>Another point of contention is that long rod engines don't
>really have much of an advantage in dwell time, and lose the
>advantage of peak angle when it counts.
>
>The short rod engine puts the unit force vector closer to the
>perpendicular to the crank at an earlier point then a long rod
>engine. For example, in this simple drawing (MS Paint OWNS!):
>
>
>The rod angles are the same at TDC, but the rod moves towards
>the tangent of the rod journal's path radius quicker then the
>long rod engine. In other words, the piston will push harder
>on the crank earler then the long rod motor will. At "just
>after TDC," the short rod engine will create a higher torque
>moment, based on the force vector. At "way after TDC," neither
>will have a real advantage, and at "90 degrees past TDC," the
>long rod motor is optimal, as the rod angle from the piston to
>the rod journal is a smaller number of degrees. Unfortunately,
>most of the force exerted on the crank occurs right after
>combustion. This gives the advantage to the short rod motor.
>Even at high RPMs, there will not be a high amount of force on
>the piston near 90 degrees. This means that not only do you
>lose the force vector advantage, but you lose the rotational
>mass and inertia advantage. Rotating mass is the enemy of rev
>speed.

What you are saying here doesn't completely make sense to me. You want peak cylinder pressure to occur 20 deg ATDC. If that happens, the long rod motor will create more torque because it's got a better rod angle to push the crank downward. Near TDC where cylinder pressures are the highest is where you gain the most torque. Because a long rod setup causes the piston to stay in that region for a longer period of time, it will exert that high amount of force longer than a short rod will and still turn the crank the same distance. The long rod will always have the rod angle advantage (except at TDC and BDC as you pointed out lol). As for the rotating mass, that is not as much the enemy of rev speed as steeper rod angles that are created by short rod motors. The rod:stroke ratio is much more critical than the rotating mass in this case. If you were trying to build a 10k+ rpm motor then obviously you would want some billet aluminum or ti rods.

Matt
1995 Eclipse GS
2.0L, S16g Turbo, 8 Injectors, 26psi

1998 Eclipse GSX
2.3L Stroker, AEM EMS Converted to Speed Density, FP3065 Turbo, 35psi , and so on...