Author Topic: Gas Tacho / Revcounter Conversion to Diesel W terminal  (Read 138691 times)

Reply #30November 30, 2008, 04:53:36 pm

blkboostedtruck

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #30 on: November 30, 2008, 04:53:36 pm »
pics!!! :D  and are you taking orders on? :D
Duane
injector rebuilds call  414-840-1395 for faster service not on line much!
'66 variant 1500S
'81 2dr n/a 1.6 diesel rabbit 8"lift 260K R.I.P.
'81 caddy gas 1.8 turbo/stroker W/N.O.S.
'81 caddy 1.9 turbo diesel
'82 caddy gas 1.8 G60
 3 jettas '82' '04 '14TDI
+1 rabbit,03 HD sc.eag. duece,46,&5

Reply #31November 30, 2008, 05:40:09 pm

jimbote

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #31 on: November 30, 2008, 05:40:09 pm »
Quote from: "blkboostedtruck"
pics!!! :D  and are you taking orders on? :D
Duane


Ha ha....yeah place your orders now!!!....this should be simple and straight forward enough for anyone with a cutoff wheel a drill press and a mig to accomplish with ease....as far as the wiring very simple....one leg of the sensor goes to the tacho input....one goes to ground....of course you need battery positive and ground to the tach.....Ohh yeah....I have a dakota digital tach converter I'd like to get $60 shipped lower four eight...i've never hooked it up only took it out of the box and and read the instructions..... :D

Reply #32November 30, 2008, 06:59:13 pm

blkboostedtruck

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #32 on: November 30, 2008, 06:59:13 pm »
yep jimbote very nice! what would you need for all the parts? i can take care of the welding here! i have a MIG welder in the garage!
Duane
injector rebuilds call  414-840-1395 for faster service not on line much!
'66 variant 1500S
'81 2dr n/a 1.6 diesel rabbit 8"lift 260K R.I.P.
'81 caddy gas 1.8 turbo/stroker W/N.O.S.
'81 caddy 1.9 turbo diesel
'82 caddy gas 1.8 G60
 3 jettas '82' '04 '14TDI
+1 rabbit,03 HD sc.eag. duece,46,&5

Reply #33November 30, 2008, 08:44:32 pm

jimbote

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #33 on: November 30, 2008, 08:44:32 pm »
Don't have a part number right now...but the sensor I used came from a T45 mustang transmission....my pop rebuilds T5's and T45's so he has   parts "laying" around.....I think the year model would be a 2001 mustang V8....but I think the late model T5's and 3650's have the same sensor....it has to the be a tranny with the reluctor wheel on the output not the gear driven sensor as on some earlier models....now I think you can get any inductive sensor to work even the smaller ones because of the speed at the crank pulley mine was generating 1.2 volts AC at idle....you can even make the inductive sensor from a distributor work....inductive pickups are commercially available


http://store.summitracing.com/egnsearch.asp?Ntt=vdo+340+020&searchinresults=false&Ntk=KeywordSearch&DDS=1&N=700+115

....but there is no need to spend fifty quid on a sensor....as for the bracket....3/16 X 1" strap cut drilled and tapped for the sensor hole and sensor hold down bracket....I attached the bracket to the front of the block using two available bolt holes (early will be 7mm late will be 8mm)....also make sure you leave enough "slop" in the bolt holes to allow for gap adjustment.....the bracket needs to be relatively stiff so as to avoid vibrational contact with the "poles" ie nuts....again have fun and report back!!!

Reply #34December 01, 2008, 09:31:53 am

saurkraut

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #34 on: December 01, 2008, 09:31:53 am »
Does the Ford probe have its own signal conditioner?  IE you hooked 12 volts up to it, and it puts out the wave signal when the crank is turning, at a lower voltage.

I don't know if that VDO probe will drive the VW tach, as I suspect the VDO speedometer sends a couple volts to the VDO probe, and the probe switches it on and off.

The Ford probe may be the better choice for driving the VW tach with out extra electronic stuff. (technically speaking)
'79 1.6TD RABBIT
'84 1.5TD RABBIT
'83 Diesel Westy
'86 Audi 5000 Turbo Quatro Wagon
92 Audi 100
'93 Eurovan
'82 Porsche 930

Reply #35December 01, 2008, 10:10:25 am

jimbote

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« Reply #35 on: December 01, 2008, 10:10:25 am »
Quote from: "saurkraut"
Does the Ford probe have its own signal conditioner?  IE you hooked 12 volts up to it, and it puts out the wave signal when the crank is turning, at a lower voltage.

I don't know if that VDO probe will drive the VW tach, as I suspect the VDO speedometer sends a couple volts to the VDO probe, and the probe switches it on and off.

The Ford probe may be the better choice for driving the VW tach with out extra electronic stuff. (technically speaking)


If you have a sensor that takes voltage and sends back a switched signal then that is a "hall effect" switch....this sensor(the ford speedo sensor) and all "inductive" sensors produce current with no needed voltage input only a bit a metal passed through the magnetic field will "move" electrons in the windings around the magnet....in this application there is NO external voltage going to the probe, that would probably prove destructive to the probe itself IE complete meltdown or at best a non functioning part.....Not sure what VDO probe you refer to but if it is an inductive probe it should work

Reply #36December 01, 2008, 09:30:18 pm

jimbote

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #36 on: December 01, 2008, 09:30:18 pm »
Quote from: "saurkraut"
Does the Ford probe have its own signal conditioner?  IE you hooked 12 volts up to it, and it puts out the wave signal when the crank is turning, at a lower voltage.

I don't know if that VDO probe will drive the VW tach, as I suspect the VDO speedometer sends a couple volts to the VDO probe, and the probe switches it on and off.

The Ford probe may be the better choice for driving the VW tach with out extra electronic stuff. (technically speaking)



OK I feel dumb.....to answer your question about the VDO unit it will drive the tacho....the one in the link is an "inductive" pickup the same one Dakota digital recommends for their diesel tach converter....it does NOT recieve any voltage from the tach to operate....and yes this unit is used for tachs speedos etc.....I guess I failed to notice that the link I provided was actually a VDO unit I was assuming it was generic.... :oops:

Reply #37December 01, 2008, 09:58:57 pm

Smokey Eddy

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« Reply #37 on: December 01, 2008, 09:58:57 pm »
This is probably written somewhere but I've tried searching with no sucess.
I assume the W signal puts out 12V? I put a voltmeter to it and spun it by hand (its off the car right now) and i got a good solid 12v but there was some very strange behavior of the needle before it stabalized. can anyone verify 12V output of the w terminal? If it's already posted just pm me please  :oops:
Ed
Blacked out mk2 AAZ Jetta RIP. You will be are missed.
White 1999.5 ALH Golf 2dr. 2" wider. 2.5" lower.

Reply #38December 01, 2008, 11:10:55 pm

Vincent Waldon

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #38 on: December 01, 2008, 11:10:55 pm »
Square wave:



8 volts AC:

Vince

Edmonton, Alberta, Canada
2001 silver TDI Jetta Malone Stage 1.5 , 2001 blue TDI Jetta SBIII 216s Malone Stage 3, 1970 Bay Window bus

Gone but not forgotten: 1969/1971 Beetles, 1969/1974 Westies, 1979 Rabbit, 1986 TD Jetta, 1992 gas Jetta, 1994 TD Jetta

Reply #39December 02, 2008, 09:40:09 am

saurkraut

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« Reply #39 on: December 02, 2008, 09:40:09 am »
Quote from: "jimbote"
If you have a sensor that takes voltage and sends back a switched signal then that is a "hall effect" switch....this sensor(the ford speedo sensor) and all "inductive" sensors produce current with no needed voltage input only a bit a metal passed through the magnetic field will "move" electrons in the windings around the magnet....in this application there is NO external voltage going to the probe, that would probably prove destructive to the probe itself IE complete meltdown or at best a non functioning part.....Not sure what VDO probe you refer to but if it is an inductive probe it should work


Okydokes,

The Ford probe (with no voltage applied) can drive the VW 4 cylinder gas engine tach and produce an accurate RPM if it sees two chunks of steel every rotation of the crank shaft.

True or no

does the Ford probe have only two wires (signal and ground)?
'79 1.6TD RABBIT
'84 1.5TD RABBIT
'83 Diesel Westy
'86 Audi 5000 Turbo Quatro Wagon
92 Audi 100
'93 Eurovan
'82 Porsche 930

Reply #40December 02, 2008, 10:00:51 am

jimbote

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« Reply #40 on: December 02, 2008, 10:00:51 am »
Okydokes,

The Ford probe (with no voltage applied) can drive the VW 4 cylinder gas engine tach and produce an accurate RPM if it sees two chunks of steel every rotation of the crank shaft.

True or no

does the Ford probe have only two wires (signal and ground)?[/quote]

True.....the ford probe and "most" magnetic inductive sensors (found in automotive applications) have only two wires that are interchangeable signal or ground as in it does not matter which wire goes to ground and which wire goes to signal....the two leads or pins in "most" sensors are only the termination of a coil of copper windings around a magnet....now all "inductive" sensors do not have a "magnet" some are merely a coil of windings around a laminated core and the moving poles are magnets ie the magneto on a lawn mower.....but for this application it would probably be easiest to source and use a "magnetic inductive" pickup ....being as how it can be difficult to attach magnets to the crank pulley....

Reply #41December 02, 2008, 02:03:20 pm

Smokey Eddy

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #41 on: December 02, 2008, 02:03:20 pm »
Quote from: "Vincent Waldon"
Square wave:



8 volts AC:




What kind of alt do you have? Maybe we have different ones?
I got a very solid 12v
Ed
Blacked out mk2 AAZ Jetta RIP. You will be are missed.
White 1999.5 ALH Golf 2dr. 2" wider. 2.5" lower.

Reply #42December 02, 2008, 03:03:23 pm

Vincent Waldon

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #42 on: December 02, 2008, 03:03:23 pm »
The W signal is the W signal... a square wave from the diode bridge in the alternator that varies in frequency... which is what the tachometer translates into RPM.  All 12V alternators with the same number of stator windings will have pretty much identical signals.... although different size alternator pulleys will result in different calibrations.

Your DC voltmeter will try its best to approximate the peaks of this square wave (and the peaks do go to around 12V on the scope, as luck would have it!) and various meters will do a better job than others... particularly if the frequency is low (as in, turning the alternator by hand) but the important thing is that it's the frequency that varies with RPM, not the voltage.

Same thing actually with a gasser BTW... the frequency of the signal from the points/hall effect transducer to the coil (which is where the tach is connected) varies with RPM, but the voltage to the coil is the same boring ground it always is.   :wink:

Clear as mud, right ??!!

The other possibility is that you're reading the D+ terminal rather than the W terminal... the D+ line will show you a steady 12V at all times (assuming the BAT light isn't burnt out !).
Vince

Edmonton, Alberta, Canada
2001 silver TDI Jetta Malone Stage 1.5 , 2001 blue TDI Jetta SBIII 216s Malone Stage 3, 1970 Bay Window bus

Gone but not forgotten: 1969/1971 Beetles, 1969/1974 Westies, 1979 Rabbit, 1986 TD Jetta, 1992 gas Jetta, 1994 TD Jetta

Reply #43December 04, 2008, 08:46:47 pm

jimbote

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« Reply #43 on: December 04, 2008, 08:46:47 pm »
Just wanted to say I drove the caddy all day and not even a blip out of the tacho...it works perfect....also when choosing an inductive pickup for this mod I would recommend one that will put out at least a 1VAC I tried others that put out less (much smaller ones) they put out from .3 to .5 VAC and they would not drive the test tacho.....distributor mounted inductive coils seem to work great and they are CHEAP!!! ie...everywhere!!!

Reply #44December 05, 2008, 12:23:31 am

Smokey Eddy

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Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #44 on: December 05, 2008, 12:23:31 am »
What im trying out which is an extreme poor man's method is...
im making a flip flip out of three "D-latch"s that will divide the frequency the W terminal puts out by 8.

It's a crude method i know, but the micro controller is to come later.  :roll:

I  bought 2 paired d-latches for about $1.43 each(you only need three so one is going to be unused).  Chip mounts, a piece of bread board and some soldering later and you're good to go.
Make a case for it and bolt it in the engine bay somewhere. Run the w terminal straight to it (as they can handle up to 15V) and then straight to an aftermarket  tach. Dunno if this works yet as my engine isn't running but i WILL make a thread about it.

Just my ideas for what they're worth. (in the tuning world, worth nothing :P in the "keeping my vw diesel alive for pennies" world, invaluable)
Ed
Blacked out mk2 AAZ Jetta RIP. You will be are missed.
White 1999.5 ALH Golf 2dr. 2" wider. 2.5" lower.