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The higher efficiency with the Honda 1.5L Turbo in the new Civic is from its use of direct injection and a head integrated exhaust manifold. Direct injection is probably worth 1-1.5 points of compression ratio. IEM helps keep the engine out of enrichment under boost, but to really work well it needs a second thermostat and a split cooling system (ie., seperate the block and run it slightly warmer than the head and IEM at high torque). Honda doesn't do that on the Civic, but it is showing up on some VW engines in Europe.
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