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Naturally aspirated internal combustion (IC) engines with a fixed intake assembly are generally tuned to produce an induction boost at a single engine speed by capitalizing the induction pressure waves only over a narrow speed range. This paper investigates the individual and combined effects of varying intake runner length and intake valve timing on the performance parameters of an IC engine at engine speeds from 3000 rpm to 9000 rpm. The 1-D model of the KTM SI engine built for simulations in Ricardo Wave software is validated with 98% accuracy against experimental test results. The performance parameters thus obtained, as a combined effect, show an average improvement of 7.02% throughout the engine’s speed range. With the co-existence of variable length intake runners and variable intake valve opening timing, the required number of variations to boost the engine performance are found to be reduced making variable intake assembly more feasible.

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Changes to engine geometry and specifications can produce better torque, power, volumetric efficiency and more. The technique known as wave tuning can lead to better engine torque and power. This paper focuses on increasing the engine torque by improving the exhaust fluid flow through the exhaust manifold. Phasing and intensity of the pressure waves in the exhaust manifold have significant effects on scavenging, valve overlapping and pumping losses. In this research, individual and combined effects of variable exhaust runner diameter and exhaust valve timing on the fluid flow from exhaust of the engine are studied using computer simulation. An engine simulation software, Ricardo Wave, is utilized in this research. The analysis is conducted on a 1-D model of a KTM 510 cc single cylinder, four-stroke Sl engine. The data gathered shows that varying only the exhaust pipe diameter continuously with speed yields an average of 4.23% improvement in torque from the original engine model. However, due to practical constraints, the diameter is limited to vary in three steps (36 mm, 45 mm and 60 mm). This has reduced the average improvement of torque to 3.78%. Varying the valve timing alone gains an average of 1.94% improvement in torque. Varying both the exhaust pipe diameter in three steps and the exhaust valve timing yields an average of 4.69% improvement in torque. This average is conducted over the engine speed ranges from 2000 to 11,000 rpm.