Another TPS Option for 90-93MT: TPS4185
 

My trusty TPS201 died after about 30K miles of faithful service. The TPS201 saga can be found here:

https://www.miataturbo.net/megasquir...9/#post1060119

Because I wanted to get this fixed RIGHT NOW, I went to the zone to get a replacement. Low and behold . . . no TPS201s in stock . . . I'd have to wait a couple of days. Apparently, whatever car the TPS201 goes on is now too old for the zone to stock replacements. Same story at O'Reillys when they cross-referenced the TPS201.

Since I still wanted to get it fixed RIGHT NOW, I took the opportunity to see if there was another TPS that was stocked and might work. It turns out there is. Meet the TPS4185 (as used on mid-2000s Kias -- many of which used Mazda B6s and BPs):
https://www.miataturbo.net/attachmen...1&d=1381116232

It actually has the right connector!
https://www.miataturbo.net/attachmen...1&d=1381116232

And the right shaft fitting!
https://www.miataturbo.net/attachmen...1&d=1381116232

Costwise, it's ~$13 more than the current list for the TPS201 ($53 vs. $40 -- at Rock Auto the TPS4185 is $33+shipping). But the good thing is that it can be used without modification so that the lifetime warranty stays intact. I felt that was worth $13.

To use this TPS, there are two minor issues that need to be addressed:

1. The power and ground pins are reversed relative to the stock 90-93 MT wiring harness. Some minor harness surgery is required. The wires that have to be reversed are the Red (+5VDC, goes to pin 1N on the ECU connector) and Black/Light Green (ECU ground, goes to engine block and pin 2C on the ECU connector). I did the surgery in the harness about 3 inches from the TPS connector.

2. Although the TPS fits the shaft end, the Miata's throttle body shaft is too long. So, you either need to add some spacers or drill a hole in the TPS case for the shaft to pass through. I opted to add spacers. This leaves the TPS completely intact so I can take advantage of the lifetime warranty.

Here's some pictures of how I mounted the TPS:

The TPS mounting holes are neither far enough apart nor at the correct angle to bolt directly to the throttle body. This plus the spacing problem means that I needed to fabricate an adapter plate. I made one out of 1/8" aluminum stock using my old TPS as a template:
https://www.miataturbo.net/attachmen...1&d=1381116232

Here are the parts for the assembly. I trial-fitted the adapter plate and TPS to the car to get the correct angle (you can see my mark on the adapter plate). The adapter plate holes are 3/8" for the mounting screws and 9/16" for the TPS shaft. The TPS shaft hole is exactly centered between the mounting holes. I placed the TPS into the 9/16" hole and lined it up with the mark to create TPS mounting holes. These were 3/8" as well and fit the long aluminum rivets in the picture.
https://www.miataturbo.net/attachmen...1&d=1381116232

Finished assembly:
https://www.miataturbo.net/attachmen...1&d=1381116232

https://www.miataturbo.net/attachmen...1&d=1381116232

I used a nylon spacer along with two 3/8" aluminum rivet backing washers to space the TPS.
https://www.miataturbo.net/attachmen...1&d=1381116232

Mounted on the car:
https://www.miataturbo.net/attachmen...1&d=1381116232

https://www.miataturbo.net/attachmen...1&d=1381116232

It works perfectly. :party:

Just saw that this TPS is about $33 at Rock Auto. Squarely within TPS201 territory for price.

could it be opened and the leads swapped within?

Looking at the physical TPS, it looks like the top cover could be pried off. Haven't tried it -- want to keep my warranty intact :giggle:.

BTW, you might also be able to compensate for the reverse action with calibration. With my MSPNP, I was able to accomplish this with a custom throttlefactor.ini file. The problem was that MS1 uses different types of TPS measurements for different parts of the code (some parts used %TP which I could correct, some parts used ADC which I couldn't correct). So with MS1 I had no choice but to swap the wires.

What about MS3? Maybe you can just compensate for the reverse action with calibration and be OK?

no. you cant and the code isn't open source.

That's too bad. You really should be able to calibrate a reverse-sensing TPS and have everything in the software use the post-calibration value. Oh well.

would be very easy to do in software.
If TPSclosed > TPSopen then TPScalibrated=1024-TPSvalue or something of the likes.

It is easy to do. I did it on my MSPNP. Worked fine. It's the throttlefactor.inc file in your project directory.

Problem is that the MS algorithms don't always use the final result ("TPScalibrated" in your example). Oftentimes, they are using the raw ADC value.

Not great code architecture.

https://www.miataturbo.net/attachmen...ine=1440397013


I decided to take on Brainack's challenge and get on of these TPSs and crack it open and re wire it.<br/><br/>First, opening it was a pain because it is fully sealed and I'm honestly not sure how they assembled it as it has no parting lines. I carefully sawed it apart hoping not to hit something inside.<br/><br/>Once open I can tell this is going to be trickier than just unsoldering wire and re soldering in a new configuration.<br/>

Ok so I've got the thing open and here is what I have found using my multimeter:

On the connector side the pins are labeled as 3,2,1 going from top to bottom and they correspond in the box as 3,2,1 going from left to right.

When I test the connectors I get the following readings:

3&1 - wide open 2.75ohms to closed .89ohms

3&2 - wide open.89ohms to 2.75ohms closed

2&1 - same 2.08ohms continues no mater the throttle position

So, how should I rewire it for my manual 91 assuming I can get wires into that tight space without interfering with the movement of the contacts as they sweep across the PCB?

too early to think, but looks ez.

looks like like pin 1 is ground and you just need to swap 2 and 3.

im assuming the leads on the bottom of the case in that pic go directly to the harness connector? if so then that looks like a really ezpz quick fix.

https://www.miataturbo.net/attachmen...ine=1440434009


Here are the connectors labeled just to make sure. I don't want to try wiring this twice.

okay, let me look at this and your findings and see if i got it straight.

pretty sure this:


https://www.miataturbo.net/attachmen...ine=1440437460

flipping the 5vref and ground.

More progress on the not really Plug-n-Play VTPS.

Rewired

https://www.miataturbo.net/attachmen...ine=1440744315
Rewired ground and Vref

After what seemed like quite a bit of fabricating I finally got the whole thing together. Seems to work well but it is an absolute bitch to thread in the lower bolt now. After seeing that everything
turns soothly I took it off so I can glue the top I cut off back on. I really wish that it mounted in the same direction as the original but the key to the throttle shaft does not allow for it. At least this means I can get it off and back to stock relatively easily every two years for smog.

https://www.miataturbo.net/attachmen...ine=1440744315





https://www.miataturbo.net/attachmen...ine=1440744315


https://www.miataturbo.net/attachmen...ine=1440744315

but did it work?

Waiting on my IAT to show up and to figure out a few more things on the MS1 piggyback that I've got before I get everything up and running.

I'll report back on this thread with results when I do.

Oh stupid me! I must have labeled the pins wrong in my picture. This is what happens when you rush and try to send something from Starbucks before a dental appointment.

I will switch the pins and report back.:facepalm:

Just for the sake of it, can you tell from these pictures of the MS1 piggyback board I got from Drewkeen if it was ever wired for a VTPS?
https://www.miataturbo.net/attachmen...ine=1440800249


https://www.miataturbo.net/attachmen...ine=1440800249


https://www.miataturbo.net/attachmen...ine=1440800249

Ok, so hopefully if someone else is going to do this internal mod they read far enough to see that I screwed up and mislabeled the original picture leading Brainack to give the wrong wiring instructions.


https://www.miataturbo.net/attachmen...ine=1440830752


Here are the correct labels and wiring to work with the stock harness. This time I actually double checked the outputs with the multimeter and verified against the info Brainack quoted.

:P

This is awesome. Thank you! :eggplant:

My apologies for bringing this thread back from the dead, just curious if the OEM 90-93 engine harness TPS connector can be re-pinned to function correctly without the need to cut open the TPS and solder inside of it. I am thinking just swap wire position 1 and 2 and be done with it on the TPS connector.

Anyone know if this will work?
Thanks!

That's the way a normally sane person would do it. The reason I went through the trouble of rewiring it was so it was fully reversible every 2 years when I have to take it in and get it smogged.

Between this, the intercooler, bigger injectors, etc., the list of things to switch out every 2 years is getting longer!

Thanks!

Searching now to see if anyone has a how to for de-pinning that connector, not having much luck yet...

As much as I hate altering the OEM harness, I just cut and swapped the two wires in the harness. Bit of solder and shrink wrap and everything is happy.

^ No more invasive than depinning the connector and probably a lot faster and easier if you are going to permanently alter things.

As a follow up, I ended up trying for about two hours with jewelers screwdrivers to de-pin the TPS connector, couldn't get it to budge, I just cut 1 &2 and soldered them together and put on some shrink wrap tubing, wrapped in 3M electrical tape, plugged it in , for the base plate I used flat aluminum and a few small flat head washers stacked on top of each other to act as bushings between the TPS and the base plate, with a small bolt/lock washer and nut combination to hold it in place. works flawlessly.

Duralast Part Number TPS4185 - $53.99

It took about 30 minutes excluding the failed attempt at DE-pining the connector.

Sorry to bring this back from the dead but I wanted to mention I recently used a TPS4158 on my '91. I did the internal mod. Dremeled the top off and resoldered the pins to match the Miata harness and hot glued the top back on. I previously had a TPS201 and in my experience, this is significantly less noisy.
https://cimg7.ibsrv.net/gimg/www.mia...2ca331bb1f.jpgWells TPS4185 internal mod

Bumping this, as either I am confused or something is screwy.

I have been tasked to make a 3d printed bracket for these, which I have done. I installed the assembly onto my 1.6 for testing purposes and did not have to rewire or modify the sensor.

Referencing the earlier pic in the thread that numbered the external pins to their internal connection, this is the schematic diagram of the TPS.
https://lh3.googleusercontent.com/--...2017-07-04.png
Its a weird pot. The dual element explains why the value across the "apparent" element can be less than the value of the wiper to either of the other pins.

The ground must be connected to either end of the element and cannot be connected to the wiper. You cannot make provisions for this at the ECU side because the ground connects somewhere in the harness to chassis and engine. So, as long as ground is on pin 1 or 2, nothing needs to be rewired, and literally any other combo can be made to work by wiring the ECU side accordingly.

My issue: my car(1990, unmolested to my knowledge) has the ground on the middle pin, #2. 1 then gets 5V from MS and 3 is TPS sig back to MS.

This is Ricks showing the black, which is one end of the element going to the middle pin, which has a 50/50 of being ground, because orange is the other end, and I suppose that could be ground which would still work with the KIA TPS without rewiring.
https://www.miataturbo.net/attachmen...1006-00287.jpg

The OEM schematic shows the middle pin, #2, as ground (although theres no way it can work with the wiper grounded as shown(unless they are using some whacky circuit topology that ive never seen used(even though the 90-93 didn't have a wiper but only a switch, and none of this matters anyway, this is a run on sentence, so whatever)))
https://lh3.googleusercontent.com/-m...2017-07-04.png

So why are we cracking these open and rewiring them? My car is running with the KIA and all I did was remove the TPS201 that i had, plugged in the KIA TPS and did the min value, max value thing in tunerstudio.

@shuiend

@Braineack

I will publish bracket STL soon

Correct, Middle pin is ground.

IIRC it's Idle Switch, Ground, WOT from top to bottom.

Traditionally, we've wired the connector 5v, ground, sig at the ECU. If ground can stay in the middle, and you just need to swap 1 and 3, then it can be done at the ECU harness and no mod to the TPS itself has to be made.

Yea you have two choices on ground, either end of the element, and since the factory harness lands on one of those, no need to open the TPS. I didn't think of the PNP type ECUs that don't utilize an adapter harness that allows you to customize where the wires go, but... I still think it'd be easier and cleaner to re-pin the TPS connector, or ECU connector than to modify the TPS itself. Also saves your warranty since we seem to kill a lot of TPSs on our cars.

https://www.thingiverse.com/thing:2425389

This has made me so happy! Now to get a friend with a 3D printer to print one.

Thank you, so very very much!

PM me if you need one printed.

Thanks for creating this. Printing one for sure.

Here are some crappy photos of it the TPS bracket printed and installed. I repinned the TPS connector. Thanks again for designing this.
https://cimg8.ibsrv.net/gimg/www.mia...ac12367d7d.jpg
https://cimg4.ibsrv.net/gimg/www.mia...2526ae19ea.jpg

Looks great. I have also printed a couple but have yet to install it as I try and figure out my Auto TPS issues. Which sensor are you using in the photo? What year/car is it from originally?

Its the Kia TPS, you can find the part number in the thingiverse link.

Ha, that's what I thought, but it just looks so OEM! <3

Good to see people using this. Anyone foresee long term issues with ABS and heat? I have been waiting to market these until I get my printer setup for polycarbonate, but maybe my worries are over blown? Glass transition temps are roughly 105 and 140 degrees C, respectively.

I've been using ABS parts around radiators for quite a while. Don't know if that's the same as something attached to the engine mass though.

Really cool design Sean!

I don't have many hours on mine yet but Ill keep you posted. If anything funny happens with this one I'll print another one and try acetone bathing it.

I have a grand total of about 30 minutes of run time on mine. 110+ ambient though. Doesnt even get really warm, but im not really heat soaking the engine bay, and I have all the intake/TB "coolant" (warmant?) lines removed and barbs plugged.

How did you repin the connector? I can't figure out how to get the pins out :( I'm using the same kia tps btw, and I swapped the 5v and sig wires at the ecu end with no improvement to my issue. In TunerStudio when I have closed throttle, my value is 165 and at WOT my value is 53, so I'm guessing the ground is swapped with another wire.

Why would you be repinning? The whole point is not to repin... Your ground is fine, swap the signal and 5v

I figured it out, it wasn't the 5v and sig.. I tried swapping those at the ecu. I had to swap 5v and ground to get it to read right on tuner studio. I got one of the TPS you linked before in reply to my post, so maybe the pins were different inside that one than most? I'm not really sure, but I know that all the docs that said to swap 5v and sig were not working for me lol. I have everything working in my setup now, but it just cranks and cranks, never turns.

Sounds like you sent 5v straight to ground then. Figuring out the pins is easy with a dmm.

Has anyone experienced an issue where regardless which way the red and green wires are connected, the throttle signal stays inverted? I had my TPS harness wires swapped for a while now without issue while running an FM VTPS kit, but now that the sensor has gone noisy i've replaced it with the Kia sensor and bracket to save a couple bucks. I've swapped the wires back and forth and just can't get it figured out, any ideas? 1990 short nose running ms2.

Yes, it isn't just them, the third one has to be switched too. Just try all the combinations until you get it right, that's what I had to do.

A knowledgeable moderator let me know that TS will let me calibrate it with the values being opposite regardless.. So for now the issue is fixed. Will go back due to OCD and try to figure it out in the future though.

Hmmm, ok. It didn't work like that for me when I was setting it up, but that was months ago.

Simply calibrate the TPS as normal, regardless of the higher value input being for no throttle and the low value being for full throttle. TS will ask you if you are sure you want the values this way, accept and do it 2-3 times and it will calibrate normally and operate as it should. Posting to help out anyone like myself who may find themselves in a similar situation.

I've read "SOMEWHERE" that it's not healthy to do this because the MS code will SOMETIMES use the raw adc value instead of the calibrated tps% fors SOME calculations.

google should get you some other details..

Im pretty sure all 3 iterations of my vtps were "backwards" and ive never had an issue afaik.

can't thank you enough, I've just finished converting my 1.6 to VTPS.

bought the TPS on ebay UK for a ridiculus 8 pounds shipped ( object 182634520178 )

printed the bracket at a local shop for 15 eur.

bolted straight on!

another thing to consider is that I've seen people having to take out the CF to be able to replace the TPS.
in my case it was enough to pop the plastic cover of the OEM TPS, slide out the cover, then the TPS itself.

reassembly: first the 3d printed bracket, then the tps, then screw everything in and JOB DONE.

Wouldn't something like this be the easy button, instead of futzing with jewelers screwdrivers repinning or cutting the thing open to adjust internal connections?

https://cimg6.ibsrv.net/gimg/www.mia...1c3f709916.jpg

Are you running a PNP?

No. Gonna be trying a Speeduino.