Exhaust Systems - Everything You Need To Know

Every engine requires an exhaust system, but not all systems are made equal and there's a great deal of variety when it comes to the design and engineering involved - whether that's from factory or aftermarket.

We've covered how an engine works in the past, but we've never really explained what happens after the engine burns all that fuel. With a rudimentary understanding, you would know that those gasses end up travelling out through the exhaust pipe that (usually) leads to the back of your car - but the journey is long and complex.

Even between different cars and engines, exhaust systems can be largely different depending on the goal and purpose, as well the function. The exhaust system in a Ferrari 458 is nowhere near the same as what you would find on a Perodua Myvi, and yet there are going to be common elements as well. Let's break it down from tip to tail.

Extractor 

Sometimes known as exhaust headers or collectors, the extractor is the first point of contact for exhaust gasses on their way out of the engine. Headers will have pipes that connect to each individual cylinder's exhaust ports and will consolidate them as they head down the exhaust system. 

How the gasses are consolidated and merged can be very different as well. For a naturally aspirated engine, some manufacturers will opt for having all of the ports merge simultaneously - known as a 3-into-1, 4-into-1, 5-into-1 and so on, with the first number indicating the number of cylinders. 

Some will opt to merge cylinders in a way that promotes exhaust scavenging and massive gains in mid-range torque, and this staggered merging can result in more intricate designs. Careful calculation and engineering, with tuning for the different lengths and diameters of the piping, can produce truly impressive results.

And then there are some extractors that are ridiculously simple, though not uncommon in both factory and aftermarket applications. Known as log manifolds, they are quite literally a pipe that connects all cylinders (or all cylinders on one bank of cylinders) and usually are made to feed a turbocharger of some description. These simple designs are usually known to promote faster turbocharger response at the expense of peak power - and manufacturers go so far as to integrate it into the head casting for more modern engines.

You may also see this design of extractor on naturally-aspirated cars for packaging reasons, as it can heat up a catalytic converter very quickly by positioning it as close to the engine as possible. Emissions regulations usually drive these engineering choices, and going aftermarket will see fairly substantial gains over a compromised factory setup.

Downpipe

Something that applies more specifically to turbocharged engines, the downpipe is essentially what comes out of a turbocharger and connects to the rest of the exhaust pipe. With a turbocharged engine, the turbocharger sits between the extractor and the rest of the exhaust pipe, so a downpipe is literally as the name describes. Sizing and design does have an impact as well, though that's a more technical subject.

Catalytic Converters

Perhaps the biggest contributing factor to reducing car emissions, catalytic converters have become an integral part of a car's exhaust systems in order to clean the air that comes out the back of your car. Some cars have small ones, some have large ones, some even run two or three - but they all perform the same function. Ultimately they do restrict flow so you could go with a larger high-flow version that is available aftermarket - or remove it entirely, but you'd be doing the environment an injustice.

Resonators

Some call them bullets, some call them tabungs - a resonator is a much smaller section of pipe that runs a perforated inner core, sitting somewhere along your exhaust system. It doesn't do so much to muffle noise as it does to help cancel some less pleasant frequencies, which you can attenuate by the size and shape of these resonators. Some cars position the resonators much further back in the exhaust system or even combine them with your muffler - if you've ever heard a loud, droney exhaust noise from a passing car there's a high chance it no longer has a resonator.

Cross Pipe

An item that exists only on V and flat shaped engines, a cross pipe helps to connect the exhaust flows from the left and right backs of the engine - provided that they have separate exhaust pipe setups running from the engine bay to the rear. The function of these pipes is to help promote scavenging for the engine to draw in more air - much like staggered extractor merges.

Muffler

Sitting right at the end of your exhaust system is usually an exhaust muffler, which as the name suggests is designed to reduce the volume of the exhaust noise coming from your car. There are different kinds of mufflers with different internal shapes that trade-off the ability to deaden noise with overall exhaust flow, but they all aim to reduce noise. Much like resonators, the shape and design can also change the tone of the exhaust noise, some providing more bass and some with a higher pitched note.

And there you have it - the names of the various components you will find in your exhaust system. We have intentionally glossed over the technical details and the various myths you will find because this article would simply keep going on and on if we did - but we can always do a deeper dive another day.