Working principle of the Flowtech Afterburner?

Dec 23, 2003 3 Replies

Hi all,



ok, I know this is a controversial product that some say sucked big time. I'm not here to start a war on whether it works or not, but just wanna find out at least the theory of how it's supposed to work. From its design, and even from the cut-away diagram, I simply can't figure how it can be better than the 4-1 or 4-2-1 design... I'm always interested in special designs and like to improve on it, if possible. Well, improved in my head, at least! ;)



Oh yeah, is it only suitable for V8's? Coz there's no model available for 4-cylinders on the Holley website.


Well, from what I know, David Vizard, in one of his books, describes how the V8 reacts to exhaust pulse tuning. The usual firing order for early SBC's, for example, is 1-8-4-3-6-5-7-2; the odd cylinders are on the drivers' side, the evens on the other. However, notice the 8-4 and the 5-7 in the firing order are two cylinders firing on the same side, only 90 degrees apart, unlike the 6 & 2 cylinders, and the 1 & 3 cylinders, which fire 180 degrees apart. So, the drivers' side idles at (1 3 5-7), the passenger side is (8-4 6 2). Vizard says that because of this firing order scheme, the SBC acts like two inline "3 cylinder" engines, with one cylinder firing at a slower rate than the other two. I looked over the Flowtechs once, after reading about this. I don't remember, though, if that had anything to do with the design.

Ken

Thanks for the feedback. I found the following explanation from jcwhitney.com, hope it helps with others who are also as curious as me about the Afterburner:

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Big-tube headers offer plenty of horsepower but lack the low-end torque twisting capabilities of small-tube systems or proven "tri-y" designs. Afterburner? is a unique tubular exhaust that directs exhaust gases of the out-of-sequence cylinder into a secondary collector. There, the fumes are scavenged at a flow rate equal to that of the 3 other cylinders. Relieving the crowded condition in the primary collector allows for a smaller tube design, resulting in increased exhaust velocity (for added horsepower and torque) and a straighter power and torque curve paralleling the engine's RPM range.

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