Hi there,

Recently bought my second Impreza, a 2007 WRX, and it's (supposedly) fully standard apart from the exhaust.

Don't know a great deal about exhausts, but it looks to be a racebox exhaust (not sure how much of the exhaust is aftermarket) and I was just wandering what this exhaust is like in comparison to the standard 2007 WRX exhaust system.

Ultimately, I'd like to know if there is much difference in MPG or power. I am thinking of changing it back to the standard but only if it is practical.

Many thanks.

 

The exhaust is in several sections. Replacing the back box alone will make it noisier and maybe 1 or 2 bhp more powerful but that is all. Insignificant change to MPG

Start replacing the sections with cats in with either a straight through sections (de-cat) or a free flowing sports cat and you will see significant benefits in terms of power gain.

If memory serves me correctly the new age WRX has three cats, one in the up pipe, one in the down pipe and one in the centre section. Realistically you can pass an MoT with only one fitted so most either replace the entire system and have a sports cat in the downpipe only or get rid of all cats but keep the centre section one in the shed so it can be put back for MoTs

Also note that if you do fit a significantly more free flowing exhaust system then the turbo is prone to boost spiking and ideally the car should be re-mapped to compensate. As mentioned though if it's just the back box then no re-map required.