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Thread: R1150 Alternator Start-Up Fix & AFR

  1. #1
    Registered User roger 04 rt's Avatar
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    R1150 Alternator Start-Up Fix & AFR

    The other day while taking some AFR data on cold start and warm up I noticed that my alternator light was on. I haven't noticed it before but after going back through a year's worth of data I can see that it has happened several times in the past. After a couple minutes the alternator started on its own and the light went out. Or if I blipped the throttle the alternator came on-line and the Batt light went out. So I might have lived with it by blipping the throttle. However:

    During the time the light was on, there was no alternator output and the battery voltage was at the Motronic was about 12V. When the alternator came on-line the voltage jumps to 14V.

    Then I noticed something very interesting. During warm-up when the voltage was at 12V, the mixture was about 8% leaner than a moment later when the voltage jumped to 14V. Thats too lean and i could feel it in a slightly rough idle. The Motronic sensed the lower voltage and lengthened the injector pulses, trying to compensate but in Open Loop it didn't compensate enough. If the alternator stayed off line until the bike went closed loop, the AFR was at the correct level before and after the step up in voltage. This means that the Motronic closed loop algorithm could fully compensate for the low voltage. That was lesson 1 for me.

    So then I tried to understand why the alternator wasn't self starting. I for some feedback that many bikes do this. The starting current for the alternator flows though the Batt bulb on the Instrument Panel. I decided to try a resistor across that bulb and found that with a 220 ohm resistor across the bulb, the alternator aways starts.

    The bulb is 1.7W and let's about 140 mA through the alternator rotor to start it. Adding the 220 resistor boosted the start-up current by a mere 50 mA for a total of 190 mA. BTW if the Batt bulb burns out the alternator may not start, it depends how much residual magnetism is in the rotor. Lesson 2.

    Looking at the parts list, it originally specified a 1.7W bulb. But that is crossed-out now and a 3W bulb is now called for. So to get at the Batt bulb I first had to pull the High Beam bulb (they're both in a knuckle-busting location). As luck would have it, the High Beam was 3W even though the Batt bulb was only 1.7 W. So all I had to do was swap the bulbs, its hard to tell the difference of brightness. I plan to carry a 3W spare (Toshiba A14V3W).

    Running the numbers, the magnetizing power with the 1.7W bulb was about 75 mW. The 3W bulb boosts that to 225 mW--a big jump

    So if your alternator doesn't start on its own you might want to check the Batt bulb and see what it's power is.

    RB

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    Smile

    Huh??

    I don't have any idea what you're talking about. It's way over my head.

    Dave

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    Registered User roger 04 rt's Avatar
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    BMW used to ship a 1.7 watt bulb in the Instrument Display that shows the battery symbol. Surprising as it sounds, that little bulb is what is used to start the Alternator charging! On some bikes from what I've heard (and mind) that bulb doesn't flow enough current to get the Alternator charging.

    Later BMW changed that bulb to 3 watts. This seems to be enough to start the Alternator charging at idle.

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    Quote Originally Posted by Roger 04 RT View Post
    If the alternator stayed off line until the bike went closed loop, the AFR was at the correct level before and after the step up in voltage. This means that the Motronic closed loop algorithm could fully compensate for the low voltage.

    I get it, where can I buy 1.3 watts?

    I understand the whole thing, GM had a similar situation. The wrong bulb (or a blown bulb) and it would not work correctly.

    When I changed the backlights in the speedometer of my oilhead, I did both bulbs. They are different than the ones in the tach. Speedometer is much brighter. I think its the same bulb as in the battery light.

    Techlusion fixes all that too lean stuff.

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    BMW used to ship a 1.7 watt bulb in the Instrument Display that shows the battery symbol. Surprising as it sounds, that little bulb is what is used to start the Alternator charging! On some bikes from what I've heard (and mind) that bulb doesn't flow enough current to get the Alternator charging.

    Later BMW changed that bulb to 3 watts. This seems to be enough to start the Alternator charging at idle.
    Just like an electric generator. If you let it sit too long, it will discharge the head. Then when you need the generator, it will not produce electric. You then have to pre-charge it with a battery to get it to produce electric.

    The bulb is an odd way to pre-charge the alternator. I do wonder why they used a smaller watt bulb.

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    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by DROOT153718 View Post
    I get it, where can I buy 1.3 watts?

    I understand the whole thing, GM had a similar situation. The wrong bulb (or a blown bulb) and it would not work correctly.

    When I changed the backlights in the speedometer of my oilhead, I did both bulbs. They are different than the ones in the tach. Speedometer is much brighter. I think its the same bulb as in the battery light.

    Techlusion fixes all that too lean stuff.
    After spending an hour to avoid paying BMW $3 for the bulb, I'm conceding and ordering one from Max BMW. This needs to be a shock-proof long life bulb.

    Here is he bmw P/N:
    02 62 14 2 306 126 BULB - 12V 3W 3 $3.44


    Quote Originally Posted by 23217 View Post
    Just like an electric generator. If you let it sit too long, it will discharge the head. Then when you need the generator, it will not produce electric. You then have to pre-charge it with a battery to get it to produce electric.

    The bulb is an odd way to pre-charge the alternator. I do wonder why they used a smaller watt bulb.
    After I scouted around I saw that some automotive applications put a resistor from B+ to the D+ terminal on the alternator so that if the bulb burns out the alternator will still start. It might take as much as a 56 ohm 5 watt resistor. That's about equal to the bulb.

    I don't think it's something to be too worried about but with the testing I do, sometimes I want a "correct" start sequence. I will say that one way or another when the generator starts running after a cold start the bike runs better. When a get a minute I'll post a couple pictures showing the difference.

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    Talking

    The only thing I checked is the 5 volt reference for the TPS.

    With the key on engine off (KOEO), there is still the same voltage IN and OUT of the TPS as with the Key on Engine Running (KOER). I was not worried about it on the alternator.

    So I could set the TPS at .399 volts engine off. When I fired it up with the alternator charging its still .399 volts.

    David

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    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by DROOT153718 View Post
    The only thing I checked is the 5 volt reference for the TPS.

    With the key on engine off (KOEO), there is still the same voltage IN and OUT of the TPS as with the Key on Engine Running (KOER). I was not worried about it on the alternator.

    So I could set the TPS at .399 volts engine off. When I fired it up with the alternator charging its still .399 volts.

    David
    Yes, that's because the voltage to the TPS is regulated and controlled to be 5V even as the battery voltage drops. It would be a good feature to add regulated 14v to the injectors.

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    Quote Originally Posted by Roger 04 RT View Post
    BMW used to ship a 1.7 watt bulb in the Instrument Display that shows the battery symbol. Surprising as it sounds, that little bulb is what is used to start the Alternator charging! On some bikes from what I've heard (and mind) that bulb doesn't flow enough current to get the Alternator charging.

    Later BMW changed that bulb to 3 watts. This seems to be enough to start the Alternator charging at idle.
    So, are you saying that the alternator doesn't use permanent magnets, and the alternator requires current flow through the bulb to initially establish a magnetic field within the alternator every time you start the bike??

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    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by 141987 View Post
    So, are you saying that the alternator doesn't use permanent magnets, and the alternator requires current flow through the bulb to initially establish a magnetic field within the alternator every time you start the bike??
    That's right. Kind of interesting.

    I'm told there is a small amount of residual magnetism and that with enough RPM it will "usually" start with no bulb but not always.

    But as you said when you turn the key, the current flowing through the bulb provides the initial magnetism. The magnetizing power more than triples when you go from the 1.7W lamp to the 3W lamp.

    And as I've mentioned a couple times, the injectors are MUCH slower at 12V than at 14V leading to rougher running until the Alternator comes on line when it is cold, like here in the NE.

    Of course you can just hold the idle lever up for several seconds so the higher RPM helps the 1.7W bulb start things.

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    wikipedia

    If I remember right an alternator does not have magnets like a genitor does. And has what is call ÔÇ£excitation currentÔÇØ to work.

    http://en.wikipedia.org/wiki/Alternator
    Thanks
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    They put the permanent magnets in the starter.

    David

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    In the old days, the generators did not charge at Idle at all. The Gen light would glow until you stepped on the gas. (like my airhead) Alternators are smaller, lighter, produce more power and more RPM friendly.

    My sister was looking at a 58 Plymouth Savoy to buy. It had a Gen Light and Oil Light right next to each other. My dad switched the sockets and bulbs on a test drive. Took it back to the seller and said "Nice car but the Oil light comes on when its Idling. My sister got a good deal on the car.

    Back to your regular show....

    David

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    Quote Originally Posted by 141987 View Post
    So, are you saying that the alternator doesn't use permanent magnets, and the alternator requires current flow through the bulb to initially establish a magnetic field within the alternator every time you start the bike??
    That system/principle is used for most automotive alternator systems.
    Serves two purposes - Idiot light for system monitoring and excitation.
    Cheap and effective.
    '
    Ufda happens..........

    It's all about the details.

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    Quote Originally Posted by DROOT153718 View Post
    In the old days, the generators did not charge at Idle at all. The Gen light would glow until you stepped on the gas. (like my airhead) Alternators are smaller, lighter, produce more power and more RPM friendly.

    My sister was looking at a 58 Plymouth Savoy to buy. It had a Gen Light and Oil Light right next to each other. My dad switched the sockets and bulbs on a test drive. Took it back to the seller and said "Nice car but the Oil light comes on when its Idling. My sister got a good deal on the car.

    Back to your regular show....

    David
    And you are proud of this ?
    '03 R1150R, '03 F650GS, '97DR200SE,'78 Honda CT-90, '77Honda CT-90

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