Author Topic: port mapping (easy way)  (Read 1521 times)

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Offline 1manband

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Re: port mapping (easy way)
« on: October 18, 2015, 08:53:52 pm »
first thing that i would do is figure out 'angle area'

you need a couple of things before a number can be had.

looking about, most folks here and elsewhere talk in degrees.

seems where the port opens in degrees is talked about more often than port durations.   (opposite is true most everywhere else).

going with that.

looking at a typical exhaust port:

degrees where the port just starts to open, for example is 97 degrees ATDC.  ATDC = after top dead center.  TDC is top dead center, where the piston is physically located at the uppermost point of its travel. (at TDC = 0 degrees).

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to find 'durations'.........the amount of angle degrees a port is open can be done a few different ways.

Port Open Durations:

Exhaust Port Opens @ 97 degrees ATDC.  so, 97 x 2 = 194; then 360 degrees - 194 degrees = 166 degrees duration.
Transfer Port Opens @ 121 degrees ATDC. so, 121 x 2 = 242; then 360 - 242 = 118 degrees duration

Blowdown is simply: Degrees Trans first opens - Degree Exhaust first opens = 121 - 97 = 24 degrees duration.

Intake is a little different, because most it seems measure the opening degrees BTDC in saws.  (before top dead center).

Intake Port Opens @ 75 degrees BTDC.  so, 75 x 2 = 150 degrees duration.




hiatus

 

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