Abstract: A land vehicle comprises an engine having a closed loop cooling system. The cooling system includes a heat exchanger and a switching valve arrangement. The valve arrangement allows coolant to bypass the heat exchanger until the coolant temperature has exceeded a preset temperature.

Abstract: An improved two stroke, multiple cylinder engine having combustion chambers and a single exhaust conduit for discharging exhaust gasses from the combustion chambers. In accordance with one feature of the invention, the combustion chambers are unified to two groups and respective combustion chambers belonging to the same group are generally simultaneously fired by a firing system. Otherwise, the entire combustion chambers are generally simultaneously fired. In accordance with another feature, the exhaust conduit has an attenuation mechanism for positive pressure reflection waves generated in the exhaust conduit. In a preferred embodiment, the attenuation mechanism comprises an inner pipe tapered downstream and having a plurality of apertures.