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Old 08-06-2018, 03:06 PM   #9
paulb
 
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Name: paulb
Title: Too Much Time
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Join Date: Jul 2006
Location: Klamath Falls, OR
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It's not so much about making it easier on the engine, as it allow you to concentrate where the peak pressure occur in the combustion cycle. Generally we want the peak pressure to occur in the area of 7 to 13 degrees after top dead center. This value will vary depending on a lot of mechanical and thermodynamic variables. For simplicity sake, if we say that we want the combustion to go out in that range, then as rpm increases the start of the injection must start earlier. The earlier the combustion starts then the more reverse pressure (pressure while the piston is still moving up), will happen on the piston. Having a shorter duration and still deliver the required amount of fuel will reduce the amount of reverse pressure that's applied. The higher the rpm, the more this comes into play.

For mileage though a nice steady push works better then a hard sledge hammer like blow. This is competition diesel though. Who cares about mileage! I can race the whole weekend on a 1/4 tank of fuel. Pretty good mileage in my book! :-)

Paul
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