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Cylinder identification 
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1N4001 - Signed up

Joined: Thu May 29, 2008 1:23 am
Posts: 307
Location: Long Beach CA
shameem wrote:
Thanks for the help. I havent scoped the signals yet - i am planning to use my labjack u12 to acquire some of those timing diagrams - once i get some free time.

From the website -
You can see the two unequal pulses from the SGC. The engine computer uses the unequal length of SGC to tell when the cylinder #1 of the motor is at top dead center (TDC). The SGT pulses are all the same. The computer knows it is time to fire a spark plug when an SGT pulse occurs.

The computer knows it's time to start a 'countdown' to firing the spark. The edge usually precedes the point of maximum spark advance.

Instead of a scope, the info can be more easily collected with a meter, and a wrench to turn the crank. The rising or falling edge of the SGT signals correspond mechanically to a piston position that is well before TDC.

Knowing which edge, and about how many degrees before TDC the edge occurs, is the info needed to make your home-brew ignition control.

If you put a meter on the SGT signal, and turn the crank by hand, it will be obvious which edge, rising or falling, corresponds to a piston being well before TDC. You can probably make a guesstimate as to the degrees before TDC from the crank wheel degree markings.

Some stand-alone ignition modules also control spark advance based on the input pulse frequency. The degree alignment of the SGT signal to the crank might allow the use of stand-alone ignition modules. Maybe in this case, 2 or 4 separate stand-alone ignition modules. Prolly the 4 separate modules would be of a type designed for single-cylinder motors.

I'm sure some folks here or on the MS site would know about the various ignition modules available.

- Jim

Tue Jul 01, 2008 12:26 am
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