Attention: TDR Forum Junkies 
it is equally at both TDC and BDC
The shorter the rod the faster the piston accelerates down the bore , in a fast burn drag motor a rod to stroke ration of 1. 65 to 1 is what most people use , this causes the piston to tug harder on the port , and allows you to make a bigger port with out it going lazy. In the old days with slow combustion chambers, and little ports you would put a longer rod in the motor to keep the port from developing Sonic Choke at 15 to 20 degrees after TDC.
Sonic Chock is when the air goes super sonic in the port, and the resulting shock wave kills flow.
Now in a diesel you are dealing with half the Rpm, this cancels out the flame propagation issue, but you have very large sweep volumes and very small ports. This would make a longer rod be of some benefit, changing the rod also dose not have any thing to do with displacement.
Another thought, the pressure that is developed behind the valve when the valve closes is very good, this is the reason for tuned runners in the intake track, its is called resonance tuning. In a normal aspirated motor that is the reason you can have volumetric efficiently higher then the theoretic pumping efficiency’s of the sweep volume of the motor. You are by the effects of inertia in the moving air column supercharging the motor. Bottom line diesel fuel when not in a severe over fueling situation is not as slow as you might think. , and there ways to speed it up. Forget it’s a diesel, in the cylinder head and cam department, and you will go faster.
The shorter the rod the faster the piston accelerates down the bore , in a fast burn drag motor a rod to stroke ration of 1. 65 to 1 is what most people use , this causes the piston to tug harder on the port , and allows you to make a bigger port with out it going lazy. In the old days with slow combustion chambers, and little ports you would put a longer rod in the motor to keep the port from developing Sonic Choke at 15 to 20 degrees after TDC.
Sonic Chock is when the air goes super sonic in the port, and the resulting shock wave kills flow.
Now in a diesel you are dealing with half the Rpm, this cancels out the flame propagation issue, but you have very large sweep volumes and very small ports. This would make a longer rod be of some benefit, changing the rod also dose not have any thing to do with displacement.
Another thought, the pressure that is developed behind the valve when the valve closes is very good, this is the reason for tuned runners in the intake track, its is called resonance tuning. In a normal aspirated motor that is the reason you can have volumetric efficiently higher then the theoretic pumping efficiency’s of the sweep volume of the motor. You are by the effects of inertia in the moving air column supercharging the motor. Bottom line diesel fuel when not in a severe over fueling situation is not as slow as you might think. , and there ways to speed it up. Forget it’s a diesel, in the cylinder head and cam department, and you will go faster.
