The best aftermarket exhaust components are designed to work at least as well as, and sometimes better than, the original equipment. EuroFlo Premium Emission Systems says that apart from keeping noise to an acceptable minimum, a quality replacement exhaust system helps create the correct balance between exhaust gas flow capacity and velocity, crucial in getting the exhaust gases out of the combustion chamber efficiently.
Any resistance to flow creates backpressure, reducing performance and increasing 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, leading to increased fuel consumption and reduced performance.
Because of the nature of a 4-stroke engine, exhaust gases are not produced in a steady, smooth stream, it produces 4 distinct pulses per complete engine cycle. The pulses in the exhaust flow create low pressure areas behind them, creating a vacuum which assists with the scavenging of the exhaust gases from the cylinder – think of the way F1 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, the pulses get closer and closer together, becoming more like a constant flow and the vacuum effect becomes greatly diminished.
An exhaust system, 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, shown in the illustration below, to see some of the key features that provide the highest levels of performance.
Within a typical EuroFlo silencer box, each perforated inner pipe (baffle) has a unique configuration of holes 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. This ‘one size fits all’ approach can only negatively affect performance (see main image above, EuroFlo above, other product below 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. 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). The fibres also trap water and exhaust gas materials that produce harmful chemical reactions and compromise the sound absorption efficiency, durability and performance of the silencer.
A fully aluminised 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.