[NA6 1991 Miata, MRE48] How to convert to Kia TPS

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fan
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[NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by fan »

I have printed the adapter plate with ABS and bought a Kia TPS with the Miata plug. There are documentation on the wiki that touches on how to jump the MREAdapter48 for a Kia TPS, but the information is outdated (Schematic is at 0.4 now). From what I see from the schematics I think

1N: IDL for stock sensor
2D: GND for stock sensor (GND_SENS)
2L: WOT for stock sensor (why is this not connected on the MRE48?)

For stock, 1N and 2L will all be pulled up by the ECU, so they will be grounded at different depression levels. When the TPS is between IDL and WOT, 2L and 1N will all be "HIGH".

For the vTPS, since the center pin is still GND, it should still be pulled up by R22, so R22 should NOT be removed.

Basically what I see is that no schematic change is necessary. However the schematic notes say I should remove R22.

@stefanst Could you explain what is actually happening? Thanks a lot in advance :)
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by stefanst »

You can leave R22 installed. It's just a pull-up which will essentially run parallel with the TPS, not really causing any harm.
Please note that the KIA TPS solution is, to the best of my knowledge, as of yet untested.
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by AndreyB »

For now I've added a link to this topic into https://github.com/rusefi/rusefi/wiki/Miata-NA-48-pin-board-for-MRE but we shall do better :) As is, https://github.com/rusefi/rusefi/wiki/Miata-NA-48-pin-board-for-MRE promises "instructions later"
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by fan »

Just tried the KIA TPS, it does not work sadly... Don't know why yet.

@stefanst
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by fan »

image.png
image.png (519.55 KiB) Viewed 5541 times
Also, I think JP53 in the comments here is incorrect?
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by fan »

OK. I reversed the top and bottom pins on the TPS connector. Now it works. However the 10K resistor is too high for a proper pull-up for the KIA sensor.

@Andrey maybe this should be updated to the wiki?
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by AndreyB »

please help by pointing at exact pages or diagrams which do not look right to you
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by mck1117 »

fan wrote:
Thu Jul 22, 2021 7:09 pm
OK. I reversed the top and bottom pins on the TPS connector. Now it works. However the 10K resistor is too high for a proper pull-up for the KIA sensor.

@Andrey maybe this should be updated to the wiki?
I think the 10k should be removed if you have an analog TPS
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by fan »

AndreyB wrote:
Thu Jul 22, 2021 7:19 pm
please help by pointing at exact pages or diagrams which do not look right to you
https://github.com/rusefi/rusefi/wiki/Miata-NA-48-pin-board-for-MRE should be updated: KIA TPS is now tested.

Need to swap the pin 1 and pin 3 of the TPS connector. Also the 10K pull-up resistor should be replaced with a smaller resistor.

@mck1117 I think removing it will not work, as the TPS need a 5V pull-up. Just need to be a smaller resistor like 1k (KIA TPS is around 3k Ohm).
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by AndreyB »

I am very confused:
a) resistors with three wire pots? why?
b) swapping pins? pots do not care if we swap GND and power?

I am a software guy so it's easy to get me confused but still :)
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by BeerMoneyMotorsports »

@fan the resistor is there for the factory On/off tps. You remove it and replace with a jumper so that you have a full 5v to the TPS.
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by fan »

AndreyB wrote:
Thu Jul 29, 2021 12:09 am
I am very confused:
a) resistors with three wire pots? why?
b) swapping pins? pots do not care if we swap GND and power?

I am a software guy so it's easy to get me confused but still :)
Let me explain: the KIA TPS POT has 3 pins, 1 2 3 -> CENTER LEFT RIGHT. The stock harness will connect 1 to WOT, 2 to GND and 3 to THROTTLE, thus the sensed resistance will always be the same regardless of the pot position.
BeerMoneyMotorsports wrote:
Thu Jul 29, 2021 1:57 pm
@fan the resistor is there for the factory On/off tps. You remove it and replace with a jumper so that you have a full 5v to the TPS.
Yep I'll do this when I have time. Maybe I'll just bypass it with a flywire.

In later editions of the MRE board could you also wire the WOT signal to the controller? In 0.4 it's not wired at all.
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by BeerMoneyMotorsports »

No plans to add the WOT switch. No need for it. With the mre48 being a legacy product, it wont get any revisions other than firmware.
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Re: [NA6 1991 Miata, MRE48] How to convert to Kia TPS

Post by BeerMoneyMotorsports »

Here is how the ecu handles vtps for 90-93.

1N- 5v supply
2D- GND OEM
2L- TPS input - was WOT not it's not WOT

To answer your questions of why 2L isnt connected, its simply because it was overlooked. I have fixed this for current revisions(See H64b). @keith here, as you have seen, is up and runnin(plugged right in) with kia tps.
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