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National Clean Diesel Campaign (NCDC)

Working Together for Cleaner Air

Clean Diesel Technologies, Inc.
(formerly Engine Control Systems Limited)

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Retrofit Technologies

Clean Diesel Technologies, Inc's Purifilter EGR Diesel Particulate Filter (DPF)
Verification Letter Amended (PDF)  (3 pp; 100K; October 31, 2013); • Attachment A. Applicable Engine Families (PDF) (28 pp; 100K; September 26, 2013) • Verification Letter Amended (PDF)  (2 pp; 200K; April 18, 2013) • Verification Letter (PDF)  (3 pp; 100K; November 20, 2012)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%) †
PM NOx HC CO
Purifilter EGR Diesel Particulate Filter (DPF) Highway; light, medium and heavy heavy-duty engines (EGR and non-EGR) certified in model years 1993-2010 and listed in Attachment A dated September 26, 2013 15 90 n/a 90 80

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

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 40% of the time the vehicle operates. In addition, the Duty Cycle Index (DCI), as defined by CDTi, must be achieved.
  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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Clean Diesel Technologies, Inc's Purifilter OR Diesel Particulate Filter (DPF) for Non-Road Applications System
Verification Letter (PDF)  (3 pp; 200K; December 16, 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%) †
PM NOx HC CO
Purifilter OR Diesel Particulate Filter (DPF) for Non-Road Applications System Nonroad, Tier 1 or Tier 2 or Tier 3 diesel engines certified with a maximum PM level of 0.20 g/bhp-hr with power ratings 100 ≤ Horsepower ≤ 603hp 15 90 n/a 90 85

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

  1. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  2. Nonroad engines must have EPA particulate matter (PM) certification levels less than or equal to 0.20 g/bhp-hr (0.27g/kW-hr) and greater than 0.015 g/bhp-hr (0.02g/kW-hr).
  3. The engine’s exhaust must produce a NOx/PM ratio of at least 18 or more. CDTi will make an assessment of the suitability of candidate engines, based upon certification emission levels or emission test data.
  4. CDTi approved dealer shall perform an engine pre-assessment that assures the engine is at a minimum operating condition to prevent excess soot build up. The dealer will provide the owner with a copy of the pre-assessment.
  5. CDTi will install the Emissions Device Monitor with the Purifilter OR System to constantly monitor backpressure and temperature on all vehicles equipped with this DPF that notifies the operator when the backpressure limit is reached.
  6. The engine must be well maintained and not consume lubricating oil at a rate greater than that specified by the engine manufacturer.
  7. The vehicle may not be equipped with an oil burning system and lube oil or other oils may not be mixed with the fuel.
  8. The engine must not have been originally certified or equipped an original equipment DPF, DOC, or SCR system.
  9. All engines with power ratings below 100 hp or above 603 hp or 19L engine displacement are excluded.
  10. To ensure engine out opacity levels are comparable to those reported by the original engine manufacturer, written approval must be given to the installer/distributor prior to retrofit for engines with OE reported peak opacity values above 30%.
  11. Minimum duty cycle requirements of 10% above 300 C must be met.

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CDTi’s AZC Purimuffler or AZC Purifier Diesel Oxidation Catalyst (DOC)
Verification Letter (PDF)  (2 pp; 500K; October 29, 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO
AZC Purimuffler or AZC Purifier Diesel Oxidation Catalyst (DOC) Highway, heavy-duty, 4-cycle engines 1991 through 2006 engines 15 20 n/a 50 50

The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  2. The engine exhaust temperature must achieve at least 150 °C during its duty cycle.
  3. This verification includes catalyst substrates with different cell densities. AZC DOC’s converter part numbers beginning with A16D and converter mufflers beginning with A17D prefixes employ 300 or 350 cells per square inch (cpsi) substrates which may be used on 1991 to 2006 model year engines. AZC DOC’s converter part numbers beginning with A16C and converter muffler part numbers beginning with A17C employ 400 cpsi substrates which may be used only on 1994 to 2006 model year engines.
  4. The engine must be well maintained and not consume lubricating oil at a rate greater than that specified by the engine manufacturer.
  5. The vehicle may not be equipped with an oil burning system and lube oil or other oils may not be mixed with the fuel.
  6. The engine must not have been originally certified or equipped with a DOC or diesel particulate filter.

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CDTi's AZC Purimuffler or AZC Purifier Diesel Oxidation Catalyst (DOC) plus CDTi Closed Crankcase Ventilation (CCV) System
Verification Letter (PDF)  (2 pp; 500K; October 29, 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%)
PM NOx HC CO
AZC Purimuffler or AZC Purifier Diesel Oxidation Catalyst (DOC) plus CDTi Closed Crankcase Ventilation (CCV) System Highway, heavy-duty, mechanically or electronically injected, turbocharged or naturally aspirated, originally manufactured from 1991 through 2006 model years which meet a 5 or 4 g/bhp-hr NOx standard 15 25 n/a 50 50

This technology is approved for use with an open crankcase ventilation and no after treatment engines. The following criteria must be met in order for appropriately retrofitted engines to achieve the aforementioned emission reductions:

  1. Pre-installation and post installation inspections are to be performed to insure correct functioning of the installed CCV. The CCV filter indicator must be used to access blow-by rates are satisfactory. The pre and post installation inspections must be documented for each vehicle.
  2. The filtered oil from the CCV must be returned back to the engine oil sump. There is no catch bottle to be used with the CCV system.
  3. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  4. The engine exhaust temperature must achieve at least 150 °C during its duty cycle.
  5. This verification includes catalyst substrates with different cell densities. AZC DOC’s converter part numbers beginning with A16D and converter mufflers beginning with A17D prefixes employ 300 or 350 cells per square inch (cpsi) substrates which may be used on 1991 to 2006 model year engines. AZC DOC’s converter part numbers beginning with A16C and converter muffler part numbers beginning with A17C employ 400 cpsi substrates which may be used only on 1994 to 2006 model year engines
  6. The engine must be well maintained and not consume lubricating oil at a rate greater than that specified by the engine manufacturer.
  7. The vehicle may not be equipped with an oil burning system and lube oil or other oils may not be mixed with the fuel.
  8. The engine must not have been originally certified or equipped with a DOC or diesel particulate filter.
  9. The 4500 and 6000 model filter cartridges must be replaced every 750 engine hours or every other oil change or when indicated by red filter service indicator, whichever occurs first. The 3500 and 3550 model filter cartridges must be replaced every oil change or when indicated by the red service indicator, whichever occurs first.

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Clean Diesel Technologies, Inc.'s Purifilter DPF
Verification Letter (PDF)  (2 pp, 570K, November 2003)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%) †
PM NOx HC CO
Purifilter, passive regenerating diesel particulate filter
Environmental Technology Verification Logo
Highway, Heavy Heavy-Duty, Medium Heavy-Duty; Urban Bus; 4 cycle; model years 1994 - 2003; turbocharged or naturally aspirated; non-EGR engines 15 90 n/a 85 75

† - Baseline assumes an unmodified engine running on regular 2D (<500 ppm sulfur) fuel.

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

  1. The engine exhaust temperature must be at least 280° C for at least 25% of the applicable duty cycle. (As there may be significant variations from application to application, CDTi will review actual vehicle operating conditions and perform temperature data-logging prior to retrofitting a vehicle with their PM filter system to ensure compatibility.)
  2. The engine should be well maintained and not consume lubricating oil at a rate greater than that specified by the engine manufacturer.
  3. CDTi installs a back-pressure monitor and malfunction indicator light on all vehicles equipped with a Purifilter.
  4. The engine must be operated with a fuel that contains a sulfur content of no more than 15 ppm to achieve the reductions listed above.

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Clean Diesel Technologies, Inc.'s Purifilter Plus DPF for non-EGR Engines
Verification Letter (PDF)  (2 pp; 810K; March 25, 2009)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%) †
PM NOx HC CO
Purifilter Plus (Diesel particulate filter on the engine, electrical panel for active regeneration at the garage/maintenance yard) Highway; heavy, medium, and light heavy-duty; Urban Bus; 4 cycle; model years 1994 - 2006; turbocharged or naturally aspirated; non-EGR engines 15 90 n/a 85 75

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

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 is required to ensure Purifilter Plus compatibility. CDTi will provide a recommended schedule for active regeneration of the device.
  2. In most applications, the Purifilter Plus must be periodically actively regenerated with the off-board regeneration control panel. The frequency of active regeneration will vary based on vehicle use or other conditions.
  3. The engine should be well maintained and not consume lubricating oil at a rate greater than that specified by the engine manufacturer. Lubricating oil may not be mixed with engine fuel with this technology.
  4. CDTi installs the Back-Pressure Monitor and Logger unit and the Remote Driver Display on all vehicles equipped with a Purifilter Plus.
  5. The engine must be operated with a fuel that contains a sulfur content of no more than 15 parts per million (ppm).

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Clean Diesel Technologies, Inc.'s Purifilter Plus M DPF - 1994-2010 applicable EGR and non-EGR Engines
Verification Letter Amended (PDF)  (1 pg; 200K; May 20, 2013) • Verification Letter (PDF)  (2 pp; 600K; May 17, 2012)   Table A. Applicable Engine Families - Amended (PDF) (24 pp; 100K; May 20, 2013)
Technology Engine
Model/Application
Retrofit Fuel, Max Sulfur (ppm) Reductions (%) †
PM NOx HC CO
Purifilter Plus M (diesel particulate filter on the engine, electrical panel for active regeneration at the garage/maintenance yard) Highway; light, medium, and heavy heavy-duty EGR and non-EGR engines, not originally certified or equipped with DPF, originally manufactured from 1994-2010 and listed in Table A 15 90 n/a 30 75

† - Baseline assumes an unmodified engine running on fuel with 15 ppm sulfur or less.

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 is required to ensure Purifilter Plus M compatibility. The installer must provide the fleet owner and/or operators with a copy of the pre- and post-installation checklists, as well as copies of the data logging results and recommended regeneration schedules. Fleet owners/operators are responsible for adhering to the recommended regeneration schedule. At a minimum, CDTi recommends that all fleets proactively regenerate the Purifilter Plus M every four to six weeks.
  2. The engine must be operated on ultra-low sulfur diesel fuel (ULSD) of 15 ppm or less.
  3. 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.
  4. The vehicle may not be equipped with an oil burning system and lube oil or other oils may not be mixed with the fuel.
  5. CDTi installs the Back-Pressure Monitor and Logger unit and the Remote Driver Display on all vehicles equipped with a Purifilter Plus M.

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