I've actually looked into using a bicycle computer as a tachometer for
my wife's Eurovan.  It is trivial to hook up, and one can compensate
for the 5-cyl. engine using the tire size calibrator (most
J.C. Whitney and other tachs are not set for 5 cyl. engines).

One small problem: when you hook it up, (I beilieve) the counter is
wrapping back to 0 a little too quickly, so under idle, I get a cyclic
pattern of readings (typical).  A set of dividers made of flip-flops
is not too hard to do, but like everything, I'll probably get around
to it in the next two years or so.

Good luck,
Cetin

Erik O. writes:
 > List,
 > 
 > 	I like the ideas of some listmembers reguarding a master computer to
 > moniter engine specs. My question, can a digital tach. be produced
 > inexpensively and if so what would it take. For instance, stationary
 > bikes have tachs that measure the rotation speed of the front tire.
 > Couldn't a digital meter of some sort be hooked into one of the plug
 > wires to measure RPM? 
 > 
 > Erik
 > 87 Syncro Westy