Toyota Lean Burn Engines
In 1984, Toyota released the 4A-E engine. This was the first engine in the world to use a lean burn combustion control system with a lean mixture sensor. It was used in Japan on Toyota Carina T150, Toyota Corolla E80, and Toyota Sprinter. The lean mixture sensor was provided in the exhaust system to detect air-fuel ratios leaner than the theoretical air-fuel ratio. The fuel injection volume was then accurately controlled by a computer using this detection signal to achieve lean air-fuel ratio feedback. For optimal combustion, the following items were applied: program independent injection that accurately changed the injection volume and timing for individual cylinders, platinum plugs for improving ignition performance with lean mixtures, and high performance igniters.
The lean burn versions of the 1587cc 4A-FE and 1762cc 7A-FE 4-cylinder engines have 2 inlet and 2 exhaust valves per cylinder. Toyota uses a set of butterflies to restrict flow in every second inlet runner during lean burn operation. This creates a large amount of swirl in the combustion chamber. Injectors are mounted in the head, rather than conventionally in the intake manifold. Compression ratio 9.5:1. The 1998cc 3S-FSE engine is a direct injection petrol lean burn engine. Compression ratio 10:1.
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