Why 2 plugs per cylinder? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 8 (permalink) Old 05-30-2011, 01:52 PM Thread Starter
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Why 2 plugs per cylinder?

What do think was the reason for the design of two plugs per cylinder? More Power.......or to burn better for emissions? Also do our coils only fire on power stroke or do they also fire on the exhaust stroke too.......Like all distributorless car ignitions do?
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post #2 of 8 (permalink) Old 05-30-2011, 03:08 PM
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What do think was the reason for the design of two plugs per cylinder? More Power.......or to burn better for emissions? Also do our coils only fire on power stroke or do they also fire on the exhaust stroke too.......Like all distributorless car ignitions do?
Manual says Suck Squeeze Bang Blow...guess that means traditional 4-Stroke
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post #3 of 8 (permalink) Old 05-30-2011, 04:10 PM
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The double plugs per jug is not really for power per sae, but to insure a complete combustion.... Likely to pass EPA emmissions.


Spark plug placement, head shape as well as the angle of the valves can all have an effect on how the mixture burns....as well as how much power the motor puts out.

I saw a film on MV Augusta's factory, and one of the engine designers showed how just changing the angle the intake valves 1.2 degrees added almost 2 hp.

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post #4 of 8 (permalink) Old 05-30-2011, 10:39 PM
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Originally Posted by BRET H View Post
What do think was the reason for the design of two plugs per cylinder? More Power.......or to burn better for emissions? Also do our coils only fire on power stroke or do they also fire on the exhaust stroke too.......Like all distributorless car ignitions do?
Without a cam position sensor it has to be a wasted spark, the ignition only knows where TDC is, not which stroke it's on.
Oh, and not all distributorless ignition systems fire on the exhaust stroke, most coil on plug systems do not.

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Last edited by E-Town; 05-30-2011 at 10:41 PM.
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post #5 of 8 (permalink) Old 05-30-2011, 10:42 PM
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unless one is set to fire at tdc and the other just after
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post #6 of 8 (permalink) Old 05-31-2011, 03:16 AM
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Both plugs fire at the same time. With two plugs the mixture burns faster. If you want to burn down your house, it is faster if you start the fire in multiple corners.
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post #7 of 8 (permalink) Old 05-31-2011, 09:13 AM
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Both plugs fire at the same time. With two plugs the mixture burns faster. If you want to burn down your house, it is faster if you start the fire in multiple corners.
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post #8 of 8 (permalink) Old 06-01-2011, 12:38 AM
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Originally Posted by Knifemaker View Post
The double plugs per jug is not really for power per sae, but to insure a complete combustion.... Likely to pass EPA emmissions.


Spark plug placement, head shape as well as the angle of the valves can all have an effect on how the mixture burns....as well as how much power the motor puts out.

I saw a film on MV Augusta's factory, and one of the engine designers showed how just changing the angle the intake valves 1.2 degrees added almost 2 hp.

KM
Pull just one plug wire off one cylinder, and you'll notice the power loss; pull one off each cylinder, and you'll _really_ notice it...

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