In an embodiment, a method for turbocharging a stratified charge engine includes flowing, in a turbocharged mode, exhaust gas from the engine into a turbocharger based on the engine having a load greater than a threshold load and the engine operating in a first range of engine speeds, the threshold load comprising a peak load for engine operation in a naturally-aspirated mode using a lean air-fuel mixture and providing, by the turbocharger while in the turbocharged mode, an increased amount of air to a combustion chamber in the engine based on the turbocharger receiving the exhaust gas. The method also includes restricting flow, in the naturally-aspirated mode, of the exhaust gas into the turbocharger based on at least one of: the engine having a load less than the threshold load or the engine operating in a second range of engine speeds, the second range being greater than the first range.