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What is an Up Pipe on a Subaru WRX?

What is an Up Pipe on a WRX

My dad’s second car was a Subaru with a manual transmission.

But back in the 80’s Subarus weren’t the lauded vehicles they’ve become. Since then, however, no Subaru model has become more coveted than the WRX.

Launched in Japan back in 1992, the Subaru WRX has lived on to become a pro-rally global phenomenon that you can still get with a turbocharged flat four.

An up pipe like a down pipe is part of a turbocharged engine’s exhaust system. The up pipe in a WRX is the same as in any turbo engine – exhaust gases enter the turbo from the up pipe.

We’re going to contrast a down pipe from an up pipe on a WRX even more as we consider how a WRX might benefit from an aftermarket up pipe.

A Closer Look at Up Pipes

Up pipes and down pipes are different parts of an exhaust system.

An up pipe helps exhaust gases get to the intake side of a turbocharger (keep reading to find out more about how a turbocharger works).

Exhaust gases are created after the combustion cycle of a cylinder – a WRX has four cylinders.

Exhaust gases from all four cylinders travel to the exhaust manifold where they go into the up pipe to be sent into the turbo’s turbine housing.

But the factory manifold and up pipe are usually points of restriction in the flow of exhaust of any engine.

What’s a Down Pipe?

Exhaust gases exit the combustion chamber which is the area in the cylinder of an engine where fuel mixes with air to create combustion. Then they flow to the turbo with help from the up pipe.

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A down pipe connects to the other side of a turbocharger to help those gases exit the turbine housing and flow out through the rest of the exhaust system until they exit the tail pipe.

All this is important to help us understand how a turbo works which will shine more light on the importance of an up pipe.

And it may shine light on why an upgrade may not be such a bad idea.

How a Turbocharger Works

How a Turbocharger Works

An engine is a big air pump.

And the more air you can get into it, the more horsepower and fuel efficiency you can enjoy. A turbocharger is a type of forced induction – it compresses air flowing into the engine.

Compressing the air helps squeeze more oxygen into the cylinder where combustion takes place. Not only does more air create a bigger combustion. But it doesn’t require as much fuel to create.

A turbo is made of two halves connected by a shaft. One side called the hot side is where exhaust gases get fed into the turbo’s compressor via the up pipe.

The down pipe connects to the hot side of the turbo at the turbine housing to direct exhaust gases into the exhaust system.

Benefits of an Aftermarket Up Pipe

As mentioned earlier an aftermarket up pipe will be less restrictive when it comes to the flow of exhaust than the one that comes on a stock WRX.

An up pipe is the last piece of tubing to carry exhaust gases into a turbo. This unrestricted exhaust gas flow means the turbo can spool up more to deliver more compressed air to the combustion chamber.

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Aftermarket Up Pipe and Horsepower

You can even get a modest gain of up to 10 horsepower with an aftermarket up pipe. While that may not sound like a lot. Think about how that adds to the rest of your modifications.

Aftermarket Up Pipe and Fuel Economy

Anything you do to improve an engine’s ability to breathe will mean that more oxygen can get into the cylinders.

The result is a more powerful combustion with the use of less fuel, which means better fuel economy.

By how much your fuel economy will increase with the installation of an aftermarket up pipe depends on the engine and other mods you’ve made.

And most importantly, your driving style.

Does an Up Pipe Change the Sound of a WRX?

Does an Up Pipe Change the Sound of a WRX?

Another benefit of upgrading the up pipe in a WRX is that you get more sound from the engine since exhaust gases will be able to move more freely.

But if you really want to change the sound of your WRX to give it a more aggressive presence, consider upgrading the muffler.

Adding resonator exhaust tips is an even easier solution, and much cheaper.

Should I Get a Tune After Installing an Up Pipe?

An ECU tune helps the engine take full advantage of all the performance mods you’ve made to your ride.

That said an up pipe is one of the rare exhaust system enhancements you can make that doesn’t require a tune.

But if you want to get rid of that check engine light after installing an aftermarket up pipe, then you really should consider a tune.

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While you may assume that if you can buy an aftermarket component and install it on your car that it must be legal. Truth is stranger than fiction.

To our complete surprise up pipes and down pipes aren’t legal.

Like straight pipes, these are a strictly track use upgrade. But if your Subaru WRX has a turbo and you want to increase horsepower for track use.

An aftermarket up pipe isn’t a bad way to go.

Sources:

fastwrx.com; howstuffworks.com; eagleridgegm.com