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    Thread: 1.6 Diesel Tachometer. A "How To" Thread

    1. Member Bowcaster's Avatar
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      03-05-2012 02:02 AM #1
      So recently I set up a tach on my jetta and I thought I would share how I did it.

      First off, I know there are several other ways to do this and it might be worth checking them out as well. Also, I am posting this in the MK1 forum only because I did it on a mk1. It works on all 1.6d and tds.

      Now. Here is the part list for this.
      -Bike speedometer sensor(5 bucks online or $20 at wallyworld)

      -A pack of super magnets(5 bucks from a hardware store)

      -1 led and 1 1k ohm resistor(5 bucks at radio shake or 75 cents online)

      -A stick of jb weld putty(5 bucks from hardware store)

      -A metal braket about 2''x1/2'' with a 6mm hole in one end(the lower anti rattle clip from a set of injector lines is perfect)

      -Standard 4 wire tachometer with a 4 cylander[2pulse/rev](20 bucks online and up)

      -Misc wire and conectors

      Ok, now for tools needed

      -wire cutter
      -10mm wrench
      -soldering iron
      -rag and cleaner
      -boxcutter
      And here we go.
      First step
      -remove the upper timing belt cover if installed(will need to be left off) and clean the camshaft pulley at 12,3,6, and 9 o'clock on the engine side.
      -Take your putty and glue 4 magnets onto the camshaft pulley at 12,3,6,and 9.

      Second Step
      -Take your metal braket and bend it into an L shape with the 6mm hole on the short end.
      -Cut the sensor wire off of your bike speedometer close to the head unit. There should be two wires. We will get to them in a bit.
      -Trim any zip ties on the sensor off and jb it to the braket.
      -take the 10mm nut off of the front passenger side of your valve cover. mount your sensor and braket with that nut and shaft. It should be close to the magnets on the pulley.

      Third Step
      Wiring time.
      -follow the instructions to wire in your tach minus the wire that would go to the coil. That will be conected to the circiut made by the sensor.
      -Connect one of the lead from your sensor to the fuel celiniod wire on your injector pump. Connect your other one to the resistor and coil wire to the tach.
      -Connect the resistor to the + lead on the LED. connect the - lead to a ground.
      -Cover the led and resistor in jb to prevent shorts

      Final Step
      -Allow the jb weld to set for 60 minutes(perfect time to install the tach in the dash if you haven't yet.)
      -Make sure you tach is set to 4 cylander.
      -Fire her up and enjoy your new tach!

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    3. Member polloloco's Avatar
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      03-05-2012 09:35 AM #2
      Thanks for posting this, it will give me something to do this weekend.

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      03-05-2012 10:01 AM #3
      i do not know... i think you need to rethink this... if any 1 magnet falls off.. it is enough to let the timming belt jump a tooth and major destruction due to it..

      i think id move it to the alt fan..

    5. Member 8v-of-fury's Avatar
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      03-05-2012 12:02 PM #4
      Quote Originally Posted by crsmp5 View Post
      i do not know... i think you need to rethink this... if any 1 magnet falls off.. it is enough to let the timming belt jump a tooth and major destruction due to it..

      i think id move it to the alt fan..
      What about the crank pulley?

    6. Member RabbitJockey's Avatar
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      03-05-2012 12:41 PM #5
      i wouldn't do it that way, i'd put those on the crank, maybe on the outside of the accessory pulley, no way would i jb weld anything inside the timing belt cover

      what is the led for?
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    7. 03-05-2012 01:49 PM #6
      Why not get a later Alt with a "W" output and connect one wire?

    8. Member 8v-of-fury's Avatar
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      03-05-2012 01:52 PM #7
      Quote Originally Posted by wilm13 View Post
      Why not get a later Alt with a "W" output and connect one wire?
      I do not believe it is as easy as "1 wire".

    9. 03-05-2012 02:06 PM #8
      It's not? It pretty much is. Maybe 2 wires.

    10. Member Rockerchick's Avatar
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      03-05-2012 02:17 PM #9
      W-terminal alt is pretty easy to get a tach working. Take the wire from the W terminal and use a converter box and bam, you have a working tach. That's what we use and it works great. Converter box from Dakota Digital.
      Quote Originally Posted by TM87 View Post
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    11. Member Dub_Monster's Avatar
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      03-05-2012 03:05 PM #10
      Not a bad idea or way of going about it, but I too would be worried about a magnet flying off, and i think you should note that the camshaft is moving at half the speed of the crank so if you don't have a programable tach, your RPM's are off.

      I have done this but I used a speed sensor with a bracket holding it near the cam gear using the six holes as intervals with a programable tach, thus no magnets, but it does require some math skills and a good electrical knowlegde.

    12. Member Bowcaster's Avatar
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      03-05-2012 06:50 PM #11
      Quote Originally Posted by 8v-of-fury View Post
      What about the crank pulley?
      The thought did cross my mind. If you are worried about the magnets flying off then this would probably be a safer spot. The main issue I had with this idea was placement of the sensor. rigging up a bracket would be tricky.
      Also running it off of the alternator fan wouldn't work. The speed is not the same or a usable faction of the speed of the crank

      Quote Originally Posted by Trev0rBr View Post
      i wouldn't do it that way, i'd put those on the crank, maybe on the outside of the accessory pulley, no way would i jb weld anything inside the timing belt cover

      what is the led for?
      The LED is to provide a little more resistance. If you were to run just the resistor it would likely over heat pretty quickly. With out both the led and reistor you would have a straight circiut and would melt wires lickidy split. Also..it looks cool.

      Quote Originally Posted by wilm13 View Post
      Why not get a later Alt with a "W" output and connect one wire?
      A new alternator costs a little more then this project. Also the whole programming/adjusting it. My dad ran a stock tach of a w terminal in his audi 4000 back in the day and it was wayyy off.

      Quote Originally Posted by Dub_Monster View Post
      Not a bad idea or way of going about it, but I too would be worried about a magnet flying off, and i think you should note that the camshaft is moving at half the speed of the crank so if you don't have a programable tach, your RPM's are off.

      I have done this but I used a speed sensor with a bracket holding it near the cam gear using the six holes as intervals with a programable tach, thus no magnets, but it does require some math skills and a good electrical knowlegde.
      Yes, the cam turns at half the speed. Thus the 4 magnets to provide the 2 pulses per rev. With a 4cyl tach you get an accurate reading with the 4.
      This would be ideal and I looked into it. But the price of the sensor and the wiring involved turned me away. If you're up for it this is the way to go. Also, you should be able to do this with a 6 cylander tach. That should take 3 pulses per revolution which you would get from the 6 spokes of the pully.

      Thanks guys!

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      03-05-2012 11:32 PM #12
      why did i say alt vs crank pully... easy.. ever seen a v belt get sucked into the timming belt of a diesel... i have... trying to keep the magnets from getting sucked into it... also the fan is flat.. lots of room fo rhis sensor.. so on.. so why i suggested it..

    14. Member Dub_Monster's Avatar
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      03-06-2012 04:13 PM #13
      [QUOTE/]Yes, the cam turns at half the speed. Thus the 4 magnets to provide the 2 pulses per rev. With a 4cyl tach you get an accurate reading with the 4.
      This would be ideal and I looked into it. But the price of the sensor and the wiring involved turned me away. If you're up for it this is the way to go. Also, you should be able to do this with a 6 cylander tach. That should take 3 pulses per revolution which you would get from the 6 spokes of the pully.

      Thanks guys![/QUOTE]


    15. Member 8v-of-fury's Avatar
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      03-07-2012 12:34 AM #14
      Honestly, JB WELD has been used to fix a cracked block, and ran that way for 20-30,000 miles..? I don't think the little magnets are EVER coming off with the amount of JB the OP used. lol

      I will be doing this this week I want to know what my MTDI is spinning lol.

    16. Member VWCaddy's Avatar
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      03-07-2012 02:06 AM #15
      I used something similar except with an optical instead of magnetic sensor:
      - http://www.4crawler.com/Diesel/Cheap...ml#TachInstall


      Has worked flawlessly for 11 years on my '82 and I had run a similar system for several years on my old '81. Just need to double up the pulse count on the injector pulley since it spins 1/2 the engine speed.
      '82 diesel pickup, Missing LinkZ custom shift linkage, Quaiffe transaxle, Bilstein shocks F/R.

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      03-07-2012 06:36 AM #16
      8v... do not try it.. ive had issues with jb weld holding smaller magnets on center drive shafts of rc cars.. aka speed sensors.. i do not trust them.. or jb weld.. but same token much more rpm.. keep the magnets away from the timming belt..

    18. Member shwak23's Avatar
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      03-07-2012 12:35 PM #17
      Or just buy a diesel boat tach for the same cost as the materials you listed....

      Sent from my DROID X2
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    19. Member 8v-of-fury's Avatar
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      03-07-2012 09:32 PM #18
      Quote Originally Posted by shwak23 View Post
      Or just buy a diesel boat tach for the same cost as the materials you listed....

      Sent from my DROID X2
      A lot of diesel boat tachs only go to 4k rpm. I don't think any are as high revving as our 4cyl diesels. Most marine diesels are 5 and 6 cylinders.

    20. Member Bowcaster's Avatar
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      03-07-2012 09:47 PM #19
      Quote Originally Posted by 8v-of-fury View Post
      A lot of diesel boat tachs only go to 4k rpm. I don't think any are as high revving as our 4cyl diesels. Most marine diesels are 5 and 6 cylinders.
      According to the tach I've rev'ed mine up to about 6. I hear they start throwing valve shim disks at around 9?

    21. Member 8v-of-fury's Avatar
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      03-07-2012 09:52 PM #20
      You would only have hopes of hitting 6+ if you missed a shift, or had some serious pump work done.

      The rollers in the pump start skipping on the cam plate around 59-6000 rpm. Pretty much the VE pumps top end.

    22. Member Bowcaster's Avatar
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      03-07-2012 10:42 PM #21
      Quote Originally Posted by 8v-of-fury View Post
      You would only have hopes of hitting 6+ if you missed a shift, or had some serious pump work done.

      The rollers in the pump start skipping on the cam plate around 59-6000 rpm. Pretty much the VE pumps top end.
      Even with the governor mod?

    23. Member 8v-of-fury's Avatar
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      03-07-2012 10:56 PM #22
      Quote Originally Posted by Bowcaster View Post
      Even with the governor mod?
      Yes. The governor mod doesn't change how the pump physically moves. What the governor mod does is increase the pumps fueling and stops the governors action, which is to limit fuel. The stock governor starts limiting fuel around 2500 and is fully cut (20% of total fueling left) by like 3300 or something like that.

      There is a cam plate inside the pump that turns with the shaft of the pump driven by the pulley.



      This spins and rides on four rollers inside the pump, when it goes up on the humps it compresses two large springs in the head of the pump. These two springs can't over come the cam plate spinning at 6000+ so the cam plate does not return to make the next injection.. The engine will physically not turn anymore rpm.
      Last edited by 8v-of-fury; 03-07-2012 at 11:00 PM.

    24. Member Bowcaster's Avatar
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      03-08-2012 01:28 AM #23
      Quote Originally Posted by 8v-of-fury View Post
      Yes. The governor mod doesn't change how the pump physically moves. What the governor mod does is increase the pumps fueling and stops the governors action, which is to limit fuel. The stock governor starts limiting fuel around 2500 and is fully cut (20% of total fueling left) by like 3300 or something like that.

      There is a cam plate inside the pump that turns with the shaft of the pump driven by the pulley.



      This spins and rides on four rollers inside the pump, when it goes up on the humps it compresses two large springs in the head of the pump. These two springs can't over come the cam plate spinning at 6000+ so the cam plate does not return to make the next injection.. The engine will physically not turn anymore rpm.
      Ahhhh. Makes sense. Thanks! So if one wanted an engine that would spin in the high rpms could one rebuild the pump with heavier springs to keep them from skipping the cam? I don't see the point of it but...people do things, it's a fact.
      Cheers on knowing your sheet.

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      03-08-2012 10:50 PM #24
      I have various MKII and MKI parts. Mostly Diesels and some Gasser stuff.
      www.facebook.com/blackdogjunkyard <---------Here for pictures. PM me for More Info.


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    26. 03-02-2016 04:03 PM #25
      "#1 1.6 Diesel Tachometer. A "How To" Thread"


      This works perfectly! I made it in my VW Passat 1.9 TD yesterday and work without problem. Thanks for this elementary solution!!
      Last edited by batio; 03-04-2016 at 04:41 PM.

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