The cylinder heads and the camshaft carriers consist of separate pieces instead of one metal casting. That allows a reduction in metal thickness, simplification of the engine's structure, and reduction in weight.
Revisions to the valvetrain include the use of roller rocker arms instead of lifters to actuate valves. These components and their layout contribute to reducing the width of the cylinder heads and overall engine width.
The fuel injectors were moved to the cylinder heads. In the EJ engine, they were mounted in the intake manifolds. The relocation enhances the flow of atomized fuel, helping to improve fuel efficiency and reduce exhaust gas emissions.
Both intake and exhaust systems are designed to optimize the flow of gases and improve performance.
In the intake system, the intake manifold no longer requires a large intake chamber, which reduces the number of parts in the engine. The size and shape of the large and small resonators along the intake manifold are streamlined. These revisions help reduce overall engine weight as well as manufacturing costs.
Another modification resulting in the elimination of parts is the addition of a cooling function to the exhaust gas recirculation system.
Intake and exhaust ports and valves have been revised, too. Valves have been engineered to reduce drops in pressure when they're open, which helps improve performance. Their design increases tumbling (keeping fuel mixed with air) when closed, which improves fuel efficiency and helps reduce exhaust gas emissions.
The exhaust system features improved tuning. The diameters and lengths of the separate tubes have been modified to improve catalytic converter warm-up (reducing emissions) and to increase power output.
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