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Standard/manual trans - Does the computer know or sense what gear?

ECU computer tach gear

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21 replies to this topic

#1 mrjim

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Posted 24 February 2014 - 09:34 AM

I've got a couple of strange questions. 

  1. I've got a 2000 OBS w/ standard transmission and was wondering if there is a sensor telling the computer what gear the car is in.  I was thinking it's pretty unlikely but was just curious.  If so is it possible to get this information from the computer to an external circuit? 
  2. Does the computer read the tach?  Again, if so is it possible to get this info from the computer to an external circuit?

Thanks in advance.

 

Jimbo



#2 1 Lucky Texan

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Posted 24 February 2014 - 10:05 AM

what kind of circuit for the tach? an elm 327 and a smartphone app like Torque , Or a tactrix cable and laptop running something like RomRaider should display the tach.

 

might be able to derive the gear with tach and speed sensor info.


Edited by 1 Lucky Texan, 24 February 2014 - 10:07 AM.


#3 mrjim

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Posted 24 February 2014 - 10:44 AM

"what kind of circuit for the tach?"

 

Homebrew.  I've got some LED arrays that I've used in the past with a VU meter (volume level indicator) for the sound system and would like to reuse them but base it on the tach instead of the sound system.

 

For the gear I was going to do another "homebrew" circuit and stick a nixie tube somewhere in the dash or center console to indicate the gear.  What you say about the speed and tach makes sence but would require a circuit a bit more compliated than I had first intended.

 

8rsGiaz.png<---- Nixie tubes (in case you didn't know what they are)


Edited by mrjim, 24 February 2014 - 10:47 AM.


#4 Fairtax4me

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Posted 24 February 2014 - 10:56 AM

It does have a switch to tell when it is in gear, but it does not know exactly which one.

Best place to get the tach signal is right off the back of the tachometer. I would have to look at a diagram for that car to know exactly which wire.

#5 mrjim

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Posted 24 February 2014 - 11:13 AM

The signal off the back of the tach sounds like a good way to go.  So if there's a wire for the tach signal I'm guessing there's also one for the speed?  If so it looks like I'd have to go about it like 1 Lucky Texan said.  I'll have to pull out the manual I used when I swapped out the engine.  I know it had wiring diagrams in there.

 

On second thought it might even be easier to set up an array of 6 proc sensors under the shifter boot and determine gear from that.

 

   v   v   v

   1   3   5

> |__|__|

> (neutral)

> |    |    |

  2   4   R

 

(Planning on using 0 for Neutral and 9 for reverse)


Edited by mrjim, 24 February 2014 - 11:23 AM.


#6 1 Lucky Texan

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Posted 24 February 2014 - 11:40 AM

"what kind of circuit for the tach?"

 

Homebrew.  I've got some LED arrays that I've used in the past with a VU meter (volume level indicator) for the sound system and would like to reuse them but base it on the tach instead of the sound system.

 

For the gear I was going to do another "homebrew" circuit and stick a nixie tube somewhere in the dash or center console to indicate the gear.  What you say about the speed and tach makes sence but would require a circuit a bit more compliated than I had first intended.

 

8rsGiaz.png<---- Nixie tubes (in case you didn't know what they are)

 

yeah, I know what they are;

 

12749798645_83639e5bea_b.jpg



#7 mrjim

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Posted 24 February 2014 - 11:57 AM

Haha nice.  Is that a pic of you?  When was this taken?



#8 987687

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Posted 24 February 2014 - 12:00 PM

I think the pins on the back of the tach are actually labeled on the PCB. Either way, there are three wires. v+, ground, and signal. So it's pretty easy to figure out which one you're looking for.



#9 1 Lucky Texan

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Posted 24 February 2014 - 12:13 PM

Haha nice.  Is that a pic of you?  When was this taken?

 

 

yeah, me approx. 1975. That HP counter up there has a nixie tube display. (in all fairness, I never built anything with them, but have built 7 segment LED displays using discrete drivers and encoders and stuff like that)


Edited by 1 Lucky Texan, 24 February 2014 - 12:14 PM.


#10 mrjim

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Posted 24 February 2014 - 12:38 PM

My work is scrapping an old bridge that's got some nixie tubes in it that I'm going to salvage.  I've never built anything with nixie tubes yet either but I think they look super sweet.  They remind me a lot of cold war era "high tech" equipment.  I figured since so many of the newer semi-auto cars have the 7 seg display of gear, it would be cool to do the same thing in my OBS but with some retro flare.



#11 1 Lucky Texan

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Posted 24 February 2014 - 12:53 PM

My work is scrapping an old bridge that's got some nixie tubes in it that I'm going to salvage.  I've never built anything with nixie tubes yet either but I think they look super sweet.  They remind me a lot of cold war era "high tech" equipment.  I figured since so many of the newer semi-auto cars have the 7 seg display of gear, it would be cool to do the same thing in my OBS but with some retro flare.

 

sounds like a fun project - be careful. I think neon needs 160-170 volts doesn't it? (been a long time since i messed with neon bulbs!)


Edited by 1 Lucky Texan, 24 February 2014 - 01:55 PM.


#12 mrjim

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Posted 24 February 2014 - 01:15 PM

I think nixie tubes are actually more like a typical lightbulb with a heated coil providing the light but I'm not sure what the source voltage has to be.

 

Nevermind, I don't know what I'm talking about. lol :blink:

But yeah, I'll definitely look into what all's got to be done before juming in too far.

 

Thanks for the help everyone.


Edited by mrjim, 24 February 2014 - 01:24 PM.


#13 Fairtax4me

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Posted 24 February 2014 - 01:39 PM

Have to be careful putting sensors under the shift boot.
Problem with that is the bushings in the shifter linkage wear out over time and let the shifter flop all around. It makes it so you have to move the shifter about 4 times as far side to side to find the gears.
One day you'll end up breaking your sensor array without even realizing it.

If you can make something weather-proof, you could attach the array directly to the selector shaft on the transmission and it would not be affected by wear in the linkage.

#14 presslab

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Posted 24 February 2014 - 02:58 PM

Nixie tubes are cool.  I built a clock a while back with them and used it on my nightstand.  The girlfriend was always afraid of it because of the high voltage and I never put it in a case.  :D

 

You can easily take the tach input and the vehicle speed sensor and figure out what gear you are in with simple math.  Take care to "sanitize" these signals before hooking them to your Ardunio/whatnot.  Something like a 10k series resistor and a 4.7V zener diode would suffice.  If the clutch is in, of course this doesn't work but you could wire into the clutch switch to not change the gear indicator until the clutch is released.

 

Your 2000 model ECU would use the Subaru Select Monitor interface II. You could read the vehicle/engine speed over this, but it's probably easier to just use the signals as above.



#15 mrjim

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Posted 24 February 2014 - 03:59 PM

Easy to do with pen and paper and a calculator but harder to do with a circuit (unless I program a processor).  I'd need to know each of the 6 gear ratios (1-5 + the final drive).  I could use a PIC I suppose but if I didn't I'd need a circuit to take the tach and speed as inputs to calcualte the ratio then compare it to each of the actual ratios...  Sounds like a proc chip is the way to go then.


Edited by mrjim, 24 February 2014 - 04:06 PM.


#16 1 Lucky Texan

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Posted 24 February 2014 - 04:09 PM

well, did you see this?

http://arduinix.com/index.html

#17 mrjim

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Posted 24 February 2014 - 04:15 PM

Hey nice, thanks for the link.



#18 987687

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Posted 24 February 2014 - 04:19 PM

Easy to do with pen and paper and a calculator but harder to do with a circuit (unless I program a processor).  I'd need to know each of the 6 gear ratios (1-5 + the final drive).  I could use a PIC I suppose but if I didn't I'd need a circuit to take the tach and speed as inputs to calcualte the ratio then compare it to each of the actual ratios...  Sounds like a proc chip is the way to go then.

 

It wouldn't be that bad with PIC. 

You can just look up the gear ratios, then multiply them by the final drive. Writing code to convert mph into rpm of the wheel isn't bad. Then divide that into your rpm and you should get approx. your gear ratio. so it can just check whether you're within a few percent of each gear ratio.



#19 mrjim

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Posted 24 February 2014 - 04:29 PM

Right.  Definitely easier with a PIC.



#20 mrjim

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Posted 24 February 2014 - 05:15 PM

Don't suppose anybody's got a link to the 2000 OBS gear ratios?  If not I'll just do some searching tonight.

 

Thanks again for the help guys!



#21 987687

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Posted 24 February 2014 - 05:19 PM

See the list here  http://www.northursa...trannychart.pdf

 

Should be the one listed US Impreza EJ22 MY99-01

 

You can always look at the code on your bellhousing and match it up to the list if you're unsure.



#22 mrjim

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Posted 25 February 2014 - 09:07 AM

Thanks!

 

I'm not sure how near in the future I'll be able to work on this but when I do, I'll try to remember to post some pics.


Edited by mrjim, 25 February 2014 - 09:10 AM.






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