High output alternator
 

Hi there guys:
I am looking to see if anyone has a high output alternator that can part ways with. I think I need to replace mine on my 1986.5 928.
Thanks!

it looks like the standard replacement is the Bosch AL-170-X.

If you're looking for something higher, then assuming that the 170 = 170amps, you might possibly be able to find something like a AL190X or AL200X (if such models exist).

-Matt

Matt, can you confirm that? I thought the factory alternator was 100-115 Amp.

Stock output is 115 Amps.

I'm running a 3G style alternator on my 1987 (same mount as any 32v 928, including 1985). 200 amps. I'm extremely happy with it. There are higher outputs available, but you'll need to upgrade your wiring if you really need that kind of output. The main advantage to the 3G route is much better idle output performance.

I would attach supporting documents. Technical reference, step-by-step, and alternator RPM calculator. But, the Pelican forum doesn't support uploading them. So, here is where you can find them:

https://rennlist.com/forums/928-forum/1260910-how-to-mount-a-ford-3g-alternator-in-a-32v-1985-or-later-928-a.html

Or, send me your email address and I'll email them to you.

Matt, do you have access to the spec sheet to verify if the 170 actually means the amp rating?
Thank you

The Bosch AL170X is a remanufactured 115 Amp alternator. It is NOT 170 amps.

Thank you. The search continues...

There was no OEM high output alternator for the 928.

What about the link I posted above about using a 3G alternator?

3G stands for third generation design, and would be my choice for an alternator upgrade. If you have done something to draw a LOT more power, then maybe Greg Brown's reworked one.

Greg Brown uses a standard Bosch alternator stripped and put into an aluminum case that a local CNC shop makes so it will mount to the stock 928 mounting holes. That alternator suffers from the same low idle output as all Bosch alternators of that ilk. I forget the specific numbers off hand, but you're talking about under 70 amps for sure, but I think it's in the 30 amp range. You'll pay north of $1,000 for that alternator that has poor idle performance but fairly high output at higher RPM's. However, he doesn't offer an output curve with the four figure purchase, so there's no telling exactly what you're getting.

Or, go with the Ford 3G large case alternator that has very good idle output (90+ amps for the basic versions)and will cost around $200 for a brand new one with all of the fixings for ~130 to 150 maximum output. Or, go for a 200+ amp version (~110 amps at idle) with an output curve for ~$400 that will outperform the Bosch alternator by a mile. Plus, it's easy to swap in different pulleys to match your particular idle RPM and needs.

I will look at your link attachment to see if it can appease my installation anxiety. I am not mechanically inclined, so was trying to get the most plug and play possible.

Gotcha. Where are you located? I'm hosting a 928 wrenching meet in May in the DC area if that's anywhere near you.

Michigan. Too bad that is too far...

That would definitely not be worth it :)

At one point, 928 Motorsports had a high output alternator and Pelican resells a lot of their stuff. It was about $1k, and was basically just a Mechman 6G small case alternator with a custom case to fit the 928. Supposedly, the 6G small case alternators don't handle high RPMs as well as the large case alternators, but I don't have first hand experience with that.

They might still have that available, if you're looking for true plug and play.

Let us know which route you end up going. Feel free to drop me a line if I can help.

Thank you for the clarification!

It looks like we still carry 928 Motorsports products, but i combed through and found no mention of an alternator in our catalog nor on their website.

Feel free to drop us a message and we can try to reach out to them or try to find a vendor who might have a solution for you!

-Matt

Thank you all. I am getting some advise from Dave K to see if I really need it, and if I do, he might have a solution. I will keep updating.

i also thought i needed a new alternator last year - battery would die if i didn't start it every week - needle would bounce around at speed - i replaced the voltage regulator - once with a cheap one (around $30) i found online somewhere - didn't help - then i got the better one (around $70) - it seems to have fixed my problem - this is the first winter i haven't had to put a charger on it in many years - and my battery is old - might that be your problem? - seems like you are not sure you actually need a new alternator

I actually do not need to even charge the battery after the winter, I do take it out and recondition it with the trickle charger, but the battery has actually survived the winters. I just don't see the charging needle high enough when the engine is running.

I would not rely on the factory voltage gauge to give definitive numbers. use a DVM and measure at the jump post and also confirm at the battery. if these voltages are good you should be fine, then use the dash gauge to monitor trends. if it reads lower than typical, reconfirm with a good meter.

In my opinion, you don't really need a true high output alternator if you're only running stock electrics. That doesn't preclude the possibility of the current alternator failing and being in need of replacement.

With respect to the voltage gauge in the dash, it is adjustable. When you pull the pod and gauge assembly out, there is a small dial on the side of the volt meter that can be adjusted so that the gauge matches the true volts. I did this on mine, using a reference source and multi-meter to confirm the voltage, and it is now spot on. I also have a TPMS receiver plugged into the cigarette lighter that displays voltage, and it matches the dash gauge.

I don't know for sure if this is true for all years, but it's true for at least '87+. I would assume that it's true for all years, though.

I agree with Mr. Shifted

My voltmeter was always reading less than 12 volts. When I had my instruments out to repair speedo, I zeroed my voltmeter with a digital VOM multi-meter. Now it reads correctly.

Also, I installed a race type battery kill switch, easily accessible. When I park the car for more that a day, I just turn off the switch. Never a battery problem.
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