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Old 06-02-2014, 11:20 AM   #122 (permalink)
MoulaZ
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Location: Sydney, Australia
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Drives: '09 Z34 BP Turbo V2
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Quote:
Originally Posted by Boosted Performance View Post
That essentially sums it up. Each exhaust pulse is able to travel independently through it's own bank/runner. Because of this, one exhaust pulse will scavenge the exhaust out of the following combustion chamber once the exhaust valve opens...allowing more air to enter it on the next compression cycle. More air in = more power. There is simply no exhaust interference between exhaust pulses, allowing for a very efficient flowing system.
As I was writing my response, it dawned on me where I was becoming confused. I'll explain it below for those curious.

All of this stems from a natural occurring issue, Exhaust/Intake Valve overlap.

Had this been a twin Twin-Scroll Turbo setup, the Twin-Scroll Turbos would fare no better then standard Single-Scroll Turbos. This is because by the simple nature of the V6 arrangement and using 2 separate exhaust manifolds to feed each Turbo completely independent of the other bank.

...............................................Time: --------------->

Turbo 1 / Scroll 1 would see Cylinders: 1-NP-3-NP-5

Turbo 2 / Scroll 1 would see Cylinders: ....2-NP-4-NP-6


(NP = No pulse)

The above is ideal, as it provides that necessary time to avoid that brief negative pressure window (through valve overlap), introduced into the exhaust manifold impacting the next flow/pulse that is set to come out. This happens because the Cylinder pulses are spread out, from a time perspective, as they occupy different exhaust manifolds. This design allows for better scavenging and better exhaust efficiency.

__________________________________________________


The below is the most unideal scenario involving a single Single-Scroll Turbo and using a single exhaust manifold to collect all gasses and push them through said Turbo. Had Sasha not selected a Twin-Scroll Turbo, this is what our scenario would be.

...............................................Time: -------------->

Turbo 1 / Scroll 1 would see Cylinders: 1-2-3-4-5-6


The problem here is while Cylinder 2 is pushing out it's exhaust gases, Cylinder 1 very briefly introduced negative pressure in the exhaust manifold which slows gasses from Cylinder 2 down, which reduces scavenging effectiveness and Turbo efficiency. Repeat this many times over and suddenly you've reduced your Turbo's efficiency quite a bit.

__________________________________________________


The solution is a Twin-Scroll Turbo to 'mimic' a traditional twin Single-Scroll Turbo setup. This is what the Boosted Performance Turbo kit is. Even though both exhaust manifolds go to the same Turbo, they are kept separated throughout... until they finally meet at the Turbine when exiting the Turbo.

Thus you have:

...............................................Time: -------------->

Turbo 1 / Scroll 1 would see Cylinders: 1-NP-3-NP-5

Turbo 1 / Scroll 2 would see Cylinders: ....2-NP-4-NP-6


Even though the above is actually just one Turbo.

Look familiar? ^^^


Hope this clears it up for others that were wondering.

Cheers,
MoulaZ
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