Making A Borla Exhaust Flow Better (Subaru WRX)
Although not the prettiest outcome, after modifying this borla exhaust, in theory it should flow alot better. The original design necked down from 3" all the way to 2.4" then back to 3" again, and it was not a smooth transition at all. There were blockages all through this this "dam" of a restriction.
Because I am trying to squeeze every last horsepower out of this engine I figured to increase turbo efficiency i should reduce the backpressure behind the turbine. I welded in a 3" pipe in place of the restriction and then decided last minute to add a flex pipe also to reduce the chance of exhaust damage from it being too stiff. Like I said it isn't the prettiest, but looking inside the pipe it was obvious that this needed to be done. Now the exhaust is 3" all the way and incorporates a flex pipe allowing the exhaust to bend as the engine torques, something it couldn't do very well before.