Euro Headers Installed on the E46 M3

There is a single proven modification when it comes to extracting more power from BMW's naturally aspirated S54 engine: headers. Sure, forced induction is an option, but I wanted to stay naturally aspirated. My E46 M3 is my only car so reliability was the highest priority. Next, I commute 50+ miles per day so I did not want to lose any drive-ability. I opted for headers because I would get more torque, more horsepower and a deeper exhaust note. Three wins.

There are plenty of headers for the S54 to choose from. Do I go with aftermarket headers from a world renowned manufacturer such as Super Sprint or do I go with an OE upgrade such as the headers found on the M3 CSL? I spent a lot of time researching on the M3Forum discussion boards and found that pretty much any aftermarket header will gain considerable power. This is because the North America spec E46 M3 had the catalytic converters built in to the header, restricting top end power.

All other markets received race-style inconel headers from BMW with the cats positioned further down stream on the section 1 pipe. That’s the pipe that connects right after the headers.

While looking for options I found $400 headers on eBay and other options north of $2k. The difference seemed to boil down to fitment and small difference in peak power gains.

Make no mistake, replacing the factory S54 header with anything aftermarket will only yield more power on the far end of the tachometer. In my research, I found that differences never amounted to more than about extra 5 peak horsepower at redline and 5 torque in the mid range. I’d consider myself in-tune with my car and there’s no way I’m noticing that.

With that, I opened to for the guaranteed fit of the factory headers found on the European M3. These are essentially the exact same design used on the M3 CSL, but made of a thicker material so they aren’t quite as lightweight.

S54 Euro headers vs USDM header comparison

I found my set from the M3Forum classifieds for under $600. Next was to find a section 1 pipe with cats. The European section 1 is the most popular as well because it is a direct fit and is about half the cost of an aftermarket pipe.

But then I had to purchase all of the random nuts, bolts and gaskets for the installation. I had no idea that nuts and bolts were this freaking expensive so be sure to find somebody with a BMW Car Club of America membership if you plan on buying from a dealer. I recommend ordering the header installation kit from ECS Tuning and all new oxygen sensors from Rock Auto. No, oxygen sensors are not required but you do not want to do this job twice if one of them goes bad or is damaged during the installation. And replace the leaking PCV o-ring while you’re at it.

Josh's 2004 M3 on the dyno

I scheduled the installation with Frank Smith at his small shop in Maryland called Tuning Tech FS. I arrived bright and early to start the day with a dyno run so that we could baseline the car’s power at 163k miles and measure actual horsepower gains after the installation and custom tune.

For reference, a stock E46 M3 will typically put down 280 horsepower, give or take a few. My car, with factory headers put down 300! Frank informed me that my M3 already had a tune (unknown tuner) and its confirmed because the factory ECU will not let the engine run past 6500 RPM on a dyno. Whatever the tune, Frank informed me that my car was running rich on the top end.

My car was up on the lift at 9 AM and by noon the stock headers were on the floor. Shortly after 2 PM the European headers were installed and the remainder of the exhaust remained as it came from the factory. Yes, that meant catless.

Buttoned up and strapped back on the dyno it put down 310 horsepower and 254 torque. That’s a solid 10 horsepower and torque gain with the unknown tune. Not too bad, but now it was time for Frank to work his magic.

For the post-Frank Smith tune, I present the following video. Dyno runs are loud. Sorry for the audio quality. This and all of the photos were taken with my HTC One.

With Frank’s tune it made 325 horsepower. That’s a gain of 15 horsepower over the unknown tune.Back on the road, my M3 drove every bit as well as before, only now the exhaust was noticeably deeper, a bit louder and raspier — okay, a lot raspier! I’m sure much of this had to do with the catless setup, but if you hate the rasp for which the E46 M3 is known then you won’t like this one bit.

E46 M3 Dyno with Euro Header
The dip in power which I originally found at 3k RPM is no longer present. Instead, it is buttery smooth pull all the way to redline. Mid-range power feels about the same. The top end of the power band is crazy, pulling well past 8k and all the way to the new 8,400 redline like a banshee!

What’s more is that Frank also included his software for the SMG transmission. This really tightened up the shifts and eliminated the uncertainty of the gear changes I had become accustom with the factory SMG software. Frank, Kyle, Dave and Tuning Tech team did a fantastic job and I couldn’t be happier with the results! Be sure to check out my BMW M3 and all the modifications on WheelWell.com