Research Projects

Project at a Glance

Project Status: complete

Title: Assessment of emission control technology and cost for engines used in handheld equipment.

Principal Investigator / Author(s): Chan, Lit-mian

Contractor: Engine, Fuel, and Emissions Engineering, Inc.

Contract Number: 93-324

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels, Stationary Sources


The California Air Resources Board (ARB) has established two tiers of emission standards for handheld utility engines. The Tier I standards took effect in 1995, and have been met with only simple engine and carburetor modifications. The more stringent Tier II emission standards will take effect in 1999, and are considered technology-forcing. Controversy has arisen over their technological feasibility, costs, and cost-effectiveness of the Tier II standards. To help resolve this controversy, Engine, Fuel and Emissions Engineering, Inc. (EF&EE) was contracted by the Air Resources Board to examine two-stroke engine control technologies, the associated costs to manufacturers and consumers, and the cost-effectiveness of the resulting emission reductions. Building on earlier studies of two-stroke engines in motorcycles, EF&EE reviewed the technical literature on emissions and control technology for two-stroke engines and identified four potential technological approaches to meeting the Tier II standards, of which three are considered to have very high probability of success. These approaches are:

* Direct In-Cylinder Fuel Injection Combined With a Catalytic Converter,
* Port or Crankcase Fuel Injection Combined With a Catalytic Converter, and
* Conversion to Four-Stroke, Overhead-Valve Technology With or Possibly Without a Catalytic Converter.

Less certain of success, but potentially much lower in manufacturing costs, is the fourth option, the use of stratified scavenging in conjunction with a catalytic converter. The use of a catalytic converter alone would not be feasible, since pollutant concentrations in present Tier I engines are high enough to overheat and destroy a catalytic converter. It is therefore necessary to reduce these concentrations substantially by other means before the catalytic converter can be durable and effective.

EF&EE estimated the increase in the retail price equivalent (RPE) of a typical item of handheld equipment using each of these approaches. The estimated RPE increase due to implementing these technologies ranges from $39 to $66 per unit. This increase would be offset by fuel cost savings of at least 30 percent (representing that portion of the fuel that is presently wasted out the exhaust in the form of HC emissions). For commercial handheld equipment, the fuel saving would be about $151 and for residential equipment about $6. EF&EE also calculated the cost-effectiveness of the Tier II standards, compared to continuing the present Tier I standards. For commercial equipment, the costs were negative, due to the fuel cost saving. Thus the Tier II regulations represent a "win-win" solution for commercial equipment. For residential equipment, if all lifecycle costs were allocated to the HC reduction, the costs per ton of HC eliminated would be between $4,129 and $7,531 per ton, depending on which technology is employed. This is within the range of cost-effectiveness for other WC control measures that have been adopted by ARB.


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

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