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New Alternative for US EPA Part 1065

US EPA Rules Partial Flow Dilution Alternative to CVS

Monterey, CA — April 12, 2011 — The US EPA has ruled that Partial Flow Dilution (PFD) technology, as demonstrated in conclusive testing with Sierra Instrument’s BG®3, is now legally recognized as an alternative to traditional Constant Volume Sampling (CVS). The new ruling in favor of light and heavy duty engine particulate emissions certification over transient test cycles can be found in 40 CFR part 1065 of the United States Federal Register.

A 5-year cooperative effort between Sierra and the US EPA resulted in a BG3 vs CVS multiple engine, two-lab correlation study  (this required the measurement of PM over a two-decade range in concentration levels). The study was performed to prove that Sierra’s BG3 complies as a suitable, fully compliant alternative method to CVS for certification of engines tested on 2007 and Tier IV transient test cycles.

“It’s been a long time coming, but we’ve made history,” says Matthew J. Olin, President of Sierra Instruments. “We’re delighted to be able to provide an alternative to expensive and cumbersome full-flow CVS systems and open the door to cost-effective light and heavy duty engine particulate emissions testing.” BG3 technology is the recognized PFD standard in the industry. BG3 is the most widely used PFD technology of its type and boasts the world’s largest installed base.” 

 Efficiency and productivity benefits of BG3 include:

  • Can be used on engines of any size and on any fuel in both engine and chassis test cells 
  • Approximately 1/10th of CVS system cost of ownership
  • Approximately 1/100th to 1/1000th the annual energy usage versus a CVS, depending on CVS size and design
  • Satisfies all requirements of 40 CFR 1065; ISO 8178; ISO 16183; CFR Part 89; UN ECE regulation No. 49; Global Technical Regulation No. 4
  • Add and control other emissions measurement devices easily such as particle counters, soot mass measurement…etc.
  • Portable from cell to cell to maximize flexibility and return on investment
  • Patented partial flow dilution tunnel has ultra-low particulate loss and requires no cleaning with proper operation
  • Integrity of internal flow systems and proprietary daily mirror calibration method yields excellent accuracy and repeatability of PM results over wide range of dilution ratios
  • Ability to accurately measure PM either pre and post catalyst and/or DPF for research or DF testing 


Sierra Instruments has been a global leader in flow measurement and control for over 35 years and is well known for its high performance flow instrumentation for gas, liquid and steam applications commonly found in the semiconductor, environmental, scientific research, petrochemical, energy, aerospace, and general manufacturing industries. Founded in 1992, Sierra’s Engine Emissions Measurement Division manufactures high performance particulate matter sampling systems (Model BG3), engine intake air mass flow meters, soot measurement instrumentation and a wide range of engine emissions sampling accessories used in the engine and vehicle emissions testing industry.  With over 150 offices in 50 countries, Sierra is uniquely positioned to provide their innovative products and lifetime support for the leading companies of today and growth enterprises of tomorrow.


  • In 1990, Sierra received the exclusive worldwide license for Caterpillar’s patented micro-dilution technology, today known as Partial Flow Dilution (PFD) technology.
  • Sierra's knowledge of mass flow measurement and control, a key to partial flow dilution sampling, and Caterpillar’s vast engine development and emissions testing knowledge formed a formidable technology partnership.  
  • For well over a decade, this technology partnership has yielded a line of world-class partial flow sampling systems: The BG®1, BG®2, and now the very versatile BG®3 provides accurate, repeatable Engine Particulate Matter (PM) emissions measurements for transient and steady-state test cycles for engine and vehicle testing.    


Press Contact:
Maryadine Washington, Marketing Manager
831-373-4402 (fax)