[Boss330]

Originally Posted by jlh335i

You over complicate things too much. Before the divided turbo housing was put to use, twin scroll manifolds were used to optimize exhaust flow to turbos. Colloquial in the tuning world.

https://www.google.com/webhp?tab=ww&...croll+manifold

Over complicate?

I just pointed out basically the same you said about a twin scroll turbo and exhaust manifold, but also pointed out that the N55 manifold doesn't really advertice that it feeds a twin scroll turbo.

However, a twin exit exhaust manifold (or a twin scroll manifold) wouldn't really bring any advantage on a single scroll turbo. So, IMHO the concept of a twin scroll manifold makes little sense without a twin scroll turbo...

From one of the pages in your link:

http://www.forcedinductionsonline.co...roduct_id=1136

Full-Race's legendary twin-scroll turbo manifold is now available for the Mitsubishi 4B11T Evolution X. The Big Runner's 40mm runner diameter is intended for our drag race applications which typically have ported cylinder head, high flowing valve job, largely oversized cams and plan to run 30+ psi of boost.

This header is designed to be versatile and fit a variety of different style twin-scroll T4 turbochargers from many manufacturers - Borg Warner, Garrett, HKS, Precision, FP, etc will all fit. The twin-scroll turbo manifold design spools large turbos fast for torque gains and faster transient response than traditional undivided single-scroll turbos. Single-scroll T4 will also fit, but loses low end torque/midrange and transient response.

So, as you can see. The manifold design doesn't really bring any major advantages if not coupled with a twin scroll turbo. It's the turbo, with it's dual exhaust channels that gives the name to "Twin Scroll". The manifold is "just" a means of optimizing exhaust flow to the twin scrolls in the turbo.

Notice that the "twin scroll" part is referring to the turbo design (turbine housing):



http://en.wikipedia.org/wiki/Turbocharger


Twin Scroll refers to turbo design and not to a exhaust manifold design. A "twin scroll manifold" is just a manifold that is made for a twin scroll turbo. The name "twin scroll" comes from the turbo, not the manifold


Difference (and similarity) between a twin scroll style manifold and a single scroll style manifold:



A single twin scroll turbo I6 manifold:



As you can see, it's not THAT easy to tell them apart when they are on the engine with a turbo attached...

Good info on turbo and manifold design:

http://forum.ih8mud.com/80-series-te...-faq-info.html

A design feature that can be common to both manifold types is a " DIVIDED MANIFOLD" , typically employed with " DIVIDED " or "twin-scroll" turbine housings. Divided exhaust manifolds can be incorporated into either a cast or welded tubular manifolds (see Figure 5. and Figure 6.).

The concept is to DIVIDE or separate the cylinders whose cycles interfere with one another to best utilize the engine's exhaust pulse energy.

For example, on a four-cylinder engine with firing order 1-3-4-2, cylinder #1 is ending its expansion stroke and opening its exhaust valve while cylinder #2 still has its exhaust valve open (cylinder #2 is in its overlap period). In an undivided exhaust manifold, this pressure pulse from cylinder #1's exhaust blowdown event is much more likely to contaminate cylinder #2 with high pressure exhaust gas. Not only does this hurt cylinder #2's ability to breathe properly, but this pulse energy would have been better utilized in the turbine.

The proper grouping for this engine is to keep complementary cylinders grouped together-- #1 and #4 are complementary; as are cylinders #2 and #3.

Because of the better utilization of the exhaust pulse energy, the turbine's performance is improved and boost increases more quickly.