An owner with a standard, quiet 2.2 NA asked in 2017 what an exhaust upgrade would do. Here is what the replies said. They are owners' recollections, not tests.
The basics
- The standard system is 2 inch. Owners say don't go larger than 2.5 inch on an NA.
- One owner says the standard exhaust isn't that restrictive, and that a few people run it with a supercharger without losing much.
- The NA system is pretty basic from the manifold back, so a fabricator should be able to make one without much difficulty. One quote was a 2.5 inch custom stainless system, with the pre-cat removed, for £650 built and fitted (2017). Another owner said that sounded reasonable, as used backboxes alone go for around £200 or more.
- The fabricator warned of a slight torque loss low in the rev range. Nobody in the thread confirmed or denied that.
What power to expect
- One owner says you might get another 10 to 15 bhp with a good exhaust, and the removal of the pre-cat is "pretty essential" for that.
- The same owner says his previous NA had a full 2.5 inch system including the manifold, intake and a remap, and he thinks it made 167 bhp. He says it wasn't massively noticeable on the road, and the whole lot would have cost £2,000 to £2,500, about the cost of a DIY supercharger conversion.
- Another owner's car had similar mods and a similar power level. The previous owner had paid a lot for a remap and got 7 bhp, so he wouldn't bother with one, as the power and torque curves weren't much different.
- One owner says you won't see power gains from an exhaust and intake alone, and says to expect noise rather than power. A manifold swap, by comparison, was said by one owner to help the mid-range. See Exhaust manifold options.
Intake
One owner suggests modifying the standard airbox to let in more intake noise and keeping the standard panel filter, or fitting an aftermarket one. His favourite was an ITG, which he says filters well, unlike some stories he has read. The original poster had a K&N cone and liked the induction noise under hard acceleration.
Identifying what you have
An NA owner whose car came with paperwork for a Miltek system wasn't sure whether it was fitted. Owners suggested posting photos of the exhaust, as those in the know can tell what you have.
See also Post-cat lambda sensor replacement and Dropped exhaust and the hanger bracket.