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Verified Technologies for SmartWay and Clean Diesel

Clean Diesel Technologies, Inc. – Purifilter EGR Diesel Particulate Filter (DPF)

This retrofit technology is included on EPA's Verified Technologies List for Clean Diesel.

On this page:

Technology specifications

Engine Model/Application

Highway, light, medium, and heavy heavy-duty engines (EGR and non-EGR); certified in model years 1993-2010, listed in Table A

Retrofit Fuel, Max Sulfur 15 parts per million (ppm)
Reduction in particulate matter (PM)1 90%
Reduction in nitrogen oxide (NOx)1 n/a
Reduction in hydrocarbons (HC)1 90%
Reduction in carbon monoxide (CO)1 80%

1 Baseline assumes an unmodified engine running on fuel with less than 15 ppm sulfur. 

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Criteria to achieve emission reductions

The following operating criteria must be met in order for appropriately retrofitted engines to achieve the above emissions reductions:

  1. As there may be variations from application to application, data logging and a review of actual vehicle operating conditions are required to ensure Purifilter EGR compatibility. The installer must provide the fleet owners and/or operators with a copy of the pre- and post-installation checklists, as well as copies of the data logging results. Fleet owners/operators shall be responsible for adhering to the recommended maintenance schedule.
  2. The engine exhaust temperature must be at least 240°C for at least 30% of the time the vehicle operates, or alternatively, 10% of vehicle duty cycle exhaust temperature must be greater than 300°C for the time the vehicle operates.
  3. The engine NOx-to-PM ratio must be greater than or equal to 18.
  4. The engine must not have engine out opacity greater than 20% as measured by the SAE J1667 Recommended Practice.
  5. The engine must not have been certified with an original equipment manufacturer (OEM) DPF.
  6. The engine must be operated on ultra-low sulfur diesel (ULSD) fuel containing at maximum 15 ppm sulfur.
  7. The engine must be operated with low-ash lubricating oil.
  8. Fuel additives may not be mixed with fuel unless explicitly approved by EPA for use with this device.
  9. The engine must be in proper operating condition, well maintained, and not consume lubricating oil at a rate greater than that specified by the engine manufacturer. 
  10. The vehicle may not be equipped with an oil burning system, and lube oil or other oils may not be mixed with the fuel.
  11. CDTi installs a back-pressure monitor and logger unit and the remote driver display is visible to drivers while seated in the driver’s seat.

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Verification Letters from EPA

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