How the SCR system works

The Volvo SCR system is simple and effective, with few components.  It consists of a DEF tank positioned near the standard diesel tank, plus a DEF tank pump, an injector unit and an SCR catalytic converter.

The advantage of using DEF is that it enables the engine to use less EGR -- and higher oxygen levels -- for better combustion, while easily meeting the EPA's near-zero NOx emissions requirement of 0.2 g/hp-hr NOx.  By using DEF, we avoid the disadvantages of increasing EGR to massive levels.

This results in better fuel efficiency from your Volvo engine.  With rising crude oil prices, achieving maximum fuel efficiency has become the single most important attribute of modern truck engine design. 

  1. Diesel engine optimized for high performance, low particle emissions and low fuel consumption.
  2. DEF tank.
  3. The DEF tank and injection system's control units continuously vary the amount of DEF injected in response to the engine's current load conditions.
  1. DEF is injected into the exhaust gases in between the DPF (5) and the Catalytic Converter (6).
  2. Diesel Particulate Filter.
  3. In the Catalytic Converter, nitrogen oxides are transformed into harmless nitrogen gas and water.
  4. The system notifies the driver when it is time to top up with DEF.

Volvo Trucks North America offers a thorough look at the 2010 EPA emissions for heavy-duty truck engines and a detailed description of the Volvo solution: Selective Catalytic Reduction (SCR).  Heavy-duty salesmen and customers alike will benefit from this podcast, designed to answer questions and educate listeners on SCR, the technology that brings emissions to a near-zero level while maintaining the performance and fuel economy the industry has come to expect from a Volvo engine.