Choosing a Performance Exhaust

Fitting a custom exhaust system is just not a matter of finding the biggest pipes you can. Car performance can even be decreased by using large-diameter piping.

People may think the 4 inch piping on their Dodge Neon is pretty good, but they will almost certainly be losing power because the pipes are too big, and it’s all to do with air. Cool air is dense while hot air is less dense and so will flow better.

Ideally, the exhaust gas should be as hot as possible to ensure it flows quickly, but if it is fed it into too large a pipe it expands and cools down, becomes denser, and therefore it’s harder to push the gas through the exhaust system.

Choosing the right exhaust piping

But at the same time if the pipes are too narrow the gas jams up in the pipes and can’t get out quickly enough. As a rule of thumb 250 to 350hp engines should be using 3 inches to 3 1/2 inch while 400hp and more should be using four-inch systems. Another concern is ensuring the piping will fit under the car without slamming into the ground every time the car goes over a bump.

And while Mandrel bent piping – which remains circular through the bend – is obviously better than compressed bends in the pipes, it doesn’t make that huge a difference in power and mandrel bending is more expensive.

Catalytic Converter

Welcome to the Catalytic converter. This article will not go over exactly what the catalytic converter does, but it essentially cleans up most of the gases that come out of an engine. Most modern designs flow much more freely than any resonator or muffler, so removing the cat doesn’t increase power production much, and in many countries, it is illegal to remove the catalytic converter in any case. There are freer flowing aftermarket catalytic converters, but any effect on performance is likely to be negligible.

Mufflers

Mufflers are there for one reason – to get the noise of the exhaust down to acceptable levels. There are three types of equipment that make your exhausts quiet, Resonators, Restrictors, and Reactive. Restrictors are usually found in new cars and do exactly that, restrict the exhaust flow and so do little for power production.

Resonators

Resonators essentially run the exhaust pipe through a larger diameter pipe packed with sound absorbing material such as steel wool. Holes cut into the exhaust pipe allow the wool to soften the sound, which passes through the pipe in vertical waves.

Reactive Mufflers

Reactive mufflers use baffles and route the exhaust gas through special pipes and turn to reduce the sound. In terms of restriction, the resonators are the best for ensuring the exhaust gas moves smoothly, while the Reactive mufflers restrict a little more.

Tuning an exhaust for performance is a complicated practice, which is why it is best left to the professionals. Choose large, well-known shops to do the work, and remember that bigger is not always better.