Originally Posted by EtekRestos
Jerry - when #6 is like this, is #1 at TDC?

Yes, #6 and #1 are "companion cylinders" meaning that both pistons come to the top of the cylinder at the same time. The difference is the position of the valves. The #1 valves have been closed for almost the entire upstroke of the piston, creating compression, while the #6 piston has been pushing the burned gases out past the open exhaust valve. #6 is getting ready for its next intake stroke, so the intake valve is beginning to open. #1 gets the spark, and the burning gas is getting ready to push the piston down the cylinder on the power stroke. Both pistons are traveling the same direction at the same time, just on different strokes in the 4-stroke cycle. The other companion cylinder pairs are #2 and #5, and #3 and #4.

My students used to love my description of the 4-stroke cycle. Instead of having them memorize "Intake, Compression, Power and Exhaust", I called it "Suck, Squeeze, Bang and Blow!"
grin grin grin
Jerry


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