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I took the time tonight to measure the capacity of one combustion chamber in order to calculate the true compression ratio of the turbo engine. Even with oversized valves and substantial milling to true the head surface, the final chamber volume was barely smaller than a stock 1.9 chamber, at exactly 52 cc's. Much of this is attributed to the generous chamber unshrouding I performed in order to improve airflow.
Taking into account the head gasket ID and thickness, the piston's compression height, the ring land volume, the valve notches, and the swept cylinder capacity, I came up with a calculated compression of 8.75:1. This is just a bit high for a turbo engine, but it will aid in off-boost performance. Still, with restricted ignition advance, there should be no trouble running 14-16 psi of boost on pump gas. We'll see.
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