Cobb Tuning Mazdaspeed 3 SF SRI - Short Ram Intake - Part 1: » Design 1: Velocity Stack

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2 - Design 1: Velocity Stack

Design 1: Velocity Stack

At first glance, it appears to be a simple intake piece. We are all familiar with the assortment of intakes out for the Mazdaspeed 3 today. Some of the intakes on the market today are considered half baked concepts. The inside diameter of these MAF housing vary among intakes. Some, have been known to cause lean conditions within the ECU and created an assortment of driveability issues or MIL codes, which illuminate on your instrument panel. Some of them are just plain junk and are avoided among the community.

So what makes Cobb's so much different than everyone else? Well, if we look back at the 60's, a lot of top hot rodders used velocity stacks in their carburetors to smooth the incoming air. A velocity stack is a usually cylindrical tube of some type with a radiused inlet end device. When this device is added onto the air entry location or locations of an engines intake system, it will:

1. Allow smooth and even entry of air into the intake duct with the flow streams boundary layer adhering to the pipe walls
2. Modify the dynamic tuning range of the intake tract by functioning as a small reverse megaphone which can extend the duration of pulses within the tract
3. Alter the dynamic tuning speed (dynamic engine compression) if the overall length is changed thereby changing the tuned length to a lower or higher rpm.

Look at the below image as an example how the Cobb SF SRI works to smooth incoming air into the MAF housing.


The next image below shows you an example of how air enters typical intakes.


Cobb's velocity stack:




Next Up: Air Straighteners, Build Material & MAF Sensor Housing

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