Evolution of Engine Air Induction System Hydrocarbon Traps

Engine air induction systems hydrocarbon trap (HC trap) designs to limit evaporative fuel emissions, have evolved over time. This paper discusses a range of HC traps that have evolved in engine air induction systems. (AIS) The early zeolite flow through HC trap utilized an exhaust catalyst technology internal stainless steel furnace brazed substrate coated with zeolite media. This HC trap was installed in the AIS clean air tube. This design was heavy, complicated, and expensive but met the urgency of the implementation of the new evaporative emissions regulation. The latest Ford Motor Company HC trap is a simple plastic tray containing activated carbon with breathable non-woven polyester cover. This design has been made common across multiple vehicle lines with planned production annual volume in the millions. The cost of the latest HC trap bypass design is approximately 5% of the original stainless steel zeolite flow through HC trap. There have been a variety of HC trap designs between the original zeolite flow through and the latest bypass HC trap. All have met evaporative emissions vehicle sealed housing evaporative determination (SHED) testing with a trend of HC trap simplified design and decreasing cost. HC trap media has varied from zeolite, to activated carbon pellets or granules in a container or extruded, on paper, foam, or non-woven polyester. HC traps can be packaged as a flow through or bypass design. This paper will present and discuss the various types of HC traps, packaging, uses, and evolution in engine AIS.