In the world of racing exhausts, a Perrin Subaru downpipe is a common upgrade to make. Many drivers who purchase one of Subaru’s turbo models do so for the sole purpose of owning a performance car. Sport compacts naturally have a racing profile and owning one of these vehicles has become a status symbol. Impreza owners are usually very aggressive when it comes to overhauling the exhaust. After all, the factory exhaust system is not meant for competition on a racetrack.
Because of this, it is incumbent upon car owners to make modifications on their own. Often, the first order of business is finding WRX/STI turbo exhaust parts that meet their needs. That is where Perrin Subaru downpipes come in. This is the pipe that connects the manifold to the catalytic converters. The stock tubing that comes with your car is not “high performing.” In other words, it presents a slim pathway for exhaust to flow out of. When this happens, it is known in automotive circles as “restriction.”
Most restrictive exhaust flow is caused by one main factor: Narrow piping. That means the objective of a Perrin Subaru downpipe is to end the restrictive influence. How this happens is due in large part to the overall construction of the part. Unlike the OEM’s pipe, a Perrin Subaru downpipe has a wide diameter, usually 3”. The wider tubing provides much more room for exhaust to travel through, so there is less backpressure. Airflow is not being slowed down by a narrow passage. Instead, it is able to reach the cats or muffler and ultimately, be escorted out.
The second part of the equation is the removal of the factory catalytic converters. The automaker is forced by law to include catalytic converters due to emissions guidelines. Exhaust is hot, sticky, and dirty. With it come smelly fumes that are harmful to the environment. The cats act as a filtration hub that cleanses the exhaust before it leaves the tailpipe, cutting down on pollution. While good for the environment, this process is bad for performance. Not only is airflow already being held up inside of a slim tube, but it is also forced to hit a detour on its way out of the system.
Swapping out the stock part and installing a Perrin Subaru downpipe in its place takes away a significant amount of restriction. The catalytic converters are no longer there to keep exhaust from being ushered out. The engine runs looser because it no longer has to compensate for the airflow being choked back. Horsepower improves instantly and the car runs at higher speeds more efficiently. Even by itself a Perrin Subaru downpipe makes a big difference in how your car responds when hitting the throttle.
One of the biggest debates has been about how much of an impact this customization makes in terms of numbers. In most instances, a Perrin Subaru downpipe offers about a good, solid 15-20 extra horsepower. This estimate does not take into account other custom exhaust upgrades a particular vehicle may have. But it is rare that a Perrin Subaru downpipe is installed by itself. While it can and does function at a high level on it is own, it is usually part of a full racing setup that features other mods. When that is the case, a Perrin custom down pipe plays just as important of a role because it encourages better exhaust flow everywhere instead of just one centralized area.
A lot of concern is often expressed about material. There are many foreign parts available for Subarus that say they are made of steel when it is really aluminum. Some drivers are actually under the impression that aluminum makes for a good choice in Subaru performance exhaust pipes due to the lighter weight. Unfortunately, aluminum does not handle the rigors of racing very well and the added stress can lead to many issues. Cracked or fractured flanges and leaks are common.
All Perrin custom down pipes are made from stainless steel. They are manufactured to be both high performing and resilient due to the climate in which they function. One of their biggest attributes can be found in the flanges. These are the endpoints that mate the Perrin custom down pipe to other parts. Flanges need to enact a strong seal because if there is even the slightest bit of weakness it can cause a leak. These steel downpipes come with thick 1/2” flanges that are intended to outlive the life of your car.