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Exhaust Manifold Design

s2d4

By s2d4,
in Engines & Forced Induction

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s2d4 Rising Star

s2d4

Posted
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It really depends on your goal but I prefer smaller diameter runners, 6-2-1 with less merge area to keep the gas speed up. This may restrict your top end capabilities a little, but most don't need 800+kw of flow anyway.

Don't forget, the wastegate path is just as important as the turbo, the incorrect angle off the merge may see you struggling to control boost without a 60mm gate, and perhaps limit your top end flow unnecessarily.

Thanks for your input scotty.

Yes the wastegates will be angled correctly, even more so than most of the setups that tends to be at 90 degrees and are for sale these days.

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Would love some manifold fabricators/vendors to chime in.

This the guy who made mine - have a look through his gallery:

http://www.sincocustoms.co.nz/gallery/Custom%20Fabrication/2

s2d4 Rising Star

s2d4

Posted
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This the guy who made mine - have a look through his gallery:

http://www.sincocustoms.co.nz/gallery/Custom%20Fabrication/2

I had a look, none of those are 6-2 to the flange.

And sorry to trouble you scotty, do you have any photos of your 6-2-1 top mount setups?

bigmikespec Veteran

bigmikespec

Posted
Posted

Are you making you're own manifold, Mike?

Yes, definitely slow and steady though...

What I wanted to be able to do is have a compact billet collector, makes it as cheap as possible. But also so that you can build a 3-1 tube merge and weld it straight on.

s2d4 Rising Star

s2d4

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Posted (edited)

This is my collector effort so far... the T4 flange part is billet machined to get the transition from circle to rectangle spot on.

Good stuff! That T4 flange part is exactly what I wanted as well as a T6 variant.

The 3-1 section off the back half of the cylinders for me would be further away so just a schedule 10 2.5 inch crossing over with the wastegate off that.

The front 3-1 section would be roughly the same or slightly lower with the wastegates being about 60 degrees from vertical, as the power steering/AC will be relocated elsewhere.

Edited by s2d4
AngryRB Grand Master

AngryRB

Posted
Posted (edited)

why not merge them earlier to create more merge points for extra venturi effects and group each two that will fire close together? above collective looks alot like the usual twin scroll ..

Edited by AngryRB
s2d4 Rising Star

s2d4

Posted
  • Author
Posted

why not merge them earlier to create more merge points for extra venturi effects and group each two that will fire close together? above collective looks alot like the usual twin scroll ..

The merge earlier part is exactly what I said 1 post above yours.

Not sure what you are on about for the "extra venturi effects and group each two that will fire close together" part though.

bigmikespec Veteran

bigmikespec

Posted
Posted

Good stuff! That T4 flange part is exactly what I wanted as well as a T6 variant.

The 3-1 section off the back half of the cylinders for me would be further away so just a schedule 10 2.5 inch crossing over with the wastegate off that.

The front 3-1 section would be roughly the same or slightly lower with the wastegates being about 60 degrees from vertical, as the power steering/AC will be relocated elsewhere.

I can get the flanges made with what ever primary size going into it and a T6 one too... send me a PM.

A more progressive merge and a waste gate port that is more in line with the merge instead of 90° is a lot better but I want to keep it compact and I am using twin 44mm gates so boost control should be ok.

AngryRB Grand Master

AngryRB

Posted
Posted (edited)

The merge earlier part is exactly what I said 1 post above yours.

Not sure what you are on about for the "extra venturi effects and group each two that will fire close together" part though.

I was on about merging 1+5, 3+6 and 2+4 so you have 3 merge points then they merge into the final collector, when cyl1 fires then number 5 that fires next will have a vacuum in its runner ( venturi effect)

Each merge ( 3 pairs + 1 final merge) would step up in pipe size to encourage flow , maybe start off with a small diameter pipe and get larger at each collector like a set of TRI-Y extractors on a V8

http://www.ifs.tohoku.ac.jp/edge/library/020609ppsn(kanazaki).pdf

Edited by AngryRB
s2d4 Rising Star

s2d4

Posted
  • Author
Posted

I was on about merging 1+5, 3+6 and 2+4 so you have 3 merge points then they merge into the final collector, when cyl1 fires then number 5 that fires next will have a vacuum in its runner ( venturi effect)

Each merge ( 3 pairs + 1 final merge) would step up in pipe size to encourage flow , maybe start off with a small diameter pipe and get larger at each collector like a set of TRI-Y extractors on a V8

http://www.ifs.tohoku.ac.jp/edge/library/020609ppsn(kanazaki).pdf

Not sure how that would work for a twin scroll setup?

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