How to Enhance a Subaru 2.5 Engine

The Subaru 2.5-liter engine has been used in a variety of models, including the incredibly fast WRX STI. Some versions of this engine have been turbocharged while some are normally aspirated. Both the turbocharged and non-turbocharged versions can be enhanced quite easily for more power. Plenty of companies offer aftermarket upgrades for these cars, and the engines are durable enough to withstand the addition of significant power.

Step 1 - Replace the stock exhaust with a more free-flow exhaust system. This is often one of the first changes that enthusiasts make to their Subarus when they want more power. The stock exhaust is relatively restrictive, so opening it up to a larger diameter allows spent exhaust gases to exit the motor more efficiently, in turn producing more power. To install a performance exhaust, the old exhaust must be removed and the new one installed. This requires special tools and knowledge and can be done by an exhaust shop.

Step 2 - Install a more free-flowing air intake. The more fresh air the engine can get, the better it will run and the more power it will make. You can install something as simple as a performance air filter from a company like K&N that fits in the stock air intake but is more free-flowing than the stock filter. You can also install a cold air intake, which will replace the stock air box with a more free-flowing air intake and filter. To install a filter, remove the stock filter and replace it with the new one. If it is a complete cold air intake, remove the stock air box by unbolting it from the engine bay and bolting in the cold air intake according to the supplied directions.

Upgrade the electronics. One thing that all modern cars benefit from is an upgraded ECU (Engine Control Unit), which will reprogram the computer to deliver different fuel, air and ignition curves for a power increase. The turbocharged versions of the 2.5-liter engine in particular will benefit greatly from a performance ECU. A new ECU should be installed by a shop familiar with working on automotive electronics.

THINGS YOU'LL NEED: Socket set and ratchet, Specialty automotive tools

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