DPF Filters on Heavy Duty Trucks.

For more then over a year now, highway trucks have been coming out with the environmental friendly particulate filter engines. This complicated system has given diesel engines a virtually smoke free exhaust. Take for example the C-15 Acert from CAT. This is an inline 6 cylinder engine with a displacement of 15.2 liters. Horsepower range is from 435 to 625 HP. These engine have a tremendous torque rating of 1850 to 2050 ft/lbs. This engine by itself weighs around 1400 kilos.

The aftertreatment diesel particulate filter removes soot particles from the exhaust by passing the exhaust gases through a ceramic filter. The soot is oxidized in the filter to form invisible carbon dioxide, giving clean exhaust at the tailpipe. Ash is a by product of oil consumed during normal engine operation. Ash collects in the aftertreatment particulate filter and requires periodic cleaning. This system is designed to decrease the exhaust particulate emissions from the vehicle stack.

When you look at a truck without a DPF the exhaust stacks at the top of the pipe will be completely black from exhaust soot. Look at a truck's exhaust stacks equiped with a DPF engine and you will notice they are clean metal color. Now to get this amazing result a lot of extra's have been added to the engine. One look at the right hand side of a Cat C-15 and you think you are in Frankenstein's lab. It is hard to see the engine thru all the gadgets. Also an ultra low sulphur diesel has to be used in these engines. The filter reduces carbon monoxide, hydrocarbon and particulate matter by 85%.

This is the "frankenstein cap" I call it. Its kind of like a distributor cap and has an injector to inject small amounts of fuel to raise exaust gas temperatures for effecient regeneration. The system injects fuel behind the turbocharger and electrically ignites it, sending flame into the DPF; this burns out accumulated soot.

Heat inside DPFs and at tailpipes will get quite high - 1,000 to 1,200 F. But aftertreatment devices will be dual-walled to insulate their outer skins from heat. Their "touch temperatures" will remain about like they are now, or around 500 F. That's hot enough to smart if someone touches it, but not enough to burn flesh unless he hangs on. Also, aftertreatment devices will be mounted like mufflers, under the truck or on the exhaust stack, where people aren't likely to come in contact with it.

Cat's '07 aftertreatment will have a DPF, but not an oxygen catalyst. The system injects fuel behind the turbocharger and electrically ignites it, sending flame into the DPF; this burns out accumulated soot. As now, Cat will initially clean exhaust gasses with ACERT equipment, including double turbo chargers on larger models. Cat and other builders will also upgrade fuel-delivery systems and electronic controls; the latter will get more powerful microprocessors and more capable software. All builders' aftertreatment devices will resemble mufflers and actually muffle combustion noise, so mufflers as such will no longer be used.