Exhaust manifold work

[JGood]

I'm starting work on making the e38 manifolds fit. I've never done any exhaust work before, so this is yet another complicated adventure for me.

What size tubing is everyone using to mate with the e38 headers? They are double wall, so for space reasons, it seems best to match the OD of the inner pipe. From what I can tell, it seems like 2.5" would be best. Is anyone using 2-1/4"?

Is the best option to just order a couple 90* or 180* 16 gauge stainless mandrel bends, and start cutting and fitting? If so, what are some cheaper sources? Jegs/Summit seem priced awfully high for some of their stuff... Is there any difference from one brand to the next? Seems like they are all 304 stainless.

My space is even more limited then most as my engine is using the further forward mounting position, which cuts down on the space between the rack and the wide bell housing, in addition to using the e36 rack. It looks like it's going to be damn near impossible!

[JGood]

Actually, after adding up how much this is going to cost, I don't think I want to go with stainless. Mild steel will be about a 1/4 of the cost. Thoughts? Will I be OK welding mild steel to the factory stainless pipe with MIG, using 75/25 gas? Should I use stainless wire?

So far my shopping cart is as follows:

2 x 2.50" Aluminized Steel, 3.75" Radius, 90 Degree Mandrel Bend
2 x 2.50" Aluminized Steel, 3.75" Radius, 45 Degree Mandrel Bend
4 x 2.50" Mild 2 Bolt Universal Exhaust Flange
2 x O2 Bung - Mild Steel
8 x 2.50" OD, 16 Gauge, Mild Steel Straight Tube, 12"

$138.46 (From Columbia River Mandrel Bending)


I think that would be enough to get me towards the back of the car at least, then I can figure out muffler packaging later.

[Farbin Kaiber]

Maybe buy partial cut scraps from a local manifold builder?

[bmwmech1]

Call me tomorrow before you buy anything and I'll give you the skinny...

Garey

[Garageaholic]

I'm doing 2 x 2.25" pipes connected via x-pipe. I'm doing aluminized tubing to keep costs down.

Yes, the manifolds are dual walled. I welded the factory headers tonight and sealed up the twin walls. I had no problem with my 75/25 gas with steel wire.

I heard that dual 2.5" will rob of low end power. It's all about horsepower and I think that 2.25" is perfect for the application. I haven't bought anything yet though.

[Jean]

Call me tomorrow before you buy anything and I'll give you the skinny...

Garey

Garey , post here :)

[battlecattle]

X5 4.4 Manifolds

"Modified X5 4.4 header on the driver's side to clear the steering linkage, and a stock X5 4.4 header on the passenger'e side"

[Jonsku]

I'd be very scared driving around with that rubber joint on the steering linkage...

Exhaust manifolds are easy to modify from X5 (in the previous post the second picture is of something else than X5 manifolds). RHS bolts directly on, LHS needs couple of bends and that's it.


What E38 year model are the exhaus manifolds from (4-2-1 or 2x 2-1)?


Regarding rest of the exhaus system, in my white V8 cabrio the exhaust is 2 x 2,5" - X pipe - 2 x 2.5 => 2 x 2" - resonators - rear muffler.

In the latest project it's similar to previous one, but this time all the way with 2x2" and SS.




Personally I've found that kind of setup very good indeed and the sound is very kick-ass (bad video with ok-sound http://www.youtube.com/watch?v=YAhC2...slkhZWCrrlk98W )

There's no need to go over 2x2" if you are not planning to do additional work on the engine. Single 2" pipe is more than enough for 2 litres / 150hp ..

[Jean]

Josh - is that with E30 or E36/Z3 rack?

[quickervicar]

Justin,

What my friend did was use a heat gun on thin-walled PVC tubing of the correct size. Heat & bend to form your primaries. Then take the pieces to Red Run Auto over by Twin Pine. They were very kind and good about forming them to the plastic examples. We only had a couple pieces to bend, but if you've got 8 or 10, you might want to number them and drop them off so they can squeeze them in during their downtime.

[battlecattle]

Josh - is that with E30 or E36/Z3 rack?

E30 rack

[bmwmech1]

Garey , post here :)

Jean, there's a exhaust supply company close to us here, down in Maryland, that sells all sorts of mandrel bent exhaust tubing, flanges, hangers, etc., that I used as a source for all the exhaust stuff I needed. Since they're so close to us here, I thought I'd give Justin a heads up, before he spent more money than he needed to getting stuff from Jegs or Summit. I don't know if they would be a cheap option for you, being on the West coast, though. They have a storefront on ebay, though, if you want to check and see. It's Mandrel Bending Solutions... they have everything I used, except for the 3" to 2.5" collector reducers, which I got from Corvette Central. Now you all have the skinny, lol...:)

Garey

[einarsss]

what is the diameter of the pipes welded to the x5 manifolds? :)

[JGood]

what is the diameter of the pipes welded to the x5 manifolds? :)

The X5 pipes aren't really a normal sized, perfectly round pipe, it's just a stamped steel cover over top of two odd D-Shaped internal tubes. There are a few options as to how you want to modify the header.

I chose to cut it flush, weld all the bits in the end together like Frank did, then use the stamped ~2.75" pipes I cut off, to form the rest of the manifold as required. I ordered a 3" into 2.5" collector reducer with a 3 bolt flange on the end, which will get welded onto the manifold. So I actually didn't need to buy any pipe for the driver side. Not sure how the passenger side will work out yet, but I think I'll be able to do something similar over there, and not need to use any additional pipe.







Yes, I know, this looks like ass. The only reason I'm OK with that hard bend at the end is because I probably increased the internal cross section enough by gutting the pipe that it won't restrict flow too much. I spent 2 hours cutting, grinding, fitting, tacking everyhting in place, then spent about 5 minutes welding it all up outside the car.




This made the job a LOT easier. Picked it up on sale at Harbor Freight for $100. They have a cheaper version for $50, but I find that typically if there is ever a "heavy duty" and normal version of something at HF, you don't want anything to do with the normal version.

[einarsss]

ok, thanks for the info :)