Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Intake manifold design

Originally posted by Auto-X Fil:

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First off, flow is turbulent pretty much everywhere in the intake. There's no laminar flow in a system like this. It's pressure and velocity changes that designers try to minimize. Ideally the air wouldn't have to make a bend like it does, but it's far more important to get the length right. Packaging then dictates that it have bends. Variable intakes are now a pretty common thing on more potent engines, but it was fairly new, and quite an impressive feature on the original engine. Exhaust and intake both work best when they are long and small diameter at low revs, and short and wider at high revs. This intake, as you can see from the tubular pictures, delivers air through narrower, long tubes until the secondaries open, then through both them and the slightly wider, much shorter secondary feeds. Without the secondary design, the engine would just die at low revs. Imagine if the torque curve at 4k continued all the way down, without that hump... it would be pretty lousy at low revs, like most engines of this displacement.

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