Alternator Upgrade

[rbm]

Hm, ok. Just a thought.

[TimTyler]

I wonder if the blue wire has anything to do with it. I thought I read somewhere that this alternator outputs a slightly higher voltage than OEM to satisfy the newer AGM battery.

[Elipten]

When I put a 50 amp Kbike alternator in mine no difference noted.

[Laitch]

According to MAX, the 50A alternator weighs ~50% greater than the 30A. That may account for need for higher revs to run it. Why the idle wanders is another matter. Maybe it won't if the idle is set higher at the outset.

[TimTyler]

I've been doing a lot of alternator readin' and learnin' lately.

It seems that once the bike starts sucking power from the alternator, resistance created by the alternator's magnetic field makes it harder for the engine to turn the alternator's rotor. I didn't know that.

I also read that the Enduralast alternators apparently output more wattage at lower RMP's than the Bosch's. I need to call EME and run this by them though. They don't have any alternator specs published on their site.

[Elipten]

In a care when you kick on the AC and other electrical devices you can hear the engine rev to compensate for the load

[Bill]

Basic physics .... to get energy out you need to put energy in.  A lot of systems don't apply field current until the engine is running so it is easier to start.  Motor/generator sets for example.

[TimTyler]

Just discovered my battery light in the instrument panel was dead. Not sure for how long. Guess that means my alternator hasn't been getting excited.

Installed four fresh bulbs in the instrument panel. Too wet to go riding today though.

[TimTyler]

Rode about 100 miles yesterday without trouble. The idle remained low when stopped (about 850rpm). When I got home I kept the motor running, hooked up the Carbtune and prepared to increase the idle a little. Well, for some reason before I adjusted anything the engine had settled into a 1000rpm idle. Grrrrrr. I bumped it up to about 1100rpm by adjusting the brass idle adjustment screw on each throttle body.

Received an emailed reply from EME today:

The old original Bosch 32 amp alternator was designed in the early 1980's; the rotor and stator windings not very compact,
and the air gap between the both of these components was quite large by today's manufacturing  standards of modern alternators.
 
The later model alternator 50 amp and 60 amp alternators were designed in the mid-1990's-
both alternators are much more robust and technologically advanced-
both have much more copper electrical windings in both the rotor and stator
and
a tighter tolerance airgap between the rotor and stator .
Also  a much more sophisticated electronic voltage regulator and rectifier.
What this all means is that the 50 a and 60 a units produce a much stronger electrical magnetic field at lower engine speed / alternator speed rotation;
this creates more current at idle engine speed and thru out the amperage current output curve ,
In other words, your new alternator is producing more current and sooner than the old unit.
We include both alternator test specification output sheets with numeric amperage values
and
test bench output curves to demonstrate the difference for comparative purposes.
 
So from what you are describing is correct -
the alternator is working correctly;
Since the alternator is producing a magnetic field / creating current at lower engine speed this will create a "drag" on the engine.
producing current and maintaining battery voltage at lower engine RPMs,
(as compared to the anemic old design) .
 
Bottom line;
A 50-60 amp alternator will require more engine horsepower than a 32 amp alternator.

EME also said that "Euro MotoElectrics ships the 60 amp alternator for both types, so you actually have a 60 amp alternator."

According to the attached spec sheet the alternator starts working at about 1200rpm. I'm assuming that's RPM's on the driving dog, not engine RPM. Anybody know what the RPM ratio is between the engine and alternator driving dog is?

[TimTyler]

Anybody know what the RPM ratio is between the engine and alternator driving dog is?

It would appear that the K75 driveshaft has roughly 58 teeth and the output shaft to the alternator has about 40 teeth. With this roughly 1.5:1 gear ratio,  the alternator's RPM is roughly 50% faster than the engine's RPM. (Right?)

According to the EME docs, the 32A alternator when spinning at 1500rpm (1000 engine rpm @ idle) outputs 0 amps. The 60A EnduraLast alternator is pumping out 30 amps at that same speed. That would certainly account for some engine efficiency.

[TimTyler]

This new alternator has created an interesting idle adjustment predicament.

Back story: I figured that with the newly installed fuel injectors I ought to balance the throttle bodies today. (I removed the three brass idle adjust screws and cleaned them and their sockets up with Q-tips and brake cleaner. Put a little drop of oil on the O-rings. Replaced them one turn and a half from bottoming out.) Connected the Carbtune and began to adjust like I've done dozens of times in the past.

With the 32a alternator I've always set the idle at ~ 1100 rpm. No problem. With that 32a alternator the bike runs solely off the battery at that rpm, and probably any rpm up to about ~ 1400rpm.

With the Duralast 50a alternator, the bike seems to switch between drawing power from the battery and alternator at around 800 - 900 rpm. (Note the chart in the 12/25 post above.) With my battery meter I can see the switch between 12v and 14v happen when the rpm hits that threshold. Since 750 rpm is too low to reliably idle, the idle must be adjusted within an rpm range where the bike is running off the 50a alternator.  So if I set the idle at 1000 rpm and a minute later the bike's fan starts up and stresses the alternator, engine rpm decreases with the new alternator load, perhaps down a couple hundred rpm to the point where the bike switches back to the battery for DC power and the alternator's load on the engine is released. Then the idle rpm increases since the alternator has turned itself off, ... and then the alternator starts up again,  Do you see where this is going? Basically, it seems necessary to set the idle at about 1400rpm in order to allow for DC load changes without stalling the bike. Wacky.

Am I missing something?

[Laitch]

It is asserted that this alternator creates more power at less revs than the older model so the activation of the bike's fan shouldn't have such a great effect on it, should it? Maybe there's a defect with the fan or its circuit that's creating the problem?

From a cold start, it idles ok ±900 rpm and idles ok when riding until the fan is activated?

[Martin]

 Tim put a meter on the fan and see how much it draws.
Regards Martin

[TimTyler]

I dunno...  :dunno  I'm not learned about alternators. Just trying to figure this crap out.

According to the EME data sheets, both alternators have a "Turn On Speed" of about 1200 rpm (that's alternator RPM) which is about 800 engine rpm. According to some reading, once an alternator is turned on or excited, it remains turned on until the engine comes to a compete stop. So what I said before about power switching between the battery and alternator is apparently hog wash. It's also possible I was reading the 32a EME data sheet graph incorrectly. It looks like a 200th generation photocopy.

My fan motor is just a couple of years old.

What I noticed was that, after an hour-long ride, I parked the bike but kept it running, hooked up the CarbTune and attempted to balance the TB's and set the idle. But every time the fan kicked-in briefly the engine RPM would drop and the battery meter would read ~ 12v. When the fan stopped the engine RPM increased and the battery meter reads ~ 14v. (This is an LED meter, so not exact values.)

I never experienced any weirdness like this with the 32a alternator.

[Laitch]

Are you able to set the engine idle and balance the TBs at ~1000 rpm or does the fan cycling always interfere, Tim? It seems strange to me that with temperature between the forties and fifties out there your fan cycles briefly within ten minutes after idling. My bike's fan takes longer than that to kick in at 50ºF. Maybe it's just a cold-blooded machine.

With the correct amount of coolant, a functioning fan, a functioning water pump and a fully functioning thermostat, this is what happens? If that's so and it were my bike, I'd disconnect the fan motor, finish the tune-up, reconnect the fan and see if I liked the idle on both sides of the fan cycle. Have you done that?

EME would be on speed dial, of course, and each step of the procedure would be followed by anapana sati.

[Laitch]

I'm also thinking it could have a defective voltage regulator but I'm out of my depth at this point.

[TimTyler]

I'll try again tomorrow, and I'll put a real meter on the battery and see what's going on.

Maybe my temp sensor is kaput.

[TimTyler]

... It seems strange to me that with temperature between the forties and fifties out there your fan cycles briefly within ten minutes after idling. My bike's fan takes longer than that to kick in at 50ºF. Maybe it's just a cold-blooded machine.

You're right, Laitch.
I discovered today that my idle fuel mixture was very rich after recently upgrading to the osidetiger 4-hole fuel injectors a few hundred miles ago. I've just fixed the mixture and balance the TB's. That ought to cool things down. The idle seems more controlled now. Got a busy week coming up so won't have a chance to mess around more until next weekend.