Does a big bore exhaust take away power?

Question

On a typical crappy boy racer car that shouldn have one?

Answer 1

On it's own, yes it would take away some power to balance it out you would also need to change the air filter (to let more air in!). You would also have to adjust (remap) the cars engine management system & tune the engine correctly. Only after all that is done will you see an increase in power (as well as noise!).

Answer 2

As well as considering bore, there is an ideal 'tuned-length' for an exhaust - vary much from this and power and torque will suffer.

Answer 3

It's not that simple: Exhaust design is very complicated, and most modern engines require a degree of back pressure to function correctly.

It isn't a matter of extracting exhaust gases quickly, as without remapping injection systems, it normally results in a drop in power.

As an illustration, try running a car with no exhaust at all - if the first answer was correct, that would produce the best performance.

Doesn't go very well, does it?

Answer 4

No, larger exhaust will not take away any power, even on a stock "crappy boy racer ". Increasing exhaust pipe diameter from the header back, or at least the cat back, will generally increase HP, especially on a modified engine. Getting rid of exhaust gases faster improves performance.

Answer 5

No - a free-er flowing unit will boost performance - just if you start with a gutless engine you will just have a slightly less gutless engine.  

Answer 6

Depends on the people putting the exhaust together, if it's a simple huge rear box attached to a good system, then it will be fine. If someone has put a big bore all the way through, the likely hood is that there will be not enough back pressure, so at low revs it will be down on power, but at the top end it might be slightly better (might). Big bore is not usually a good way to go as most road engines aren't designed to run with little back pressure, so performance will drop as will fuel economy, all you will get is lots of noise and less oomph.