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Speedy Squirrel Speedy Squirrel is offline
Rocket Scientist
Join Date: Jun 2008
Location: Detroit
Posts: 896
That article is terrible, and the writer is using a bunch of terms that he/she does not understand.

For a twin scroll system to work, each pipe must be kept separate until they reach the turbine inlet flange in order to conserve the momentum of the pulse. This is more important than equal length. You can not have ANY wastegate pipes. When they are closed they provide volume for the pulses to expand into. The Ďsecondariesí of Brianís headers will do the same thing, so that system is not useful. With no wastegate pipes, an integral wastegate turbo must be used.

The part about the scavenging and overlap in the article is incorrect. They have never run this engine. I know for a fact that this engine runs very little overlap, except for when they want to force exhaust INTO the cylinder for EGR purposes.

This is a picture of the exhaust manifold. It is somewhat misleading. The individual pipes are actually in layers, so the cutaway makes it look like the ports dump into a single volume. They donít. There is an individual pipe from each cylinder all the way to the flange. Beautiful.

Here is the dirty secret about divided systems. ALMOST ALL BENEFIT IS LOST WHEN THE WASTEGATES ARE FULLY OPEN. This is not a maximum power enhancing approach, it improves the low end, but the maximum power is about the same.
Old 06-05-2010, 07:09 PM
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