Diesel Particulate Filter: Get to Know What’s Under Your Truck

All diesels from late-2007 are required to have an emissions device on them called a Diesel Particulate Filter. These filters dramatically reduce soot (particulate matter) emissions and have played a huge role in protecting diesel passenger vehicles from increasingly stringent emissions standards. Ford, GM and Dodge all equipped their trucks with these devices and in 2011 Ford and GM also equipped theirs with SCR (Selective Catalyst Reduction) as well as Dodge on their Cab and Chassis trucks, reducing emissions further and increasing horsepower by allowing the truck to be more aggressively fueled from the factory while still meeting emissions standards.

The DPF is similar in design to a catalytic converter and is placed after the catalytic converter in the vehicle’s exhaust. Its sole purpose is to block soot and reduce the emissions that make it out of the tailpipe. When the DPF filter becomes clogged, it needs to be heated to clean itself out. To accomplish this, the engine injects fuel in on the exhaust stroke so that it heats up and travels to the particulate filter, burning up any matter that is clogging the filter and allowing the truck to run correctly. The downside to this is that it takes a reasonably large quantity of fuel to clean out the DPF, or “Regenerate.”

The DPF works in conjunction with the EGR (exhaust gas recirculation) system which routes exhaust gas back into the engine to be burned again, which cleans up emissions by further breaking down the chemicals in the exhaust. The downside to the EGR setup is that it can reduce engine output because of the hot air being sent back into the engine and it dirties the inside of the engine over time. On the 6.0L Ford trucks, the EGR system was the cause of much more serious engine problems involving heightened cylinder pressures and blown head gaskets.

SCR, which is the injection of diesel exhaust fluid (DEF) into the exhaust to reduce NOx emissions, is another process that manufacturers are using to cut down on the emissions of these trucks as well as restoring lost horsepower. SCR allows the engine to fuel more aggressively while still meeting emissions standards because the urea in the DEF chemically alters the exhaust gas before it reaches the catalytic converter and the DPF, reducing the risk of damage to the DPF from over-fueling and cutting down on the frequency of the regen cycle. SCR’s biggest limitation is the requirement of fluid additions between oil changes; the fluid is not inexpensive and is not widely available yet.

That is a basic synopsis of how these devices function, but the most important thing to know is exactly how these affect your truck and the way it runs. For starters, a truck equipped with a DPF from the factory is likely going to return lower fuel economy than an older diesel that is not equipped with a particulate filter. The reason for this is simply that the regeneration process uses (potentially) gallons of fuel and that fuel is not being used to make horsepower or accomplish any work. Trucks that haul loads or are driven around town frequently will have to regen less often because the filter is more efficient under higher loads. Conversely, trucks that spend lengthy periods of time at idle or on the highway without a load will have to regen more frequently and in turn see reduce fuel economy.

Removing the particulate filter is a violation of Federal emissions regulations and is designed specifically for race and off-road use only. XDP carries all of the DPF, EGR, and catalytic converter delete setups for Dodge, Ford and GM as well as the required tuning for these vehicles.Trucks with a DPF equipped will benefit from the use of a quality fuel additive like XDP Diesel Power Plus (http://www.xtremediesel.com/xdpdieselpowerplusfueladditive.aspx). This additive boosts the cetane rating of the fuel by 5% and cleans out the fuel system so the engine produces lower emissions, which in turn means the DPF does not clog up as quickly or as frequently. These trucks are also more sensitive to maintenance, so making sure that the truck has fresh fluid and quality fuel in it will help improve the performance of the vehicle. Finally, doing a cold air intake, programmer and filter-back exhaust setup will help improve fuel economy and performance as well as lowering exhaust gas temperatures.

Particulate filter technology is evolving quickly and is going to be equipped on every diesel passenger vehicle designed and built in the foreseeable future. As the technology improves, horsepower and fuel economy will improve along with it. For now, the tips we outlined above will help you to improve the performance of your truck while abiding by federal emissions regulations, and for those looking for big horsepower race trucks, we have the delete pipes you need for those as well!

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