The calculation for the length of the tuned intake runners is based upon the duration between two events of the intake valve’s operation: the first being the closing of the intake valve, and the second being the re-opening of the intake valve on the next cycle. From the Engine Datasheet in Appendix A, the information is found to be 48°ABDC (After Bottom Dead Centre, referring to the angle the crankshaft rotates after passing the BDC position) to 14°BTDC (Before Top Dead Centre, referring to the angle the crankshaft needs to rotate before reaching the TDC position) respectively, giving a total of 474° of crankshaft rotation during which the valve is closed. Further calculations factor in the effect of the engine speed, such that various RPMs will create different time durations within which the intake valves remain closed.Taking a full 4-stroke cycle to be made up of two crank cycles, the intake valve is thus closed for 474° out of a total of 720°, giving a duty-ratio of 65.8%. Therefore, considering the RPM and how an increasing RPM will suggest a reducing time period for the wave to reflect, a33range of values is calculated for the lengths of runners required to achieve the effect of reflecting the higher-pressure air onto the intake valves are they open.