A convertible vehicle has a carbody and a retractable top connected to the carbody. The chamber includes at least one rotor within the process chamber. The engine may also be started with half the cylinders cut out and then run with stable operation in this mode during idle and light load because the increased load on the operating cylinders gives stable operation with an increased valve overlap permitting increased performance and emission control at higher load operation on all the cylinders. A commercial package is included. A method of introducing a swirl to the mixture is also described.