Variable Exhaust Control System

An apparatus for adjusting power and noise characteristics of an internal combustion engine, comprising:

• a wall configured to define an engine cylinder that includes a bore and further configured to define a compression relief passage that extends from a combustion chamber of the engine cylinder to an exhaust passage that is in fluid communication with the cylinder;
• a compression relief valve configured to selectively adjust fluid flow capacity of the compression relief passage;
• a piston configured to travel in the cylinder bore and further configured to compress a mixture that includes a fuel and oxygen;
• an ignition source configured to initiate combustion of the mixture;
• and
• a manifold configured to be in fluid communication with the exhaust passage, including
• an exhaust bypass valve configured to permit an exhaust product resulting from ignition of the mixture to at least partially bypass a noise suppressor,
• a noise suppression passage configured to accept the exhaust product from the exhaust passage and route at least part of the exhaust product to a noise suppressor when the exhaust bypass valve is at least partially closed;
• and
• an exhaust vent configured to permit at least part of the exhaust product to bypass the noise suppressor when the exhaust bypass valve is at least partially open;
• wherein operational characteristics of the engine can be adjusted along a range that extends from a first set of operational characteristics present when both the compression relief valve and the exhaust bypass valve are in a fully open position to a second set of operational characteristics present when both the compression relief valve and the exhaust bypass valve are in a fully closed position.