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Everything you need to know about SCR technology for 2010 emissions.

What is SCR?

1SCR is an established and proven technology that reduces NOx emissions by treating the exhaust stream with a spray of Diesel Exhaust Fluid also known as DEF.

SCR stands for Selective Catalytic Reduction. This technology reduces tailpipe nitrogen oxide emissions, NOx, by treating the exhaust stream with a spray of DEF (Diesel Exhaust Fluid). DEF, along with the heat of the exhaust and a catalyst, converts NOx into nitrogen and water vapor, which are clean, harmless and present in the air we breathe every day.

Thomas Built's complete line of diesel buses will be equipped with SCR technology to meet the EPA 2010 emissions standards. Thomas Built's mission is to provide reliable, durable, safe and innovative buses to our customers. And SCR technology with its near-zero emissions was the environmental choice when meeting these new standards.

SCR technology uses the existing engine offering and Diesel Particulate Filter (DPF) plus the SCR catalyst to reduce emissions and optimize performance.


Industry Standard

SCR technology is being implemented into a wide array of vehicles. Find out which companies are using SCR to meet 2010 emissions.
SCR technology has been incorporated into many different exhaust systems in Europe since 1978. Thomas Built is a Daimler AG company, one of largest manufacturers of engines, trucks, chassis and buses, and will use SCR technology across its entire line of vehicles. Additionally, Cummins, Volvo, Paccar, Hino, Mack, Isuzu and Blue Bird 1Corporation have decided to use SCR technology to meet 2010 emissions standards. And in the consumer car industry, BlueTec is becoming the SCR technology of choice. Currently, SCR systems can be found in Mercedes-Benz, Audi, BMW, Jeep, Kia, Mini, Volkswagen and Hyundai.

SCR vs. In-cylinder EGR

There are a lot of differences between SCR and In-cylinder EGR systems. When comparing both solutions, SCR with its proven experience and economical advantage was the better choice for our consumers.

To meet 2010 emissions standards, there will be two types of technologies available. SCR is one option. The other option is In-cylinder Exhaust Gas Recirculation or In-cylinder EGR. In this process, some of the exhaust gas is cooled and recycled back through the engine. This dilutes the amount of oxygen in the intake charge, reducing the combustion temperatures and lowering the formation of NOx. When looking at both systems, Thomas Built decided that SCR was the more reliable and fuel-efficient option. The charts below outline the differences of In-cylinder EGR and SCR technology

  • Lowers need for Exhaust Gas Recirculation (EGR)

  • Permits engine to operate under optimized combustion conditions, including increased temperature, increased pressure and excess oxygen

  • Less heat rejection

  • Cleanest tailpipe emissions available

  • Proven technology across the globe

  • Mainstream 2010 technology solution

  • Better fuel efficiency

  • Better power

  • Less component stress

  • Less active regeneration needed for cleaning Diesel Particulate Filter (DPF)

  • Improved durability

  • Expected lower total cost, which includes maintenance and fuel

  • End product is nitrogen, water and carbon dioxide

In-cylinder EGR

  • Less efficient combustion process requires combustion at lower temperatures

  • Increased heat rejection causes the engine to produce more heat

  • Higher injection pressures

  • Decreased power density

  • Increased diesel particulate matter (soot)

  • Increased air flow and cooling capacity

  • Decreased fuel efficiency

  • Potential increase in active regeneration and fuel burned

  • Increased complexity in turbo and air supply system

  • Additional requirements for Diesel Particulate Filter (DPF) hardware

  • Decreased engine durability

  • Oil degradation

  • Potential increase in maintenance intervals

Why Choose SCR? — 10 Reasons

SCR technology is currently used in Europe, gets better fuel-economy and lowers the total cost of ownership. These are just some of the reasons why SCR is the better choice for meeting 2010 emissions standards. The list below highlights some of the advantages of SCR technology.

  • Best fuel efficiency

  • Proven technology in Europe

  • EPA recommended and approved

  • Higher engine power density

  • No increased heat rejection, allowing for more efficient combustion

  • Lower cost of total ownership

  • Reliable

  • Durable

  • Easy to service

  • Environmentally friendly

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