Aftermarket Tach. - PeachParts Mercedes-Benz Forum

Icefire · #1 09-28-2006, 09:27 PM

Has anyone ever managed to use an aftermarket tach with thier diesel engine.

If someone has done it, can you post how you did it.

Thanks

blueranger · #2 09-28-2006, 10:30 PM

mostly we just go to the junk yard and replace
the tac control that sits near your IP...

sailor15015 · #3 09-28-2006, 10:33 PM

What's wrong with the stock tack?

Icefire · #4 09-28-2006, 11:58 PM

Im swapping a 617.951 from a 300 SD into a SEC, and I would like to use an aftermarket tach, I never managed to get my tach to work on my 300 SDL conversion.

Jeremy5848 · #5 09-29-2006, 01:25 AM

Most aftermarket tachometers are designed for use with gas engines -- they sense one thing or another in the ignition system. You would have to search for a mechanical tachometer that might be used with industrial engines, farm engines, etc., that would actually count revolutions. There are also electronic test instruments that will do such things but they are not designed to mount in a dash and I would not recommend them.

SD300 · #6 09-29-2006, 01:42 AM

There is a diesel tach for small engine, they rely on a piezo pick up.
Sensing vibration. Clamp onto the injector line.
Unfortunately I lost the web site.
Is some small engine shop in US.

rocketman93116 · #7 09-29-2006, 01:55 AM

http://www.aetnaengineering.com/tachometer-accessories.asp

Scroll down for the 41.25 tach acc., will this work?

bgkast · #8 09-29-2006, 02:00 AM

You can also find tachs that are driven by the frequency of the alternator.

namron4491 · #9 09-29-2006, 09:52 AM

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

polarisrmk · #10 04-21-2010, 10:50 PM

I am putting a 617.952 Into a boat and i want to hook up a standard tach to the engine.... my thought is that the sensor on the HB produces a current (voltage) every time the pin passes by correct? what if someone was to use an aftermarket tach adaptor such one of these....

http://www.msdignition.com/info.aspx?taxid=256&taxid2=267

I am not sure exactly how much voltage the sensor produces... I am assuming it is a hall effect sensor?

300SD81 · #11 04-22-2010, 01:54 AM

Don't think they discovered the hall effect yet when they made these... Its a VR sensor,
http://en.wikipedia.org/wiki/Variable_reluctance_sensor

I used one of these to convert it to 5V pulses,
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5822/t/al

polarisrmk · #12 04-22-2010, 03:18 AM

Quote:

Originally Posted by 300SD81

Don't think they discovered the hall effect yet when they made these... Its a VR sensor,
http://en.wikipedia.org/wiki/Variable_reluctance_sensor

I used one of these to convert it to 5V pulses,
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5822/t/al

Which one did you get? i am slightly confused by that page

300SD81 · #13 04-22-2010, 09:30 AM

Quote:

Originally Posted by polarisrmk

Which one did you get? i am slightly confused by that page

Probably easier to use the existing tach amplifier actually. I used that chip to replace mine when it went out.

techguy512 · #14 04-22-2010, 11:45 AM

Quote:

Originally Posted by polarisrmk

I am not sure exactly how much voltage the sensor produces... I am assuming it is a hall effect sensor?

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