At  3/15/2008 09:00 AM, Jim Akiba wrote:
>On 3/15/08, Jonce Fancher <streetbugs@whispllc.com> wrote:
>  At Bostig I am told I must change the Tach on my 85 to a 86-91 for
>reasons of being more sensitive for the to pick up the tach signal.
>The 85 is
> >  suppose to be LESS sensitive in sensing the signal. But IF the
> only diff is the Buzzer then I should be good to go with the 85.
>
>
>Actually the official line from bostig is that the 85 down don't work
>with the tach output on the kit which is for the 86+, there is no
>reason given as to why since we don't know either, but the electronics
>in the tachs themselves are different.  If you do end up getting it to
>work with the 85 down let us know, but it's easy to swap in the 86+ as
>Jay pointed out. Does anyone have any definitive answers on exactly
>how the two tachs are different?
>
>Thanks,
>
>Jim Akiba

With a different engine swap the 'new' ECU doesn't have enough
'output' to power the tach AND the buzzer circuit. So the '86 and
later tachs WITH the high RPM / low oil psi buzzer have to find a
different signal for the tach OR disable the whole buzzer circuit,
while the '85 and down works just fine.
Maybe the Bostig kit connector is set up specifically for the '86 and
later and it's just simpler that way?

Rob
becida@comcast.net