20 August 2010
Volvo Construction Equipment has received Tier 4 interim emission certification from the US Environmental Protection Agency (EPA) for its D11, 11 liter engine. Implementation of Tier 4i emission standards begins January 1, 2011 for engines in the 175-750 hp range. The Tier 4i standards—NOx = 2.0 g/kWh and PM = 0.02 g/kWh—represent a 50% and a 90% percent reduction from the respective Tier 3 limits.
The new D11 Tier 4i engine with V-ACT, “Volvo-Advanced Combustion Technology”, features high pressure variable fuel injection system, cooled exhaust gas recirculation (EGR), variable geometry turbocharger (VGT), a new engine management system, and an integrated exhaust aftertreatment system, equipped with a particulate filter and “thermal regenerator”.
The cooled EGR system in the new D11 engine reduces NOx by at least 50%. Ultra-low sulfur fuel required by Tier 4i regulations—15 ppm S effective June 1, 2010—permits the safe and efficient use of a new cooled EGR system, designed to allow more exhaust recirculation than previous generations of engines, said Volvo.
Reduction of PM emissions is the major target of the EPA Tier 4i regulations. The new Volvo system uses a diesel particulate filter (DPF) with active regeneration to reduce PM emissions by 90%. While no details were provided on the regeneration system, Volvo said the Tier 4i emission technology has been developed based on the experience with 2007 Volvo highway truck engines. This suggests that the DPF is regenerated via exhaust injection and catalytic oxidation of diesel fuel.
The engine management system (EMS) utilizes a new processor capable of supporting more functions than in earlier engines, at higher speeds and with more control. The electronic control unit (ECU) controls the entire EGR process, crucial to the reduction of NOx and PM emissions “while maintaining performance and fuel economy”. However, Volvo did not comment on the fuel economy of the new D11 relative to Tier 3 engines.