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  1. #1 Headlights & fuel consumption 
    Danger, Will Robinson! Lao Jia Hou's Avatar
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    Weird topic, I know. But I am sure that anyone who has run with their headlights on, during the day, in China, has been confronted with "your headlights are on!"

    A few days ago, I was stopped by the police for having my scooter's headlight on during the day. I was told that is was against the law, in China, but I was let off with a warning. Whatever.

    Thereafter, I had a healthy argument with a Chinese friend, who insisted that having your headlights on results in increased fuel consumption. His side of the argument was based on "everyone knows this, how can you be so stupid?!?!?!"

    I'm sorry, but this does NOT make sense to me. Please educate me.

    IMHO, whatever type of charging system you have (e.g., stator; generator, alternator), there is NO additional mechanical load when the system is being subjected to an increased electrical load. That is, there is no additional mechanical resistance applied to the engine, as a result of the increased electrical load. The charger (e.g., a motorcycle's stator) is producing electricity at a rate which is affected only by RPM. If your stator/charging system is not producing enough juice, for whatever reason, there is no additional drag on the engine as the system tries to produce more electricity. That is not how the mechanics work in a copper-wrapped generating system. A demand for additional electrical current can NOT cause an increase in mechanical resistance.

    This is very different than a car's A/C system, which engages the pump (connected by the serpentine belt) and therefore causes an additional mechanical load. Same with power steering pumps.

    As I understand it, charging systems put out a fixed amount of current, affected only by RPM, to a certain maximum. When there is a need for additional current, the regulator provides it - when there is no additional need, the regulator dumps it.

    Someone please explain to me how an increase in electrical requirements could possibly cause an increase in fuel consumption. It makes no sense. A stator/alternator is NOT subjected to an increased drag - the magnetic field is constant, the windings are constant, the only thing that affects current production is RPM.

    Frankly, I think that riding without a helmet probably creates drag as your hair & oddly shaped face push through the wind! And the big-nosed laowai face is probably MORE aerodynamic than the flatter Asian face! I have never heard anyone say "hey, you're using too much gas. Put a helmet on. Oh, wait, you're a big-nosed laowai - never mind."
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  2. #2 Re: Headlights & fuel consumption 
    Life Is Good! ChinaV's Avatar
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    Dude, just let it go... you're never going to win the argument. You are correct, they are idiots times two. Once for arguing about the mileage, and once for not having lights permanently on which is proven to reduce accidents.

    The other one I like is the "pulsing" drivers, these are the guys that constantly press and release the accelerator. That also increases mileage.

    Cheers!
    ChinaV
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  3. #3 Re: Headlights & fuel consumption 
    Senior C-Moto Guru Zorge's Avatar
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    Simply tell your Chinese friend that you're a decadent rich man who could pay all the lights on a bike.
    Ask me nothing - I DO NOT speak english. Really...
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  4. #4 Re: Headlights & fuel consumption 
    Senior C-Moto Guru ZMC888's Avatar
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    China is a country where actual scientific fact plays a secondary importance to 'common knowledge'.

    A few gems over the years:
    - A woman that eats an ice-cream when breast feeding will make the babies' milk cold
    - Bread should be sweet
    - Cold drinks are bad for your health
    - Coffee is highly carcinogenic
    - Hard tires are always the best as they last longer
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  5. #5 Re: Headlights & fuel consumption 
    Motorcycle Addict chinabiker's Avatar
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    Quote Originally Posted by Lao Jia Hou View Post
    Weird topic, I know. But I am sure that anyone who has run with their headlights on, during the day, in China, has been confronted with "your headlights are on!"

    A few days ago, I was stopped by the police for having my scooter's headlight on during the day. I was told that is was against the law, in China, but I was let off with a warning. Whatever.

    Thereafter, I had a healthy argument with a Chinese friend, who insisted that having your headlights on results in increased fuel consumption. His side of the argument was based on "everyone knows this, how can you be so stupid?!?!?!"

    I'm sorry, but this does NOT make sense to me. Please educate me.

    IMHO, whatever type of charging system you have (e.g., stator; generator, alternator), there is NO additional mechanical load when the system is being subjected to an increased electrical load. That is, there is no additional mechanical resistance applied to the engine, as a result of the increased electrical load. The charger (e.g., a motorcycle's stator) is producing electricity at a rate which is affected only by RPM. If your stator/charging system is not producing enough juice, for whatever reason, there is no additional drag on the engine as the system tries to produce more electricity. That is not how the mechanics work in a copper-wrapped generating system. A demand for additional electrical current can NOT cause an increase in mechanical resistance.

    This is very different than a car's A/C system, which engages the pump (connected by the serpentine belt) and therefore causes an additional mechanical load. Same with power steering pumps.

    As I understand it, charging systems put out a fixed amount of current, affected only by RPM, to a certain maximum. When there is a need for additional current, the regulator provides it - when there is no additional need, the regulator dumps it.

    Someone please explain to me how an increase in electrical requirements could possibly cause an increase in fuel consumption. It makes no sense. A stator/alternator is NOT subjected to an increased drag - the magnetic field is constant, the windings are constant, the only thing that affects current production is RPM.

    Frankly, I think that riding without a helmet probably creates drag as your hair & oddly shaped face push through the wind! And the big-nosed laowai face is probably MORE aerodynamic than the flatter Asian face! I have never heard anyone say "hey, you're using too much gas. Put a helmet on. Oh, wait, you're a big-nosed laowai - never mind."
    The guy is right, there is an increased fuel consumption with your lights on, negligible for the individual though.
    In some European countries driving with light during the day is mandatory for all vehicles and later this decade it will be a EU wide regulation. Some of the Eco driven political parties fight against this with the increased fuel consumption argument.
    My GS doesn't even have a switch to turn the headlights off and I had some funny encounters about this in China too.

    Generator and alternator are the same, converting mechanical to electrical energy. The term alternator is mostly used for AC (alternating current) systems, while generator is the common term for both, AC and DC current systems. The stator is the non rotating part, the rotor the rotating part of a generator.
    On typical AC generators the output comes from the non rotating part (fried stator derives from here), while an old fashioned DC generator delivers electricity from the rotor, aka armarture.
    The system is the same in cars and bikes, while the difference is that it is driven by a v-belt in a car and mostly directly coupled to the engine on a bike.
    As soon as any electrical consumer is powered by the vehicles electrical system it uses electrical energy which is provided by the generator. Being a converter, the generator has to receive this energy from the mechanical side, thus puts additional load to the engine and therefore adds to fuel consumption.
    Electrical consumers have very little power compared to the engine. A 200cc China bike engine provides max 10kw, a light bulb for the high beam consumes less than 50W - 0.5% of the engine power. There are other, much bigger, electrical loads on a bike such as heated grips or efi fuel pumps.
    The regulators job is only to keep the voltage in a small range, typical 10.8 to 13.2 Volts, as the output voltage of an electrical generator increases linear over speed and the voltage is to be in the range from engine idle to engine max speed.
    Vehicle batteries are usually charged by applying a higher voltage than nominal to the battery, hence creating current flowing into the battery and charging it. The value of the current depends on the charging state of the battery. Some small devices batteries (mobile phones, ...) may be charged by driving a constant current into the battery, which allows faster charging.

    Hopefully this sheds some light on this topic for you

    As others posted before, there is widespread ignorance for technical basics all over the middle kingdom.
    Andy
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  6. #6 Re: Headlights & fuel consumption 
    Danger, Will Robinson! Lao Jia Hou's Avatar
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    Quote Originally Posted by chinabiker View Post
    Being a converter, the generator has to receive this energy from the mechanical side, thus puts additional load to the engine and therefore adds to fuel consumption.
    This is what I don't understand. In any electrical generation found on vehicles (generator, stator, alternator), there is no physical/mechanical contact between the windings and the magnets/poles. Because there is no physical contact, how can drag/load be created? The only possible way (in physics) would be for a magnetized force to increase, thereby effectively pulling on the spinning windings (or, in bikes, generator's spinning basket) - but it doesn't - magnetization (if present) is a fixed amount.

    What I understand is that the output varies, based on RPM, to a ceiling amount (regulated).

    Where the "problems" can occur are when the electrical load exceeds either the generator's output, or the regulator's output, or both. For example, if your bike generates 300 watts, but your load is 400 watts, you have a negative drain. Eventually, your battery goes dead because it's storage has been topping up the system requirements.

    In the old days, with oil-filled coils (pre CDI), when the electrical power production was insufficient, the spark would be weakened. There was a linear relationship, and this would be why cars would sometimes drop the idle speed, and/or lose torque, when you turned on the lights (an indication of a poor alternator, regulator, coil, wires, ect). It is my understanding that one of the advantages of CDI was that it helped compensate for these oddities.

    But I still can't see how there can possibly be an increase in fuel consumption due to lights. There is no mechanical connection, anywhere, and the generators cannot be "dragged" due to an increased draw. The direction of electrical power production is unidirectional - from the generator outwards.

    If it were true (headlights/mileage), presumably, the boom-box cars must get poor mileage with their 1,000 watt amplifiers.

    Essentially, the generator's output is fixed, regardless of the demands being required down the line.
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  7. #7 Re: Headlights & fuel consumption 
    Senior C-Moto Guru ZMC888's Avatar
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    Lao Jia Hou, I also don't understand how having a headlight on uses fuel, albeit my understanding (or lack of) is somewhat simpler...

    Logically a headlight draws it's power from battery which is constantly trickle charged by the alternator regardless of whether the headlight is on or not, meaning that there is practically no fuel whatsoever used by having a headlight on.
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  8. #8 Re: Headlights & fuel consumption 
    C-Moto Regular lobotomous's Avatar
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    I have heard the 'lights off saves fuel' argument in China and Taiwan from cagers and bikers alike, and it always makes me laugh.
    +1 about the 'pulsing' or 'pumping' drivers. I thought they drive like that because they have been taught to drive on a bumper car (i.e. power is either on or off). Are they driving like that to save fuel??!
    The issue of driving w/lights remains an area of debate, though. I remember when I first had bike training (admittedly a long time ago), my instructor told me not to put lights on during the day. The belief then was that it can be misconstrued as a courtesy flash to give way to someone exiting a junction. And also that it makes it harder to determine relative speeds and distances. So I would never normally ride with the lights on during the day in the UK. I have started to do so more in China as the previous arguments are kind of secondary to making you as visible as possible. I think hi-viz vest is more important (for fuel economy as well as visibility)
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  9. #9 Re: Headlights & fuel consumption 
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    Chinabiker, I'm a little confused by your statement. Is the amount of power consumed by the generator from the engine constant? As in it makes no difference what electrical devices are turned on?

    Top Gear did an experiment a few years ago where they drove an SUV around a test track with the AC on, and another with it off to compare fuel savings. I think the experiment didn't work however because of some problems having to do with using the track.

    Here is a "How Stuff Works" article claiming that fuel/money can be saved by not using DRLs but I'm not certain about the math or science being used.

    /Edit

    K, read your response below. Thanks. Still wondering about how much of a drain running headlights would be compared to everything else however. I wonder if it could even be measured when one takes into account the amount of fuel lost through heat generation, drag, and everything else that goes on with a motorcycle that does not actually relate to the power being generated at the rear wheel.
    Last edited by Nuhaus; 11-05-2012 at 10:09 AM.
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  10. #10 Re: Headlights & fuel consumption 
    Motorcycle Addict chinabiker's Avatar
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    Quote Originally Posted by Lao Jia Hou View Post
    This is what I don't understand. In any electrical generation found on vehicles (generator, stator, alternator), there is no physical/mechanical contact between the windings and the magnets/poles. Because there is no physical contact, how can drag/load be created? The only possible way (in physics) would be for a magnetized force to increase, thereby effectively pulling on the spinning windings (or, in bikes, generator's spinning basket) - but it doesn't - magnetization (if present) is a fixed amount.
    The magnetic field is the physical connection, though not visible. When an electrical winding is rotating inside a magnetic field, voltage is induced which is available at the winding ends. As soon as a consumer, e.g. bulb, is connected to the winding, the circuit is closed and electric current flows. A winding with current flowing in a magnetic field creates force. This force creates torque which has the opposite direction of the mechanical torque driving the generator. The generator would now slow down and to keep the speed up more mechanical power is needed to keep it running --> more throttle, more gasoline.


    Quote Originally Posted by Lao Jia Hou View Post
    What I understand is that the output varies, based on RPM, to a ceiling amount (regulated).

    Where the "problems" can occur are when the electrical load exceeds either the generator's output, or the regulator's output, or both. For example, if your bike generates 300 watts, but your load is 400 watts, you have a negative drain. Eventually, your battery goes dead because it's storage has been topping up the system requirements.
    If the load exceeds the nominal load of the generator, electrical current through the winding exceeds the nominal value as the voltage is relatively constant. If you overload a winding, it will sooner or later thermally fail.


    Quote Originally Posted by Lao Jia Hou View Post
    But I still can't see how there can possibly be an increase in fuel consumption due to lights. There is no mechanical connection, anywhere, and the generators cannot be "dragged" due to an increased draw. The direction of electrical power production is unidirectional - from the generator outwards.

    If it were true (headlights/mileage), presumably, the boom-box cars must get poor mileage with their 1,000 watt amplifiers.

    Essentially, the generator's output is fixed, regardless of the demands being required down the line.
    Take an old fashioned DC gen, there is a mechanical as well as a physical connection - the rotor of the generator, where the electrical output connects to and where the engine drives it. AC gens would not have a mechanical but a physical connection, the magnetic field between stator and rotor. As said before, the influence on fuel consumption is marginal for one individual.
    Andy
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