Alternator Output for a CRF450X

[Hot Rod JayRad]

So I was doing some rough math and found the charging setup to be quite lacking on the stock Honda CRF450X single cylinder. At 5000RPM the maximum ouput is 78W to the battery. The fuel pump I would like to use is going to be drawing 134W (11.2A @ 12V) and our ECU and accessories bring the total draw upto roughly 260W.

I did some research and found 2 companies that rewind your stator for you, (Baja Designs and TrailTech) and both of them told me the max output they will do is ~180W. One told me its physically space limited by clearance between the coils and the flywheel, the other said it was a rectifier-limited issue.

The other alternative for me is to find a fuel pump that doesnt draw as much amperage for the pressure we run at.

So the question I have for you all is this: what have other single-cylinder teams done to resolve the issue of a constant-loss electrical system? Are one of these companies better than the other? Do you just run a big battery and say "screw it!"? The main thing im concerned about is idling around waiting in line for the dynamic events puts a huge load on the system that wont get returned quickly.

Your thoughts?

[A Richards]

We had to get the stator re-wound on our KTM 525. Not sure of the exact output now but it manages to charge a system pulling somewhere around 18-20A. Look at a smaller fuel pump for sure, 11amps is a bit over the top, from memory ours is about 5A

[JaredC]

Don't bother trying to run your electrical system at a loss. You'll get sick of flat batteries and run the risk of not being able to start the car at the driver change in endurance. You'll also have to pack a bigger, heavier battery.

Do a comprehensive power budget experimentally and work out how much power you need, then get your stator rewound to suit (add in an extra few amps overhead).

Then you'll need to find a rectifier that can cope with the increased current - just grab one off a 4 cyl from a wrecker. F4i rectifiers are good for at least 480W apparently.

11A for a fuel pump is huge. Our old pump was 7.5A and we considered that slightly excessive.

We've been running at a slight loss for the past couple of years, so one of my jobs has been to fix that. It really is a heap easier just to get a better alternator/rectifier combo and sort out your loads than run around charging batteries all the time.

[Grant Mahler]

We are running the stock battery and stator on our Suzuki LTR450 and as long as we drive it a couple minutes after cranking a bunch of times, the system is all charged.

We have only added a water temp gauge to the system though, so not taxing it more than it should be. Also, MS2 draws less amperage than the stock ECU.

Started the car this morning at 12.3 volts. By the end of testing, car was at 12.6 volts.

[Hot Rod JayRad]

For those teams that have gotten their stator's rewound, which company seems to offer the most sorted package? Seems to me Baja Designs has it buttoned down the most, but thats just my initial impression. Anyone have any personal experience they would like to share?

[exbaja]

No way you need a pump that big. That is insane. You don't need much of a pump for these engines. The new EFI RMZ doesn't have a battery and uses a capacitor to spin the pump up upon kickstarting. The wires going to the pump are teeny. I don't have exact numbers on what the pump draws, but I assure you it is no where near 11.2 amps.

Baja designs is a much better company.

[Kirk Feldkamp]

Originally posted by exbaja:
No way you need a pump that big. That is insane. You don't need much of a pump for these engines. The new EFI RMZ doesn't have a battery and uses a capacitor to spin the pump up upon kickstarting. The wires going to the pump are teeny. I don't have exact numbers on what the pump draws, but I assure you it is no where near 11.2 amps.


Baja designs is a much better company.

Yeah, but they're also not running at 65psi, are they? What pressure do the new efi offroad bikes run at? The pump Jared is using is certainly way oversized, but there don't seem to be many easy to find (so far) off the shelf pumps that have a small flow capacity and have a high fuel pressure capability. The current with the pump is that high because the pump is constantly moving probably 5X-10X the required amount of fuel at that high pressure.

Anyone want to suggest a different pump?

-Kirk

[exbaja]

45 lbs of pressure at the injector, the pump is capable of more without the regulator.

Use a small motorcycle pump, LTR pump is external and small. RMZ pump is internal (mounted on a flange), about 180 bucks, internally regulated, no need for swirl tank, filter built in, cool little no leak quick connect, and ultra reliable.

[Kirk Feldkamp]

What are the electrical connections like for those pumps? Guessing a replacement pump doesn't come with a pigtail or intermediate harness. Is it any sort of standard Suzuki fuel pump connector?

I suppose the fiche would say, but I figured you might know off the top of your head.

-Kirk

[exbaja]

Same as the coil connectors on any of the Japanese bikes. Available from K and L motorcycle supply in relatively useful bulk with terminals, seals, etc.

The RMZ pump is very cool because there is only pump to injector plumbing, nothing else. LTR pump needs an external regulator, swirl tank, etc.

http://www.motorcycle-usa.com/Photos/tank-bottom.jpg

There is a picture of the pump,' pretty dang cool.

By the way, the fiche won't say that sort of thing

[exbaja]

just checked the price of the pump, it retails for about 360 bucks, but like I said, it is pretty darn cool packaging wise and everything else. If you are buddies with a Suzuki dealer they can get you one much cheaper. There aren't many in the US if you want to get your hands on one. Act quickly!

[Grant Mahler]

Ron Ayers (http://www.ronayers.com/browseparts.cfm?SearchString=15100-45G00&adv=5&kw=fiche.ronayers.com) has them for less. About 145$ less. Still expensive though.

[Motohead]

Do any of you know the power draw of the two suzuki pumps? Exbaja mentioned that they could push 45psi, but what about flow?

[exbaja]

Don't know exact numbers, I guess I could check on it for you, but empirically, it feeds a 50-60hp 11k RPM 450cc single with room to spare, my gut tells me it would be fine for anything you guys could come up with in the single cylinder variety.

It is also extremely reliable and like I mentioned above, completed self contained with filter, swirl tank system, and regulator. If you need to adjust pressure you could fab an adjuster for the preload, but I would just leave it alone. No idea what it would do with E85 however.

I may have a used one in my hands this week that just got removed from one of our race bikes. I will post some pictures if I get it.