When it comes to extracting more power from BMW's S54 engine found in the E46 M3 and Z4 M, there are several proven go-to options. Sure you can add a muffler, under drive pulleys and other reasonably inexpensive bolt-ons but if you want measurable butt dyno results your options are essentially headers, gears or forced induction. I knew I wanted to stay naturally aspirated because my M3 is my only car so reliability was 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.
My second choice was to actually choose a header. And there are plenty 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 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 right from BMW with the cats down stream on the section 1 pipe. That's the pipe that connects to the headers. The BMW engineers spent a shit ton of time developing the exhaust system for the S54.
Okay, so what's the difference between a $400 eBay special and a $2k Super Sprint header? Well, it seems to boil down to fitment. Different header designs yield slightly different gains in the power band but what I found was that it never amounted to more than about extra 5 peak horsepower at redline or 5 foot pounds of torque in the mid range. Price played a huge role in my decision so I opted for the guaranteed fitment of the factory headers found on the European M3. These are essentially the exact same design used on the M3 CSL, only not as lightweight.
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. 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 to 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.
Parts are in so we're ready to go. My M3 now has 163,000 miles on it but we're doing this anyway.
I schedule for the installation to be done at a small shop in Maryland called Tuning Tech FS. I arrive at 8 AM and meet up with Kyle at TTFS. We begin with a base dyno run so that we can see actual power gains before and after the installation.
A factory spec M3 will typically put down 280′ish horsepower. As it turned out, my car already had some unknown tune. We know this because an unmodified ECU will not let the engine run past 6500 RPM on a dyno and the fact that it made 300 horsepower! I had no idea my car was previously tuned but it made pretty good power. Frank tells me whatever the tune, it was running rich on the top end.
Read the original article here (opens in a new window or tab). On to the header installation. This takes some time and patience meaning I didn't do it. David Foerster, a local guy known for header installs and valve jobs, had the pleasure of turning wrenches. Dave also owns a beautiful Laguna Seca Blue M3.
Dave began working around 9 AM and by noon the stock headers were on the floor.
Finally the European headers were installed and the remainder of the exhaust remained as it came from the factory. Button it all back together and roll it on the dyno. But not before eat some crack chicken with a side of crack hush-puppies.
Back on the dyno it put down 310 horsepower and 254 torque. Ten and ten. Not too bad but there's gotta be more in there, right?
Here we see Frank doing work. I think it's the crack chicken that gives Frank his magic tuning abilities.
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 on the first run and 320 on the second. That's a gain of 15 horsepower over the previous unknown tune and plus 25 on the day.
So how does it drive? It drives every bit as well as before, only now the exhaust is a bit louder and raspier. Okay, a lot raspier. And it seems to come on at lower RPMs in between multiple RPM windows and loads. If you hate the rasp for which the E46 M3 is known then you won't like this one bit.
As far as power goes, the deliver seems to be smoother. The dig 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 very noticeable. The S54 now sprints to 8400 RPM like a cheetah. Why in the world couldn't BMW have given us an M3 like this from the start?
Frank also gave me their CSL software for the SMG transmission. This really tightened up the shifts and eliminated the uncertainty of the gear changes 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!