Drawings exhaust manifold!?

[elCrillo]

Anyone have plans or ideas on how a manifold to q4 be built!?

[#84]

Hi,

The exhaust manifold in the attached pictures is designed to:

A. Provide good pulse separation; cylinders 1-4 v.s. 2-3
B. Minimise volume to get best possible spool-up; that is the reason why it is 4-2-1 and not 4-1
C. Have good flow properties for high peak power

The compromise is unequal pipe lengths.

It is built in Carbon Steel (due to the complicated shape) by Custom Parts Service in Sweden.

[corriedw]

I prefer 4:1 manifolds. 1,4 + 2,3 will work for a twin scroll turbine, IF the pipes are seperated in the collector, but you need a long duration exhuast cam to make it work well.

On 4:1 manifolds, the gas must form a clockwise rotation where the tubes join at the collector, to spool the turbo quicker, because it is the direction the turbine is turning. There will be at least one tube crossing, which makes the manufacturing more difficult in the given space. For an anti clockwise rotation there should be no tubes crossing and it looks nicer but do not work so well.

It also spool better if the tubes cut equally into each other on the turbo. But it is difficult to make and you need a propper craftsman. Collectors that have four pipes ending with square ends next to each other, with a plate collector taking the gas to one hole for the turbo, do not work as well as four pipes cut angled to join on the turbo.

I build exh manifolds from std steam pipe bends like the one on the photo, welded together with TIG welding (not MIG welding), because there is no drops running into the tubes. 38mm tubes spool quicker due to smaller volume but if you are pushing for max power with a large turbo use 48mm tubes.

I hope this make sense.

[#84]

Interesting. Can you possibly post some picture which illustrates your theories realized?

In my manifold we have used 37 mm inner diameter pipes since the intention has been to maximize performance on standard injectors.

Regarding the clockwise/anti-clockwise properties, that is something we have adressed as much as possible in the turbine design, based on trials on Garrett T3's among others. Unfortunately I haven't been able to test much after I made most modifications, so I cannot say for sure how well the result works in reality.

A rhetoric question; do anyone series MIG weld exhaust manifolds?