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Old 10-03-2022, 05:19 PM   #13 (permalink)
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Originally Posted by Blacktree View Post
Engines don't need exhaust backpressure. What they actually need is flow velocity, for exhaust scavenging. Closing off part of the exhaust during cylinder deactivation should help maintain flow velocity.
* Okay, the interior volume of the exhaust system is a constant.
* The engine rpm varies from say, 600 at idle, to 6,000 at redline.
* A variability of 5,400 rpm.
* 1,000%.
* Are we concerned with acoustic velocity?
* Velocity of blowdown?
* Or the velocity of remnant gases pushed out by the pistons on the exhaust stroke?
* One size fits all?
* 'Perfect' at all rpms?
* Are the other pressure pulses from the other cylinders setting up a 'train' within the system, which aid in the 'scavenging'?
* If we kill these pulses, have we shot ourselves in the foot?
* Under transient loads, 'conventional' exhaust systems appear to have performed okay for over a hundred years now.
* What is Vizard actually bringing to the table, and does it really move the dial?
* Does the 'velocity' of the gases leaving the exhaust port change at any given load and rpm?
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Last edited by aerohead; 10-03-2022 at 05:22 PM.. Reason: add data
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