Re: [T3] how's it work?

[Russ wolfe <russella@prairieinet.net>]

On Sun, 2002-06-09 at 08:29, Iamkeen@aol.com wrote:
> Hey all.
> 
> I got a general knowledge sorta question here,  regarding engine RPM:
> A tach gives a reading based on pulses thru an SP wire... "But", I say to 
> myself, "the plug only fires every OTHER revolution."
> So is my tach telling me distributor RPM, and the crank is actually spinning 
> twice as fast?  
> 
NO, the tach does not read the RPM from the SP wire. It reads it from
the points wire. This means that it gets 4 pulses for every revolution
of the distributor, in the case of a 4 cyl. engine. Therefore, you Tach
should be for a 4 cyl. engine, and have the proper electronics in it.
(Actually, a analog tach is just a glorified voltmeter.)

-- 
Russ Wolfe
'66 FB MT (It drove)
'71 FB AT 
'65 Bug (not running)
russw@classicvw.org
http://www.classicvw.org



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