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

Tony Drews tony at tonydrews.com
Mon May 19 16:37:19 MDT 2025


In my experience, 14.5 v is normal when charging.

Regards, Tony Drews

On 5/19/2025 4:52 PM, Chuck Gee via Fot 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^th Street
>>
>> Erie, PA 16506
>>
>> Phone: 814-616-8652  ext 100
>>
>> Fax: 888-865-5279
>>
>> Email: mmoore at mtmcpafirm.com <mailto:mmoore at mtmcpafirm.com>
>>
>> This electronic mail message contains confidential and legally 
>> privileged information intended only for the use of the recipient. If 
>> the reader of this message is not the intended recipient, the reader 
>> is hereby notified that any dissemination, distribution, copying or 
>> other use of this message is strictly prohibited and is hereby 
>> instructed to notify the sender immediately by return email and 
>> destroy this copy of this message.
>>
>> *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 <http://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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>> <image001.jpg>
>> <image002.jpg>
>
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