BG3 Elite

The BG3 Elite is a high performance next generation transient Partial Flow Dilution (PFD) system ideally suited for gravimetric sampling of engine exhaust Particulate Matter (PM).  Used widely for new engine research and development, the BG3 Elite is also used for engine certification work. BG3 was designed to replace large CVS systems with a more compact, affordable and dynamic device.

The BG3 can also be used to provide a conditioned accurately diluted sample to a Bag mini diluter for gaseous analysis.

BG3 Elite is refined for applications requiring 47mm filter media such as Part 1065, and combines smaller, more precise flow control valves and flow measurement components with an upgraded pressure transducer suite to build on its industry-leading technology base. 

BG3 Elite is the most widely used PFD systems boasting an installed base of more than 300 units globally.


Sierra’s Automatic Filter Changer (AFC) is a compact and portable automation tool designed to meet US EPA 40 CFR Part 1065 regulations.  A plug-and-play upgrade to any BG3 Elite Partial Flow Dilution system, the AFC should be a part of every emissions test cell.

As facilities become both increasingly automated and attentive to safety concerns, test cell access during engine operation is no longer a universally accepted practice. In response to industry trends, Sierra developed the AFC for up to a 24-puck canister capacity, a 10 second filter indexing time, and split access doors to ensure temperature compliance.

The AFC is now available with optional 2D filter bar code reader, supplied by Keyence. The unit reads the filter number during final indexing of the filter puck prior to sampling and transmits filter number information to BG3 Elite and is available via AK.

Exhaust Flow Meter

The Sierra ExhaustTrak, in production since 2014, is a highly capable and flexible exhaust mass flow meter with great flow turndown capability consistent with competitive systems.  It is available in a wide range of sizes and flow capacities. 

ExhaustTrak measurement accuracy, as shown during independent studies, is on par with, or better than, competitive units, while possessing significantly higher tolerance to heat, low pressure loss and high flexibility of sharing different venturi’s throughout your test facility depending upon the flow requirement of a specific test cell.

The exhaust flow meter can use a twin dP transducer set with seamless switchover between devices during measurement. This provides a wide turn down ratio.

The venturi itself utilises our Patented anti-clogging sintered ring technology, this provides high levels of continuous running as well as a natural circumferential averaging to correct for asymmetrical flow profiles.


Real time PN measurement enables increased regulatory focus on the employment of best available technology diesel particulate filter (DPF) and gasoline particulate filter (GPF) to minimize human exposure to exhaust particles.

While previous regulatory activity has focused on solid particles greater than 23nm, research activity is now focused on the viability and value of PN regulation down to 10nm.

Partnering with Southwest Research Institute (SwRI), Sierra has commercialized a UN-ECE R49 and R83 compliant Solid Particle Number System (SPNS) utilizing SwRI patented high-efficiency Catalytic Stripper Technology (1).

The system is brand named Sierra SPNS Elite™ and is the only patented (US 6,796,165) R49-compliant PN certification-grade system available.  The system is specifically engineered to enable testing with either partial or full flow systems to yield simultaneously sampled PM and PN results that are fully compliant with all current and anticipated PM and PN regulations.

The system measures particulate concentration down to 23nm with future versions to 10nm. Sierra has licensed the SPNS technology from SwRI. 

Read our Solid Particle Number System Whitepaper for more information