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Old 03-07-2010, 06:18 PM   #1
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Default BMW VTPS / Braineack MS, no worky

I wired it up using this guide My Turbo Miata Photo Journal - Variable TPS/VTPS18

I think i did all the wiring corretly.. i tested the tps at the connector and got a range of 500 ohms to 3500 ohms resistance when varying throttle.. is that normal?

Regardless, the MS did not see any activity when in the 'calibrate tps' screen & pumping the gas..

also does the car have to be running or just in the pre-start / on position for the 5V ref line to get juice? right now my battery's discharged so i am testing w/the car in 'on' but not running.

-tomaj
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Old 03-07-2010, 06:43 PM   #2
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Pin 1-black wire-5volt in
Pin 2-shielded wire-ground
Pin 3-yellow wire-signal out
Pin 4-ground
Pin 5-WOT switch
Pin 6-Closed switch
_
6 1
5 T 2
4 3
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Old 03-07-2010, 09:48 PM   #3
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i am very confused.

i have my the 'signal' running into the green / white line on the miata harness.
i have the '5v reference' running on the red wire from miata into VTPs
I guess the middle wire is ground? (middle on miata harness).

with the car in 'on' position i tested voltage on the signal line, it ranged from around 2v down to 0.5v when 'WOT'.

---

somewhere along the way (at the boomslang harness) i've created some nasty problems... i am trickle charging my battery and it was showing a battery issue when the TPS was plugged in. now that i disconnected the vampire taps i added to the boomslang, it's' charging again.

i hate wiring!!
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Old 03-07-2010, 10:09 PM   #4
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If I made you a parallel boomslang before 2009 chances are the harness is not prewire to accept a vTPS signal at all...If so there'd be a solid blue (tps) and solid gray (vref) wire coming off the loom to the unused middle connector...Open up the db37 hood and check to see if those wires are present.
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Old 03-07-2010, 10:29 PM   #5
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i believe you are correct... i took apart the db-37, and found that the blue & gray wires lead back to the middle connector's two unused wires.

i vampire-tapped those two wires into the boomslang harness, but it didn't work.

now my car's acting very funky.. a while ago it was clicking rapidly when 'on', now the MS's lights are blinking, and earlier one of the coils was making nasty noise until I unplugged them.

EDIT: to clarify, now the car is still acting funny even though i already disconnected the VTPS and the two vampire tapped wires..
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Old 03-07-2010, 10:33 PM   #6
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where did you put them? you are backfeeding 5 volts into the ECU if you do that, which can do some interesting things, you need to make sure you cut the wire that goes back to the ECU. As illustrated below:

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Old 03-07-2010, 10:45 PM   #7
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*LOL* i was looking at the same picture from a differeent thread, but it didn't say "CUT WIRE TO OEM ECU" so... i didnt cut those wires lol.

That's some funny ****.. if only i knew!

Do you think that explains my issues? I'll give it a shot hopefully tomorrow!
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Old 03-08-2010, 09:20 AM   #8
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then that picture probably didn't say boomslang harness
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Old 03-08-2010, 09:42 AM   #9
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I had a few issues when installing my BMW VTPS. The wiring shown on that site you linked is backwards. The guy who did the writeup mentions that on the forums, but the pics he has show the old way (IIRC). I too wired mine incorrectly and actually ending up damaging my ECU in the process. No big deal until I returned it to stock to sell it and it didn't quite run right (idled high and bogged at part throttle just for a few minutes on cold startup). It felt TPS related and remembering the mis-wiring, I opened up the ECU and saw a few burnt resistors. Posted a WTB thread for a stock ECU and rharris sent me one for no cost (not even shipping). Thanks again! That fixed my problems. I hope you don't have the same issues, but thought I'd share my experience in case it helps.
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Old 03-08-2010, 07:42 PM   #10
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Hey thanks for the post.. i actually read about your issues, and now i think i may have gotten myself into a similar situation.

regarding the wiring, you didn't happen to take pictures of the 'right' way to do it did you
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Old 03-08-2010, 09:09 PM   #11
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yahoo. Braineack's instruction to cut the wires leading to the stock ECU were what did it.

So my wiring was actually 99% correct yesterday, but i just didn't cut those damn wires.

Now i'm getting a range of "3" with closed throttle to "44" or so if i jab the throttle.. then it settles down to mid 20s if i hold the throttle WOT.. is that normal?

-tomaj

P.S. -- thanks guys
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Old 03-09-2010, 08:51 AM   #12
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My readings were more like 20 ADC closed, 240 ADC WOT, and somewhere in between anywhere else. Once you calibrate closed and WOT, change one of your gauges to show TPS % and it should go from 0% to 100% when you press the throttle from closed to WOT. Oh yeah, after calibration, close and re-open Megatune for it to work right IIRC. As for the wiring at the TPS being backwards, I can't exactly remember. I do know that two of the guy's pics on his site show confusing info:
This pic

and
This pic


The top pic makes it look like the Green/White Signal wire is in the middle on the Miata sensor, but it's not. The second pic he redlined it to show the order. Here's a pic of the Miata harness:


I think his issue is the pic of the wiring diagram of the BMW VTPS he used (and many used on the web) is of the sensor side of the plug and not the pigtail so be sure you flip everything if you are looking at the pins on the pigtail. Again all of this is from memory. Just make sure you check your resistances.
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Old 03-09-2010, 11:56 AM   #13
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You're 100% right... his pictures confused the **** out of me but eventually (2 hrs later..) i figured it out and swapped the connections.

now i have to figure out why my closed throttle -> WOT range is only 2 to 25 ADC...

Do you think simply adjusting the rotation of the sensor may be the culprit?

-Tomaj
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Old 03-09-2010, 10:46 PM   #14
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OK someone please edumacate me on how a VTPS is supposed to behave.

i can't get it to go to very high on the ADC count.. i've fiddled with tilting the tps back and forth, twisting it all the way til it 'clicks' at WOT, peaks around 70.

Also the action of this particular TPS seems to reflect more on the SPEED of throttle actuation vs. position of throttle.. In other words if i put my foot down realll slow, i can get it to stay at 3 or 4% all the way to like 90% throttle, then it slowly climbs to 18%.. if i jab my foot down real quick, i can get it to register like 50% or so, occasionally it'll even hit 100% (rarely)..

Is that normal?? My impression was that 0% throttle should always look like 0, half-way down would be 50%, and WOT would be a steady 100%..

Someting's not right!
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Old 03-10-2010, 01:10 PM   #15
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Your impression is correct. Sounds like your wiring is wrong. Stick a voltmeter on your Green/White signal wire coming out of the TPS and manually operate it. Should be getting ~0V at closed throttle, ~5V at WOT and ~2.5V at half throttle. Again this is all from memory, but I'm pretty sure. If you are getting the opposite, you need to swap your power and ground wire going into your TPS. If you are measuring resistance across pins, you should get continuity between ground and signal at closed throttle and continuity between Vref (5V) and signal at WOT.
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Old 03-10-2010, 01:38 PM   #16
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Just did a quick search to find the mistaken info. Here are some threads that deal with it.

https://www.miataturbo.net/forum/t11746/

https://www.miataturbo.net/forum/t33024/
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Old 03-11-2010, 07:39 PM   #17
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heh.. it stinks! i spent another hour and at least i figured something out.

the vtps works, i tested voltage right at the pins of the vtps by pulling back the rubber cover and it does in fact go from 0 to 5 volts, nice and steady.

however, at the connector going into the miata, the voltages are all fucked up. basically, it appears that my wiring jobs is generally screwed up at that point.

what i find very odd though, is that i tested connectivity from end to end on my harness and its fine???? so i'm really at a loss... i can only think that my solder job sucks (quite likely) so i'm probably going to eliminate the miata wire and splice directly into the car's harness after the connector.
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Old 03-21-2010, 12:13 AM   #18
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OK so i'm still not able to get this working.

Can someone please test their BMW TPS and tell me what the resistance range is between closed and WOT? Mine goes from 3.2kOhms (closed) to 500 ohms (wot).

I had it all wired up and the voltage doesn't make sense.. Though the reference voltage reads 5V at the TPS, the signal voltages aren't going from 0 to 5V as they should (?)
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Old 03-21-2010, 09:30 PM   #19
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FIXED finally.

I decided to bypass my little harness and start from scratch. i used three wires with alligator clips on one side (to clamp onto bmw tps pins) and raw wire on the other (to stick into miata tps harness).

i swapped around the alligator clips until the values made sense.. Then i compared the results to my DIY harness. It turned out i had the 5V input and the signal line swapped (oops).

So now my TPS values go from around 18 (closed) to 200+ (wot), so i'm happy. Now i get to play with the accel enrichments!
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Old 04-04-2010, 09:33 PM   #20
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Here's a little update on my MS saga.

It turns out that since i snipped a couple wires to get the stock ECU in order to get the BMW TPS working, some other things changed

In other threads i've discussed my problems with the IAT sensor registering differently in megatune vs. the megasquirt... also, i had to alter the function which converts the AEM uego to AFR. Instead of base 9.00 + 0.888?x i had it set as 9.72 + 0.888x....

Now that i snipped the 5v ref and tps lines to the ECU, it appears those issues went away?!

i put the formula for volts to AFR back to stock, re-flashed the firmware with stock bias resistor values, and tested to ensure that the MS sees IAT temps the same as tunerstudio is reporting them.

What is strange though -- it appears that the car was running super lean so now i'm letting VEAL (ve analyze live) do its thing, and it's enriching the cells by like 20% ??.. Who knows. i'm going to let it tune for a while and see if everything is OK
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