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  #16  
Old 04-22-2010, 01:27 PM
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Quote:
Originally Posted by techguy512 View Post
The standard scheme uses variable reluctance sensor, so it's necessary to pass a constant current through the coil, and then watch for the voltage change as the pin passes by the coil face. The voltage produced is tiny (about 0.6V), and very short in duration, and it's the job of the tach amp to sense it and send a pulse to the tach of the proper amplitude and duration (5.5V, 3ms). The amp does this once per crank rev, and the diesel tachs are calibrated for that "one pulse per rev" signal.

Aftermarket tachs generally require a different amplitude, duration, and "pulses per rev" in order to work properly.

All that being said, I've got the aftermarket tach thing mostly figured out...

http://www.mbelectronicupgrades.com/Project-Aftermarket_Tach.html
Yes but that just plugs into the stock location.... I need something that will work out of the car.... i guess i could get the wire harness from the pnp and wire it up ..... is this possible? what tachs will it work with? Could you help me with the wiring?
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  #17  
Old 04-22-2010, 03:08 PM
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Quote:
Originally Posted by polarisrmk View Post
I am putting the engine in a boat .... I would like to not us the stock tach
Use the stock amplifier though, it outputs 12v pulses, should make it easy to drive an aftermarket tach.
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  #18  
Old 04-22-2010, 03:09 PM
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tach

here is a link
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  #19  
Old 04-22-2010, 03:10 PM
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www.autometer.com
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  #20  
Old 04-22-2010, 03:17 PM
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Buy a VDO that runs from the alternator, I've run them with no problems.
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  #21  
Old 04-22-2010, 03:28 PM
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Quote:
Originally Posted by 300SD81 View Post
Use the stock amplifier though, it outputs 12v pulses
Actually, the stock amp outputs 5.5V pulses......
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  #22  
Old 04-22-2010, 03:33 PM
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Originally Posted by polarisrmk View Post
... I need something that will work out of the car.... i guess i could get the wire harness from the pnp and wire it up ....
The wire harness from a PNP would be easiest, but you could use discrete wiring instead.

Quote:
Originally Posted by polarisrmk View Post
...what tachs will it work with?....
Choose a tach you'd like to use and get the docs. From that we can determine if it will work....

Quote:
Originally Posted by polarisrmk View Post
Could you help me with the wiring?
Yes. Is this going to be a freshwater or saltwater boat? Does your engine have the pickup coil and bracket installed already? Is the cable and connector on the pickup intact?
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  #23  
Old 04-22-2010, 03:49 PM
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Quote:
Originally Posted by techguy512 View Post
The wire harness from a PNP would be easiest, but you could use discrete wiring instead.



Choose a tach you'd like to use and get the docs. From that we can determine if it will work....



Yes. Is this going to be a freshwater or saltwater boat? Does your engine have the pickup coil and bracket installed already? Is the cable and connector on the pickup intact?
freshwater boat.... here is the thread

617 Turbo into a Boat

The pickup coil is there .... however someone cut the wire off when pulling something else out of the car at the pnp but if i remember correctly the tach amp plug harness is still on the car just no tack amp....
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1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it
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  #24  
Old 04-22-2010, 03:53 PM
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Heres a question....

My 85 SD has the same round plug on it with no tach amp pluged in and in the fsm it says its a diagnostic port.... and my tach still works?
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1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it
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  #25  
Old 04-22-2010, 03:55 PM
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Quote:
Originally Posted by babymog View Post
Buy a VDO that runs from the alternator, I've run them with no problems.
My only thing against the VDO is that it is an external mount ... I have used one of them on a snowcat with a cummins. They work well but in the boat i want to mount the gauge in the dash.
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1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it
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  #26  
Old 04-22-2010, 09:47 PM
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Quote:
Originally Posted by polarisrmk View Post
Heres a question....

My 85 SD has the same round plug on it with no tach amp pluged in and in the fsm it says its a diagnostic port.... and my tach still works?
You have a different system. In the late '83 to '85 models, the EGR computer controls the 3 wire tach. This will cause a lot of trouble for folks in the short term future as the EGR computers fail. They are 'unobtainium' now and in the future except as PNP treasures.

I'm assuming you're not transferring any EGR computer into your boat.....
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  #27  
Old 04-22-2010, 10:37 PM
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I'm not aware of an external mount tach, mine have always been mounted in a standard hole in the dash.

Quote:
Originally Posted by polarisrmk View Post
My only thing against the VDO is that it is an external mount ... I have used one of them on a snowcat with a cummins. They work well but in the boat i want to mount the gauge in the dash.
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  #28  
Old 04-22-2010, 11:09 PM
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Quote:
Originally Posted by techguy512 View Post
You have a different system. In the late '83 to '85 models, the EGR computer controls the 3 wire tach. This will cause a lot of trouble for folks in the short term future as the EGR computers fail. They are 'unobtainium' now and in the future except as PNP treasures.

I'm assuming you're not transferring any EGR computer into your boat.....
No i am not... But I did think about it Totally kidding of course.
__________________
1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it
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  #29  
Old 04-22-2010, 11:10 PM
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Quote:
Originally Posted by babymog View Post
I'm not aware of an external mount tach, mine have always been mounted in a standard hole in the dash.

And see the only one i have seen is a external mount ie pillar mount .... where do you get yours from? How accurate is it?
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1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it
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  #30  
Old 04-23-2010, 10:08 AM
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Tiny Tach for Diesel engines...

Hi -

I needed a tach for my 1980 300TD - found and installed this one from Tiny Tach -

http://tinytach.com/tinytach/diesel.php

It has a little piezo which bolts to any of your 5 fuel injector lines. Mounted the display on the center of my instrument cluster (just abouve the stearing column. It's got a backlit display and also counts hours.

Good luck !

Jeromie
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