This may or may not make sense. I did a copy and paste to filter out some of the "noise" and picked up the relative info.
Copy and paste of several posts below
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quote author=jimbote link=topic=3741.msg126313#msg126313 date=1227996627]
tried this today....gonna keep posted on the workability....basically hooked up an 83 GTI tach to a battery and a ford V8 distributer....no coil no module....just the inductive pickup and trigger wheel....with my 750 rpm drill at full blast the tach registered just under 3K....and was smooth down to almost zero rpm....so I cut six of the trigger "arms" off of the wheel leaving two at 180 apart and buzzed the drill up to full speed...the tacho was smooth reading around 500 rpm....probably could be adjusted out with the pot.....I have already built a bracket to house an inductive speedo pickup from a late model ford tranny....it will be pointing at the four balancer bolts at the front of the crank....two of which will be spaced out so as to trigger the sensor only twice per rev....I'll be working this manana and I'll keep posted (with pics)Â but looks promising so far
quote author=jimbote link=topic=3741.msg126428#msg126428 date=1228081592]
tried this today....gonna keep posted on the workability....basically hooked up an 83 GTI tach to a battery and a ford V8 distributer....no coil no module....just the inductive pickup and trigger wheel....with my 750 rpm drill at full blast the tach registered just under 3K....and was smooth down to almost zero rpm....so I cut six of the trigger "arms" off of the wheel leaving two at 180 apart and buzzed the drill up to full speed...the tacho was smooth reading around 500 rpm....probably could be adjusted out with the pot.....I have already built a bracket to house an inductive speedo pickup from a late model ford tranny....it will be pointing at the four balancer bolts at the front of the crank....two of which will be spaced out so as to trigger the sensor only twice per rev....I'll be working this manana and I'll keep posted (with pics)Â but looks promising so far
OK this works like a charm!!!
.....for anyone not wanting to solder new caps or resistors on your tach this will work and give an accurate tacho signal with no mods to the tach or calibration of the tach for that matter.....some things I changed from my original idea of pointing the sensor at the pulley bolts was to use two 3/8 nuts welded to the outside of the crank pulley exactly 180 apart and have the sensor pointed at the nut facet with about .020 clearance....the old idea simply had too much bracket hanging over the sprocket add to that thrust clearance variance and it may have thrown off the gap and thus the reading.....good luck!!
quote author=jimbote link=topic=3741.msg126434#msg126434 date=1228084809]
pics!!! Â and are you taking orders on?
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.....
quote author=jimbote link=topic=3741.msg126452#msg126452 date=1228095872]
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!!!
quote author=jimbote link=topic=3741.msg126501#msg126501 date=1228144225]
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
quote author=jimbote link=topic=3741.msg126607#msg126607 date=1228185018]
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:
quote author=jimbote link=topic=3741.msg126659#msg126659 date=1228230051]
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)?
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....
quote author=jimbote link=topic=3741.msg127103#msg127103 date=1228441607]
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!!!
quote author=jimbote link=topic=3741.msg127215#msg127215 date=1228510100]
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!
quote author=Rabbit TD link=topic=3741.msg132224#msg132224 date=1231993704]
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)?
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....
I really like this method of driving a tach. I was looking at one where somebody put an optical pickup sensor in the timing belt cover and it read off the pump sprocket but this seems beter to me and even less complicated. I guess the ford probe will work with other tachometers besides VW too won't it {please say yes}. I just got a mig welder for Christmas and this will probably be my first project
quote author=lord_verminaard link=topic=3741.msg150486#msg150486 date=1243951482]
still working perfectly!!!!
Good to know! I have a question- since you are using two nuts 180 degrees out on the crank, it would be feasible then if you were driving the tach with the intermediate shaft or camshaft pulley that you would use 4 "pickups" instead of two, since it turns at half the speed?
Brendan
quote author=jimbote link=topic=3741.msg151073#msg151073 date=1244319619]
still working perfectly!!!!
Good to know! I have a question- since you are using two nuts 180 degrees out on the crank, it would be feasible then if you were driving the tach with the intermediate shaft or camshaft pulley that you would use 4 "pickups" instead of two, since it turns at half the speed?
Brendan
Yes Brendan you would need four (4) "poles" for any shaft running half speed of the crank for and accurate tach signal....Jimmy
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