3.0i Header Options

[trentcdrums]

Thanks for this info! Solid work.

I need to replace my cats and I am leaning more towards not doing headers because of the smell etc. I hated it on my e46 at stop lights

I am more interested in hearing about the removal of your stock cats. Any special process?
Did your studs come out with the nut as well? Clearance issues?

[e39_touring]

I highly recommend doing headers even if you integrate cats as the stock manifold/cat combo is VERY restrictive. Maybe some of the aftermarket manifolds like pacesetter or magnaflow are better. I'm easily getting 10% better MPG's now and quite a bit more power in the mid to upper RPMS.

If I were to integrate cats, I'd use the same headers I got as they fit well and seem very well built. I'd cut the center resonator out and merge the pair of pipes into something like a single 3" cat and then Y it back out to the pair of pipes that goes on to attach to the rear mufflers. It's a straight shot, and you could probably even do it without welding if you don't mind a few extra clamps down there.

But, to answer your question on removing the manifolds, it's not that hard but is tedious. The sway bar and reinforcement plate need to be removed. My car doesn't appear to have ever seen salt, and all nuts/bolts were pretty clean so YMMV.

I don't know if it's required, but I did remove all O2 sensors first. Getting at all the nuts on the head was the tedious part. Some came off in a minute or two while others took 1/2 hour each. Have lots of extensions, wobble extensions, universals, short and deep sockets, etc., handy. They're not that tight and 1/4 ratchet worked for me on most of them even if I had to break it with a box end wrench. I'd say 1/4 to 1/3 of the studs came out with the nut. It's no big deal once the stud's out, just spin two regular nuts (M7) on and back off the bronze lock nut. Then do the same to spin the stud back into the head. I did about a third of them from above and the rest from below. The front manifold will come out first and then the rear. Both have to go out the bottom.

That's all I can think of - good luck!

[trentcdrums]

Originally Posted by e39_touring

I highly recommend doing headers even if you integrate cats as the stock manifold/cat combo is VERY restrictive. Maybe some of the aftermarket manifolds like pacesetter or magnaflow are better. I'm easily getting 10% better MPG's now and quite a bit more power in the mid to upper RPMS.

If I were to integrate cats, I'd use the same headers I got as they fit well and seem very well built. I'd cut the center resonator out and merge the pair of pipes into something like a single 3" cat and then Y it back out to the pair of pipes that goes on to attach to the rear mufflers. It's a straight shot, and you could probably even do it without welding if you don't mind a few extra clamps down there.

But, to answer your question on removing the manifolds, it's not that hard but is tedious. The sway bar and reinforcement plate need to be removed. My car doesn't appear to have ever seen salt, and all nuts/bolts were pretty clean so YMMV.

I don't know if it's required, but I did remove all O2 sensors first. Getting at all the nuts on the head was the tedious part. Some came off in a minute or two while others took 1/2 hour each. Have lots of extensions, wobble extensions, universals, short and deep sockets, etc., handy. They're not that tight and 1/4 ratchet worked for me on most of them even if I had to break it with a box end wrench. I'd say 1/4 to 1/3 of the studs came out with the nut. It's no big deal once the stud's out, just spin two regular nuts (M7) on and back off the bronze lock nut. Then do the same to spin the stud back into the head. I did about a third of them from above and the rest from below. The front manifold will come out first and then the rear. Both have to go out the bottom.

That's all I can think of - good luck!

well that's great information to know. I was kind of hoping that you would tell me it's not worth it but now you have me leaning towards getting headers again. Can you elaborate a little bit on the smell from the car. do you have to always keep the windows rolled up and would it be to the point where my neighbors would be complaining as my car is on idle?

Did you also do everything by yourself or did you get help?

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[e39_touring]

Originally Posted by trentcdrums

well that's great information to know. I was kind of hoping that you would tell me it's not worth it but now you have me leaning towards getting headers again. Can you elaborate a little bit on the smell from the car. do you have to always keep the windows rolled up and would it be to the point where my neighbors would be complaining as my car is on idle?

Did you also do everything by yourself or did you get help?

Sent from my Pixel 2 XL using Xoutpost.com mobile app

I imagine the smell would be the same as your old e46. In the e53, you're a little farther away, but if the air is stagnant, I can see it wafting up front or to the car behind you with the windows down. Nobody has ever mentioned to me that my car stinks, but it's rarely stagnant around here.

It's definitely a one-person job, not really room for two.

Regarding the CEL, if you don't have emissions, it's very easy - just flash it with the BMW EU2 calibration (can be done using all BMW tools - basically makes the car euro spec). If you do, it's a little more involved as you have to do a custom tune that turns off the post-cat sensors so it doesn't throw a code for those. In either case, the front sensors are still used and the mixture is correct. The rears are only there to monitor cat efficiency and make very minor fuel trim adjustments if the front sensors are a little lazy.

[lo_jack]

I am definitely doing this the hard way. I got headers that look like they are the same as those pictures until the flange...I don't have any flanges. I am adding cats there, so I chopped down the headers and MIGed on some vbands. Tonight I hope to weld vbands and 02 bungs onto my new 400 cell cats, and then I can put the front section back on and see if it runs. I haven't run it in a long time.

I have been having a deuce of a time getting the new studs in the head with the two nut method. I get them in, but then when you expect to feel the stud bottom in the hole, the second nut will start turning as well so you never really feel them hit--even though they are probably threaded all the way.

The cat on my daily driver is hitting the end of life. It smells awful, and it's a tin can VW with a 2.5. I can't imagine an m54 with no cat. Probably reeks, and should come with a Prop65 warning.

[trentcdrums]

Originally Posted by e39_touring

I imagine the smell would be the same as your old e46. In the e53, you're a little farther away, but if the air is stagnant, I can see it wafting up front or to the car behind you with the windows down. Nobody has ever mentioned to me that my car stinks, but it's rarely stagnant around here.



It's definitely a one-person job, not really room for two.



Regarding the CEL, if you don't have emissions, it's very easy - just flash it with the BMW EU2 calibration (can be done using all BMW tools - basically makes the car euro spec). If you do, it's a little more involved as you have to do a custom tune that turns off the post-cat sensors so it doesn't throw a code for those. In either case, the front sensors are still used and the mixture is correct. The rears are only there to monitor cat efficiency and make very minor fuel trim adjustments if the front sensors are a little lazy.

Wonder with the angled adapter of you used them for the post 02 sensors if the light would even come on!!?


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[lo_jack]

Did any of you chase the manifold stud holes? I know they are 7mm and most go in no problem, but the ones that never had a stud before are a bit belligerent.

[trentcdrums]

Originally Posted by lo_jack

Did any of you chase the manifold stud holes? I know they are 7mm and most go in no problem, but the ones that never had a stud before are a bit belligerent.

Not understanding what you're referring to when you say the ones none had a stud in? Should they all have studs in them when you're removing them?

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[e39_touring]

Originally Posted by trentcdrums

Wonder with the angled adapter of you used them for the post 02 sensors if the light would even come on!!?


Sent from my Pixel 2 XL using Tapatalk

Certainly worth a shot - it's cheap and easy and others have had success with this method. I would guess the longer the adapter the better, and I've also seen some with restrictors (smaller hole into the exhaust pipe).