As some of you are aware, I installed the BMW Performance Exhaust on my E92 323i about a month ago. This report is long outstanding simply because Freddie of Obermaier quite rightfully advised me to let the exhaust run in for 500-1,000 kms before I make any judgment. Because the E92 is a second car, it took a while for me to get there (should have joined the Singapore drive!)
I remember the first day the exhaust was installed, it made all the wrong noises - sounded rough and overly metallic. No improvement in performance felt. Over time, the sound has changed. It sounds gorgeous now in the right amounts. Firstly, it's amazing how you can hear it most when your windows are down, only for it to be more subdued (in a nice kind of way) when the windows are up. Hence, it's not intrusive at all. Then, the exhaust sound actually diminishes at higher revs where the engine sound completely takes over. Amazing! This makes the occasional sprints off the traffic lights and toll booths so much more satisfying and oh, driving through tunnels too.
In terms of performance, I must objectively say that a bit of low end torque has gone missing from about 1,000 to 2,500 rpms, only for meatier torque to develop after 2,500 rpms. Essentially, it's just a fraction of a second of flat spot before a nice swell builds up. Overall, I think the meatier torque in mid range makes up for the slight loss and certainly, the more aggressive scream towards red line. Even my gear change is a bit more jagged at high revs (which I like) as the revs climb more convincingly towards the red line. Here, there's a discernible performance gain albeit quite slight for some of you.
Is this a worthwhile mod for the money? Yes! The sound is really nice, not too loud for you to look pretencious, not too soft for you to feel absolutely nothing, just nice to put a smile on yer face and make you think you got a V8 in your hood even if you can't quite kill off scarlet ferraris yet. The chicks might be fooled into thinking you can though, hahahahaha....
My next project is to work out the low end flat spot. E90-1000's suggestion to replace the silencer back to stock comes to mind but I love the sound too much to sacrifice any of it, as well as the very immaculately made and inscribed BMW Performance silencer. I think it can be redressed with ecu tuning with Bernard, just a matter of tweaking the air fuel mix I hope.
P.S. I must compliment Freddie of Obermaier on a superb, problem free job they did with the installation..!