Production function:

The exhaust valve opens early because the working stroke piston descends to the bottom dead center, the pressure of the exhaust gas itself after combustion is high, so that the exhaust gas in the cylinder is discharged quickly, and the pressure in the cylinder is reduced as soon as possible, which can reduce the resistance of the piston rising in the exhaust stroke. , Shorten the time that the exhaust gas stays in the cylinder and avoid overheating of the engine. The exhaust valve closes after the piston reaches the top dead center in the exhaust stroke. This not only prolongs the exhaust time and enables the exhaust gas to be fully removed, but also due to the inertia of the exhaust gas flowing in the exhaust manifold, it can promote Exhaust gas in the cylinder continues to flow out, so the exhaust valve should also be closed late. The cleaner the exhaust gas in the cylinder is, the lower the temperature of the cylinder at the end of the exhaust, which creates favorable conditions for the intake stroke and can increase the combustible mixture entering the cylinder.