DIY_EFI Digest V4 #609

[William T Wilson]

On Fri, 29 Oct 1999, DIY_EFI Digest wrote:

> new one.  Does anybody have any ideas for a tach adapter to convert a
> 6 or 8 cyl signal to a 4 or 6 cyl tach?  I am hopping that I could
> make one thing that can do all this, like convert a v8 or 6 cyl to a 4
> or 6 cyl signal in one package by changing some dip switches.  Would a
> 555 or a op-amp work on something like this.

You probably can't do it by flipping dip switches, unless that same
vehicle had a V6 factory option.  In that case, it's highly likely that
they used a configurable tachometer.

Anyway, you need some sort of circuit to throw 1/3 of the pulses away.
You'll need buffering and filtering so the whole thing doesn't blow.  How
to do it is up to you.  I'd use a counter circuit set to reset at 6 and OR
together the first 4 outputs.  Two chips.  The 555 wizards out there can
probably do it with one of those, too...