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Hey all, I’m wondering what some out of the box options might be to get a much higher amperage output on a hayabusa engine. I’m running mine in a car (Jeep actually), and don’t want to end up having to figure something out after it fails. I’d rather deal with this during the build portion.

The stock ones apparently are close to 30a, and I could get an aftermarket one but those are still only good for 36a ish.

has anyone seen something significantly better? Or has anyone tried something crazy out of the box like a car alternator on a driveshaft? Hahaha

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Attaching an alternator would probably be the easiest way to go. No need to partially dismantle the engine to upgrade the stator. All you would need to do is find a pulley you could run the alternator off of. You could technically run it off the drive shaft, would just need to integrate the pulley into your driveshaft adapter.

Two ways to do it as well, you could get a relatively small alternator (30-40a) and just use it for your accessories, lights, radio, etc. and let the stator take care of the 'busa. But you may have to run a second battery, and keep the two systems separate.

The other would be to get a larger alternator, disable your stator, and re-wire the entire thing to be a unified system. This option would be cleaner, but would need a little more skill. (Beyond my knowledge for sure.)

What all are you running that you would need more than the 30a (or 36a)? Have you thought about switching to LED lights to lower your amp pull?

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Cheers,
Logan

Years ago, running 24hrs bike races, we would take the stator off the crank end, and install a pulley, on the crank shaft, cut out about 40% of the top of case cover for belt clearance . You will only need a pulley slightly larger then the alternator you will be using. Shot for around a 12k avg. alternator RPM. The hardest part will be putting a taper in the pulley hub to match the crank. With a V4 you may need an idler pulley, sent you have to run a much longer belt. davew

Hmm. I think I get what you’re saying. Would it not work to directly couple to the end of that shaft with some type of adapter? Would the rpm be too low then? I have the room to go straight out the end without having to use a belt if it’s possible.




I have an electric fan (so far just one but might be two later), 044 fuel pump (might end up being another if I use this in the surge tank), electric water pump, digital dash running PI, water pump for water intercooler, plus all the usual equipment.
Not sure if I’ll need something yet, haven’t checked all the ratings

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Some stock cars ("NASCAR") run the alternator off the driveshaft

https://www.speedwaymotors.com/9-Inch-F ... 27898.html

That's a pretty neat set up. Not sure what the OP is using his jeep for, but I'd be worried about putting my alternator on a diff of a 4wd.

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Cheers,
Logan

It’s a street rod, 2wd

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If you have the room to fit the alternator direct off the end of the crank with a hub drive, that should work. I would want to first find amp out-put Vs rpm chart, for the selected alternator, to see what it looks like at lower rpm's. I would think that those 100 to 150 amp alternators should met your needs, even at low rpm's. You should probably look at a rubber cushion drive hub, because most alternators are not subject to quick rpm chances that you see from a M/C engine, plus it would give a little leeway on alignment. davew

Kinda what I was thinking too. Thanks

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Just be aware that alternators have some maximum speed, typically around 12K rpm. A few are higher but usually cost more due to being custom. To stay cheap, just use a stock OEM unit.

First, do a power budget, all the stuff that you might have on at the same time. An example would be sitting in stopped traffic, at night. In that situation, the lights are on (10A), the engine running (5A?), fuel pump (5-20A), and the cooling fan (15-30A). Add those up and there you go.

In my case I'm running a Honda K24 built to handle 9400 rpm, though the rev limiter is set to 8000 rpm. A stock Chevy pickup alternator is used, a compromise between size and power output. Given its limit of 12K rpm, it means that I cannot use a pulley set with a ratio of more that 1.5 in order to keep the altnerator below 12K. The potential downside is at the other end - idle. There, the alternator may - or may not - be making enough power to keep the battery at 12+ volts. "Usually" this isn't a problem. Usually.

FWIW, my brother didn't bother doing any of the above figuring when he put in an alternator with a small pulley, and couldn't understand why it kept blowing up. One time he took it apart and found that the rotor windings had stretched outward due to the centripetal force and ground through against the stator housing. Physics is always at work.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
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FWIW, my brother didn't bother doing any of the above figuring when he put in an alternator with a small pulley, and couldn't understand why it kept blowing up. One time he took it apart and found that the rotor windings had stretched outward due to the centrifugal force and ground through against the stator housing. Physics is always at work.

There, Fixed it.

I stand corrected, good sir.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/