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View Full Version : Tubular Vs Cast Manifolds?



C
12th March 2004, 10:50
Right got a situation & im trying to source a manifold for my Evo.

Now I know this is a Subaru forum but i'm trying to draw on peoples general experiences with them...

Originally I was going for a tubular design, specifically for my car (primary length, diameter etc etc) all based on knowledge of turbo, headwork, cams, anticipated power levels etc.

But!, 1 it doesnt fit :( by quite a way (need custom radiator etc to make it work) & 2. I keep hearing more & more horror stories about tubular manifolds cracking under heat & stress?

The HKS turbo kits are apparently appalingly bad, people bring them in covered in welds etc..

Now know I can resolve this with a cast manifold & people are reworking the originals to have a garrett flange & also porting them to flow more air.

But - has anyone got an experience of problems with cast designs?

Ideally I want a fit & forget part smile.gif

nom
12th March 2004, 11:06
Erm, cast manifolds have a knack of cracking too, don't they? I thought they would be 'better' at cracking than tubular actually - tubular just over-expanding itself if not put together very well smile.gif

C
12th March 2004, 12:27
The HKS ones seem to split at all the weld points & one of the primaries I have actually seen with a big split down it!! which I assume is just poor quality steel maybe?

Is a cast one likely to crack as much as a tubular? the other advantage of cast is I dont have to ponce about with a new radiator!

Simon_
12th March 2004, 12:38
Sounds like time to go to H&S and get a custom made one..??

Simon

Paul@Zen
12th March 2004, 12:48
The standard cast subaru manifolds hold up to ALS much better than the tubular ones. I have also heard that using 3mm wall thickness tube to make manifolds results in much more rugged parts.

Paul

Adamantium
12th March 2004, 12:48
agree with simon,

I bet the standard cast primaries are way too small, and I would really think that a cast manifold would be less happy expanding to take the heat than a simple steel tube.

[ 13. March 2004, 07:43 PM: Message edited by: Adam M ]

fuz
12th March 2004, 22:18
http://www.tubetorque.co.uk/

did my bmw 2002tii for me :D

Andy.F
13th March 2004, 11:57
You never hear of a cossie cracking the cast manifold, even at silly powers that would shame most scoobs/evos :D
Assuming the OE manifold is well designed and of correct material then it would be the most reliable by a long shot.

Andy

nom
13th March 2004, 15:50
Isn't the cossie manifold rather shorter, though? Like a sort of, well, stump? i.e. lots less to expand?
Having said that, I can't remember how convoluted an EVO manifold is...

stevieturbo
13th March 2004, 17:23
A 2wd cossy manifold is quite long. It is almost like a U-shape.

What type of manifolds do the rally cars use?? Dont Mitsubishi have a WRC car this year?? or are they still using GrpA ?

If you can get someone to make you a pattern, then getting manifolds cast isnt actually that expensive. I know a guy who does this for various engines. The most difficult and time consuming bit is actually making the patterns for casting.

johnfelstead
14th March 2004, 13:41
Originally posted by Andy.F:
You never hear of a cossie cracking the cast manifold, even at silly powers that would shame most scoobs/evos :D
Assuming the OE manifold is well designed and of correct material then it would be the most reliable by a long shot.

Andy It's a common fault on 4x4 cossies for the exhaust manifold to crack, they have a fairly short service life when running ALS on groupA rally cars. The 2wd manifolds seem to be less prone to cracking.

Andy.F
15th March 2004, 12:42
Aggressive anti lag will destroy most manifolds/turbos eventually :D
The 4wd cossie manifold is an example of where accountants and NVH people had too much input at the design stage :rolleyes: The earlier 2wd casting is a work of art in comparison, with its perfectly sealing jointless flanges and 4:2:1 design :cool:

Andy

ScoobyTJames
26th March 2004, 09:55
Yup - HKS manifold needed welding in the collector - all four edges of the cone had gone, also leaking around flange to uppipe.