FSAE Intake and Exhaust Systems
Final Design Report:
November 29, 2001
Table of Contents
D) Morphological Chart
E) System Architecture
F) Function Analysis
When dealing with the internal combustion engine it is important to note that the engine itself is extremely inefficient in its use of the energy added into the system. Some of theses losses are innate inthe combustion engine while others are limited to manufacturing trade offs. One such area that can greatly improve the characteristic of an internal combustion engine lies in the tuning of the intake and exhaust manifolds. Considerable increases in the volumetric efficiency of the engine and power output can be achieved by optimizing the design of these components. By focusing in on manifolddesign and options currently available the complexity of this topic becomes evident. A thorough and carefully thought out design must be employed to insure the best possible performance of the engine.
Design of an intake and exhaust system for a prototype racecar, scheduled for mass production at minimal cost for the weekend autocross racer. Intake and exhaust system must providemaximum horsepower and torque across the power band, provided a restricted intake and decibel limits placed on the design.
On the intake side of the engine air and fuel are mixed together and their flow to the cylinders is regulated. Several different components must work together for the intake system to perform these tasks successfully. The main components of the intakemanifold include the air filter; throttle body, plenum, fuel injectors, and runners. The air filter removes impurities in the air so it will not hinder the combustion process. The throttle body provides the user with a means to manage the flow of air into the engine itself, increasing the opening to supply more air. The plenum serves as a reservoir for the incoming air to be pulled from wheneach cylinder requires a charge of air. Fuel can be regulated and mixed with the air through a number of methods from carburation to electronic fuel injection into the port. Then finally the air flows through the runners and into the engine where it is combusted. Choices exist for each system when tuning your intake, and this is where the complications begin.
Intake manifolds use a widevariety of shapes and sizes to take advantage of every possible combination of all the various components to maximize the needs of a particular engine. In doing so it is important to understand a few qualities that are desired in an intake system. First of all a smooth laminar flow is wanted in areas of the intake where no fuel is present. This will minimize the losses due to wall friction and bendsin the manifold system. Yet, when fuel is introduced into the system it is necessary for the flow to become turbulent. This will increase the flow velocity at the same time increasing the atomization of the fuel air mixture to create a proper burn once in the combustion chamber. Variations in the lengths and bends can be seen in Figure, where four types of plenums are illustrated.
TheMain goal behind tuning an intake manifold is to increase the volumetric efficiency of the engine. The volumetric efficiency itself is a miss leading term, in that it is actually a measure of the mass flow of air into the engine. The volumetric efficiency takes into account the losses throughout the system from the air filter to the intake valves themselves. With the right kind of components...
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