snip

   For all interested,
     Issue 46 of "Contact Magazine" has excellent article
on converting the Mitsubishi alternators commonly used
on 86-91 RX7(and perhaps 93+ RX7 and Cosmo 20B)to either
stock internal reg with external shutdown or external reg
and shutdown.The article also includes the same info for
some Nippondenso alternators.The Mitsubishi is said to
be the better design and easiest to convert.

   Kelly Troyer

Mark Steitle wrote:

I was just looking at my 90A Mazda alternator and feel I have discovered how

to disable the internal regulator in order to convert to an external regulator.
However, it would be reassuring to read up on it before I take the wire cutters
to things.  Can someone summarize the Contact article, or tell me how to get a
copy of the appropriate issue?

I read up on Bob Nuckolls' Aero-Electric book to find out why I would want to

convert to an external regulator system.  Bob states that the benefit in
switching to the external regulator is to replace the "switching" regulator with
a "linear" regulator.  He states that he is unaware of any automotive
alternator/regulator that is of a linear design.  He sells a linear a/c
regulator with a "crowbar overvoltage protection" circuit that will cut out
within 5 miliseconds in case of an overvoltage type failure.  That should
prevent one frying their expensive avionics.  Sounds logical to me.

Mark Steitle

I might add the drawback to a linear regulator is less efficiency and as a
result
increased heat dissipation in the regulator. Make sure you have a big enough
heat sink on the regulator transistor and it is placed in a cool spot.
The up side to a linear regulator is less electrical noise on the power buss.

Also BTW most modern avionics use low cost linear regulators on the input that
have
a capability of probably handling as much as 35 volts input with out blowing.
They also probably have a diode to prevent being hooked up to the battery
backwards. If not they should.

I am sure Tracy uses such low cost regulators in his EFI/IGN computer.
What is max input voltage Tracy?

Paul Lamar

   Mark,
    The modification would be difficult to summarize.The
"Contact" article contains pictures which are worth a
thousand words to help identify the various parts of the
alternator.Publisher Mick Myal has back issues
available.Post him at <contact1@dcnet2000.com>

   Kelly Troyer

Dyke Delta/13B Rotary Power

 
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