Research Projects

Project at a Glance

Project Status: complete

Title: Clean air two-stroke (CATS) for utility engine applications. Final report

Principal Investigator / Author(s): Johnson, William P

Contractor: BKM

Contract Number: 94-351

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels, Stationary Sources


BKM has developed and demonstrated a unique electronic fuel injection system known as the Single Plunger System (SPS). The SPS is currently being applied to a low cost, single cylinder two-stroke engine that is applicable to mopeds, small outboard marine and utility engines.

The unburned hydrocarbons found in the exhaust of conventional two-stroke engines are due to the basic design and operating principles of the engine. These engines produce from 10 to 15 times the levels of unburned hydrocarbons compared to four-cycle engines. In the conventional carbureted two-stroke engine, the fuel / air mixture is pumped into the cylinder during a portion of the cycle in which both the intake and exhaust ports are open. This is known as the scavenging cycle, or removal of combustion byproducts from the previous engine cycle.

The SPS direct fuel injection system has demonstrated that it is capable of reducing unburned hydrocarbons emissions by approximately 80 percent by eliminating the scavenge loss of fuel, therefore meeting the 1999 CARB emissions standards for utility engines.

BKM formed a consortium of industry and governmental agencies to provide funding for the program by offering non-exclusive license agreements to the industry members. Current members include:

BKM, Inc


Honglin Machine Factory (PRC)

Yamaha Motor Corp. USA

Suzuki Motor Corporation

Tohatsu Corporation

Tanaka Kogyo Co. Ltd.

Taiwan Motorcycle Company
(Who wishes to remain anonymous.)


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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