Patent ID: 8534261

Claim:
A four-cycle engine comprising: a first cylinder, and a second cylinder different in combustion timing from the first cylinder and structured to introduce fresh air into a cylinder via an intake port opened/closed by an intake valve and suck exhaust gas back into the cylinder via at least one of first and second exhaust ports opened/closed by at least one exhaust valve, and including a controller for controlling a valve opening system so that the exhaust gas is sucked through the first exhaust port and secondary air is sucked through the second exhaust port to form, in the cylinder, a first temperature layer having a high temperature containing the exhaust gas in the fresh air and a second temperature layer having a temperature lower than that of the first temperature layer containing the secondary air in the fresh air, a blowdown pressure wave supercharging system structured to cause a pressure wave from a combustion chamber at opening of the exhaust valves of the first cylinder to act on the exhaust ports of the second cylinder during a reopen period during which the exhaust valves of the second cylinder are reopened; and a secondary air supply system supplying secondary air to the second exhaust port, wherein the reopen period of the exhaust valves of the second cylinder is set from near a bottom dead center of an intake stroke to near a bottom dead center of a compression stroke of the second cylinder and the blowdown pressure wave from the first cylinder acts on the exhaust ports of the second cylinder during the reopen period to introduce the exhaust gas through the first exhaust port into the second cylinder and introduce the secondary air supplied into the second exhaust port by the secondary air supply system into the second cylinder.