Standard exhaust systems are very restrictive because they have to adhere to emissions regulations and are generally made to be quiet at the expense of performance. Aftermarket exhausts have a wider diameter pipe to accommodate better flow and reduce back pressure. Resonators, back boxes and even the materials are carefully chosen in order to make the perfect performing and sounding exhaust.
What exhausts do.
Exhaust gases are a by-product of an engine. An exhaust system is used to move these gasses to the rear of the vehicle and expel them to the atmosphere.
The exhaust has resonators or silencers to reduce noise levels, on a straight steel tube when it gets as long as the body of a car starts vibrating and reverberating and silencers are required to dispell this vibration.
Modern vehicles have catalytic converters which ‘clean’ exhaust gasses before they are expelled. Catalytic converters contain platinum in them to reduce the harmful gasses entering the atmosphere.
Stock exhausts are built with catalytic converters and small diameter pipes and can be very restrictive. This is done to pass emissions laws.
By simply removing the catalytic converter, power can be increased. There is less back pressure and less restriction.
Bigger diameter pipes on the exhaust system also work to increase flow and power.
Sizing of pipes must be calculated in order to achieve maximum results.
Some Exhaust terms to understand:
This is done on a dual pipe exhaust system, it is where the pipes connect to each other looking like an ‘X’.
The X pipe produces a more aggressive exhaust tone.
This is done where a dual system becomes a single system, the 'Y' shaped connector is the best for flow.
These are hollow boxes that are built into the exhaust to decrease sound levels or to change the tone of the exhaust depending on specifications on how it is built. Some model exhausts with resonance chambers do not require silencers.
This refers to when an after market system is built after the catalytic converter.
A Muffler or back box, is used to reduce noise. Muffler use baffles internally, this causes the exhaust gas to ‘bounce around’ therefore dissipating energy and lowering the sound levels.
This is the pipe that connects the turbo to the exhaust. Systems that include a downpipe are called turbo back exhausts.