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The exhaust system is an integral part of any internal combustion engine. A well- designed exhaust system efficiently removes exhaust gasses expelled from the cylinders. If tuned for performance purposes, the exhaust system can also exhibit scavenging and supercharging characteristics. This project reviews the major components of an exhaust system and discusses the proper design techniques necessary to utilize the performance boosting potential of a tuned exhaust system for a four-stroke engine. These design considerations are then applied to Arizona State University's Formula SAE vehicle by comparing the existing system to a properly tuned system. An inexpensive testing method, developed specifically for this project, is used to test the effectiveness of the current design. The results of the test determined that the current design is ineffective at scavenging neighboring pipes of exhaust gasses and should be redesigned for better performance.
ContributorsKnutsen, Jeffrey Scott (Author) / Huang, Huei-Ping (Thesis director) / Steele, Bruce (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
The paper presents a new exhaust header design to replace the current design on Arizona State University's Formula SAE car. Also, the thought process of the design was presented as well as a method of analysis for tuning the exhaust headers. The equation presented was then compared with a computational fluid dynamics model using ANSYS Fluent. It was found that the equation did not match the timing of the CFD model. However, the design does allow for simple changes to be made in order to reduce the length of the exhaust and allow for the correct tuning. Also, the design minimizes interference between the individual headers which is ideal to increase engine performance. The exhaust meets the Formula SAE regulations, and is designed to fit in the new chassis for the FSAE car that ASU will run in 2015. Recommendations were also made to further improve the design and analysis model.
ContributorsKaashoek, Kevin Jason (Author) / Huang, Huei-Ping (Thesis director) / Trimble, Steven (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
This thesis focuses on the effects of an engine's induction and exhaust systems on vehicle fuel efficiency, along with the challenges accompanying improvement of this parameter. The aim of the project was to take an unconventional approach by investigating potential methods of increasing fuel economy via change of these systems outside the engine, as finding substantial gains via this method negates the need to alter engine architectures, potentially saving manufacturers research and development costs. The ultimate goal was to determine the feasibility of modifying induction and exhaust systems to increase fuel efficiency via reduction of engine pumping losses and increase in volumetric efficiency, with the hope that this research can aid others researching engine design in both educational and commercial settings. The first step toward achieving this goal was purchasing a test vehicle and performing experimental fuel efficiency testing on the unmodified, properly serviced specimen. A test route was devised to provide for a well-rounded fuel efficiency measurement for each trial. After stock vehicle trials were completed, the vehicle was to be taken out of service for a turbocharger system installation; unfortunately, challenges arose that could not be rectified within the project timeframe, and this portion of the project was aborted, to be investigated in the future. This decision was made after numerous fitment and construction issues with prefabricated turbo conversion parts were found, including induction and exhaust pipe size problems and misalignments, kit component packaging issues such as intercooler dimensions being too large, as well as manufacturing oversights, like failure to machine flanges flat for sealing and specification of incorrect flange sizes for mating components. After returning the vehicle to stock condition by removing the partially installed turbocharger system, the next step in the project was then installation of high-flow induction and exhaust systems on the test vehicle, followed by fuel efficiency testing using the same procedure as during the first portion of the experiment. After analysis of the quantitative and qualitative data collected during this thesis project, several conclusions were made. First, the replacement of stock intake and exhaust systems with high-flow variants did make for a statistically significant increase in fuel efficiency, ranging between 10 and 20 percent on a 95% confidence interval. Average fuel efficiency of the test vehicle rose from 21.66 to 24.90 MPG, an impressive increase considering the relative simplicity of the modifications. The tradeoff made was in noise produced by the vehicle; while the high-flow induction system only resulted in increased noise under very high-load circumstances, the high-flow exhaust system created additional noise under numerous load conditions, limiting the market applicability for this system. The most ideal vehicle type for this type of setup is sports/enthusiast cars, as increased noise is often considered a desirable addition to the driving experience; light trucks also represent an excellent application opportunity for these systems, as noise is not a primary concern in production of these vehicles. Finally, it was found that investing in high-flow induction and exhaust systems may not be a wise investment at the consumer level due to the lengthy payoff period, but for manufacturers, these systems represent a lucrative opportunity to increase fuel efficiency, potentially boosting sales and profits, as well as allowing the company to more easily meet federal CAFE standards in America. After completion of this project, there are several further research directions that could be taken to expand upon what was learned. The fuel efficiency improvements realized by installing high-flow induction and exhaust systems together on a vehicle were experimentally measured during testing; determining the individual effects of each of these systems installed on a vehicle would be the next logical research step within the same vein. Noise, vibration, and harshness increases after installing these systems were also noticed during experimental trials, so another future research direction could be an investigation into reducing these unwanted effects of high-flow systems. Finally, turbocharging to increase a vehicle's fuel efficiency, the original topic of this thesis, is another very important, contemporary issue in the world of improving vehicle fuel efficiency, and with manufacturers consistently moving toward turbocharged platform development, is a prime research topic in this area of study. In conclusion, the results from this thesis project exhibit that high-flow induction and exhaust systems can substantially improve a vehicle's fuel efficiency without modifying any internal engine components. This idea of improving a vehicle's fuel economy from outside the engine will ideally be further researched, such as by investigating turbocharger systems and their ability to improve fuel efficiency, as well as be developed and implemented by others in their educational projects and commercial products.
ContributorsCurl, Samuel Levi (Author) / Trimble, Steven (Thesis director) / Takahashi, Timothy (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Formula SAE is a student design competition where students design and fabricate a formula-style racecar to race in a series of events against schools from around the world. It gives students of all majors the ability to use classroom theory and knowledge in a real world application. The general guidelines for the prototype racecars is for the students to use four-stroke, Otto cycle piston engines with a displacement of no greater than 610cc. A 20mm air restrictor downstream the throttle limits the power of the engines to under 100 horsepower. A 178-page rulebook outlines the remaining restrictions as they apply to the various vehicle systems: vehicle dynamics, driver interface, aerodynamics, and engine. Vehicle dynamics is simply the study of the forces which affect wheeled vehicles in motion. Its primary components are the chassis and suspension system. Driver interface controls everything that the driver interacts with including steering wheel, seat, pedals, and shifter. Aerodynamics refers to the outside skin of the vehicle which controls the amount of drag and downforce on the vehicle. Finally, the engine consists of the air intake, engine block, cooling system, and the exhaust. The exhaust is one of the most important pieces of an engine that is often overlooked in racecar design. The purpose of the exhaust is to control the removal of the combusted air-fuel mixture from the engine cylinders. The exhaust as well as the intake is important because they govern the flow into and out of the engine's cylinders (Heywood 231). They are especially important in racecar design because they have a great impact on the power produced by an engine. The higher the airflow through the cylinders, the larger amount of fuel that can be burned and consequently, the greater amount of power the engine can produce. In the exhaust system, higher airflow is governed by several factors. A good exhaust design gives and engine a higher volumetric efficiency through the exhaust scavenging effect. Volumetric efficiency is also affected by frictional losses. In addition, the system should ideally be lightweight, and easily manufacturable. Arizona State University's Formula SAE racecar uses a Honda F4i Engine from a CBR 600 motorcycle. It is a four cylinder Otto cycle engine with a 600cc displacement. An ideal or tuned exhaust system for this car would maximize the negative gauge pressure during valve overlap at the ideal operating rpm. Based on the typical track layout for the Formula SAE design series, an ideal exhaust system would be optimized for 7500 rpm and work well in the range
ContributorsButterfield, Brandon Michael (Author) / Huang, Huei-Ping (Thesis director) / Trimble, Steven (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05