(tighter spec than PI) you get different resistance numbers.
Cost is a factor for PI. They purchased TPS with a wide spec variable. A tight tolerance TPS costs $$.
As you have found, the DW reads a different number than our old school way of setting the TPS.
Voltage, historically, has been a concern with the Polaris stator. We now set the TPS with DW. Reason for this, the ECU reads what DW references when proper voltage is supplied.

 

[p40bri]

Very interesting...
Thanks for sharing.

 

[roughrider99]

Thanks for the info! Tps sensor has been a problematic issue for me, I beleive partly due to the turbo causing major heat swings and high moisture/humidity. Been trying to see if a better spec sensor can be adapted but no luck so far. I set tps with a aftermarket version of DW which has yielded better results than 12V and multi meter

 

[mtncat1]

This is my first post ever but I really wanted to share my findings with the community. I happened to have access to DW this week and was able to test some of the various theories about this subject.

Here's my experiment:
* First I set my TPS Baseline to .700 using the old school tool with 9V battery approach. The reference wire read 4.99 on the TPS when I was doing this.
* Second I hooked up a fresh 12V battery to the ECM power plug and checked the voltages on both wires with a back probe. The reference wire read 5.03 and the signal was now reading 0.708(.008 higher then what I set it to)
* Third I hooked up DW to the same sled and was surprised to find that DW was only showing 0.698 (which was even lower than when I was using the 9V battery tool)

I am a software engineer who works at hardware electrical levels so I know a couple things about low voltage electricity and this type of sensors. I have also worked as a mechanic in snowmobile shops and still do side jobs out of my garage for Polaris only. The only way I can explain these discrepancies is that the formula for what DW shows(and uses to adjust fuel) is actually something like this.

DW value = Signal wire voltage * (5 / Reference Voltage) * (temp compensation)

My biggest takeaway from all this is that you should NOT use the 12V battery approach unless you plan to compensate for the high reference voltage. If you set your TPS to .700 with a high reference voltage you will make it lean and will have a bad time eventually.

The reason a formula like this is necessary is because during actual operation the reference voltage will change constantly because of the way our sleds generate electricity. They are not large changes but enough to mess with the computer. If you don't believe me insert a backprobe into the reference wire, start your sled and rev it a few times. You will see the voltage change.

If people find this research interesting let me know and I will update this post once I run some more experiments regarding temperature compensation.

If anyone knows a software/electrical engineer at Polaris and can find out what the formula is in their code that would greatly help all of us.

it's a 12v system i have always used a 12v battery to adjust , on the rare occasion that the tps needs adjustment ,it has worked just fine

 

[Teth-Air]

As far as I know these TPS are a carbon plate with a wiper that moves back and forth over it. The carbon has electrical resistance so its just a fancy potentiometer. The carbon can scrape and fine carbon dust can accumulate in it over time which can create an unstable output. Not saying this is what happens all the time but for well worn units I would not be surprised if this is one of the problems Polaris discovered which prompted them to redesign for the 850.