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WR250R/X electrical power making question

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I am generally clueless about how motorcycle electrical systems work, so cut me some slack.

The WR250R/X makes 350 watts at steady max output, right? Would that be at 11,000 rpm, or when?

I read somewhere that 5,000 rpm is needed to start charging the battery. Does that seem right? Has anyone measured "base loads", with just the engine running and lights on, and again with the fan running?

350 watts is just under one half horsepower (1 hp = 746 watts). Is the electrical system sapping the engine of a half a hp at all times?

:):D:worthy:

/dh

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I don't think it works that way on a bike does it?

Does the stator cause parasitic drag?

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I don't think it works that way on a bike does it?

Does the stator cause parasitic drag?

It has too, right? Unless Yamaha has invented a perpetual motion machine:D

I guess (*guess*) the drag is proportional to rpms of whatever shaft it encircles - the crankshaft? So directly proportional to rpms. So power from the engine goes to the electrical system in direct proportion to rpm?

What I can't even guess at is what happens when excess electricity is generated. I fear that it is simply shed as heat. But I dunno.

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of course it adds drag, but its so minimal, you wouldnt notice any difference if you where to remove it all, other than it wouldnt run 👍

any type of "generator" "alternator" setup has to have the equal and opposite reaction type of theory, or the "if then" if I spin this....then it will generate electricity in watts.

I come from a cycling background and this is how we trained was by wattage and how long we could keep an average wattage (around 400) so for the motorcycle to generate 350 watts is probably not much load at all for it.

I would "guess" that it would do this around 40mph, mainly because that was usually my max average....

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It has too, right? Unless Yamaha has invented a perpetual motion machine:D

I guess (*guess*) the drag is proportional to rpms of whatever shaft it encircles - the crankshaft? So directly proportional to rpms. So power from the engine goes to the electrical system in direct proportion to rpm?

What I can't even guess at is what happens when excess electricity is generated. I fear that it is simply shed as heat. But I dunno.

I suppose you could ditch the alternator and run it as constant-loss. Good on a full-on dirt or roadrace bike. Not much use to you and I though.

Excess electricity is taken up by the regulator/recitifier and released as heat. That's why if you upgrade your alternator you must also upgrade the r/r.

On that note: I always wondered - people often say after they've added a bunch of electrical accessories that they're alternators have to work harder to power everything. It sure seems to me that the alternator works the same regardless. I would think that if you add electrical accessories that draw current up to the capacity of the alternator, you're just making the r/r's job easier. Maybe I'm naive though....

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Manufacturers usually size a street-bike alternator to keep the battery charging slightly at idle with the lights on. Alternator output rises as rpms rise, but the inductive reactance of the windings also increases as rpms rise, and this tends to make the alternator "self-regulating" somewhat. Motorcycle regulators usually use one or more SCRs to short some of the ac half-cycles to ground as output rises above load, and as Longview points out, this is released as heat in the SCRs, rectifying diodes, and alternator windings.

A 350W alternator really does take 1/2 hp to run. Actually, it takes more than 1/2 hp to run because the alternator isn't 100% efficient at converting mechanical energy to electrical energy. Adding electrical accessories, up to the point that the SCRs stop conducting and no more, shouldn't overstress the regulator/rectifier.

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Manufacturers usually size a street-bike alternator to keep the battery charging slightly at idle with the lights on. Alternator output rises as rpms rise, but the inductive reactance of the windings also increases as rpms rise, and this tends to make the alternator "self-regulating" somewhat. Motorcycle regulators usually use one or more SCRs to short some of the ac half-cycles to ground as output rises above load, and as Longview points out, this is released as heat in the SCRs, rectifying diodes, and alternator windings.

A 350W alternator really does take 1/2 hp to run. Actually, it takes more than 1/2 hp to run because the alternator isn't 100% efficient at converting mechanical energy to electrical energy. Adding electrical accessories, up to the point that the SCRs stop conducting and no more, shouldn't overstress the regulator/rectifier.

Man, if you don't know what you're talking about, you sure sound like it!👍 I think "help has arrived".

- How might one measure the total base load in watts at idle of the existing electrical doodads? The fan when it comes on?

- How might one measure the output of the alternator at idle? Is it possible to measure at a few rpm levels, say every 2k rpm and draw a simple chart?

Cheers for the info!

/dh

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I could easily get the amperage for you with my carbon pile and amp meter. My only problem is I don't think my fan works.👍 Well I guess I could jump the relay to get it to come on.

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I heard our bike has a lot of power overhead which is good for adding accessories and lights potentially

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Man, if you don't know what you're talking about, you sure sound like it!:worthy: I think "help has arrived".

- How might one measure the total base load in watts at idle of the existing electrical doodads? The fan when it comes on?

- How might one measure the output of the alternator at idle? Is it possible to measure at a few rpm levels, say every 2k rpm and draw a simple chart?

Cheers for the info!

/dh

dh, I think the easiest way to "measure" the load is not to measure it, but just look at the schematic and add up all the light wattages. The headlight will be the heaviest load and the brake light probably the 2nd heaviest.

The best way to measure the load, I think, is to use a clamp-on current meter around the positive or negative battery cable and measure current with the engine off, but all electrical accessories on. This way all current is being drawn from the battery at the time of measurement and it's easy to measure. Be sure to work the brake as you measure because the brake light is a major load. Measure battery voltage at the same time and voltage x current is power.

This measures total power except the relatively small amount to run the engine. If you want to measure that also, unplug the voltage regulator and start the bike, and measure as described just above. Be sure to use a clamp-on current probe because when you start the bike it will blow the fuse in your in-line current meter.

You can measure voltage output fairly easily at 2k rpm intervals and calculate power if you already know the current. All this measures, though, is how well the rectifier/regulator module regulates. The load won't change much as rpms go higher, nor will voltage change much. (The FI pump may draw more current). This is easy at low rpms, but as the rpms get higher you'll probably not want to rev your engine without load to the redline. To graph the higher rpms you'll probably want to measure as you ride. Use a cheap meter for this. Don't ask me how I know. 👍

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I could easily get the amperage for you with my carbon pile and amp meter. My only problem is I don't think my fan works.👍 Well I guess I could jump the relay to get it to come on.

There's a connector in the fan wiring just above and to the right of the coil, plastic-clipped to the EGR tube. Pop that apart, and you've got the two lead wires right there. If you can find a 12V source that isn't frozen solid, I bet you can get the fan to run:)

i have no idea what a "carbon pile" is, but if you are curious, go for it. I hope nobody does things to their bike solely on my account, I'd feel bad if/when something goes wrong. For a little while, anyway:)

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dh, I think the easiest way to "measure" the load is not to measure it, but just look at the schematic and add up all the light wattages. The headlight will be the heaviest load and the brake light probably the 2nd heaviest.

The best way to measure the load, I think, is to use a clamp-on current meter around the positive or negative battery cable and measure current with the engine off, but all electrical accessories on. This way all current is being drawn from the battery at the time of measurement and it's easy to measure. Be sure to work the brake as you measure because the brake light is a major load. Measure battery voltage at the same time and voltage x current is power.

This measures total power except the relatively small amount to run the engine. If you want to measure that also, unplug the voltage regulator and start the bike, and measure as described just above. Be sure to use a clamp-on current probe because when you start the bike it will blow the fuse in your in-line current meter.

You can measure voltage output fairly easily at 2k rpm intervals and calculate power if you already know the current. All this measures, though, is how well the rectifier/regulator module regulates. The load won't change much as rpms go higher, nor will voltage change much. (The FI pump may draw more current). This is easy at low rpms, but as the rpms get higher you'll probably not want to rev your engine without load to the redline. To graph the higher rpms you'll probably want to measure as you ride. Use a cheap meter for this. Don't ask me how I know. :worthy:

Ya know, maybe I don't *always* know when to quit, but this stuff is clearly beyond my ken. Maybe someone more electrically savvy will want to dig into it sometime, and maybe they will post here.

Thanks for the follow-up.👍

BTW, I checked, and "www.jksgvb.com" is available:D

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Ya know, maybe I don't *always* know when to quit

Yes. I have to confess I have been wondering for quite some time now: "Where the hell is he going with all of this"???? Of course, I don't even understand the concept of "motard" so....

However, you do remind me of an old joke - supposedly true - where one officer's annual fitness report was marked:

"This officer's men would follow him anywhere - mostly out of a morbid curiosity to see what he will do next"

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Yes. I have to confess I have been wondering for quite some time now: "Where the hell is he going with all of this"???? Of course, I don't even understand the concept of "motard" so....

Did you think there was a "punch line" or grand unveiling coming?:busted: I don't know where it ends either. But I'm used to it.👍

I tried to ignore labels when I was bikeshopping. I found tourers, cruisers, road racers, and offroad racers. I wanted a "universal motorcycle", with a fuel-efficient modern engine and a sturdy adjustable suspension. I wanted something with lots of retail outlets for parts and service, so that leaves H-D and the 4 Japanese, particularly Honda and Yamaha.

The WR250R/X became the unfortunate object of my attention.:worthy: Even these are too specialized for me in the wheels and tires selected.

I'll have to read up on the evolution of motorcycle wheel and tire sizes, I'm really curious about the history (why we ended up where we are). "Overspecialized" is a word that comes to mind:), but I think that about motorcycles sold in the US in general. No so in most other parts of the world, where they are mainly used for transportation, not recreation.

Cheers!

/dh

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I hope nobody does things to their bike solely on my account, I'd feel bad if/when something goes wrong. For a little while, anyway:)

Anything to help get you where you are going, where ever it is.👍

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Quoted from Yamaha's website on features for WR250R/X:

Rare earth-type ACM alternator keeps the weight down while providing all the current needed to run the FI and lighting systems.

Tech info I found expalining, what an earth type alternator means and the ratio to motor rpm. Our bikes are fuel injected so they need more power.

The compact ACM uses rare earth magnets and spins at 1.24 times the engine rpm to produce ample electrical current to power the bikes electrical requirements.

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dh, I think the easiest way to "measure" the load is not to measure it, but just look at the schematic and add up all the light wattages. The headlight will be the heaviest load and the brake light probably the 2nd heaviest.

The best way to measure the load, I think, is to use a clamp-on current meter around the positive or negative battery cable and measure current with the engine off, but all electrical accessories on. This way all current is being drawn from the battery at the time of measurement and it's easy to measure. Be sure to work the brake as you measure because the brake light is a major load. Measure battery voltage at the same time and voltage x current is power.

This measures total power except the relatively small amount to run the engine. If you want to measure that also, unplug the voltage regulator and start the bike, and measure as described just above. Be sure to use a clamp-on current probe because when you start the bike it will blow the fuse in your in-line current meter.

You can measure voltage output fairly easily at 2k rpm intervals and calculate power if you already know the current. All this measures, though, is how well the rectifier/regulator module regulates. The load won't change much as rpms go higher, nor will voltage change much. (The FI pump may draw more current). This is easy at low rpms, but as the rpms get higher you'll probably not want to rev your engine without load to the redline. To graph the higher rpms you'll probably want to measure as you ride. Use a cheap meter for this. Don't ask me how I know. :busted:

Yeah, I kind of did it in reverse fashon with my KLX250. I started the engine, then inserted a shunt between the negative terminal of the batt and ground, read votage and current and did the ohms law. I then added additional loads in the form of sealed beam headamps until charging voltage couldn't be held above 12.5VDC.

All totaled, the KLX250S charging system could handle about 150W, which amouned to 80W drawn by the OEM equipment + about 70W of additional loads. What's crazy is that the manual rates the KLX charging system at 14V/15A which would amount to 210W! That's a far cry from the readings I observed at ANY RPM. If Yamaha is computing their capacity the same way, I would take about 75% of that 350W figure...which still isn't too shabby for a 250CC dual sport...easily the best in its class. It would be intesting to actually put meter to bike.

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