Tach

[regcheeseman]

I don't know about having to remove the components with the red Xs.

It works doesn't it?  :roll:

RV2 isn't variable so should it have an R designation instead of the RV?

Well actually.... looking at it again, it would appear to be a cap, so it should have a C designation?

Anyway, I'm doing this stuff at work, with boss in same room, running it in a small a window as possible, hidden amongest menus on my auxillary monitors whilst thinking about work and convincing my boss I am doing some - apologies for any mistakes.

[RabbitJockey]

i did everything i was told, and the first time i hooked it up it worked, i just had to adjusting the variable resistor a tad, and then i was golden, thanks for the help

[RabbitJockey]

ok now that i've been driving i've been recording different rpms at what speed, then i went to scirocco gear up and checked the accuracy and heres what i have.  i did try and adjust it to get it at the right rpm anways

gear-speed-rpm-true rpm

2-20-2400-2231
3-30-2400-2225
4-25-1400-1308
4-40-2100-2093
5-55-2400-2245

seems a little inconsistent, i'll have to get someone to ride with me, it needs to be adjusted to have a little less sweep though, i'll mess with it tomorrow or this weekend, after all the driving i've done with out it though, it seems so useless since i already know where the power is at and stuff.

[jtanguay]

lmao... unleaded fuel sucks! haha

[RabbitJockey]

i wondered when someone would catch that haha

[fatmobile]

Quote:I don't know about having to remove the components with the red Xs.
 
It works doesn't it?

 It works without removing them too.

Quote:
RV2 isn't variable so should it have an R designation instead of the RV?


Well actually.... looking at it again, it would appear to be a cap, so it should have a C designation?

 It's not a cap, it's a 22k resistor. It's one of the things that is common on all these different styles of gasser tachs. The 22k resistor that goes between pins 3 and 4. Someone earlier in this thread didn't swap it and the tach would only go to about 4k (I think).

i did everything i was told, and the first time i hooked it up it worked,

 Did you remove everything with a red x on it?
 
Eventually I want to figure out the fewest parts that need changed and what component(s) determines the rate of change.

[RabbitJockey]

i did everything he said, i dunno if it was all necessary as said, but it definetly works now, and its not like it takes long to do any of this work, took me more time to setup a board and a sponge and let my iron warm up than it actually did to solder all the pieces in and remove them

[RabbitJockey]

has anyone else had any trouble converting the westmoreland tach conversion, i have made mine exaclty as the instructions said in the faq, accept for usinga 75 ohm in place of the 72 ohm, and my tach will not even move, and i have converting 2 and have the same problem on each, they don't work at all, can anyone help or suggest anything?

[Hillshy]

Hi TrevO,

if all else fails, i have an idea as this was the route i took in the end, i couldnt find a gauge that matched mine (caravelle) from the info on the prev posts,

find the picture below this post from reg:
Re-worked into diesel w terminal version,

i built the circuit on a small pcb, then mounted it in sealable plastic box(matchbox size) tapped into some power feeds, the wires to the tack and Alt terminal feed. its mounted 3 inchs away from the tach on velcro, i can get to it easy as i fine tune it, i made a small hole in the side of the box so i can adjust the pot to calibrate.

it works for me, althoungh not as neat as some or most who have managed to intergrate onto the existing board so it all looks factory, i tried to do the same but my clocks just didn't match any, it really wanted the tach hence took this option, never the less it works!

i hope this helps.

hillshy

[RabbitJockey]

that's actuallly something i was considering, but this is for someone else and not for me, and it has me befuddled because other people have gottent heres to work with the same changes... argh, i might just take and stick a board from a jetta/cabriolet into the westmoreland tach and see how that goes haha

[greendub]

I've been working on my tach conversion for months (tinkering here and there), but my VDO tach is not the same as the one in the FAQ.  It's what I'm calling VDO style #2. The board and elements are similar to the tach that fatmobile posted at the beginning of this thread from his '85 TD.  Despite all my tinkering, I've come to realize that I just don't understand this electronics stuff as much as I need to in order to create the schematic for a diesel tach conversion for this tach style.  So, I'm raising my hand to those that know more than me.  I've posted my pictures in hopes that someone can lend a hand to outline what caps and resistors go where.  

My '87 Jetta gasser tach pics that I picked up on ebay:

newbielink:http://img526.imageshack.us/my.php?image=tachovdostyle2frontpm6.jpg [nonactive] newbielink:http://img237.imageshack.us/my.php?image=tachovdostyle2backmy2.jpg [nonactive]

Btw, I've been reading this forum since July and the Jetta wouldn't be running without it.

[MikeyT]

If you are interested in a external tach, I purchased one of these recently, and amazingly it works perfectly with my '90 1.6L, straight out of the box.

http://cgi.ebay.com/ebaymotors/SEA-RAY-SEARAY-BOAT-ALT-DIESEL-TACHOMETER-TACH-TELEFLEX_W0QQcmdZViewItemQQcategoryZ26455QQitemZ280073780873QQrdZ1QQsspagenameZWD1V

MT

[lusob]

Hi,
I have motometer with MFA. I read whole topic but i can't find solution for my tacho. My is totally other than all in this topic.
Here are photos of it:
http://img135.imageshack.us/img135/3138/0704111235pj7.jpg
http://img139.imageshack.us/img139/9611/0704111234jk6.jpg
I don't know how to make it for diesel.

[Xenington]

This is an excellent thread. Kudos to Cheesey, Fatty and all the other people involved.

I have a VDO aftermarket tach and have converted it to work off the alternator using the ideas posted here. It works great.

However I was wondering if it would be possible to take this idea and apply it to other vehicles, in particular Land Rovers.

The only difference between the two vehicles that I can see is the pulley size ratio (both alternators emit 6 pulses per alternator rev). The VW ratio is 1:2.38 whereas the LR ratio is 1:3.6.

This tach will work on the signal from the W terminal on the alternator
The Bosch alternator that i used gave 6 pulses on the W terminal and the ratio between the cranck and the alternator is 1:2,38. When you calibrate it do it on the higest RPM possible you get a better reading on lover RPM:s.

I've just re-read though and it may seem that the 25 pulse per engine rev quoted elsewhere may be a little excessive and 14.3 is nearer the mark....

This is quite a big difference (14.3 pulses per second in the VW compared to 21.6 in the LR).

Which component controls the pulses entering the circuit? Is it C5 - the capacitor between pins 3 and 4 of the SAK215? Is there a fomula for calculating the correct value for C5?

By the way, the big pink rectangular thing of earlier messages which was labelled RV2 is in fact a 220nF capacitor (= 0.22uF).

Cheers
Dean

[Hexar]

Excellent information!

I have a 83 Turbo Diesel Rabbit that does not have a tach, I am thinking to add one, what options do I have? I read that there is no mk1 diesels with tach, is this correct?

I went to the junk yard, and all mk2 gassers have different tach, I mean, they have oil/water temperature meters at the bottom, the top of the tach is round.

On my rabbit, I have water temp on top, then in the middle is the huge clock, down in the bottom is the oil temperature gauge

If I use the method discussed in this thread, do I take the whole instructment panel off a gasser car, or I just take the tach only (including its niddle, indicator, display panel with number 0-7k) ?

If I only take the tach , then it will block my stock water temp gauge...

Sorry for being slow...

Thanks!
Hexar