Volvo brought its 9- to 16-liter off-highway diesel engines into Tier 3/Stage IIIA-compliance with its V-ACT system (Volvo Advanced Combustion Technology). It uses a new "flexible" high-pressure fuel-injection system, new fixed-geometry turbochargers with improved airflow characteristics, enhanced electronic control units, new camshafts, new charge-air coolers and radiators — plus a patented, "switchable" internal exhaust gas recirculation system. The latter feature works through a specially designed exhaust-valve rocker arm that activates a second opening of the exhaust valve to allow a controlled amount of exhaust gas back into the cylinder during the inlet stroke to lower peak combustion temperatures.
