HD engine sound
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The classic Harley-Davidson engines are two-cylinder, V-twin engines with the pistons mounted in a 45° "V". The crankshaft has a single pin, and both pistons are connected to this pin through their connecting rods.
This design causes the pistons to fire at uneven intervals. This is due to an engineering tradeoff to create a large, powerful engine in a small space. This design choice is entirely vestigial from an engineering standpoint, but has been sustained because of the strong connection between the distinctive sound and the Harley-Davidson brand. This design, which is covered under several United States patents, gives the Harley-Davidson V-twin its unique choppy "potato-potato" sound. To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor, which is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark." The exhaust note is basically a throaty growling sound with some popping.
The 45 degree design of the engine thus creates a plug firing sequencing as such: The first cylinder fires, the second (rear) cylinder fires 315° later, then there is a 405° gap until the first cylinder fires again, giving the engine its unique sound.[49]
The classic Harley-Davidson engines are two-cylinder, V-twin engines with the pistons mounted in a 45° "V". The crankshaft has a single pin, and both pistons are connected to this pin through their connecting rods.
This design causes the pistons to fire at uneven intervals. This is due to an engineering tradeoff to create a large, powerful engine in a small space. This design choice is entirely vestigial from an engineering standpoint, but has been sustained because of the strong connection between the distinctive sound and the Harley-Davidson brand. This design, which is covered under several United States patents, gives the Harley-Davidson V-twin its unique choppy "potato-potato" sound. To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor, which is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark." The exhaust note is basically a throaty growling sound with some popping.
The 45 degree design of the engine thus creates a plug firing sequencing as such: The first cylinder fires, the second (rear) cylinder fires 315° later, then there is a 405° gap until the first cylinder fires again, giving the engine its unique sound.[49]
Last edited by Some Guy Who Rides; Aug 13, 2008 at 11:39 AM.
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