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Motorhoming | Family Motor Coach Association

As new diesel emissions technology develops, motorhome owners have new things to learn. For drivers of new diesel-powered Type A motorhomes, a new set of warning lights for particulate buildup is especially important to monitor. Otherwise, engine damage could result.

Workhorse Custom Chassis has noticed instances of driver failure in this regard. According to the Workhorse technical team, drivers should read the owners manual so they understand what their gauges and warning lights mean.

The Diesel Particulate Filter

All diesel engines produced after Jan. 1, 2007, must comply with the new regulations requiring the reduction of nitrogen oxide (NOx) and hydrocarbons (HC) by 50 percent and particulate matter (PM) by 90+ percent over the previous 2004 emission standards.

To reduce particulate matter, a Diesel Particulate Filter (DPF) is used on all Class A diesel motorhomes. The DPF captures soot and larger sulfate particles in a series of ceramic honeycomb channels as gas passes through the porous material. The particulates are trapped and accumulate on the channel walls. After thousands of miles, the DPF will eventually become clogged if nothing is done.

To prevent the DPF from clogging, the trapped particulates are burned off, and the filter is cleaned using a high-temperature (around 1,700 degrees Fahrenheit in the Particulate Filter) regeneration process that leaves a harmless ash and residue. There are different regeneration processes for different diesel platforms, including automatic regeneration, manual regeneration and DPF removal for an exchange or off-vehicle regeneration.

Regeneration and warning indicators

Workhorse’s new W16D, W20D and W22D chassis with MaxxForce™ diesel engines are examples of how both manual and automatic regeneration are used. The driver must monitor a series of instrument cluster system lamps that indicate various levels of low to full soot load with the DPF as determined by engine exhaust back pressure.

For motorhome owners who drive their coaches mostly at highway speeds, automatic regeneration will kick in. However, if much low-speed driving occurs, manual regeneration may be needed.

For this typical system, there are four levels of warning indicators that signal potential hazards and the action needed:

First Level — Low soot load buildup: requires the driver to get up to highway speed to engage the automatic regeneration or to safely pull over and engage in manual Parked Regeneration.

Second Level — Exhaust filter is full: requires the driver to safely pull over and begin Parked Regeneration to prevent loss of power.

Third Level — Exhaust filter is full and engine performance is limited: driver needs to safely pull over and begin manual regeneration to prevent engine shutdown.

Fourth Level — Soot overload: a serious engine problem has occurred and the engine may shut down soon. Safely pull off the road, turn on flashers, place warning devices and stop engine. DO NOT USE Parked Regeneration, but call for service.

Manual Parked Regeneration is a simple process of hitting a switch that increases the engine speed to a set RPM that achieves the temperature needed to burn off the soot. Of course, this will make the exhaust very hot, so the driver should park away from people or combustible materials and vapors. Manual generation takes about 30 minutes.

To thoroughly clean the DPF system, the motorhome should also be run at highway speeds for 20 minutes after a manual regeneration.

Soot buildup occurs over thousands of miles, so the typical motorhome owner might not experience regeneration frequently. If the warning lights do go on, however, it’s important that drivers know what to do to prevent serious engine damage.

Operating Conditions for EPA Emissions for Diesel Engine Equipped Vehicles (PDF)
Includes steps for performing a parked regeneration procedure.

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