Trying to remember basic pipe tuning basics.
On the intake side the longer the intake runner the lower the rpm that reflective ram effect or resonance occurs. The rpm when the inertial pressure is highest when the valves opens. The shorter, the higher the rpm when max pressure occurs.
IIRC, it is the same for the exhuast side, except the inertial pulse, as it is traveling out, is pulling a pressure drop behind it, instead of compressing gas in front of it as an intake pulse does.
The longer the primary tube, the lower the rpm for maximum peak scavanging. This is partly due to the velocity of the gas pulses, but mostly due to the time between pulses (time between valve openings for that cylinder). Low rpm - longer time between each pulse, so need a longer distance (longer primary) for the pulse to travel so it will just starting to exit the primary tube as the exhuast valve opens again for max pressure drop.
High rpm - shorter time between pulse, shorter distance for the pulse to travel before the next valve opening.
Hope that makes sense, best I can explain.
Once upon a time had a formula for calculating length to rpm. Basically the same formula as length to frequency for resonance in a given dia. Each calculation is for a particular tubing ID.
So you would need longer primaries for torque to come in at a lower rpm.
And again IIRC a smaller dia/ longer collector(s) will help amplify.
Feel free to check my memory with FTF or others.
No problem.
