MTU Detroit Diesel offers a Tier 4i-compliant Series 900 compact engine with selective catalytic reduction (SCR) technology. Inline four- and six-cylinder Series 900 engines have ratings from 120 to 322 hp (90 to 240 kW), while V-configuration six- and eight-cylinder Series 500 engines cover ratings from 349 to 644 hp (260 to 480 kW). The same technology also is used in a 460 inline six-cylinder engine, which covers a power range from 348 to 483 hp (260 to 360 kW). As designed, Series 900 and 500 engines exhibit low particulate matter emissions. The SCR system injects urea into the exhaust stream, where it reacts with nitrous oxides to produce nitrogen and water.