Dedicated Exhaust Discussion

[hoveringuy]

As far as the flex, I'm thinking about doing one on each mid pipe, fairly close to that flange. Reasoning is that I'm pretty sure the stainless will move between tacking and fully welding but I'm open to suggestions, figuring this out as I go.

you don't want two flex pipes, because then it will flex. Constantly. And you'll be replacing cracked flex sections in short order.

You just need one, if any, so you can align the second flange.

[Striker01]

Ugh thank you so much for doing this. Great work, great pictures. Welcome to the "it's really hard to get a picture of this and explain to everyone what's going wrong" club. I LOVE the plate to align the flanges. I wish I'd done that. hoveringuy and I did a bunch of "do we need a flex on one side before they come together?" arguing, so we'd love your thoughts on that.

Is there any hope to match up to an existing catalog rear section or rear and mid?

I think you guys went into a single exhaust, if I remember correctly. My plan is 2" dual with an x pipe before the cats. I want it to match up to my M20 stromung catback. I didn't even look at any of the existing mid section stuff, figure any catalog option will need adjusting so probably easier to just start from scratch. I ordered a 2" "build your own" kit, 2 high flow cats, flanges for the front and a donut/flare connection for the rear. I'm hoping the flare donut thing will work for the rear as the stromung pipes are slightly smaller at 1 7/8" OD. Have to play that by ear as I go, I don't really want to modify the stromung in case decide to go a different route. As far as the flex, I'm thinking about doing one on each mid pipe, fairly close to that flange. Reasoning is that I'm pretty sure the stainless will move between tacking and fully welding but I'm open to suggestions, figuring this out as I go.

[hubcapboy]

Ugh thank you so much for doing this. Great work, great pictures. Welcome to the "it's really hard to get a picture of this and explain to everyone what's going wrong" club. I LOVE the plate to align the flanges. I wish I'd done that. hoveringuy and I did a bunch of "do we need a flex on one side before they come together?" arguing, so we'd love your thoughts on that.

Is there any hope to match up to an existing catalog rear section or rear and mid?

[Striker01]

I mean, that bend isn't the greatest thing in the world but it's not a big deal, either. Oxygen sensors have room, sway bar and CAB clear, room for AC.

This is legit, and I'm guessing it would be easy to duplicate if the motor was out of the chassis once you know where the flanges need to fall.

good job!!

Thanks! It should work fine, i did tilt the O2 sensor more toward the engine just to keep the cable clear of the firewall. I probably could've tried pie cutting sections out of the primaries to get the whole thing tucked closer to the block but this solution seemed easier.

[hoveringuy]

I mean, that bend isn't the greatest thing in the world but it's not a big deal, either. Oxygen sensors have room, sway bar and CAB clear, room for AC.

This is legit, and I'm guessing it would be easy to duplicate if the motor was out of the chassis once you know where the flanges need to fall.

good job!!

[Striker01]

Here is a shot from above




Clearance from the sway bar, about 1/2"



From the side, it doesn't hang down past the frame rail anymore and should give me plenty of room to work around the CAB for the mid section.

[Striker01]

Did some more work on the headers. The front set was just a couple cuts and took a couple inches length out.


Rear set took a few hours of messing with it in the garage. Multiple cuts, tacks, and re-cuts but I think I have them sorted.

Once I had it close to where I think it will work, I drilled a scrap piece of thick sheet metal to mount on the other flange. Clamped the flange to it and tacked it together.



I have no idea how that weird bend after the collector will affect performance but they fit now.

[JRowe]

Great feedback. Thanks for sharing.

[Striker01]

These header flanges point down way too far for my taste, they could also be much closer to the transmission. I cut the flange off the rear set so I could actually get them mounted flush on the head. I think the only work required will be behind the collectors. My plan is to get the front set turned towards the rear of the car and moved up and in closer to the transmission then pull the engine to get the rear set matched as close as possible to the front. I want both flanges above the CAB.





Lots of clearance between the frame rail and headers, about 1/2 between the headers and sway bar.


This flange is too low and pointed down too far.

[Striker01]

I finally got my engine arms and test fit the engine. The cheap headers I posted above are going to need some work to fit. First of all the primary tubes that fit into the head were too long on 5 of the 6 cylinders and required a little trimming.


The countersunk holes do not line up on all cylinders and will need some dremel or drill press work to get the nuts on and tightened.





These headers do try an occupy the space where the CAB is, treehouse type may be fine if you want to go that route.



Sorry for the poor picture here, hard to hold the header and get my phone lined up. With the flange against the CAB there is about 1/4 before the header will sit flat against the head. This rear set could've been tucked much closer to the front set.

[hubcapboy]

hubcapboy You have your files on Google drive or something, right? Can you host this DFX?

https://drive.google.com/file/d/1jH2NTVyfXpbvH98rMXtXlgL9ND-waoTZ/view?usp=drivesdk

it’s in my master DXF file I linked from the other thread. I didn’t want to link directly because I didn’t want it to look like new work , but here it is. This has everything I’ve drawn and ordered that shows up in my posts… if anyone wants a specific part they’ll need to copy it out with a dxf editor.

[hubcapboy]

A solid option might be to get a set of N52 euro headers and de-cat them. Or you could probably even leave the cat...

Why didn't the US get these, I don't know.

I chased these for a long time. I don’t think they were on *many* n52’s in Europe. They certainly didn’t seem to be the default. I’ve ordered a lot of car parts from very weird countries just to see if they’d arrive, and I was never able to source a set of these.

[hoveringuy]

Here is the DXF for the header flange I created for my equal length headers. The three exhaust ports are about .015" undersize for my design because I put them on a fixture and bore them to exact dimensions. However, they could be used to attach to a set of S54 headers and work just fine. I had my flanges laser cut from 1/8" 304SS, but whatever works for your application will probably be suitable. I have always used OSHCUT for my laser cutting and now they do bending as well. I haven't had any problems with quality from OSHCUT and haven't needed to consider using another supplier.

Well.... I tried to post the DXF for the header flange, but the website won't allow me to do it. Would someone let me know what needs to be done to share this DXF to Rev. Thanks!!

hubcapboy You have your files on Google drive or something, right? Can you host this DFX?

[Striker01]

Did some digging for the euro part numbers today and found these:

18407568613 & 18407568614

Nice work. I searched ebay.de for every N52 vehicle and never came across those.

I can confirm the cheap AA look alike headers fit fine with the Z4 arm. The left side mount is scheduled for delivery this Friday, depending on my son's soccer schedule I may test fit the engine this weekend.

A couple things to note, these headers came with standard style flat gaskets, not sure if I should use them in addition to the donut ones or just stick with the donut gaskets. The additional gasket will help with clearance for the bell housing bolt hole on the block. The countersunk holes look like a few of them will need to be enlarged to get the flange nuts to sit flush.

[FredK]

Also stumbled on this nutjob with a homebrew Locost project that seems relevant. Dig deep for an ITB adapter as well...

That's quite a lot of work! Pretty freakin cool Locost, I love seeing these extreme DIY projects.