Manifold Question

[shmiddy]

im looking at getting a new exhaust manifold and have been looking at alot of different sites with different styles.. one thing i noticed is where the turbo mounts, one style has all 6 runners going into the mount with one big mounting hole, and others have runners 1,2,3 going into the mount and 4,5,6 going into the mount sperate, with the mount having 2 seperate holes instead of one (split pulse i think it is) .. anyways what is the difference in these 2 if any? is one better then the other?... cheers

[Dale FZ1]

The OE manifold separates 123, 456 groups until the turbine inlet flange. Most likely an effort to stop the pulses from each group affecting each other.

A true split pulse system should carry the separation into the turbine scroll. Check the pictures of a GT3271 at turbobygarrett.com as an example.

[shmiddy]

is this better or worse though? would there be much difference?

[Dale FZ1]

Try a search on this forum and also Google for split pulse turbine.

It's done in an attempt to keep a large-ish (high flow capability) turbine that responds as a smaller one does. The idea is to maximise the pulsing effect that comes with the two cylinder groups. The firing order and layout of an I6 are evidently best suited to using this spec, but I think they do it with rotaries too.

Do a search and see what you come up with.

cheers