Of all the mods I have been doing to my 330ci, I have been neglecting the engine. While it is relatively fun, it lacks the punch of the SR powered S13 I previously owned. The problem is that naturally aspirated performance goodies for the 330ci are relatively expensive for no other reason than being associated with the blue and white roundel. However, there is one part that is guaranteed to produce real power and is cheap and plentiful: replica headers.
The stock headers on the 330ci are very restricted. Besides the basic limitations of cast headers, the catalytic converters are built into the headers, further restricting the exhaust flow. Aftermarket headers optimize the flow of the exhaust gases
Unfortunately, obtaining headers that fit has been an ordeal. The first set of headers I received was ordered from an Ebay user(surewinproducts). The headers did not fit. Based on information in kpeng’s Ebay Header thread on E46fanatics.com, I have come to the conclusion that the headers I received are for a 328.
The dimensions I have are as follows:
CL to CL of bungs: 9″
Bottom weld of 3-1 Collector to flange: 9″
Laying the header to head flange flat, measured from ground to bottom of exhaust flange: 4 1/2″
CL to CL of bungs: 5″
Bottom weld of 3-1 Collector to flange: 6 1/2″
Laying the header to head flange flat, measured from ground to bottom of exhaust flange: 7 3/4″
I contacted the company, and was instructed to send them back so I can either recieve a refund or another set of headers. Neither was worth the expense or risk that they would still send the wrong headers. I guess I lost my gamble.
With this unfortunate setback, I purchased a set of headers from Bimmerbrakes through E46Fanatics.com. These headers were around $200 shipped. However, these are guaranteed to fit. Upon recieving them, I compared them to the Surewinproducts headers and found many differences right away. The spacing of the O2 bungs and the dimensions of the headers are substantially different. The quality of the workmanship is much better as well, definitely worth the difference in price, as long as they fit.
Installing the Bimmerbrakes headers was relatively straight forward. I followed one of the several guides available on E46fanatics.com, utilizing the tips and tricks mentioned in the threads. The most important one is to make sure you have an 11 mm ratchet wrench. This is invaluable, and I cannot imagine tightening the header nuts any other way. The headers went in without much protest. The only snags I had were regarding the passenger side motor mount and the exhaust to header connections. The header is very close to the heat shield on the motor mount and occasionally taps it when the engine is cold, causing a slight rattle sound when I let of the gas. I wrapped some header wrap around the motor mount to cushion the header to motor mount.
Unfortunately, I underestimated the volume that the installed exhaust system would create. The previous owner installed a Kpeng Special Exhaust (pair of glass packs with tips) and deleted the stock resonator and replaced it with an h-pipe. This is too loud for anything that is not a race car. To alleviate this sound problem, I planned to add two spun cats, a magnaflow resonator, a magnaflow muffler, and a new tip. I used the magnaflow system as a base line and found the same parts on magnaflow’s website. I took these items and my car to a local muffler shop. Unfortunately, the layout of the exhaust made it very difficult. The installer could not fit the resonator with the current piping layout and the catalytic converters would not fit as planned. Installing the custom system would cost more than a Magnaflow exhaust system! Dejected, I headed to Ebay looking for a Magnaflow exhaust system. I found a Magnaflow exhaust system listed for $600 shipped brand new with a Best Offer option. I figured, might as well offer $550 and see what the seller says. Within an hour, he had accepted the offer! Sent payment, returned the muffler, resonator and tips, and after a week of suffering with the straight pipes and glass packs, I was installing the exhaust.
What a difference! The car sounds much better, but still had a bit too much rasp between 3-4k RPM. So, I cut the exhaust just after the headers and added two spun cats to the system. While there is a slight drop in power (not even noticeable from the butt dyno), the elimination of the rasp was worth it. The car is also substantially quieter. Definitely a recommended addition to this install.
Even though I installed cats, the O2 sensors would still register an error. Initially, I installed the BimmerBrakes O2 sim, but it failed on me within 500 miles. I then added an O2 sim from O2simulators.com. This worked great. However, being the car guy I am, I could not resist the group buy listed on E46fanatics.com for an Active Autowerke tune. This tune was at a substantial discount, would get rid of the potential for the CEL to come on again, and would give a bit more power to boot.
I plan to get the car dyno’d at the next dyno day that the local clubs throw. It will be nice to see how much power car with its current bolt on mods generates.