1.6 Auto TB for TPS
 

I have an auto TB with TPS.

from what I've read I just need to swap the WOT signal from the MT with the TPS signal from the AT.

https://www.miataturbo.net/braineack/MS/autoTB.jpg

If I've read correctly:
RED / BLU - Wiper (TPS)
BLK / LTGRN - Ground
RED - Switch Idle
LTGRN / RED - 5vref

so as long as I just swap my WOT signal for the TPS signal I shoud be golden right? Do I need to do anything else special to the board? Just in MT correct?

here's the kicker...dont have the connector. I know I can determine the TPS signal...what about the other two?

Don't have an auto TB here, but the manual tps I have has a removable plastic cover that exposes the wiring.

I guess there will be 4 contacts in there. Wire colors should be obvious once the cover is removed, but poke around with your DMM set to measure resistance. Finding the ground wire should be easiest--it is usually black. Put one probe on the ground, and then check the other 3 pins and watch the DMM for change in resistance with change of throttle position. The one that shows the same resistance despite throttle position will be the +5V in.

The easiest way to check a TPS is to unplug it and put an ohmmeter on its pins. Observe the resistance as the throttle opens and closes. Each pair of pins will behave differently:

The resistance between the VREF and ground pins will remain constant.
The resistance between the ground and signal pins will be low with the throttle closed and high with the throttle wide open.
The resistance between the VREF and signal pins will be high with the throttle closed and low with the throttle wide open.

Am I correct with thinking I can replace my regular signal with the TPS signal?

If that's an MSPNP, it doesn't really pay attention to the regular signal, so it will need a few mods (which I've described in the manual). If it is a standard Megasquirt, wiring this up will be very straightforward.

nope DIY, not PNP.

My plan is to run three wires off the new TB. Ground, Switched Idled, and TPS Signal to my oem harness. Basically just replacing the WOT signal from before with a TPS signal. So no need to run a new wire to the MS.

The variable TPS needs a +5v ref, otherwise it can't generate the signal.

If R1 is the resistance between ground and signal, and R2 is the resistance between signal and +5v, then:

signal = 5v * R2 / (R1 + R2)

The 5v ref needs to come from the MegaSquirt.

I apologize if I'm missing something, because I'm not familiar with the 1.6 setup, only my 94 setup. And I'm running standalone so I don't have a stock ECU to worry about.

-Mike

Nope, you're on the right track Mike: ground ref (from ecu), +5V ref (from ecu), and variable output should do it

Ben

ok, hows this sound.

I bring in a 5vref into the TB. from the LG/R wire from my AFM harness.

wire switch idle to switch idle in the harness

wire the TPS signal to WOT in the harness.

and GND to GND.

Looking at the diagram the AT's TPS signal goes to PIN 2M and the MT's WOT to 2L...Do I assume my harness should have the wire and whould I wire it there and leave the WOT pin unused, or should I just wire the TPS to the WOT pin?

I don't have diagrams or parts in front of me to verify wire/color codes. But what you need to do is replace the WOT switch signal with the variable signal. The other wiring is the same.

Another option might be to take the 3 existing wires from the 1.6 TB, and use them for +5v/signal/gnd on the variable TPS, and then use one of MegaSquirt's outputs to send an idle signal (does it get power or ground at idle?) to the stock ECU.

-Mike

here the diagram with labels.

The signal wire for WOT with the Non-TPS and the TPS wire go to different pins. If I take the TPS wire and wire it the WOT to 2L will I run into probelms? or should I wire it into the ECU through 2M, or does it not matter since the MS runs the show?

https://www.miataturbo.net/braineack/random/tps.jpg

yeah those differences are for the manual vs auto ECU. Has nothing to do with the MS. I would bring the variable signal at 2L in place of the WOT switch signal. That way you use the existing wire and don't have to dick with moving a pin in the harness. The key is you may have to modify your MS board to accept the signal. My board requires adding a jumper to meet the 2L wire and removing a couple of resistors.

MY MSPNP has +5V at 1N. It really doesn't matter where you get the 5V from though. Nor, really does it matter where you ground. If there's a voltage offset, so what, the ecu is programmable to compensate.

Ben

ok that's what i thought. I dont believe i have to do anythign with my megasquirt, just give it the signal. I'll just pull the 5vref from somewhere in the bay in the tps. the rest is easy enough....now to find a pigtail.

When you find one please post it up. I have an unwired at the moment AT Throttle Body as well.

It's either that or soldering diretly into the TB and then filling it with silicone.

electical tape shell filled with epoxy works well....

Granted, I have not looked at it very close as I was just trying to get the damn thing back on the car, so the car would run, but could you put a female crimp terminal on male tap on the TPS? Then solder it to make sure it stays put?

I got a connector for mine at the pull-a-part. Just look for an early '90s protege. The use the same tps switch.

ARGHHHHH!!! I was at the pull-a-part last weekend and there were 10000000 proteges!!!

I'll get one next time.

Thanks!