I also have voltage q's....

[amalventano1@home.com (Allyn)]

    The regulator works on a function of voltage input and its output is
actually field current (current going to the rotating part of the
alternator). When you rev, with the same field current, output voltage would
go up (roughly proportional to speed, so it would try to hit 28 volts at 2k,
56 volts at 4k, etc). Thus the regulator sees this and drops field current,
trying to keep output voltage at 14(ish).
    Some regulator designs may fail conservative and are designed maintain a
lower voltage at higher rpm, this minimises the transient voltage rise as
rpms go up and the regulator drops the field current. I'm not sure of bosch
alternators use this type of regulator, though.
    More power for ignition is also possible. Regulators have a 'droop',
where the output voltage drops as you raise the output current (i.e.
increase load). This helps with generator stability (trying to regulate to
the same exact voltage in every situation will cause excessive overshoot
when you change load on the generator). I do have some doubts that ignition
coil alone would cause a .5v drop in alternator output voltage (i dont even
think it drops that much when i turn on my 80w/ea euro lights).
Hope this helps,
Al

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX (shell donor ready to rock, still
planning)
87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch,
driveshafts, wheels :)

----- Original Message -----
From: "Dan S" <danws@tampabay.rr.com>
To: "'Nate Mellom'" <bronson@inwave.com>
Cc: "roc (E-mail)" <scirocco-l@scirocco.org>
Sent: Friday, January 04, 2002 2:09 PM
Subject: RE: I also have voltage q's....


> nah, that's the voltage regulator's job, it protects your system from
> getting fried when your RPMS go higher then idle.
>
> I'm speculating here, but I'd think the drop is related to additional
spark
> (power) being used??
>
> (I know somebody - Al - has a better explanation for this)
>
> Dan
> Tam-pa, FL
> '81 Rabbit Sportruck
> '87 16v Scirocco
> '00 Jetta
> http://home.earthlink.net/~danws69/index.html
>
> -----Original Message-----
> From: scirocco-l-admin@scirocco.org
> [mailto:scirocco-l-admin@scirocco.org]On Behalf Of Nate Mellom
> Sent: Friday, January 04, 2002 13:41
> To: Scirocco List
> Subject: I also have voltage q's....
>
>
> Well, one q really.  At idle, my '81 shows right around 13.5v, but when
> i rev it the voltage actually drops (by .5 or so, usually.)
> Just wondering why, I'd think higher RsPM  would yield higher voltage.....
> Nate
> '81
> '84
>
>
>
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