Tach adapter needed?
Posted: 03 Sep 2007 21:16
Hi,
my engine builder is about to mount the ignition system, an all MSD system (6AL, coil and distributor). I have two questions.
1. The MSD box produces a 12 volt square wave signal with a 20% duty cycle. Does anyone know if this is close enough to trigger my ralley dash tach? MSD says a "current triggered tach" needs a tach adapter. I guess the opposite would be a voltage triggered one?
2. The engine builder says he's not too sure about using the old ralley dash tach together with this modern ignition system, and therefore he suggests I should use a modern tach to be sure not to damage the MSD box in case the tach short circuits. MSD has kept me in the phone queue for 45 minutes now, from overseas, so I figured I'd ask you guys instead; MSD wouldn't build a box as sensitive as that, would they? I'd rather use my old tach and not litter the coupe too much with more gauges.
Thanks in advance
/Fredrik
my engine builder is about to mount the ignition system, an all MSD system (6AL, coil and distributor). I have two questions.
1. The MSD box produces a 12 volt square wave signal with a 20% duty cycle. Does anyone know if this is close enough to trigger my ralley dash tach? MSD says a "current triggered tach" needs a tach adapter. I guess the opposite would be a voltage triggered one?
2. The engine builder says he's not too sure about using the old ralley dash tach together with this modern ignition system, and therefore he suggests I should use a modern tach to be sure not to damage the MSD box in case the tach short circuits. MSD has kept me in the phone queue for 45 minutes now, from overseas, so I figured I'd ask you guys instead; MSD wouldn't build a box as sensitive as that, would they? I'd rather use my old tach and not litter the coupe too much with more gauges.
Thanks in advance
/Fredrik