Envirofit - Media - Publication Archive :: BAQ 2003 Development of Direct Injection Retrofit Kit

DEVELOPMENT OF DIRECT INJECTION RETROFIT KIT FOR REDUCING EMISSIONS FROM 2-STROKE CYCLE ENGINES IN ASIA

By Dr. Bryan Willson - Professor and Research Director
Nathan Lorenz, Tim Bauer - Research Assistants
Engines & Energy Conversion Laboratory
Department of Mechanical Engineering, Colorado State University
2002

ABSTRACT
There are over 50 million 2-stroke cycle engines in Asia, powering motorbikes, mopeds, "three-wheelers", "tuk-tuks", and "tricycles". There are over 100,000 2-stroke "tricycles" in Metro Manila used in taxi service, and over 1.7 million in the Philippines. The tricycles’ 2-stro ke engines are characterized by high levels of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM) emissions. A project has been initiated in Metro Manila to demonstrate the potential of "direct in-cylinder fuel injection" (DI) to reduce these emissions. Based on other retrofit applications of the technology, expectations are for a 70%-90% reduction of HC, 50%-70% reduction in CO, 80% reduction in PM, 50% reduction in oil consumption, and 35% reduction in fuel consumption. Phase I of the project involved demonstration of a single tricycle with "retrofit DI". The initial demonstration was performed in Manila in November of 2003. A complete emissions characterization of the vehicle will begin in January 2004. Phase II (2004) is a 10-15 vehicle field test in Metro Manila to document in-use emissions reductions and fuel savings. Phase III (2005) involves the establishment of the infrastructure for widespread dissemination and initiation of a large retrofit program. The final installed cost of the unit has been targeted between $10,000 - $12500 Philippine Pesos ($200-$250USD). An important part of the project involves capacity building; Colorado State University is the technical lead, but is working with NGOs, universities, development agencies, and driver organizations in Metro Manila to develop the necessary skills, technical capabilities and organizational infrastructure. If successful, expansion of the project throughout the Philippines and to other Asian countries will likely occur.

INTRODUCTION
Air pollution is on the increase in many Asian cities due in part to the widespread use of carbureted two-stroke cycle engines. These engines are typically used as the power source for "two-wheelers" (i.e. motorcycles, mopeds, etc.) and "three-wheelers" such as tricycles and tuktuks. The main reasons for this are the rugged construction, low cost and high power-to-weight ratio of the two stroke engine. Unfortunately, two-stroke cycle engines are also characterized by high levels of unburned hydrocarbons, carbon monoxide, and particulate emissions. The high hydrocarbon emissions result from the scavenging process used by two stroke engines. Scavenging refers to the process by which the burned exhaust gasse s are flushed from the engine. In a conventional "carbureted" two-stroke engine the fuel is entrained in the intake air stream before the combustion air enters the crankcase. The charge is compressed in the crankcase by the underside of the piston, and enters the cylinder when the piston uncovers the transfer ports. Combustion products from the previous cycle are forced or "scavenged" from the cylinder with this new air/fuel charge. Unfortunately, the exhaust ports are also open at this time, allowing 30%-40% of the fuel to be lost directly into the exhaust stream.1 At idle conditions the losses can be as high as 70%. The high carbon monoxide emissions result from the unstable combustion inherent to carbureted two stroke engines. This instability requires that the engine be operated with rich air/fuel ratios to maintain acceptable combustion stability. This leads to incomplete combustion and high carbon monoxide levels. Finally, the high particulate emissions result from the unstable combustion, excessive lubrication (typical in small two stroke engines), and a lubrication system which allows lubricating oil to be dissolved in the fuel. In a typical 2- stro ke, the oil mixes with the fuel at the carburetor. As the air/fuel/oil mixture transfers into the crankcase, the fuel dissolves the oil. This action reduces the amount of oil deposited on the cylinder wall (or other critical components) as it is essentially ‘washed’ out of the engine by the fuel.

DIRECT IN-CYLINDER FUEL INJECTION
Direct in-cylinder fuel injection (direct injection, DI) is a technology that has shown the ability to greatly reduce emissions from two-stroke engines. In a DI system the carburetor is eliminated, and the fuel is introduced into the combustion chamber via an injector mounted in the top of the chamber’s cylinder head. This allows exhaust products to be scavenged from the cylinder using air only. Fuel is injected into the cylinder later in the cycle, greatly reducing the amount of unburned fuel that is allowed to escape during scavenging. The DI process allows for a locally rich region around the spark plug, eliminating the need to enrichen the entire cylinder to achieve stable combustion. Elimination of rich air/fuel ratios significantly reduces carbon monoxide emissions.

RETROFIT APPLICATIONS
The goal of this project is to implement a widespread dissemination program which would enable widespread conversion of carbureted two stroke engines to operation on direct injection. The direct injection technology has been well proven in original engine manufacture (OEM) applications, but has never been commercialized in a retrofit application. In order to successfully implement a widespread retrofit program, a three-phase plan has been established. Phase I of the project involves conversion of a single vehicle. This Phase I milestone was achieved on schedule, with the successful demonstration of an "alpha" prototype DI tricycle at the Clean Air Now conference in Manila in November 2003. The vehicle used was a Kawasaki HDIII 125 cc motorcycle; it was selected because it is the most popular motorcycle used in tricycle service in the Philippines. Phase II involves retrofitting 10-15 motorcycles in 2004 with a near production level "beta version" retrofit kit and testing them extensively, primarily in Metro Manila. Phase III is the launch of the widespread retrofit program and is scheduled for 2005.