The Ports
Both the intake and exhaust ports were designed to have unimpeded flow into and out of the combustion chamber. The line-of-sight “tumble port” intake ports are designed to have high-flow capacity as well as generating high levels of in-cylinder air motion. The in-cylinder motion, in concert with careful shaping of the combustion chamber, enables fast burn rates and high knock resistance.
The intake port design and the fuel injector targeting allow for all the fuel to be aimed at the backside of the intake valve via:
Closed Valve Injection Timing: Allows for better fuel vaporization (heating) in part-throttle light load operation
and optimizes combustion efficiency for best fuel economy and lowest emissions.
Value Open Injection Timing: This same fuel targeting allows for very effective strategies at high load full-throttle performance. The fuel enters the chamber in atomized state (liquid – small droplet diameter), which cools the combustion chamber and allows for higher compression ratio and more optimized spark timing. In this way, a more cost efficient port fuel injected (PFI) engine can return similar knock resistance to a direct fuel injection (DI) engine.
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