DIY_EFI Digest V4 #617

[Todd Israels]

>Date: Mon, 1 Nov 1999 22:40:56 -0500
>From: brucep at ptd.net
>Subject: non-DFI tach question
>
>I've searched high and low and haven't been able to find any info that was
>of any use on this subject so I am turning to the "minds" of this group.
>
>I am building a steady state dyno and need to add a tach to it. I want to
>measure the shaft speed of the dyno. (I don't want to read the engine
>ignition) I can't afford a digital tach setup so I am looking to use a
>analog 4 cylinder tach I have laying around till I can afford to upgrade.
>What would be the easiest way to make this work? Does the tach sense the
>drop of the ground when the points open. Could I use parts from a GM 4
>cylinder HEI coil ie: coil pickup and ignition module. I think I am headed
>in the right direction just need some advice on different ways I could do
>this. Ideally I would like to have a digital display which would allow me to
>have a more realistic reading of rpm's as opposed to well it looks like it
>is 2000 not 2010, 2020 or 2050. Any help would be greatly appreciated. And
>sorry for taking up bandwidth for the non-dfi post but this was my last
>place to ask . . . thanks in advance.
>
>Bruce
>
>------------------------------


You can use a small bit of reflective tape and a photo diode.  send the
output of this to a  frequency counter.  The Fluke automotive meter manual
describes this well, but this feature is available on cheaper meters or use
a PIC microcontroler to drive a display and do any calculations required.  
Best of luck
			Todd Israels