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65amp Denso FYI

Posted By: Leigh

65amp Denso FYI - 04/30/21 10:17 PM

I just finished the Denso conversion. I used to throw belts before slowing the old mopar stuff down. Given that, I went with a 4.5” alternator (Jones), 5” crank (Doty Eng). Solid 14.5 volts at idle. (1,000 rpm). Just a fyi for not needing supersonic alternator rpm? I’ll report more data, after using it more.
Posted By: AndyF

Re: 65amp Denso FYI - 04/30/21 11:12 PM

Yeah the Denso alternators that I've been using are always 14 volts at idle, even with a stock pulley setup. I have a Denso alternator on both of my cars and they both go right to 14 volts as soon as the engine starts. No weird blinking lights like with the factory alternator.
Posted By: Leigh

Re: 65amp Denso FYI - 04/30/21 11:26 PM

What was (is) the ratio? I’m currently at .782 overdrive.
Posted By: Mopar Mitch

Re: 65amp Denso FYI - 05/04/21 06:34 PM

Are you comfortable with 14.5V?

I recently did the Denso swap on my SB... new AutoZone. I had a first one... that was reading around 15V.

I've just exchanged it (lifetime warranty)... reading 14.5V ... and when I put on the headlights... 14.0V... heater motor full blast... together (lights and heater)... about 13.5V.

So, is 14.5 OK without any load?
Posted By: 440Jim

Re: 65amp Denso FYI - 05/04/21 07:00 PM

Originally Posted by Mopar Mitch

So, is 14.5 OK without any load?

IMO, 14.4 is perfect with a small load.
The real question is when pulling 30 amps or more, plus whatever the battery is charging soon after starting, what is the Voltage at various rpms?
Posted By: krautrock

Re: 65amp Denso FYI - 05/04/21 07:54 PM

Originally Posted by Mopar Mitch
Are you comfortable with 14.5V?

I recently did the Denso swap on my SB... new AutoZone. I had a first one... that was reading around 15V.

I've just exchanged it (lifetime warranty)... reading 14.5V ... and when I put on the headlights... 14.0V... heater motor full blast... together (lights and heater)... about 13.5V.

So, is 14.5 OK without any load?


there are some Denso replacement voltage regulators with a 14.9v set point. i got a rebuilt 65amp alt for my old truck and it runs at 14.9v. kinda worried me until i did some research on it. seems 15.2v is about the limit for factory electrical parts so i haven't had any problems with it running 14.9v.
Posted By: Moparteacher

Re: 65amp Denso FYI - 05/04/21 08:14 PM

You can get the Jones alternators with an adjustable voltage regulator if you see the need. And, with a 5" crank pulley and a 4.5 inch alternator pulley the ratio is1.1:1
If crank speed is 1000 rpm then the alternator is cruising at 1100 rpm at idle.
Posted By: MR_P_BODY

Re: 65amp Denso FYI - 05/05/21 12:20 AM

On my HotRod I have been using a Denso 65A with a drag race regulator.. they allow a 14.5A.. this is on my
83 Dodge Rampage.. its been on there like 3 years so far
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