New Mitsubishi high-speed diesel uses SCR technology (credit: MTEA). New Mitsubishi high-speed diesel uses SCR technology (credit: MTEA).

Mitsubishi has augmented its range of four-stroke, high-speed marine diesels by introducing a new vee-engine model meeting the latest US environmental standards, writes David Tinsley.

Targeted at the potential for a multiplicity of small vessel applications in the tug, inland waterway, service vessel, workboat, special-purpose and fishing sectors, the latest addition to the S12R series is EPA Tier 4-compliant through the adoption of selective catalytic reduction (SCR) technology.

The Mitsubishi S12R-Y4MPTAW-3 propulsion engine is a comparatively large displacement (49-litre), 12-cylinder design in 60-degree vee configuration, rated for an output of 1,260hp (940kW) at a crankshaft speed of 1,600rpm.

One of the most significant aspects of the design is its marriage of the wherewithal for continuous emissions abatement to the Tier 4 level with the retention of mechanical engine control, in the interests of overall simplicity, in consideration of many vessel owners’ preferences. The mechanical rather than electronic emphasis bears on ease of maintenance and presumably also on production requirements.

EPA Tier 4 mandates substantial curtailment of NOx and particulate matter (PM) emissions, plus more stringent hydrocarbon (HC) criteria.

MHI Engine & Turbocharger (MHIET) has been taking a different approach to many of its competitors in the four-stroke, high-speed category. According to Mitsubishi marine engine manager Takeshi Yoshida, although most of the industry moved to complex, electronically-controlled engines in 2007, the company opted for a series of mechanical engines to meet EPA Tier 2 regulations. “It was remarkable that Mitsubishi met Tier 2 with a simple mechanical engine,” said Mr Yoshida.

That policy was perpetuated in the subsequent development and launch of Tier 3-certified engines, which achieved the requisite compliance without incorporating electronic controls, and has again been applied in the S12R Tier 4 entrant.

Part of MHIET, Mitsubishi Turbocharger & Engine America (MTEA) is responsible for the distribution of the company’s marine propulsion machinery in the US, Canada, Mexico, Central and South America.

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