They could control CR with variable valve timing. They could delay opening the intake valves (ala simulated Atkinson cycle), shortening the intake stroke in relation to the power stroke. Also, turbo engines usually start with a low CR without the boost.I don't understand how Honda can run its 16.5 psi boost turbo engine on 87 octane gasoline. That kind of boost raises the effective compression ratio sky-high. All of the high-boost turbo engines I'm familiar with need the highest octane fuel they can get. Does anyone know how Honda has managed this feat?