6 October 2006
The California Air Resources Board (ARB) has verified the Donaldson DPM Low Temperature Filter (LTF), with and without the Spiracle Closed Crankcase Filtration System, for use with most 1994 through 2006 model year on-road diesel engines used in on-road applications.
The DPM LTF uses a flow-through filter (FTF) followed by a diesel particulate filter to achieve an 85% reduction in particulate matter emissions, qualifying it for a Level 3 verification. The Spiracle system filters engine crankcase emissions and directs the crankcase gases back to the engine intake.
The installation of the FTF—which reduces some of the PM emissions—upsteam of the wall-flow filter allows to lower the regeneration temperature of the system. According to the conditions of the verification, the LTF system can be installed on engines which achieve exhaust temperatures above 200°C for 40% of their operating time.
It is believed that both the FTF and the wall-flow filter are catalyzed, but no details on the catalyst system have been released. The verification order also states that verifications of systems that increase emissions of nitrogen dioxide (NO2) by more than 30% of the baseline NOx will be revoked as of January 1, 2007; and verifications of systems that increase NO2 by more than 20% will be revoked as of January 1, 2009.