With a reputation built on reliability, Cummins Marine does extensive testing before releasing a new engine to the market.The QSK50 EPA Tier 3 engines have been put through many hours of test bed operation at the Cummins factory. However Cummins believes that the real test of a marine engine is in marine operating conditions. With a need for frequent increase and decrease in power demand, push boats working the US inland water system are a particularly demanding application. One moment, while working around a down river bend, the engines may be idling while a few minutes later full power may be demanded to push a heavy tow on down the river. Backing power becomes important when working a tow off a fleeting area. Fluctuating power demands and frequent shifting put a new engine to the test.
It was with this demanding service-cycle in mind that the engineers at Cummins Marine choose the 105 by 32-foot towboat Eugenie, belonging to Houma-based Enterprise Marine Towing, for field-testing of the new Tier 3 compliant engines. Each 50-liter 16-cylinder engine produces 1800 HP at 1800 RPM. The installation saw the engines fitted to the existing Reinjest WAF-762 gears with 1:5.913 ratios. The new engines replaced a pair of Cummins 1600 HP QSK50 Tier 2 engines with only two minor alterations. To take advantage of the increased power, the propellers were changed, from 78-inch diameter with 68-inch pitch, to 80 by 60-inch props. In the engine room, since the new QSK50 T3 has the turbo chargers installed  in the top center of the engine instead of the rear of the engine as is on previous QSK50 T, the exhaust connection was moved 621 mm horizontally.
The US Environmental Protection Agency required that engines with 2.5 to 3.5 liters displacement per cylinder should achieve the stringent Tier 3 standards January 1, 2013. At 50 liters the 16-cylinder QSK50-M1 engine has 3.25 liters of displacement per cylinder. The EPA Tier 3 standard requires a 50% reduction in particulate matter (PM) and a 20% reduction in NOx compared to existing Tier 2 standards. The Tier 2 requirements apply to the popular Cummins QSK38 also.Cummins engineers achieved this standard with the established common rail fuel injection, newly designed single piece piston and high-efficiency turbo-charger and after-cooling among other refinements.
The engines were installed on August 26, 2012 and by mid-December had performed for approximately 1720 hours. As field-test engines they are closely monitored by Cummins engineers. Cummins Application Engineer John Echavarria says of the engines’ performance, “During this time no significant issues were reported. All coolant, fuel, lube, electric and mounting connections for the QSK50 Tier 3 are the same as they were for the Tier 2 engines.“
The field-testing of these engines is one more step in the continuing efforts by Cummins to maintain the high level of reliability that they have earned over the decades while meeting ever more stringent environmental standards.
Source: Cummins