[urq] Electrical Experts - Question re. Capacitor installation

[Mark R]

Ben, the cap needs to be installed in parallel.  Shorter ground leads to
chassis are better.  Remember, this is an additional load on the alternator,
so is only necessary if you have a voltage drop due to inadequate current
flow.

I've used many capacitors for large amplifiers for transient loads.  In
other words, the amplifier would use so much current for a bass note (say
30Hz), the alternator would max out and the voltage would drop system-wide.
I don't think a cap would be of benefit at such a high frequency as the
ignition system would be operating at (5K-8K RPM).  I couldn't find
recharging information on stiffening caps, so a car audio cap might work at
higher frequencies.  Besides, look at the power requirements of high output
ignition systems, like MSD.  If you are having voltage issues, the supply
line is inadequate.  There's no way you're maxing out the charging system
with ignition, and adding a cap would increase the load on the alternator
and provide little, if any benefit at high frequency.

Good luck, and let us know how it works out.
Mark Rosenkrantz


On 10/31/07, Ben Swann <benswann at verizon.net> wrote:
>
> Well I definitely don't want this acting like a choke – this is not points
> or
> hall-effect trigger. I would be using this as a stiffening capacitor,
> partially to
> compensate for inadequate wiring – even if the wiring is truly
> sufficient.    I merely
> want to assure more than adequate power delivery to the coil even when
> there are power
> lags elsewhere, especially when running at very high RPM, eg. 8000+.  The
> circuit should
> also have adequate reserve to pop the injectors open too.
>
>
>
> Of course I'll have one supplying the power amp in the rear of the car
> too.  I saw a
> diagram that showed a cap in series to a power amp – I think it was a 4
> farad.  That did
> not make sense that the cap was wired with no other + feed.  Would that be
> a correct
> hookup to an amp?  Does having it in parallel have a detrimental effect,
> or is the
> series wiring not necessarily a good idea?
>
>
>
> Just trying to gain a more practical understanding of using power supply
> capacitors.
>
>
>
> Ben
>
>
>
> _____
>
> From: LL - NY [mailto:larrycleung at gmail.com]
> Sent: Wednesday, October 31, 2007 10:19 AM
> To: Ben Swann
> Cc: quattro at audifans.com; URQ
> Subject: Re: Electrical Experts - Question re. Capacitor installation
>
>
>
> A cap installed in a series in a DC circuit will not pass
> current until the circuit is actually shut down. It MUST
> be wired in parallel to be used as a part of a filter system
> for a DC power source.  Choke Coils, OTOH should be
> installed in-line (series).
>
> The idea for both devices is to make the DC that goes
> to the head unit (or amp) more DC like, as they act as
> dampers to voltage (and by I = V/R) and current fluctuations.
>
> That being said, when we broke down one of our Magnetizers
> at work, I took a HUGE (as in 1.2 Farad) cap from the machine
> to use as a filter on my 4KQ's rear amp. It was meant for
> huge currents (around 200 Amps) at voltages well above
> automotive use (120V). Net filtering effect. Virtually nothing.
>
> YMMV,
>
> LL - NY
>
> On 10/31/07, Ben Swann <benswann at verizon.net> wrote:
>
> I found this article to be helpful and shows the concept I was referring
> to:
>
> http://www.bcae1.com/capacitr.htm#demo
>
> It looks like installing in parallel is OK, just need to be careful about
> initial
> charging and discharging.
>
> Ben
>
> _____________________________________________
> From: Ben Swann [mailto:benswann at verizon.net]
> Sent: Wednesday, October 31, 2007 8:24 AM
> To: quattro at audifans.com; 'URQ'
> Cc: 'Ben Swann'
> Subject: Electrical Experts - Question re. Capacitor installation
>
> Something new to my realm of expertise.
>
> I would like to install an electrolytic capacitor to act as a buffer for
> an ignition
> system - sort of like placing a second battery up close to the
> load..  Since the
> distance of the battery to the coil is about 7-8' and my understanding
> that a circuit
> may lag,  it seems installing a large capacitor might be a good idea.   If
> so, it makes
> sense that I'd install it in parallel with respect to feed wire and
> ground, however
> diagrams for most stereo AMP installations show the cap to be inline, with
> no other
> current path to the amp.
>
> Is it OK to install an electrolytic cap. as sort of a buffer or quick
> discharge
> batteryin parallel with the circuit?  That is basically to connect the
> positive end to
> battery post near load and ground as normal, leaving the original positive
> feed path
> intact.  I have some 1 and 2 Farad caps  and this is mainly to prevent lag
> at high RPM,
> similar to stereo clipping at high volume.
>
> Good Idea or ???  I'm doing some searches, but not finding a solid answer.
>
> TIA
>
> Ben
>
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