dori dori said:
KA's big problem is their rod length...which is also why I don't get Anthony's signature.
Having longer rods is better (when keeping it a reasonable length). When your rod pushes against the wall of the cylinder, a force is generated. The smaller the angle is between them, the better- period.
YOU HAVE AN ENGINE THAT MAKES 100 LBf/ft of torque
Say you have a rod that’s 4 inches and a stroke that’s 3.
When the angle is greatest, it will be: 41.4 degrees.
Force (to the side of the wall) = (torque)x(sin41.4) = 75 LBf/ft
Force (upward/downward) = (torque)x(cos41.4) = 66.1312 LBf/ft
NOW,
Say you have a rod that’s 8 inches and a stroke that’s 3.
When the angle is greatest, it will be: 68 degrees.
Force (to the side of the wall) = (torque)x(sin68) = 37.46 LBf/ft
Force (upward/downward) = (torque)x(cos68) = 92.72 LBf/ft
SO you see that less force is exerted on the wall of the piston with longer rods. This is because there is less force exerted between wall and piston and more force upward or downward. This is why stroker kits are bad. They increase the stroke size and actually reduce the rod size. The wall of the cylinder will wear easily and the rod could break through.
HOWEVER, when you are getting close to 100LBf/ft in the upward direction, it will take a lot longer of a rod to make an improvement. Also, when the structural integrity (because of material and shape) and the weight of the rod are compromised because of the length, the angle between them become irrelevant because your rods will break in no time.
SR rods are shorter than ka rods. That's why a 2.0 liter with a much smaller stroke has a rev limiter only a little above a 2.4 liter. As your rpms increase, the force stays the same (if torque stays constant throughout the rpms) but there is more energy transferred to the wall of the piston. Longer rods = rev higher.
I like that signature.