Headers Installed on our High Mileage E46 M3

"RightFootDown" (rightfootdown)
09/02/2014 at 16:46 • Filed to: e46, m3, dyno, tuned, header, headers

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.

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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 !!!error: Indecipherable SUB-paragraph formatting!!! 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 !!!error: Indecipherable SUB-paragraph formatting!!! 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.

Read the original article here (opens in a new window or tab).

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 !!!error: Indecipherable SUB-paragraph formatting!!! and all new oxygen sensors from !!!error: Indecipherable SUB-paragraph formatting!!! . 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 !!!error: Indecipherable SUB-paragraph formatting!!! . 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 280ish 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.

!!!error: Indecipherable SUB-paragraph formatting!!! 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.

Read the original article here (opens in a new window or tab).

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!

DISCUSSION (26)

Manuél Ferrari > RightFootDown
09/02/2014 at 16:57

"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."

Can I haz too?

BKRM3 > Manuél Ferrari
09/02/2014 at 17:08

Tons of software out there for the DCT homeslice! Check out BPM, people like what he does with that gearbox.

Manuél Ferrari > BKRM3
09/02/2014 at 17:13

For the DCT too? I was just thinking about the E46 for now! So many cool firmware upgrades to consider... Hmm. Screw it all, can we haz a E92 M3 GTS?

BKRM3 > Manuél Ferrari
09/02/2014 at 17:16

Yes for the DCT! Apparently it's a big change. I already thought that gearbox was pretty damn good, although I don't live with one as you know. Best part about that GTS is the stroker. Mmmmmmm, stroker.

AM3R > Manuél Ferrari
09/02/2014 at 17:21

you don't have any software for the SMG??

Manuél Ferrari > BKRM3
09/02/2014 at 18:11

And the factory installed roll bar is cool too :)

Manuél Ferrari > AM3R
09/02/2014 at 18:11

It's all stock!

syaieya > RightFootDown
09/02/2014 at 18:36

I have an honest question.

Is there any car that truely benefits from having those precats shoved up there on the headers? Couldn't they be fitted lower down, more accessibly and not ruin everyone's day when they go bad and cook everything in the general area?

AM3R > Manuél Ferrari
09/02/2014 at 18:37

Wow, I have no knowledge of ze E46 besides the fact that you own it. I could've sworn it was modded!

BKRM3 > Manuél Ferrari
09/02/2014 at 18:42

Yes, definitely cool but unfortunately it's only a half cage. These days I only really drool over full cages. Racecar problems lol =)

Manuél Ferrari > AM3R
09/02/2014 at 18:42

Haha no it's 100% mechanically stock!

AM3R > Manuél Ferrari
09/02/2014 at 18:44

Ah how about cosmetically? Black wheels amiright??

Manuél Ferrari > BKRM3
09/02/2014 at 20:12

But you can't use a full cage on the street, can you?

Manuél Ferrari > AM3R
09/02/2014 at 20:13

Yes they are very dark gray! And the front signals are smoked. The prior owner did those mods

BKRM3 > Manuél Ferrari
09/02/2014 at 20:21

I guess you could if you felt like it? I mean structurally it's safer than a car without a cage. I've never really thought about driving a car with a full cage on the street. I guess as long as the belts are ok with the DOT regulations then it should be all right? I don't think there's anything (at least in PA) that would cause a car with a cage to fail inspection...

Manuél Ferrari > BKRM3
09/02/2014 at 20:33

I think technically you would be allowed to. But from what I've read it's a bad idea for these reasons:

1. Full cages are dangerous when not wearing a helmet. Too much metal for your unprotected head to hit.

2. You need to use a harness with a full cage. Using regular belts lets the body travel too much during an accident. And travel is bad with all that metal surrounding you.

3. Racing harnesses are a bad idea on the street. You turn around to look behind you when backing up. And if you get in a wreck and your car catches fire it can be hard to get the harness undone and get out of the car in time. On a track there is safety personnel to get you out of the car if you are passed out or can't get out.

I've read so many racing blogs and the general consensus seems to be that it's impossible to have a road legal car that's as safe as possible on the road and track. You'll always be compromising safety in one area. The safest thing to do is have a track-only car and tow it on track day. But that's not as fun because you want to drive your performance car on the street too...

AM3R > Manuél Ferrari
09/02/2014 at 21:04

now it's all coming back to me!!

Manuél Ferrari > AM3R
09/02/2014 at 21:07

I still need to find dat post with the pics

BKRM3 > Manuél Ferrari
09/02/2014 at 21:30

I never said it was a GOOD idea lol. Just that it's not illegal! Cage is no bueno without a helmet and a HANS...but if I'm honest, I've seen people drive way sketchier stuff on the street, including old cars, street rods, muscle cars, etc that only have lap belts and no airbag. You're basically guaranteed injury in those puppies!

AM3R > Manuél Ferrari
09/02/2014 at 21:42

find it!!!!!!!

Manuél Ferrari > BKRM3
09/03/2014 at 01:30

haha true! And this reminds me of an idea I had the other day. If you had a full cage in a street legal car then you'd have an excuse to wear a helmet when driving on the street. You'd be The Stig!

BKRM3 > Manuél Ferrari
09/03/2014 at 06:50

The irony there is that THAT might be illegal. Greatly limited vision in a helmet!

Manuél Ferrari > BKRM3
09/03/2014 at 15:06

Haha probably. Damn it. There goes my plan!

FRP88 > RightFootDown
09/10/2014 at 11:11

I'd like to hear if you've encountered any issues with the SMG transmission. With people always saying, opt for the 6-speed, they wont break like the SMG, its gotten me worried about the reliability. 6-speeds have also gotten increasingly hard to find and there is an abundance of SMG e46's... i'm hoping its all just exageration

Scurvy > syaieya
09/10/2014 at 13:45

Cats work best when they are hot, they put them there typically to get them hot the fastest.

tlow980 > syaieya
11/03/2014 at 16:24

As scurvy says..they heat up faster there. Essentially, this only helps cold start emissions. Nice Job, OP. Interesting to note the Euro/header combo is more raspy then OE US set-up. I heard it's similar rasp but the rasp is slightly lower in tone.