University of Maine’s Flex Fuel Capable Four-Stroke Snowmobile

Joseph Stilwell, Kazuki Iwakura, Eric Whitman, Kevin Bowler

University of Maine

Abstract

For the 2010 Clean Snowmobile Challenge (CSC), the University of Maine is submitting a second-generation four-stroke snowmobile capable of running on flex-fuel. Through the use of an engine control unit (ECU), Microsquirt, the snowmobile can successfully be tuned to improve fuel consumption, decrease emissions, and maintain the

stock engine configuration. Engine noise and vibration is reduced using sound absorbing materials around the inside of the cowling as well as under the seat to prevent noise from the exhaust system. The Umaine Phazer meets emissions standards through the use of a new catalytic converter and is fuel-efficient.

Introduction

Snowmobiles provide outdoor enthusiast the opportunity to experience the thrill of trail riding during the winter months when snow is abundant. Although snowmobiles provide entertainment, they also contribute to environmental pollution through excessive emissions and they can be extremely noisy in residential areas. The Society of Automotive Engineers (SAE) developed the Clean Snowmobile Challenge in 2000 for the purpose of re-engineering snowmobiles to produce fewer emissions, operate quieter, and consume less fuel through a combination of ethanol and gasoline (flex-fuel). At the same time the

competition snowmobiles need to perform at the same level as the original equipment manufacturer (OEM) and are expected to significantly reduce hydrocarbons, carbon monoxide, nitrous oxide, and excessive noise.

This paper discusses how the 2010 University of Maine team has modified the 2007 Yamaha Phazer Snowmobile for the 2010 CSC in order to reduce emissions and sound while maintaining the OEM performance and riding characteristics. This paper also discusses what the team kept from the previous years team in a summary form.

Design Goals – The overall goals for the 2010 clean snowmobile team is to reduce exhaust emissions, mainly HC, CO, and NOx, and reduce noise and vibration from the snowmobile.

Through the use of a five-mode gas analyzer, emission testing has taken place to compare the emissions produced from the stock exhaust system and the emissions produced

from the custom exhaust system with the three-phase catalytic converter. In order to reduce noise and vibration, sound deadening materials have been placed around the cowling, inside the engine walls, and underneath the seat to help reduce the sound and vibration from the engine output.

Umaine Design

The Baseline Snowmobile – The stock specifications for the four-stroke 2007 Yamaha Phazer snowmobile are listed below in Table 1.

Engine Type Four-StrokeCooling Method Liquid Cooling

Cylinders 2Engine

Displacement499 cc

Compression Ratio 12.4:1Maximum Power 80 HP

Dry Weight of Sled 454 lbsSize of Fuel Tank 11.4 gallons

Fuel Type E20-E29Table 1 – Stock specifications of the 2007 Yamaha Phazer Snowmobile

EMISSIONS CONTROL- There is two methods to improving the emissions produced by the snowmobile. The first method is a mechanical method and the second method deals with the electrical wiring of the Microsquirt engine controller.

Mechanical Method: The 2010 University of Maine clean snowmobile team chose to incorporate a 3-way catalytic converter into a customized exhaust system. The catalytic converter used in the customized exhaust system is designed for automotive applications. The 3-way

catalytic converter is a Magnaflow performance catalytic converter capable of oxidizing hydrocarbons (HC), carbon monoxide (CO), and nitrous oxide (NOx). The catalytic converter features a 2.25” center inlet/outlet pipe, 9 x 5.125” round body, and is 13” in overall length. Figure 1 shows the catalytic converter mounted onto the customized exhaust system.

Figure 1 – Custom exhaust system with new 3-phase catalytic converter

Figure two shows the Yamaha Phazer with the stock exhaust system. The stock exhaust system was used to compare emission production and

sound production from the snowmobile.

Figure 2 – Yamaha Phazer with stock exhaust system

Figure three shows the custom muffler being constructed to accommodate the new exhaust system with the catalytic converter included. The muffler consists of three chambers with an expander. The exhaust will enter the muffler through a 2.5” opening in the front, move through the center chambers while expanding, and then circulate back through the side chambers and exit through the bottom of the muffler and out into the atmosphere. With the addition of the new muffler, sound and vibration from the sled will be reduced.

Figure 3 – Custom muffler with three chambers and expander

Electrical Method: The 2009 clean snowmobile team chose to implement the use of an engine controller, Microsquirt, for the purpose of tuning the engine of the snowmobile to produce fewer emissions. Microsquirt allows the user to optimize ignition and fuel delivery parameters to balance the ratio of ethanol and gasoline for better performance as well as optimize fuel economy and emissions. The Microsquirt unit is a Bowling & Grippo unit chosen for easy compatibility with the stock Yamaha Phazer sensors and for easy programmability and tuning. The 2009 clean snowmobile team varied the spark ignition, air-fuel ratio, and volumetric efficiency to determine the best combination for optimum fuel efficiency and emission production. The 2009 team used Microsquirt to control the fuel delivery with a measured air pressure to allow the most useful mixture of air and fuel to be delivered to the engine of the snowmobile. The variability of the Microsquirt unit can determine the

right ratio of air and fuel to be delivered. If the mixture is too lean then the sled will lose power and backfire. If the mixture is too rich the exhaust produces a heavy black smoke and the throttle response is very sluggish. Microsquirt allows these parameters to be adjusted in order to find the right mixture for optimal performance. The 2009 team implemented this unit into the engine controller and adjusted the parameters to produce the most power, fewer emissions, and better response from the snowmobile.

Shown below are the emissions produced from the stock Yamaha Phazer snowmobile.

SOUND & VIBRATION: In order to reduce the sound and vibration and the Yamaha Phazer, the 2010 clean snowmobile used sound deadening materials that have been placed in and around known areas where sound and vibration are prevalent. Two materials have been used to reduce sound and vibration of the snowmobile. The first material used was B-Quiet Ultimate, which is a 1.6mm thick viscoelastic deadener rated for high temperature which is being used underneath the rider seat where temperature from the exhaust is highest. The second material used was B-Quiet Vcomp which is a composite noise barrier consisting of a dense 1/8” vinyl based polymer barrier with a ¼” thick foam

decoupler [1]. The Vcomp noise barrier is being used inside the cowling as well as around the steering column and dashboard of the snowmobile where vibration is an issue. Shown below are representations of the B-Quiet Ultimate and the B-Quiet Vcomp materials used.

Figure 3 – B-Quiet Ultimate used under the riders seat. Rated for high temperatures

Figure 4 – B-Quiet Vcomp composite noise barrier used under the cowling and around the steering column and dashboard

References

[1] B-Quiet