Due to the configuration of the IHT, the hydraulic ‘commutation’ from one port to another will almost never occur at the top dead centres, but mostly at a point where the plungers move at high speeds. As a result cylinder pressure peaks will occur and port-opening losses influence the efficiency negatively. The prevention of pressure peaks is realised by absorbing a small volume of oil during the passage of a valving land. The shuttle-solution fulfils these requirements. The shuttles are small ball shaped ‘pistons’ that are free to move over a limited stroke between two end positions. The cylinder in which the piston moves is on each side connected to one of the cylinders of the barrel. In the end positions the shuttles act as a check valve, thereby closing off the connection between two cylinders. In between the two end positions the shuttle predominantly acts as a piston, displacing oil from one cylinder to the other, giving the necessary freedom to the compressed or expanded oil in the valving land. This leads to improved efficiencies and reduced sound levels.