OBD2 Headers in an S50

[bmwstephen]

I know this topic has been beat to death so sorry to the OGs for bringing it back up but hoping to get a little bit more details that I wasn't able to identify.

Long story short, my headgasket on my s50 needs to be replaced and I figure I might as well get in there and do the top end gaskets too.

But is there a reason why I shouldn't upgrade to obd2 headers from the cast iron ones? A set just came up locally with some block off plats for the EGR ports. I know they are lighter and flow slightly better, but I don't intend to change the mid-pipe for emissions reasons (in Cali).

So will changing it out yield anything, nothing, (or possibly even killing some torque since everything on the intake side is stock)?

[RBNetEngr]

The midpipe on the S50 USA market exhaust is the problem area because it takes the outputs from the exhaust manifold and combines them into a single pipe where the O2 sensor is mounted. So you end up with some restriction at that point. The S52 exhaust has dual pipes the whole way back.

S50:



S52:




-rb

[bmwstephen]

yes thank you. am aware of the different mid-pipe design. So I guess if I simply just change the header, it won't do anything because the bottle neck of the s50 mid-pipe will just end up clogging it back up again

The midpipe on the S50 USA market exhaust is the problem area because it takes the outputs from the exhaust manifold and combines them into a single pipe where the O2 sensor is mounted. So you end up with some restriction at that point. The S52 exhaust has dual pipes the whole way back.

S50:



S52:




-rb

[bluptgm3]

Years ago, Dr. Gas created a “X” pipe for the S50 to replace the restrictive pre-‘cat’ merge, now long NLA.
However, a good muffler shop could fabricate something similar.

OBDII head pipes is a good change.

[cashmancab]

I have the S52 headers and midpipe on mine. If you need to replace your headers, I would go S52. I don't think you'll notice a difference without actual Dyno numbers but they are lighter etc. I track my car and have the shrick cams, custom tune, and S52 exhaust (245HP at the wheel). But I highly doubt my Butt dyno could tell the difference on the street.

[bmwstephen]

I have the S52 headers and midpipe on mine. If you need to replace your headers, I would go S52. I don't think you'll notice a difference without actual Dyno numbers but they are lighter etc. I track my car and have the shrick cams, custom tune, and S52 exhaust (245HP at the wheel). But I highly doubt my Butt dyno could tell the difference on the street.

did you end up welding the egr pump injection bungs? Or use block off plates?

[aeronaut]

The OBD2 headers are lighter, but do not flow better, than the OBD1 cast headers.

[pbonsalb]

Do you think CA would know if you swapped in an obd2 midpipe as well? Obviously plug the unused secondary cat port.

[bmwstephen]

The OBD2 headers are lighter, but do not flow better, than the OBD1 cast headers.

might have a valid point... at least the obd 2 headers just in itself as discussed in this video

BMW M50 S50 M52 S52 exhaust manifolds - what to use for more power - YouTube

However, OBD 2 headers are likely better flowing if you consider the midpipe as well

[cashmancab]

did you end up welding the egr pump injection bungs? Or use block off plates?

Just used block off plates.

[RRSperry]

I welded them up, then machined them flat, then had them Jet Hot coated, and used a OBD2 midpipe. The only issue was that the O2 sensor (single on S50) only read one bank of cylinders. It's never been a problem. The OBD2 mid pipe does flow better. IIRC it was about 5 Hp on a dyno Dynamics. I'm also sure that with a lot more dyno time and a good chip tuner, you could get more, but mine made enough and was very safe.

[bmwstephen]

will switching over to the obd 2 manifold require you to use the updated exhaust gasket too?

[bluptgm3]

will switching over to the obd 2 manifold require you to use the updated exhaust gasket too?

Same gaskets, new is always a good idea.