I originally posted this over on e46fanatics back in August 2011 but thought I'd share here as well for the ZHP community:
I just received my magnaflow cat-back exhaust part number 16533 last week and here are my notes.
WHERE TO BUY
At the time of this post, the very best deal on the internet is from Performance Peddler, based in Michigan, but they drop ship from California.
Cost: $556.66 drop shipped.
http://www.performancepeddler.com/de...CT_ID=MAG16533
Use coupon code "audipipes"
GENERAL OBSERVATIONS
* At $556 shipped, this system is a steal, a grand slam of value. Mandrel bent, stainless steel, etc for the price of some mufflers alone.
* Overall quality is very very good on this system, I'm very impressed. The welds are flawless and it bolts up to my headers better than the OEM system
* Fitment is about as good as I could probably expect. There really is NOT a lot of room down there. Like others I've had to make a few adjustments. I am actually impressed they were able to make a system work with larger piping at all.
INSTALL NOTES
Total install time: 3hrs, including a trip to the local hardware store
* The clamps included with the kit seem like good quality and the instructions call for 65 ft-lbs. I would STRONGLY recommend only torquing to 50 ft-lbs, after my experience and some research I did on the Accu-Seal clamps themselves. Trying to torque to 65 ft-lbs caused one of the clamps to de-thread, and I had to take it to a shop to have it removed and replaced with a free clamp sent from Magnaflow (good customer service!). I did get some rasp while I waited for a good clamp to arrive due to what must have been a slight leak even though the clamp was torqued to probably 35 ft-lbs before it broke. I also learned you want to install the clamps as close to the end of the overlapping pipe as possible, this will help it seal better.
* The bracket off the transmission that holds on to the two exhaust pipes just a few inches behind the headers will not work with the magnaflow exhaust without bending the brackets a bit to accommodate the larger piping. It is very important to re-install this brace as it helps with clearance below the rear transmission mount. Also, it will keep the exhaust noise in the cabin down near stock levels and prevents drone. Bend this brace and get it installed, its important IMO.
* Like others I had to modify the isolators that connect to the tabs at about the half-way point, right in front of the x-pipe. Just a quick shave and they sit real nice. I also added a washer between the tabs and the isolators to help give a slight bit more clearance between the bottom of the pipes and the crossbrace itself. More info with pics here: http://forum.e46fanatics.com/showpos...&postcount=289
* I struggled slightly with connecting the x-pipe section to the forward section. The x-pipe section's pipes where about 1/4" too close together to slide on to the forward section flawlessly, so I had to use a hammer to beat the flanges out a bit and muscle it on there. Nothing an exhaust shop would flinch about I'm sure they deal with that all the time.
* My car required about 3/8" to 1/2" worth of spacers/washers between the second crossbrace (the one with the rubber isolators that connects to the exhaust) and the car to prevent a loud rattling/vibration. Without these spacers the exhaust piping just in front of the forward resonator/muffler rests against the transmission mount/support and makes the entire car vibrate like a mofo. I did use longer bolts too, they were M8 1.25 pitch if I remember right, about 1/2" longer than stock.
* Straight out of the box the tips will mount up flush with the rear ZHP valence. I prefer them sticking out about a 1/2" or so just like stock. After all, these tips are so damn sexy who would want to hide them?! So I simply shifted the rubber hangers for the muffler as far back as possible and slid the piping in front of the muffler back slightly, then tightened down the clamps. Looks great! Although the rear section does seem to hang a little lower now... I may have to have a shop adjust the bend on that section to get it perfect (I admit I'm getting very picky now)
DRIVING IMPRESSIONS
Sex. The sound is amazing, absolutely amazing. It growls with small quick blips of throttle and howls when you let the beast out, in the best way imaginable. Barely a tiny hint of rasp in the higher RPM range, and only under heavier throttle. I don't think I could be happier with the sound, its a great fit for a performance BMW in my opinion.
It is louder than my ZHP exhaust with the headers, but not bad. Its OEM quiet at cruising and idle, and the beast awakens at WOT. There is maybe slight drone down low but no more than I had with my OEM exhaust with headers, and it goes away above 2k RPM or so (why are you driving below 2000RPM anyway?). On a scale of 1 - 10, with 1 being a bone stock exhaust and 10 being straight pipes I'd put this system at probably a 5 or 6. My ZHP exhaust with headers was probably a 3.
I can't comment much on the power just because I don't believe in butt-dyno's. I will say that based on other dyno's and that Magnaflow spent a lot of time making sure this system performs I would expect I picked up a pony or two. I'm certain I did not lose power. Car feels good and is a lot of fun to drive, which is what I think really matters anyway
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