That Flat-4 Rumble.

Update by Per Schroeder to the Subaru Impeza project car
May 11, 2006

With our Subaru weighing in at close to 2900 pounds and our factory horsepower figures at about 130 at the crank, we decided to work on both ends of the horsepower to weight ratio. We removed the stock exhaust system, which has two catalytic converters, a resonator and a huge muffler and replaced it one that was both lighter and rally-legal. Rally cars are required to retain a functioning catalytic converter (remember,they operate on public roads) so we installed a metal-matrix converter from Supreme Performance. This welded up to a 2.25” exhaust that A&W Muffler fabricated up, including two fittings for our oxygen sensors. The muffling portion of the exhaust was handled by a titanium straight-through muffler that is also made by Supreme Performance. It weighs a scant 4.5 pounds and uses a stainless steel clamp that you can weld hangers too.

The system is relative quiet at idle, but has quite a rumble from the flat-four cylinder engine under larger throttle openings. We’ve seen about a half-second improvement in our 0-60 time, now at about 9.5 seconds for the sprint.

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