Prime-Path System with Four-Way...
Prime-Path System with Four-Way Catalyst System
Emissions
The battle against nitrogen oxides and particle emissions is the biggest hurdle for diesel engine builders who must deal with the stringent '07 federal guidelines that allow no more than 0.07 grams of nitrogen oxides per mile and 0.01 gram/mile of particulate matter-aka, soot. In addition to the requirement of ultra-low sulphur diesel, a closed crankcase filled with low-ash oil, and the fueling tricks mentioned earlier, the engines will use a particle trap, catalytic converter, and EGR system.
The variable geometry turbo...
The variable geometry turbo is mounted in the center of the V. Air enters the green section, gets compressed in the turbo, goes through the intercooler, and joins with the EGR gases before flowing into the intake.
EGR (Exhaust Gas Recirculation)
The V-engines have cast pathways that cool and route exhaust fumes that are fed to the intake. The gases are used to cool the combustion process and reduce nitrogen oxides by introducing carbon monoxide and water vapor (and everything else in exhaust) back into the cylinders. Gases not recycled are sent to the turbo located in the valley of the engine V.
Variable Geometry Turbo
The turbo is a Cummins-built unit that uses an exhaust turbine that slides along an axis to vary the volume inside that half of the compressor. This technology maximizes spool-up at low rpm then opens the chamber when large amounts of exhaust are pumping out of the engine. The downpipe after the turbo includes a built-in catalytic converter that is the start of the post-engine emissions controls.
Catalytic Converter and DPF (Diesel Particulate Filter)
That catalytic converter is a passive oxidation catalyst that's packaged close to the engine to provide a quick warm-up time and allow the engines to be easily packaged in SUVs and 1/2-ton pickups. The downpipe after the catalytic converter leads to a DPF with a ceramic honeycomb four-way catalyst that captures soot until it's rendered EPA-friendly. Sensors placed before and after the DPF measure flow and alert the engine when blockages are creating significant backpressure. When this is detected, the engine electronics will calibrate injections to raise the exhaust gas temperatures (sometimes injecting fuel during the exhaust stroke), which will burn off and catalyze particles inside the insulated chamber. Cost is a big concern with DPFs, but all light-duty diesels will have them after January 1, 2007, and the DOE/Cummins tests proved the units will last for at least 150,000 miles and still be effective.