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Caterpillar Receives First 2007 Certification for ACERT Engine

22 November 2006

Catc7acert
C7 engine with ACERT. Click to enlarge.

Caterpillar has received certification from the US Environmental Protection Agency (EPA) for the company’s first engine equipped with ACERT Technology for 2007.

The first 2007 EPA-certified Caterpillar engine with ACERT Technology is the C7, a popular choice with customers who operate medium-duty vocational and delivery trucks. It will be in full production by January 1, 2007. The C7 is also widely used in a variety of other medium duty applications, including school buses, emergency vehicles and recreational vehicles.

ACERT Technology relies on four basic systems to lower emissions:

  • Air management;
  • Precision combustion;
  • Advanced electronics; and
  • After-treatment

These four systems work to decrease particulate matter, oxides of nitrogen and hydrocarbon emissions while preserving the engine’s reliability and durability, which keep owning and operating costs low.

The Caterpillar C7 engine features an enhanced version of ACERT Technology that allows it to comply with the 2007 EPA regulations without sacrificing reliability, durability or fuel economy.

The 2007 ACERT C7s feature power ratings from 190 hp to 300 hp (142 kW to 224 kW) @ 2,200 rpm for truck and bus applications, and 300 hp to 350 hp (224 kW to 261 kW) @ 2,400 rpm for RV and fire truck applications. Torque ranges from 520 lb-ft to 860 lb-ft (705 Nm to 1,166 Nm) @ 1440 rpm.

Catc7acert2
2007 Aftertreatment.

The 2007 C7 is a 7.2-liter, in-line 6 engine that features a variable nozzle turbo and a common rail fuel system that helps optimize performance and increase fuel economy by up to 4%. The 2007 aftertreatment system uses cooled exhaust gas recirculation (CEGR) and Clean Gas Induction (CGI). (See diagram at right.) The diesel particulate filter (DPF) is self-regenerating.

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Cat ACERT technology appeared quite loudly in 2003 as an answer to tight (roughly equal with current EU regulation) emission standards imposed to heavy-duty on-road engines by EPA beginning in 2004. In fact, ACERT is combination of quite conventional technologies, such as common rail computer-controlled fuel injection, variable geometry turbochargers in different configuration, wide use of engine parameter’s sensors and computer diagnostic, etc. The outstanding fact was that sophisticated synergy of these technologies allowed Cat to meet emission regulation without use of EGR. In that Cat was the only heavy-duty engine manufacturer who managed to achieve the goal without trouble-some for turbocharged diesel engines external EGR. Now, for 2007 emission standards, it was a breeze for Cat to meet 2007 requirements by incorporating of EGR or clean gas induction (the simplest form of modern EGR), and DPF.

Cat is clearly the world leader in diesel engine technology for heavy-duty on-road engines, which is quite conclusively proved by its sales volume and stock market performance.

The big question remains: would Cat be able to meet final, extremely tough NOx emission standards of 2009 without SCR or NOx absorber?

Andrey -

Caterpillar is a leader in on-road diesel technology in the US. I'm not sure if you're correct in asserting this for the world as a whole. MAN and Scania are each pretty big as well, perhaps bigger once the proposed merger goes ahead.

Cooled EGR is indeed troublesome but actually standard on European on-road diesels by now. Traditionally, external EGR systems are part of the high pressure gas flow on the engine side of the turbocharger. That means the EGR cooler is exposed to engine-out emissions. Switching to CGI eliminates this problem, but the lower temps mean you pretty much have to switch to a more expensive gas-to-liquid EGR cooling system.

Another issue is that most HDV engines use single-stage turbos with boost ratios as high as 4-4.5. Increasing the temperature of the turbo's intake exposes the aluminium compressor wheel to increased thermal load at the rim. A related issue is the need for very high turbine efficiencies to achieve the necessary boost when using CGI. Dual-stage chargers with intercoolers are common on large marine diesels but not yet in the automotive sector.

Wrt NOx: reducing engine-out PM, as required to avoid excessively expensive aftertreatment systems, means you have to achieve more complete combustion. That's good for fuel economy but bad for peak process temps, which generate NOx. The state of the art permits reducing either NOx (via EGR) or PM (via efficient combustion) but reducing both simultaneously requires flameless (cp. HCCI) combustion. This technology is advancing rapidly in R&D but remains limited to part load due to high pressures and combustion noise. HDV engines spend much of their time at high load, though, so I expect Caterpillar will also choose SCR systems.

is there any training or online certification for operators ?

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