[Fot] How much electrical power is needed for a 30 minute race.

Sun Jan 29 08:12:31 MST 2017

Gents,

I have not seen it mentioned in this discussion yet, but some electronic ignitions (all?) have a voltage floor that they simply will not operate under.  This may not be a concern in the majority of our sprint length vintage races, but if you are contemplating running an “enduro” length race it could very well be an issue.

With all the light and efficient options now available for alternators out there I just don’t see any downside at all in running one.

Terry Stetler

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

From: MadMarx via Fot<mailto:fot at autox.team.net>
Sent: Sunday, January 29, 2017 9:55 AM
To: 'Richard Taylor'<mailto:tarch at bellsouth.net>; 'Rocky Entriken'<mailto:rocky at spitfire4.com>; 'Bud Rolofson'<mailto:levilevi at comcast.net>; fot at autox.team.net<mailto:fot at autox.team.net>
Subject: Re: [Fot] How much electrical power is needed for a 30 minute race.

For sure it does!
I see it on laptimes if the charger fades during a race and I also had a
dyno test on this issue.
Especially on top end revs the lower voltage kicking down the power of the
coil.

Cheers
Chris

-----Ursprüngliche Nachricht-----
Von: Richard Taylor [mailto:tarch at bellsouth.net]
Gesendet: Sonntag, 29. Januar 2017 15:02
An: 'MadMarx'; 'Rocky Entriken'; 'Bud Rolofson'
Betreff: RE: [Fot] How much electrical power is needed for a 30 minute race.

Does a 14V spark ignite a gas-charge bigger, faster, better than a 12V
spark?

-----Original Message-----
From: Fot [mailto:fot-bounces at autox.team.net] On Behalf Of MadMarx via Fot
Sent: Sunday, January 29, 2017 4:51 AM
To: 'Rocky Entriken'; 'Bud Rolofson'; fot at autox.team.net
Subject: Re: [Fot] How much electrical power is needed for a 30 minute race.

The main point is not so much, that a battery last 30 minutes.
It is the electrical current, what is important.
If you consume power from your battery, then the electrical system runs at
12-11.5V.

If your charger is in action your system runs on 13.5-14.5V.
This means, the ignition output is a lot higher and the engine makes more
power.

Cheers
Chris

-----Ursprüngliche Nachricht-----
Von: Fot [mailto:fot-bounces at autox.team.net] Im Auftrag von Rocky Entriken
via Fot
Gesendet: Sonntag, 29. Januar 2017 06:55
An: Bud Rolofson; FOT
Betreff: Re: [Fot] How much electrical power is needed for a 30 minute race.

I never bothered with the lightweight battery in my Spitfire (no
generator/alternator) because I needed the ballast anyway, so I moved mine
to the right side of the shelf behind the seat for better weight balance. In
fact, I got a heavier marine battery for the extra storage. My car has
electronic ignition, starter, two fuel pumps, tach, transponder, four brake
lights (none of my other gauges are electric)

That said, I found a fully charged battery would last me about a day and a
half. So for a weekend I had two batteries and I'd change it out overnight.
A two-day autocross weekend seemed to use it up more than a two-day race
weekend.

Actually, for a race weekend, one battery would probably last, but why take
chances? Hitting the starter sucks the most juice and I sure didn't want it
to fail to start just when I got the 2-minute warning for Sunday's race
(it's done that)! OTOH I've found that once started it'll do the whole race
with nearly no charge -- did that once when I had to get a push start off
the grid. None of the other stuff including sparkplugs suck much juice.

--Rocky Entriken

-----Original Message-----
From: Bud Rolofson via Fot
Sent: Saturday, January 28, 2017 11:02 PM
To: FOT
Subject: [Fot] How much electrical power is needed for a 30 minute race.

How much battery is needed to run a Spitfire for a 30 minute race without an
alternator, in terms of amps, or current needed.

I've been looking at lighter weight batteries like the Braile and don't have
a good idea of what reserve capacity is needed. Is 35 minutes enough with a
battery capacity of (C/20 rate): 21 amp/hr.

Fuel pump, ignition, some Gage's, and LED brake lights are the biggest draws
on the battery.

Thanks for any suggestions.
Bud

Sent from my Commodore 64
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