Abstract: The inlet arrangement comprises two inlet ports for a fuel and air mixture each of which terminates at an orifice openable and closeable by a respective valve. Each inlet port is of a high flow/low swirl type and a mixture of fuel and air which flows through the orifice can be deflected to enable the inlet port to perform as a low flow/high swirl at smaller throttle openings. In one embodiment, flow of mixture through the inlet port can be deflected at low throttle openings by a transverse flow of gas from inlet ducts. In other embodiments, the direction of mixture flow can be varied by members movable into and out of the mixture flow.

Abstract: A camshaft drive mechanism operates the inlet valves of a first cylinder through a variable valve timing (VVT) mechanism at one end of an engine block and the inlet valves of a second cylinder through a VVT mechanism at the other end of the block. In a four cylinder engine the first cylinder is No 1 and the second cylinder is No 4, cylinders Nos 2 and 3 having separate VVT mechanisms adjacent the VVT mechanisms of cylinders Nos 1 and 4 respectively. A preferred form of VVT mechanism includes an eccentric sleeve which provides a journal for a driving member. Rotation of the eccentric sleeve in an offset bore alters the valve timing. By having the offset equal to the eccentricity of the sleeve the potential wear of the components of the VVT mechanism is reduced.