Detroit 8V71 Tach

[glerler]

GM PD-4071 with the 8V71.  I have a tack p/u on the generator.  We got a new a tach from Dolphin with  4/6/8 cylinder settings and I think the generator rotate twice as fast at the cam shaft.  So does anyone have any insight for the best way to get this calibrated??  Thx for reading

[Lin]

The electronic tach that we had bought some years ago had a calibration adjustment.  We bought a handheld  optical tach to do it.  I  think it was in the 20-30 dollar range.

[Geoff]

The tachometer you bought is for a gas engine to work off the distributor.  You need a tach that works off generator impulses.  And even so, generator tachs are notorious for being off.  The best tach is another one that works off the crankshaft pulley or cam pulley using magnets for the impulse readings.  I use an Isspro tachometer with a pickup off the crankshaft pulley with two magnets 180 degrees apart.  The tach on the dash is set to 2:1.  I get a perfect rpm reading.  There are also tachs that work off the flywheel teeth sensor, but you probably don't have that setup.

--Geoff

[Oonrahnjay]

The tachometer you bought is for a gas engine to work off the distributor.  You need a tach that works off generator impulses.  And even so, generator tachs are notorious for being off.  The best tach is another one that works off the crankshaft pulley or cam pulley using magnets for the impulse readings.  I use an Isspro tachometer with a pickup off the crankshaft pulley with two magnets 180 degrees apart.  The tach on the dash is set to 2:1.  I get a perfect rpm reading.  There are also tachs that work off the flywheel teeth sensor, but you probably don't have that setup.

--Geoff

     That sounds perfect.  I'm bookmarking "Isspro".  Thanks, Geoff.

[luvrbus]

You can pickup the signal for the tach on the R terminal off the alternator most are 2.78 times the engine speed if that is what you are looking for   

[glerler]

Thanks for the info.  I knew it was wrong, was hoping there might be clever hack to calibrate it!  LOL.  Nope!!