Development and Design of a Formula Exhaust System - Reece Day, 2020
Monash Motorsport Final Year Thesis Collection
The Final Year Thesis, is a technical engineering assignment undertaken by students of Monash University. Monash Motorsport team members often choose to conduct this assignment in conjunction with the team.
These theses have been the cornerstone for much of the team’s success. The purpose of the team releasing the Monash Motorsport Final Year Thesis Collection is to share knowledge and foster progress in the Formula Student and Formula-SAE community.
We ask that you please do not contact the authors or supervisors directly, instead for any related questions please email info@monashmotorsport.com
Summary
This project includes a broad range of work and various investigations in the pursuit of improving the understanding of and techniques involved in designing and fabricating a high-performance Formula SAE/Formula Student exhaust system.
A stainless steel manifold and two double-pass absorptive mufflers were designed, manufactured and tested. The effect of various exhaust geometries on system back-pressure and noise results were investigated, along with the effect of an argon purge on weld quality. Major material failures are documented, as well as the nature of the degradation of absorptive material in the mufflers. This report also contains some details on avenues of study which were unable to be completed due to resource limitations or the COVID-19 outbreak.
The major outcomes of this project are:
A high-performance FS/FSAE exhaust system was successfully designed and implemented.
The double-pass design of the muffler is justified by conclusive back-pressure testing results.
Back-pressure testing reveals a relationship of approximately 0.55 competition points per kPa of pressure.
The outlet direction is justified by noise test results, and outlet geometries validated by these tests are implemented on the vehicle.
A low-budget argon purge system is fabricated and tested, resulting in limited effectiveness depending on the nature of the weld.
The rate of packing material ejection/loss from the muffler is investigated but the results are inconclusive due to small sample size.
INTRODUCTION
Formula SAE, or Formula Student as it is known in Europe, is the world’s largest engineering design competition. It involves hundreds of completely student-run teams from universities around the world who design, build, test and compete with formula-style race cars. The competitions are judged based on a “points'' system over multiple events; a vehicle which performs better at an event will score more points, up to a maximum of 1000, leading to a better ranking overall at that competition. The vehicles are also subject to an extensive and strict set of rules regarding construction or limits, such as roll cage specifications and a noise limit for internal combustion-powered vehicles.
Monash Motorsport (“MMS”) is Monash University’s Formula SAE team, and their internal combustion car is named M20-C, a continuation of the vehicle called M19-C in 2019. The car utilizes a naturally aspirated KTM Duke-R 690cc single cylinder-engine. Monash Motorsport strives to become the most respected formula SAE team in the world by continually improving their performance to the highest standard, and this Final Year Thesis endeavours to achieve this.
The overall aim of this project is to refine the design and manufacturing techniques of the exhaust system of M20-C. This will provide future exhaust designers with information which will assist in the continuous improvement of the exhaust system, through the investigation of multiple avenues of potential development. The ideal exhaust system would maximise engine performance, minimise mass, and stay within an acceptable budget.
The objectives of this project as originally stated in the Project Proposal, in order of priority, are:
To design exhaust systems for the 2019 and 2020 season with the maximum points potential possible with the team’s resources.
To improve the accuracy of Monash Motorsport’s exhaust “points delta” design philosophy.
To provide an improved groundwork of test results to allow future exhaust designers at MMS to create reliable and high-performance systems with minimal speculation or estimation of system parameters.
CONCLUSION
Through constant experimental development, this project has concluded in the following results, findings, and observations:
A high-performance FS/FSAE exhaust system was successfully designed, passed the noise test and technical inspection of multiple competitions, and the vehicle won 1st place overall at FSAE-A and FS Sydney 2020, and won 1st at FSAE-A Design Event 2019.
Information was gathered through testing and documentation of fabrication methods which will assist future MMS exhaust designers in creating higher-performance systems
Back-pressure testing conclusively found that the double-pass design is superior to a single-pass design with the same attenuation ability.
Noise testing of many exhaust configurations led to improvements in exhaust outlet placement and geometries; directed out from the side of the vehicle, and splitting the exhaust to multiple outlets.
An argon purge system is highly effective at improving weld quality in enclosed stainless steel welds. An open-top argon purge tank is not effective at improving weld quality in non-enclosing parts, though it does reduce oxidation somewhat.
To improve the service life of mufflers in the future, common failure points can be avoided by minimising and/or heat-treating welds, and avoiding over-constraining of parts.
A rough relationship was found between exhaust back-pressure and competition points, being approximately 0.55 points per kPa of pressure.
Thus, all three major objectives of the project set out in the introduction have been achieved.