Changing exhaust decrease bhp?
 

Hi, I recently stumbled across this forum and i've not long had my first scooby (wrx 2003 blobeye) so i'm a bit of a newbie when it comes to everything

If i change the standard wrx exhaust to an aftermarket stainless steel one, will i actually see a decrease in performance?

I was told that despite the fact that it says it will increase bhp up up to 35, that in order to benefit from this, i will have to remap my engine otherwise it will actually decrease bhp in my vehicle. How accurate is this? Sorry if it sounds like i'm not making much sense.

Thankyou!

Depends on the exhaust and the original, surely?

A larger bore might result in reduced back pressure, which might need a map tweak, but tbh, not so as you'd notice.

HOWEVER: my experience of Scoobs over 17 years has been to get map tweaks done, rather than let it go. The engines don't like un-mapped mods;)

Ah fair enough, I'll just fit it then see if i notice a difference in power. Thankyou!

Ah the good ole' bum dyno

Tbh it depends if you are planning on just replaceing the backbox / cat back system then you will be fine.
If you are planning to decat it and replace it with a full cat less turbo back system then you will need it mapped.