Changing the TPS to another type

Nistune topics specific to the 6802 cpu

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MechanisSan
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Joined: Wed Mar 25, 2015 7:56 pm
Location: Europe

Changing the TPS to another type

Postby MechanisSan » Tue Feb 13, 2018 8:04 pm

Hello nistuners
I have a S13 with the CA18DET
I am in the process of fitting a 60mm throttle body. I think it is from a N13 or P11, anyways it does fit perfectly concerning its dimensions and cable linkage. The only thing that is different is the TPS.
Now I would like to use that TPS from the 60mm throttle body, but when I measure the resistance it only goes from 1.4 to 5 kohms. The original S13 TPS has a range of 1.2 to 8.7 kohms.
Would it be a problem for the ECU/Nistune if I use the TPS with the smaller resistance range? Does it need to see the higher resistance at WOT for anything?
Thx

Matt
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Re: Changing the TPS to another type

Postby Matt » Wed Feb 14, 2018 6:18 am

If you use the newer TPS it may mean that the ECU sees higher voltages from the TPS earlier. For manual vehicles it doesnt need to see WOT for anything, but it will reach 5V earlier (maybe 3/4 throttle) than with the original TPS

This may have some impact with acceleration enrichment times, but I'm not too sure how much and if it would be detrimental

MechanisSan
Posts: 11
Joined: Wed Mar 25, 2015 7:56 pm
Location: Europe

Re: Changing the TPS to another type

Postby MechanisSan » Fri Feb 16, 2018 6:13 am

Thx for the answer Matt
I also thought there could possibly be a problem when it reaches 5V earlier. And I wasn't sure how the ECU might react to that. But just 5 minutes ago I found the schematics in the workshop manual. There is GND and 5V on the ends of the potentiometers resistor. Voltage gets measured via the variable center tab. Doesn't that mean that whatever resistor the potentiometer is, the voltage will always be the same in relation to the TPS position? I reckon the measuring of the TPS voltage is high impedance so there is no higher current flow on that end.

Matt
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Re: Changing the TPS to another type

Postby Matt » Sat Feb 17, 2018 7:36 pm

For your two different potto be reading different voltage at same position (say midway) it would mean the total resistance of the pot is different. Say 50K vs 100K the 100K one will show less voltage towards the lower end

MechanisSan
Posts: 11
Joined: Wed Mar 25, 2015 7:56 pm
Location: Europe

Re: Changing the TPS to another type

Postby MechanisSan » Sun Feb 18, 2018 10:06 am

Well it is hooked up like in the picture. It functions as a voltage divider.

TPS.jpg
TPS.jpg (74.26 KiB) Viewed 19 times


When the tap is in the middle it will see 2,5V, either its a 100k or a 1k pot. It's just the current that would be different.
When the tap is 75% left it will always see 3.75V, etc.
That's at least what my intermediate elec. skills tell me :roll: :)


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