Its a mild steel manifold, which i chopped up and pieced back together to suit my application, (a RHD 1st gen). The welder guy had a hard time because of the awkwardness of the job, but although not as pretty as it could be, the welds are deep and strong and i have faith in them.

Its just the shape - the runners are actually only about 1.5 - 2" different in length, but because he had to fill the gap between the two with weld where he couldnt get his tip in ( i told him to), one leg is effectively twice the length of the other where they arn't actually joined together, which makes me wonder how it will hold up once it gets a few heat cycles into it.

Will it be ok? I was thinking to maybe cut a "gusset" for want of a better word , out of 6 or 4mm plate to fill the negative space between the two runners, thinking maybe that would allow the whole manifold to "grow" as one, but maybe that would be worse? Im imagining the whole thing, apart from being more solid, would act as a bit of a heat sink and allow the flange plate to expand with the whole thing? But maybe it will also cause the plate to warp?

My other idea, going in the complete opposite direction, was to cut the weld between the two runners with a hacksaw to give the whole thing more room to move? I dunno. Im looking forward to others opinions on this, was actually going to ceramic coat, but not if its going to crack.

 

Also wondering if bracing is a good or bad idea. I used this brace just to hold the manifold together when i was tacking it, but it actually looked pretty good. Should i put it back on or not?

 

Laymen, anyone. Feel free to discuss, speculate, flame.

 

first of all what size turbo are you using will make a difference.

I am a welder and I see he (welder) filled a lot of gaps . Cracking will be determined by the heat cycling and how consistent the welds are on the first pass.

with it pieced together like that might hurt flow. the additional bracing may not be necessary all depends on the size and weight of new turbo.

hybrid

 

Design wise its fine. I wouldn't use the brace. If you want to brace it, you need to add the brace to the top of the turbo, to support its weight. Generally those manifold braces just crack. It appears there are both MIG and TIG welds there? The mig welds are the weak link. Hopefully it was back purged.

 

Thanks guys, flow wise it should hopefully be pretty good , as i die ground all the joins either before or after i tacked it( depending on where the grinder was going to fit) and paid special attention to fit and radii. and will go over the ones near the flange again, all the other joins are smooth as a baby's bum.

The turbo is T04Z size.

As to the welds, yeah, the wastegate runners are migged, they were done at an earlier time before i changed my mind on the turbo position.
The welds the guy did the other day, im not sure, but they are a bit rough and to be honest, he smelt like beer when i picked it up, lol. In all fairness though, it was a ***** of a job, and at least one of those welds are actually TWO welds, where i had a thin wedge segment ( maybe 6mm down to 1mm at the shortest end) in there ( rear runner, near exhaust flange).

You should see the welds he did on my aluminium radiator though - they are GORGEOUS. Hes like 60, welding is all he does and the machine he was using is the size of an industrial diesel generator.

And ok, thanks for clearing that up on the bracing, if i brace i will do maybe a pendulum arrangement from the UIM or something, i actually put a flexible hanger on the dump pipe to the LIM which might help a bit too.

Any thoughts on cutting in a buttress basicaly filling tho whole negaqtive space in between the two runners, maybe say 4mm plate? Good idea, bad idea, or just not necessary?

 

Any thoughts on ceramic coating the inside of exhaust manifolds?

Here are some pics of my down pipe just for laughs. Its only 3". If it turns out to be too restrictive I might try and squeeze a 3.5" in and merge the gates in further down the exhaust.
Please forgive the atrocious welds. I actually had to redo those two runners because of the warpage when i welded the merge. No-one will see it though, i'll get someone else to weld the visible parts.
Also i fucked up a little bit where those two pipes insert into the merger, they stick in to far and ones cut a bit weird.
I put a twist in the way the merger meets the main pipe to help facillitate the clockwise rotation of exhaust from the turbine. I dunno if that is something people do, the idea came to me in an opium dream. Hard to tell from pic but they are biased in one direction where they merge, and the one on the right of pic is a bend.

 

No it isnt. i didnt think purging was necessary on mild steel. Oops. Is this a worry?

 

I think if it will crack it will be because of the different length of the runners and the fact the the collector is really stiff..

a fix when it cracks due too thermal stress/cycling could be to use a slip joint on the rear runner just after the wastegate outlet. use a lathe and make a slip fit with some negative clearance. then heat the outer part, press it on the inner part and then weld it to the manifold where now the straight piece of pipe is after the WG outlet and before the bend at the collector.

this way the weight of the turbo will be just on the front runner, but with proper bracing it should be fine.

 

^ thanks man, that is an excellent idea, and actually was going to do that when an engineer i was talking to a while back suggested the exact same thing. I ended putting that idea in the too hard basket though because of the lack of clean space on the rear runner, lack of ready access to a lathe, the fact that i had already (painstakingly) tacked the thing together to fit perfectly in the car routed wastegates and all and because it was already such a frankenstein's creation, lol.
So for now im just kinda hoping that being mild steel it will just anneal itself, and if it cracks I'll either repair it or make a new one from scratch out of an appropriate grade S/S, with your slip joint designed into it if necissary.

A quick question; Iv noticed that many exhaust flanges on the market have material removed from between the inlet holes- makes me wonder if doing something similar would help with relieving stresses and movement from the unequal length runners or at least help seal around the gasket and maybe help minimise heat transfer from the flange to the engine block?

I was thinking to cut out the area i marked (roughly, for illustration purposes)
Yes or no?

(i still need to get the flanges surfaced too, they are a bit out of flat)

 

How big of gaps did he have to fill? How thick was the tubing?

I don't think there is anything wrong with mild steel, but I still would have purge welded it. I was told mild steel resist high heat better than 304ss

 

The gaps were pretty good, believe i t or not. Biggest was maybe 1mm, and all the edges bevelled, tubing is about 4.4mm.

 

He has it right here with back purging.


You want 100% penetration of the weld, you want to clean each joint well and get all the contamination out. Shielding gas (purge) is important not to have an oxidized weld. We don't weld much 10 series mild steel but we do 4130, 3 series, 17-4 steels and Aluminum.

Those welds would not pass minimum weld inspection criteria in Aerospace. If you have a good technique, the right weld settings, a nice clean part, and correct shielding gas (from both sides), you should end up with welds that are clean looking or have a blueish/bronzish tint to them.

Atleast that is what I am used to seeing. here is an example of what a good weld looks like.

Grey is not good and I would guess that the shielding gas was not sufficient enough. I am used to GTAW.


Cracks typically occur when the material is not welded completely through and a crack propagates through the weld, it can crack if the design puts the stress/strain on the weld joint itself and the weld joint isn't strong enough, or there is contamination/porosity/etc in the weld itself causing a weak spot.

In some of the pics, not how the weld areas were prepped, mechanically cleaned, you want to follow up with an alcohol clean or acetone or some chemical clean. (make sure sandblast material is completely clean). ensure you are using the correct weld rod for the material.

 

^ nice welds, and thanks for the insight. To be honest, i couldnt say the welds aren't purged but i dont think so.
Three welders have had a go at it, lol

SDR motorsports, who made me one of their 13b to sa22c manifolds, sans wastegate,
A guy who MIGed the wastegate runners and TIGed the v-band flanges
Another guy i found around the corner from me who welded my cut-and shut job

All the welds look deep - 85- 100% and have blue tinge to them, and are clean on the inside.

What should a proper back-purged weld look like on the inside?

 

Purge (shielding gas) is typically argon. It shields the weld from oxidation.

Here is a study performed on PPM (parts per million) of oxygen in the shielding gas.

Purge Pipe, Purge Weld, Purge Bladers, Weld Purging, Tig Welding, Welding Tools, from Jts-Pta