Volvo D2 50F low budget switch to 24V: which 24V school bus alternator fits?

[CaptainRivet]

Hi all,
I am converting to 24V and have a catamaran means I need 2 24V alternators.
Not interested in Balmar etc. that’s simply too expensive.
24V school bus alternator is the way to go here but which one fits or can be made to fit?
So which 24V school bus alternator fits on the Volvo D50F with serpentine belt and 115A Mitsubishi alternators as a replacement.
Slight modifications to original mounting points or on the alternator are acceptable.

24V Starter an aftermarket will fit, if someone has a link to a good one or the original Perkins part number that would be welcomed

[HeywoodJ]

Opening with - I have not actually fitted one to my engine (yet) - so all I have is book learning. But in the same process as you, and interested to hear if anyone has one actually fitted.

Mitsubishi does make a 24V replacement that is drop-in, the A003TN5288, but it is only rated at 40A. This part number has a dual v-groove pulley standard, I have not done more research to see if a ribbed pulley is available because the output is lower than I would like.

The Mitsu alternator has a J-180 mounting, short (198mm) hinge. There are lots of heavy-duty, 24V alternators that have a J180 mount, but generally a larger case that does not allow them to be tucked into the engine where the body/case needs to go. From what I have found, the 24SI (genuine Delco or a knock-off) should fit. It is available in J-180 mount (short or long hinge, so have to be specific), 24V 70A output, and shares a case size with the Mitsu. The output is comparable with the 12V Mitsu so belt, bearings, etc. should not care.

The 28SI also comes in a 24V version, but I have found it less available and believe the case has a couple of "bumps" that get in the way of fitting.

If anyone has fitted even the 12V 24SI or 28SI I would love to hear, as that would go a long way to confirming case dimensions.

There is a bit of a discussion here on CF about these alternators, with a dimension drawing from RGleason.

[CaptainRivet]

HI,


you need to be careful with the Volvo as they have differnet generation:
Volvo D2-50 A till C have single V belt with 12V 80A HItachi or the 24V 40A alternator you mentioned.


The D2-50 D till F have the serpintine belt with the 12V 115A Mitsubishi and there is a different 24V Mitsubishi avaliable, believe it was 55 or 70A. Serpentine is good for min 100A if not more so no worries here, Balmar uses that for 180A alternators.


here you see the setup well, not much room in the back:

https://www.volvopenta.com/marine/al...ne-engines/d2/


Attached you find the technical drawing of the 12V 115A Mitsubshi

that one could fit too 24V/55A
https://ab-marineservice.com/en/prod...IaAtfVEALw_wcB

[CaptainRivet]

you could also use the kit for the 2nd alternator, but that is 1800Euro.
But you could mount the large case in the position of the 2nd Volvo alternator.


Another alternativ is showed by AMEL, they turn the alternator ( a large case 140A Mastervolt=Leece Neville) by 180 degrees.


Mark Grasser is gearing all his alternators higher, the 115A is geared 1:1,63 means 3000redline is 4500RPM but orange line is 16000RPM so no problem gear to 2,5 or even 3.

[CaptainRivet]

i found this addition info on the 24V 70A delco remy
https://www.repuestosmaldonadogt.com...lco-remi-24si/


10000RPM max continous, which means you can gear it much higher too.

150mm Crankshaft pulley and 50mm alternator pulley should deliver much more current, especially low down thats the advantage of 24V less heat as less amps.

24V version 72% efficency compared to 62% 12V.


how about the D+ issue of the volvo...thats my main concern go to a non volvo alternator.

[Pete7]

What's the D+ issue with Volvos?

Pete

[Karanga]

Mark Grasser is gearing all his alternators higher, the 115A is geared 1:1,63 means 3000redline is 4500RPM but orange line is 16000RPM so no problem gear to 2,5 or even 3.[/QUOTE]

Don't be rushing to order his systems. He has gone into go-slow mode in preparation for retirement.

[CaptainRivet]

Originally Posted by Karanga

Mark Grasser is gearing all his alternators higher, the 115A is geared 1:1,63 means 3000redline is 4500RPM but orange line is 16000RPM so no problem gear to 2,5 or even 3.

Don't be rushing to order his systems. He has gone into go-slow mode in preparation for retirement.[/QUOTE]

I can resist paying 3-4000Euro for a complete kit from him. he really delivers top notch but you pay top notch...

[CaptainRivet]

Originally Posted by Pete7

What's the D+ issue with Volvos?

Pete

D+ is that the alternator gets an impulse to start several seconds later then the engine on a separate D+ connection. that's tied into the MDi Box so if D+ is not present engine won't even start. There are several hacks around but the MDi box is a case of itself...14 different version non 100% working and as long as it works you don't touch it...other then moving it away from the engine to side wall of your engine compartment so it's not vibrated and cooked to death by the heat exchanger next to it.

so it not just find a fitting alternator, get it properly lined up and fit a regulator. That's why I am looking as alternative to squeeze as much as possible from the stock 12V 115A which has lots potential to deliver 90A+ continuous, a 24V should have even more potential.

[CaptainRivet]

Installing an heavy duty from mark gasser and list of problems you run into with a Volvo d2-60, Same engine as our 50F just with a turbo.
https://svgerty.com/technical-altern...o-penta-d2-60/

That leads me to keep the original 12V 115A Mitzi, optimze it by changing gearing ratio (with an 80A 12-24V boost converter) and add a 2nd 24V later if needed

[CaptainRivet]

There is a Volvo 24V 80A Alternator available
https://www.boots-motoren.com/Lichtm...oren/VP3840183

But cost 1250Euro….

[kenbo]

Have you explored/considered swapping out the 12vdc rectifier with a 24v one. It could be an easy swap.

[CaptainRivet]

Originally Posted by kenbo

Have you explored/considered swapping out the 12vdc rectifier with a 24v one. It could be an easy swap.

No, what should that accomplish?

[kenbo]

55a at 24v from the same case. Alternatively, you could remove the internal bridge rectifier and install a 24v external rectifier. Solves two issues, about half or more of the internal heat and gets you to 24v.

[kenbo]

Ignore previous comment, serious brain cramp. Should have said swap the 12v voltage regulator for a 24v version