How Do Car Exhausts Work?

A quality exhaust system doesn’t just keep exhaust noise to an acceptable level, it plays a big role in maintaining optimum vehicle performance too.

EuroFlo Premium Emission Systems explains how.

The best aftermarket exhaust components are designed to work as well as and sometimes better than the original equipment product.

Apart from keeping noise to an acceptable minimum level, a quality replacement exhaust system is a key component in creating the correct balance between exhaust gas flow capacity and velocity, this balance is crucial in getting the exhaust gases out of the combustion chamber in the most efficient way.

Any resistance to flow creates backpressure which reduces performance and increases fuel consumption.

Too much flow capacity can negatively impact velocity while too much velocity can lead, in extreme cases, to reversion, which will negatively impact the scavenging of exhaust gases, making the engine work harder to compress the exhaust gases to a higher pressure, thus leading to an increase in fuel consumption and a reduction in performance.

Because of the nature of a 4 stroke engine, exhaust gases are not produced in a steady, smooth stream but are produced in pulses so that a 4 cylinder engine produces 4 distinct pulses per complete engine cycle.

The pulses in the exhaust flow create low pressure areas behind them which create a vacuum which in turn assists with the scavenging of the exhaust gases from the cylinder - think of the way Formula One drivers try to get into the slipstream of the driver in front.

The size of the vacuum created depends on the velocity of the flow, the higher the velocity, the bigger the vacuum behind each pulse, and the most effective scavenging is achieved.

At low RPM these pulses are relatively widely spaced so the vacuum effect is more pronounced. As the RPM rises however, the pulses get closer and closer together, becoming more like a constant flow and the vacuum effect becomes greatly diminished.

An exhaust system, which is correctly tuned for the vehicle will offer the best performance across the widest range of engine power/torque and optimised fuel efficiency at any given time.

Let’s look at the heavily engineered construction of a typical EuroFlo silencer box to see some of the key features that provide the highest levels of performance.          

As shown in the illustration, let’s take a look at a Peugeot 206 rear silencer.

It is important to notice with the EuroFlo silencer that each perforated inner pipe (baffle) has a unique configuration of holes which have been designed, in conjunction with the rest of the system, to deliver optimum performance for that specific application.

Some other manufacturers’ use standard perforated tubing for all applications, unfortunately this ‘one size fits all’ approach can only negatively affect performance - (see illustration - EuroFlo on the left – other product widely available in the UK market on the right)

EuroFlo’s heavily engineered internals incorporate multiple chambers, unique hole patterning and sound control chamber technology, all designed to maximise sound absorption.

A more traditional, older technology, used by other manufacturers is to use sound absorption materials, like e-glass. With e-glass the sound waves get trapped in the fibres instead of escaping the silencer. This can be a cheaper manufacturing solution as it drastically reduces the structural complexity of the interiors (fewer baffles and less internal pipe work). However, the fibres will also trap water and exhaust gas materials that produce harmful chemical reactions and compromise the sound absorption efficiency and the durability and performance of the silencer itself.

A fully aluminized exhaust is also a key feature of a quality exhaust system, as this provides extended product life and it is this feature that enables EuroFlo to offer a 3 year warranty on their products.

A high quality replacement exhaust really can make a huge positive difference!

Euroflo Ultra Premium Emission Systems can be purchased here Euroflo Exhausts