Why Do WRX Sound Different?

If you’ve ever heard a Subaru WRX drive past, then you’ll know that ‘Subaru burble’.

Subarus – especially the WRX – just seem to sound so different to so many other cars. We reckon that famous Subaru sound is one of the best four cylinder sounds ever to grace the streets. It is just such a distinctive sound.

But why do WRX sound different?

In this instalment of Car Facts (our series of short, sharp, informative articles where we answer your car questions) we are going to look at the reasons why WRX – and other Subarus – sound so different to other cars.

Keep reading to find out what makes that distinctive Subaru burble happen.

Two Parts To The Puzzle

There are actually two parts to the WRX sound puzzle, with one of them being more well known than the other.

The first piece of the puzzle is the “opposition”/layout of the engine.

Most car enthusiasts are aware that Subaru users ‘Boxer’ engine layouts – that is to say horizontally opposed.

Unlike a normal engine where the pistons move vertically, the pistons in a Subaru engine move horizontally.

This boxer engine layout reduces weight, lowers the centre of gravity, and means potentially smoother engine operation.

Subaru aren’t the only manufacturer to use a Boxer layout. For example, Porsche use boxer engine designs in their vehicles.

This video does a great job of explaining the key differences between a conventional engine and a Boxer/horizontally opposed engine:

 

The use of Boxer engines is one part of the reason why WRX sound different. However, there is actually a second part of the puzzle that is less well known.

Unequal Length Headers Make All The Difference

The true ‘Subaru burble’ (as per the following video) is actually more to do with the fact that engines in the older generations of WRX have unequal length headers.

Without wishing to get too technical, basically the headers for Pistons 1 & 3 are shorter than those for 2 & 4.

This difference in length means that back pressure builds up in the exhaust system. As 1 & 3s’ exhaust gasses have a shorter distance to travel, they actually create back pressure for 2 & 4.

The gasses from pistons 2 and 4 are then only able to escape once their pressure has risen above that of 1 and 3, and then the gasses force themselves out.

This process is what creates the infamous Subaru rumble, one of the best sounding (in our opinion) four cylinder engines of all time.

However, this unequal header length setup is also believed to be the cause of some reliability problems in WRX engines, with one bank of cylinders getting hotter than others.

Newer WRX models with the 2.0 engine have moved to having equal length headers in order to facilitate the use of twin scroll turbochargers. This is why new WRX don’t have that classic Subaru sound any more, despite having a boxer engine – although the boxer engine does contribute somewhat to the sound, it really is the unequal length headers that answer the question “why do Subaru WRX sound so different”.

If you found this article interesting and helpful, check out our other instalments of Car Facts here.

If you’re interested in buying a WRX, you can also check out our buyer’s guide here.

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