Exhaust
The exhaust system is designed to aid in the removal of burnt fuel and air from the engine. A sound limit is placed on the exhaust in competition.
we should also talk about header clocking by firing order into the collector - for scavenging goodness. Scavenging matters because ideally we would have a reversible and adiabatic expansion of the exhaust gases in the cylinder from the maximum cycle pressure to the ambient atmospheric pressure during the power stroke. If the gas is leaving the cylinder at some elevated pressure because of the pressure drop throughout the exhaust system, the potential expansion work relative to the ambient pressure is wasted and the engine power is reduced.
Contents
Exhaust Form Factors
The exhaust form factor should drop out of your design constraints (e.g. packaging and weight) as well as your engine system model. There is no one right answer for the best exhaust system.
4-1
4-2-1
4-2
4-4
(never seen 4-4 but it'd be sweet. A drawback would be having to include 4 mufflers).
Silencers and Noise test
Muffler/Silencer
A muffler (or silencer) is an acoustical filter designed to ensure appropriate noise control in the exhaust system of an internal combustion engine.
Manufacturing
A key quality control during manufacturing should be maintaining equal runner lengths for each stage of the exhaust and minimizing flowpath disruptions due to weld beads or tube misalignment.
Tuning
Runner Lengths
Because of the high temperatures and pressures involved, reduced order models such as Helmholtz (a linear acoustic model) start to break down. A parametric study in WAVE or GT-Power is more useful to determine realistic runner lengths.
