choice of material for turbo exhaust manifold
choice of material for turbo exhaust manifold
(OP)
I Have a customer who purchased an aftermarket turbo exhaust manifold constructed from 321 stainless. It needs a few changes and repairs to bring it up to scratch. Owner isnt too keen on having bits of metal that are falling off the welds inside going through his new $2500 turbo.
Due to the mods needed and the fact that the car will be driven VERY hard I would like to know what would be better, the 321 or build a new one from Steam pipe bends.
From the specs it seems that the 321 would be very good in this application, but i would like some first hand feedback.
Thanks,
Ken
Due to the mods needed and the fact that the car will be driven VERY hard I would like to know what would be better, the 321 or build a new one from Steam pipe bends.
From the specs it seems that the 321 would be very good in this application, but i would like some first hand feedback.
Thanks,
Ken





RE: choice of material for turbo exhaust manifold
What material are you talking about when you say steam pipe bends? if you are talking about the steam handling pipe from a boiler then I definatley would go with the 321, the exaust gas in turbocharged applications can get to temps >1500F and I just dont think that the mild steel used in boilerpipe would have the strength at temp to provide good design. (IE weight/strenght/durability) I do know that 439 adn 409 SS are also used in exaust design. I have a 439ss downpipe (on turbine exaust) on my car, while there is some redrust present it isnt excessive. I dont know what the factory headers are made of, proabably 439 or similar inexpensive ferritic grade.
RE: choice of material for turbo exhaust manifold
Steam pipe made from thick wall mild steel tubing, with cast steel bends, will have less expansion than stainless. The thicker walls and higher ductility can also make it less prone to cracking.
Stainless is probably better for a long runner light weight racing manifold where large radius sweeping compound curves can allow enough stress relieving flex.
Steel may be better for road cars with a tight compact layout, (and low internal gas volumes). Weight is also a disadvantage, but for an everyday road car manifold weight probably does not matter quite so much.
There is probably no right or wrong answer, it is more of a judgment call really.
RE: choice of material for turbo exhaust manifold
It is a road car, mainly a weekend blast through the hills type.
4 cyl Nissan i think, and is a very compact manifold. Customers main worry is if it could crack or not.
Cheers,
Ken
RE: choice of material for turbo exhaust manifold
RE: choice of material for turbo exhaust manifold
Either way it will be like starting from scratch, thus the reason for my original question.
Another question, How does 304 ss handle duties as exhaust tubing? not for turbo application.
Ken
RE: choice of material for turbo exhaust manifold
RE: choice of material for turbo exhaust manifold
We have been building both wet, dry and combo exhaust systems for diesels for about 20 years.. All types, sizes and shapes from 5 HP engines to 600++ hp engines used 1000's of hours per year--Maybe 500 systems over the years and just a small handful of re-do's during that time...
Although we do not build the manifold itself (we build the riser/adaptation sections after the turbo/manifold), both 304L and 316L has shown to give very good long term service with internal temps between 300 and 1400F... Obviously design and the quality of construction plays a big role in how well these exhaust components hold up, but I'd give my vote to these common alloys if the rest is right..If you drop me a note, I could send you pics of 100's of exhaust components we have fabricated over the years to help in your decision on what to do..BTW, we do use 321 for our flexible "bellow" sections, and if we have to mix SS with mild steel, we use 309 to weld them together.........................Tony
Tony Athens
http://www.sbmar.com