[Fot] What alternators are you using on a Spitfire?

Tue May 20 04:04:00 MDT 2025

It's my understanding that 14.5 is the normal "full charge" of a 12v
battery. When the battery discharges, the alternator will increase output
to cover the discharge state, and current usage.  So yes, yours is probably
working as designed.

On Mon, May 19, 2025, 18:08 Chuck Gee via Fot <fot at autox.team.net> wrote:

> I have a silly question, what voltage do you consider overcharging?  My
> current one charges at over 14v (maybe 14.5v) and wondered if I should be
> worried.  I’ve done total loss for years and have just started using an
> alternator again.
>
> Chuck
>
> On May 19, 2025, at 11:29 AM, Tony Sheach via Fot <fot at autox.team.net>
> wrote:
>
>  Hi all
>
> My experience is that if you are going to use one of these Nippon Denso
> derived alternators, you need to go for the OE part.
>
> The various copies all have short lives, mainly because the diode set
> lacks up and usually starts overcharging the battery and causing the output
> voltage to vary considerably, usually upwards. I’ve had this happen and
> it’s not pleasant when a dry cell battery gets fat enough to pop.
>
> You can buy diode sets for the original Denso units and these are a quick
> change ‘in the field’ so my view is to buy a decent one and a couple of
> spare diode packs (the assembly with the spade terminals on the end) and
> replace as necessary.
>
> I have one 80amp unit that’s done 10 years and is going back in after the
> current refit. I appreciate that most don’t need this sort of output, but
> it’s usually wet and dark here so it’s everything on. The smaller 45/50 amp
> units are probably longer lived.
>
> Best wishes to all
>
> Tony
>
>
>
> Sent from my iPhone
>
> On 19 May 2025, at 16:12, Michael Moore via Fot <fot at autox.team.net>
> wrote:
>
> 
>
> Do you have the part number for the powermaster?
>
>
>
> Have a Good Day
>
> Mike
>
>
>
> Michael T. Moore, CPA
>
> 3255 West 26
> <https://www.google.com/maps/search/3255+West+26?entry=gmail&source=g>th
> Street
>
> Erie, PA 16506
>
>
>
> Phone:  814-616-8652  ext 100
>
> Fax:        888-865-5279
>
> Email:    mmoore at mtmcpafirm.com
>
>
>
> This electronic mail message contains confidential and legally privileged
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>
>
>
> *From:* Fot <fot-bounces at autox.team.net> *On Behalf Of *JS Performance
> Motoring, LLC via Fot
> *Sent:* Monday, May 19, 2025 10:21 AM
> *To:* Mike Harmuth <ofracer at gmail.com>
> *Cc:* FoTTriumph <fot at autox.team.net>
> *Subject:* Re: [Fot] What alternators are you using on a Spitfire?
>
>
>
> Mike,
>
>        The mini-denso style alternators work great.  There is a difference
> in quality between the cheapest, bottom of the barrel options, and the more
> expensive options.
>
>
>
> When my $10 Amazon special failed at VIR last year (had been in service
> since 2020), the backup unit I borrowed from Henry Frye looked identical,
> but weighed substantially more!  There's clearly a difference.
>
>
>
> Currently, I'm running a powermaster brand and it seems to be well made.
>
>
>
> I also like to run a larger pulley to slow things down.  Here in the
> states, you can get a 4" pulley sold as Powermaster p/n 182.  This is a
> direct swap onto the mini denso.
>
>
>
> <image001.jpg>
>
> <image002.jpg>
>
>
>
> We were also watching the J500 at my house, did you catch the medium bore
> race, where under full course caution, the commentator shouted "Slow down,
> Henry!".  We about fell out of our chairs laughing!
>
>
>
>
>
>
>
> Jason Sukey
>
> JS Performance Motoring, LLC
>
> 440.984.7720
>
> jason at jsperformancemotoring.com
>
> www.jspmparts.com
>
> https://www.facebook.com/JSPerformanceMotoring/
>
>
>
>
>
> On Mon, May 19, 2025 at 9:01 AM Mike Harmuth via Fot <fot at autox.team.net>
> wrote:
>
> I'm getting tired of replacing the stock type alternators. They used to
> last a few seasons but now it seems like a few weekends is the norm.
>
>
>
>  Like oil, I know there will be many different opinions, including running
> without one. That being said, any suggestions/part numbers/suppliers of a
> system that works for you?
>
>
>
> BTW, I enjoyed watching the Jeff 500 last weekend on the VRG live stream
> (currently available on YouTube). Nice job against the 911 Mr. Frye.
>
>
>
> thanks
>
> mike h
>
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