How Does the Exhaust System Affect Car Performance?

Exhaust systems are essentially there to take the superheated noxious gases and fumes, such as carbon monoxide, hydrocarbons and nitrogen oxides, safely away from the engine, without compromising the vehicle occupants.

Their secondary job is to minimise the impact of these poisons on the environment in general, with the use of catalytic converters, and then of course to address the sound issue of the average unbridled engine.

A further purpose of exhausts is to use the waste gases to power turbochargers. Although they increase backpressure, the upside more than offsets the down, giving as they do such a boost to performance through the amount of air they can ram into the engine, so increasing the amount of fuel each ignition burns.

Generally speaking however, putting engine waste gas through anything, be it a series of pipes, mufflers, bends or cats only increases backpressure on the engine, thereby reducing performance and increasing fuel consumption. This would be why hot rods have the shortest, most direct pipes, maximising the power output, with no legal requirement to curb noise or emissions.

Exhaust manifolds are often manufactured out of cast iron, designed and made as cost-effectively as possible. This significantly reduces long-term production expense, however it may also have a significant impact on the engine in terms of the movement of gasses as they leave the engine, creating very inefficient or detrimental airflow. This is of very little concern to the manufacturer, but may be of concern to the buyer.

The exception to this is of course in the more expensive, highly-tuned engines such as Ferrari, where performance is the overriding issue. They utilise the variance in pressure as the cylinders rhythmically open and shut to push out their fumes.

Each pulse in the exhaust train creates a momentary low-pressure dip in the exhaust manifold and these high-end engines are specifically designed to time their exhaust release from each pot directly into the dip in pressure created by the previous exhaust port. This maximises the extraction of the exhaust gases and ensures a super-efficient, uninterrupted flow out through the exhaust system, reducing backpressure and thus increasing both fuel efficiency and power.

Accordingly, for those without a supercar at their disposal, there exist companies that specialise in aftermarket exhaust system tuning by upgrading the standard exhaust and manifold for something that is specifically designed to whisk the exhaust fumes away from the cylinders with maximum effectiveness.

As you might imagine, they don’t come cheap, but they do greatly enhance the engine performance in two key ways:

• By reducing the detrimental backpressure being exerted on the engine.

• By reducing the amount of manifold/exhaust heat being radiated back to the engine under the bonnet, thereby cooling the air sucked into the air intake.

In general, these improved exhaust systems have much wider piping with no sharp bends, creating far less turbulence and thus less backpressure. Furthermore, ceramic coating of these higher performance systems greatly reduces drag and also helps to contain the high temperatures generated, killing two birds with the one stone.

So, in a nutshell, an exhaust system does in the main have a negative effect on a car’s performance, but for very good reasons. However, this effect can certainly be greatly decreased by splashing out on something specially designed for purpose.