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How do "Pulses per Revolution" relate to Tachometer Calibration for My Marine Engine?
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When we talk about Pulses per revolution (PPR), or your tachometer's Pulse setting, we're talking about the electrical signal that our tachometers look for from your engine's ignition system.
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Typically, a "Pulse" refers to an ignition firing, so another way to think of this is sometimes as Ignition Firings per revolution, though this is not always the case. For I/O Marine applications, 4, 6, and 8 cylinder applications are normally the same as automotive. Typically 4 Cylinder engines are 2 PPR, 6 Cylinder engines are 3 PPR, and 8 cylinder engines are 4 PPR.
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Outboard applications are USUALLY 6 PPR. This signal comes from the alternator, which on multi-cylinder outboards is a 12 pole unit. In this case the Pulse Per Revolution is 1/2 the number of poles.
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