Easy to add a Tach?

[kwood]

How hard is it to add a tachometer to an MCI 9 with an 8v71 and Allison 740 auto?  My dash only has speedo and the big air gauge.  I can build a box to hold the tach, but how hard is it to hook up?

Thanks,

Kevin

[JackConrad]

Kevin,
  We installed our tach in the dash where the air gauge had been and installed a smaller air gauge. We purchased our tach from Precision Speed in Phoenix, AZ www.presionspeed.com. Out Tach only has 4 wires Ground, Hot (switched), Light, and Signal. The signal wire connects to the R terminal on the alternator. When I ordered the Tach, I told them what engine and alternator, they calibrated the tach before they sent it to me. I purchased mine about 8 years ago, but it should still be under $100.  Jack

[luvrbus]

I don't think so Jack, Don sold out this year and the prices have gone up still the best place to buy
.Kwood check the front of the engine for a tach drive on the left side looks like a place to hookup a speedometer if you have that you can use a pulse generator also cost more too. 


good luck

[Lin]

Ditto here on what Jack did.  Dan did calibrate the tach but it was not right.  He then told me how to do it, so I was able to set it using a photo tachometer.  It was cheaper to buy my own photo tach on Ebay than pay someone to do it.  That was about $20. 

[kwood]

Thanks, guys.   I will see what I can do.

Kevin

[TomC]

A few years ago, I added 5-3 wire extension cords of different colors from the engine compartment to the driver's compartment to add gauges.  I used an Isspro 3 inch 3500rpm tachometer.  It is run off the back of the blower off the existing tachometer drive.  I added the tach generator run off the blower drive (in which it really wasn't installed-had to have the special drive nut with groove added-then it worked).  It takes two wires from the blower generator to the front, then the tachometer has a ground, ignition power, power for light also.  It works well-really like having the tach-use it more then the speedo (as usual).  It is mounted in its' own enclosure bolted to the top of the dash (like an old hot rod tach).  Good Luck, TomC

[RTS/Daytona]

If you have a 50DN 24Volt Alternator --> The "R" terminal output is 12 volt (inverted sine wave) pulse  -
if yours is gear driven-
... Most 6V92 / 8V92-->(2.94 (53/18) gears & 6 pulses per rev=17.66 pulses/rev)
... Most 24 volt - 8v71->(2.75 (55/20) gears & 6 pulses per rev=16.5  pulses/rev)
... Most 12 volt - 8V71>(2.29 (55/24) gears & 6 pulses per rev=13.75 pulses/rev)     
If yours is belt driven -
measure the pulleys & calculate the ratio and multiply by 6 pulses / alternator rev   

[Jriddle]

My MC-9 was wired from the factory to the front drivers panel. All I had to do was hook Tach to these posts in the front panel. It was real simple. PM me for more info if needed. My Tach came off an MCI I purchased it off the E-place.

John

[Jriddle]

I Emailed you some pictures of my panel.

John