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HEY, WAYNE ! [message #55461]

Wed, 16 August 2006 01:55

wunhuanglo
Messages: 912
Registered: May 2009

Illuminati (2nd Degree)

I was wondering if you might consult on an engine-and-instrument-related question, since you're quite an expert at both.

I'm converting a one-lung 4-stroke portable generator from gasoline to natural gas. One thing I need to do is to lean it out to get max rpm under load, so I need a tach.

What I'm thinking is that I can wrap a piece of wire around the spark plug lead to get an inductive pulse. I can clip my frequency reading DVM to that lead and ground the DVM to the engine someplace. Then I can read RPM directly. Even if it's a two-spark per rev engine (which I don't know) it really won't matter, it's just that my reading won't be true RPM but it won't affect my finding a maxima.

Any thoughts? Am I missing the boat completely? Thanks for taking the time to read this.

Charlie

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Re: HEY, WAYNE ! [message #55463 is a reply to message #55461]

Wed, 16 August 2006 09:00

Wayne Parham
Messages: 18752
Registered: January 2001

Illuminati (33rd Degree)

You could use a pickup like that, you betcha. Connect it to a pulse counter and you're set. You might use a timing light with an inductive pickup. Some even have built-in tachometers.

Something like this

Don't use a DVM though. The signal you're reading is a pulse train, and so the DVM will not read it like you want. It won't show the rate of pulses. It will just show the DC level, and maybe bounce a bit occasionally when it happens to sample at the time a pulse flies by.

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