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| Hoganas |
Any combustion engine requires to operate in the presence of air. The intake valve controls the amount of air getting into the chambers while the air molecules escape from the chamber via the exhaust valve. Here we are going to study how the diameter of intake + exhaust valve influences the Chevy 302 engine.
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| Measurement data |
A larger intake valve draws more air into the chamber that improves the engine performance at high-rpm region. The smaller intake valve gives a tiny advantage in low-rpm region because the intake valve does not open too much when the engine runs slowly. If the valve diameter is small, the air gains extra speed that forces the air into the chambers more effectively. This also explain why the peak torque is shifted to the low-end region via the use of a smaller intake valve.
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| Measurement data |
Decreasing the exhaust valve diameter from 2 inches to 1.6 inches does not make a huge difference in the dyno data at low-rpm range because the engine runs relatively slower and the burnt-out gas molecules have enough time to leave the chamber. However, the engine is operated in superb condition at red zone and hence a large exhaust diameter allows the burnt-out gas molecules to exit the chamber more easily.
