Hexhead - Camshaft Sensor: What does it do?

Discussion in 'GS Boxers' started by Carlos M, Sep 8, 2008.

  1. Carlos M

    Carlos M www.motoxplorers.com

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    Hello all,

    Plugged a GS-911 to a friend's HP2 and there's a fault impossible to clear: "Camshaft Sensor Error".

    Anyone knows what's this camshaft sensor??? my oilhead doesn't need one :D Why would an HP2? Searched the web but nothing shows up.

    Would't such sensor be redundant with the Hall sensor on the crankshaft? :scratch

    Said bike with the error shows a certain roughness and the ocasional backfire - we plugged the 911 trying to find a clue about this.... :scratch

    Thanks in advance for any help.
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  2. Poolside

    Poolside Syndicated

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    <BR>The camshaft sensor on the 1200 lets the ECU synchronize on the cylinder cycles. The 1100/1150 doesn't use a cam sensor (or any other sensor) to synchronize on the cylinder cycles. The ECU on the 1100/1150 operates as though it is controlling a one-cylinder motor that is spinning at 2x the actual RPM.

    <BR>
    #2
  3. hp2rider

    hp2rider Adventurer

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    mine had this problem and did not come up with the code for the dealer
    had intermittent miss originally then a significant loss of power wouldn't go over 80

    #3
  4. Carlos M

    Carlos M www.motoxplorers.com

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    Thanks for both your answers :thumb

    Haven't thought about that :scratch And I couldn't understand from your explanation :doh How does the 1150 ECU know which cyl is on compression and which is on exhaust? Do you know where can I find more info on this subject?

    Thanks again!
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  5. Poolside

    Poolside Syndicated

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    Sure Carlos. The two-cylinder 'boxer' motor design has both the pistons traveling up and down the cylinders (in and out) together. The ECU doesn't need to synchronize with the cylinders. The ECU thinks it is operating a single cylinder motor, only it thinks the motor is operating at double the RPM.

    What happens is, both injectors are connected to the same ECU injector wire, and fuel is injected to both cylinders once per crankshaft revolution, when the pistons at BDC. Each cylinder gets its 'combustion load' of fuel in two '1/2 squirts' instead of one full squirt. This is commonly called 'batch injection'.

    The single ignition coil fires both plugs at some number of spark advance degrees BTDC. Just like normal. The way the boxer motor is designed, one plug operates during the compression stroke of one cylinder, and the other plug operates during the exhaust stroke of the other cylinder. This is commonly known as 'wasted spark'.

    The 'Motronic' ECU fitted to the 1100/1150 goes by another name. 'Mono-tronic'. The product is discussed in a 1985 SAE technical paper #850293 titled: "A New Low Pressure Single Point Gasoline Injection System". The subject of the paper is the Bosch Monotronic.

    The Motronic fitted to the 1100/1150 is just as happy operating a single-cylinder motor. And the way it is wired up to the 1100/1150 motor, as far as it knows, it is.

    - Jim
    <BR>
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  6. Terry

    Terry Long timer

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    Doesn't this mean that half the gas gets squirted in at the bottom of the exhaust stroke? What keeps it from being blown out the exhaust pipe unburned?

    Terry
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  7. MJS

    MJS Long timer

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    The injector is upstream of the intake valve. The fuel is mixed with the air in the intake port and drawn into the cyl when the intake valve opens during the intake stroke. A lot of european cars used Bosch CIS (Constant Injection System) in the late 70's. IIRC, that system injected fuel in a constant stream into the intake port.
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  8. Grok

    Grok Long timer

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    The fuel gets injected into the airstream before the intake valves, not directly into the combustion chamber. During the exhaust stroke the intake valves are closed (hopefully).

    D'oh! MJS beat me to it.
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  9. Terry

    Terry Long timer

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    Thanks for the explaination guys...

    Terry
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  10. Carlos M

    Carlos M www.motoxplorers.com

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    Jim,

    Thanks a lot for explaining this and keeping ADVrider an interesting place through the years!

    I had to sketch this to completely figure the whole thing :doh

    [​IMG]

    I now understand why the two sensors at the Hall sensor plate!

    And thanks Grok and MJS, I was having the same doubt as Terry.

    I had no idea that half the injection was being made into a closed admission duct... it sounds somehow inefficient :scratch

    Now let's move to the Hexhead... :evil ... Has the hexhead moved away from batch ignition and wasted spark? how many camshaft sensors? Where are they? can the bike work on some sort of limp mode without these?

    My friends HP2 has the "camshaft sensor" error present and it runs "normally".

    Thanks again!
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  11. Poolside

    Poolside Syndicated

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    <BR>
    Sure, though it really wouldn't 'limp' much. The ECU could operate with batch ignition and wasted spark. An industry standard for all motorcycle motors so far. Just recently moving to sequential fuel and spark because among other things the high rpms do not allow enough time for an ignition coil to charge up twice per combustion cycle.

    - Jim
    <BR>
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  12. Carlos M

    Carlos M www.motoxplorers.com

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    Jim,

    Thanks again! I promise to clean up that sketch!

    One last question... isn't the crankshaft Hall sensor redundant to the camshaft sensor? by the position of the right cyl camshaft the hexhead ECU could figure exactly what each cylinder is doing, wouldn't it???
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  13. Poolside

    Poolside Syndicated

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    The camshaft sensor (I think VR, based on what I've seen) operates on a single tooth attached to the cam sprocket. The cam sensor merely outputs a 'tick' signal say.

    The crankshaft sensor (a Variable Reluctance (VR) instead of a Hall effect) operates on a multi-tooth wheel (30 teeth or more) attached to the front of the crank. The toothed-wheel has either a 'missing tooth', or a 'double wide tooth', or uses the camshaft sensor 'tick' (I'm not sure which) to denote TDC.

    The ECU interprets a 'tick' from the camshaft sensor to identify that the next crankshaft rotation is, for instance, the intake stroke for the left cylinder.

    - Jim
    <BR>
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  14. big adv

    big adv I need supervision

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    And these two little sensors are what make it possible for the 1200 series eng.s to be self balancing at lower rpm's, By knowing which cylinder is which (cam sensor) and by measuring crankshaft acceleration (cranksensor). Thus knowing if one cylinder is faster than the other, and adjusting for this with the IAC(stepper motors)

    Earl
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  15. MJS

    MJS Long timer

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    Not much different than OBD-II where mis-fires are determined by measuring crankshaft acceleration for each cylinder's ignition cycle.
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  16. Poolside

    Poolside Syndicated

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    <BR>
    An ECU can "self balance" the crank accelerations using only the hall sensors as fitted to the 1100/1150, and without the use of IAC (stepper motors) or the cam sensor on the 1200. Also an ECU can determine which cylinder is on which cycle without the cam sensor.

    But since the Motronic ECU on the 1100/1150 is really a Mono-tronic for single cylinder, those features are not included.

    Regarding IAC steppers, balanced air intake isn't directly related to equal crankshaft acceleration.

    <BR>
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  17. Anorak

    Anorak Woolf Barnato

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    I would imagine that the IAC is too slow and any adjustments would be done with ignition timing and injection pulse width.
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  18. Poolside

    Poolside Syndicated

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    <BR>Absolutely the case for individual combustion cycle control, FB

    <BR>
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  19. big adv

    big adv I need supervision

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    Then why 'park' the IAC's when doing a sync.? And how do you ID #1 with two hall sensors on the crank?

    Earl
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  20. Anorak

    Anorak Woolf Barnato

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    So they don't affect the reading of the manometer.
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