Exhaust manifold material and design question

[beaner]

I've decided to build my own manifold instead of buy one. I'll be running a 37r with a t3 inlet. From RRE I bought the mild steel head flange and turbo flange, so I just need the piping for the runners. I've deleted the ac and switched to a half radiator. The bumper (not cover) has been missing for years, so there's TONS of room for me to do what I want, which is basically a straight shot with very little bending needed for the runners, each being about 12" long.

1.75" ID is a perfect match to the head flange. When porting out stock manifolds, it's always been my understanding to port the runners out larger instead of a perfect match up, creating a small step in the interest of preventing reversion. Does this mean I should go with slightly larger ID piping?

Every manifold I've seen has the turbo flange not parallel with the head flange. All I can seem to find are manifold designs where the runners have to do at least a 90 degree turn. Wouldn't a straight shot design be superior?

I've searched around for piping and this looks to be good... Any thoughts?

 

[mitsuturbo]

I'm pretty sure mild steel will take a dump on you before long.

 

[mountaineerjeff]

the main reason to not have a straight shot header, is to save space. there is no reason not to do it like that, is has been done, just not typically on 4 cylinder cars.

As far as the step question, are you sure the flange you have isnt already slightly stepped from the head? it may be an exact match, but you might already have the hard work done.

 

[JNR]

If we had the room, it would be great to have the primaries come out as straight as possible, for a reasonable length, bend down, then a long merge collector. Unfortunately this is not possible the way our engine bays are setup...

Whatever you do designwise, I would get the biggest wall thickness of steel (prefer. SS) and then coat it real good, to keep the heat inside as much as possible, since this heat energy plays a vital role in an effecient turbo.

 

[TylerAdamson]

Quoting mitsuturbo:
I'm pretty sure mild steel will take a dump on you before long.



He'll be just fine with the mild steel head flange. A lot of guys build manifolds with mild steel flanges and ss sch.10/40 pipe. Its very cost effective and will last just as long and at less than half the price.

 

[mitsuturbo]

the link provided was for mild steel pipe

 

[TylerAdamson]

Even so, mild steel will be just fine for his needs, but SS sch.10 and MS sch.10 is generally the same price. I'd also recommend Columbia River for the pipe. From my experiences they usually have the best prices.

 

[beaner]

Turns out the RRE head flange is slightly stepped compared to my head (thanks jeff). 1.81" ID is what I figured out. The pipe I found was 1.875" ID so it should be perfect size.

The reason for going with mild steel pipe is because everything else is already mild steel. I know different metals expand at different rates so it's just asking for a failure to mix it up.

Appreciate the replies.

 

[mountaineerjeff]

no prob /ubbthreads/images/graemlins/grin.gif
now make some ridiculous fast spooling header so i can beg you to make me one after you do all the hard R&D /ubbthreads/images/graemlins/wink.gif

 

[beaner]

The tube arrived today. It looks huge to me and weighs 23lbs. I got 5' of it, will probably use 4', but between that and the flanges it's going to be a brick. I wanted to do some minor sand bending to help things line up properly, but just by looking at this it's probably impossible. I also wanted to make a bracket from the front of the block to the turbo, so there would be no stress on the manifold, but that's looking completely unnecessary now.



Does this seem excessive to anyone?

 

[TylerAdamson]

What's he wall thickness on the pipe?

 

[JNR]

Is it tube or pipe? If it's pipe, looks like schedule 80 maybe? Hard to tell in the pics but almost looks like 2" pipe. Ought to keep the heat in real good though, so should be nice when it's done. Besides, as long as your welds are good at the flange(s), you won't need to be worry about any cracking!

 

[mitsuturbo]

Any of you check the link in 1st post?

if he bought that, it's as follows


OD 2.25"
Wall 0.188"
ID 1.875"


Looks about right to me.

 

[JNR]

Missed the link...so, assuming that's what he ordered, it is tube and not pipe. The two terms are not interchangeable, although it's one of those common things people do, I guess.

Fwiw, 2" pipe is 2 3/8" OD with .218" wall (sch 80), so I was close /ubbthreads/images/graemlins/grin.gif

 

[beaner]

I've been googling about this project like crazy and realized "pipe is for poop". So yeah, it's tube.

I'm going to rethink my design a little, but I guess I'll just use what I got. All the cuts will just have to be more precise which isn't a bad thing at all. I've been using cardboard tp rolls trying out different designs. The ID on those are insane close to the metal tube's, so whatever I figure out with those can be pretty much exactly copied over to the metal. Rock on.

 

[JNR]

Pipe for poop...lol. Nice thing about smaller sizes is tube is more common, as far as getting various OD, wall thickness, material, etc...Pipe is a little more limited. Fittings like ells are smaller generally (pipe has short and long radius, but can be quite long center to center)...Did you get your elbows and such already? I think once you get it all welded up (thick enough wall to chamfer the circumferences and do nice butt weld) and cleaned/coated, should look pretty cool and as I mentioned above ought to make for a nice retention of the heat and such. The fun part will be mocking it up and trying to get the nice bends, but straights/merges too...You gonna run an external wastegate and take it off the collector area? Like to see some pics later, for sure.