VEB The Volvo Engine Brake is a compression type engine brake first introduced on D12A and since used on later designed OHC engines from 9 to 16 litre displacement. The brake operates on a principle where exhaust valve cam followers act on a secondary cam profile when engine brake is activated. Engine oil pressure is used to eliminate extra valve clearance thus this action forces the follower against secondary lobes and unseating exhaust valves temporarily to achieve so-called compression bleeding as employed by similar systems from Jacobs, Cummins and Mack however Volvo system has an extra cam lobe thus giving two openings of the exhaust valves and is designed to work in conjunction with an exhaust brake so two of the engine's four strokes are used to raise engine braking effect - Exhaust and Compression strokes.