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Re: GM alt hub-bub

To: "Daniel Neuman" <dneuman@hodge.sfsu.edu>,
Subject: Re: GM alt hub-bub
From: Ronnie Day <ronday@home.com>
Date: Tue, 15 May 2001 19:07:24 -0500
>       Why all the not so favorable comments about the Gm alts???  Even if you
>got a 3000 amp model it is interally REGULATED.  If its working correctly it 
>will only put out as much power as needed to maintain a set voltage ~14.5V.
>And even if something goes horribley wrong if you hook it up in the 
>reccomended
>fashion fusable link/or fuse to the the batt connection and one to the old
>hot wire you will be okay.  Just make sure you run all of our aftermarket 
>high
>power stuff from the batt not the original fuse box.

Daniel,

Don't confuse the fact that the voltage is regulated with the amount of 
current an alternator will put out, nor the fact that the regulator 
effectively switches off the current flow to the battery once it's fully 
charged. Voltage is like pressure while current is volume. Think of 
things in fuel flow terms maybe. The carbs we use, SUs, Solexs, Webers 
all like relatively low pressure, around 2 1/2 psi, but the dual throat 
carbs like more volume than the SUs and may need a larger fuel line, but 
the line pressure still needs to be 2 1/2 psi.

Yes, all of the IR alternators are regulated as far as the output voltage 
in concerned, but they put out their rated amperage at that regulated 
voltage. I mentioned a magazine article a couple of weeks ago that stated 
that a given voltage difference measured at the alternator output and at 
the battery indicated too small a main output wire. Such a voltage drop 
is also manifested as heat since you're trying to force too many amps of 
current through too small a wire. Try to force 100 amps through a wire 
originally designed for 35 to 40 and you'll probably get a spectacular 
and unpleasant result. The regulator just switches the charging current 
to the battery on and off, and provides power to run the vehicle 
electrical loads. In any case the primary wiring has to be able to handle 
the alternator output or it will fail.

FWIW, Ron


Ronnie Day
ronday@home.com
Dallas/Ft. Worth
'71 510 2-dr (Prepared Class Autocrosser)
'73 510 2-dr (Street Toy)

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