Turbo Manifold Overview
|Turbo manifolds have one purpose, and that purpose is to expel exhaust gas into
the turbine of a turbocharger as efficiently as possible.|
There are two basic types of turbo manifold:
|The log style manifold: |
The log style manifold simply directs all of the exhaust gases to the
turbo via the shortest route possible. Generally, on a log manifold,
the runner lengths and circumferences are not equal.
Tubular style manifold:
The tubular manifold is made up of a runner coming from each cylinder,
meeting up at a collector. Tubular manifolds yield a higher efficiency
rate, as each runner is generally the same circumference. This allows
for a much smoother flow of exhaust gas to the turbo. Some tubular
manifolds use "equal length" runners. Equal length tubular manifolds
are the most effecient design. The manifold pictured above is an Equal
Length Tubular Manifold.
When selecting a turbo manifold, take note of the material. Most reputable manufacturers will have the metal type and grade clearly stated. (eg 304 Stainless) Do a Google search on the metal to find out some of its properties. Some metals cannot withstand repeated heating and cooling to the extreme temperatures that are required of a turbo manifold.
Another thing to look for is wastegate placement. It is best, on manifolds with an external wastegate, for the wastegate to be placed in an area where the exhaust gasses from all runners have an equal chance to escape from it. This will prevent "boost creep". The angle at which the wastegate is placed is equally as important. If the wastegate doesn't get any of the primary flow of exhaust, chances are you may experience boost creep to some extent.
This is an example of poor wastegate placement
This is an example of average wastegate placement. . . this style manifold flows so much that the wastegate could be angled a little bit more downward to make it receive more of the primary flow.