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unclebilly unclebilly is offline
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Join Date: Nov 2003
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Originally Posted by jyrkilaune View Post
Thanks for the comments. With all due respect, I don't quite agree with the quote above. If the manifold is the bottle neck and the flow varies between cylinders, then the amount of air will vary too.

I wonder if anyone has measured this in a reliable way. There are plenty of high hp cars with pancake manifold. If you would know the flow of each intake path, you could implement a compensation map, decrease the AFR safety margin and make more power without hurting the engine.

Anyone with measured data? How about common knowledge: which cylinders run lean, which cylinders run rich?

You are stuck on NA engines where the vacuum created by the down stroke of the pistons pulls in the air. In this case, the resistance of the flow path must be equal. This can be from playing with equal lengths or other geometry.

The turbo generates pressure that is equal for each cylinder. Think about a lawn sprinkler, by your thinking, the holes closest to the hose would spray more (have away bigger jet). In reality, the pressure drop across the manifold plenum (analogous to forced induction) is about an order of magnitude lower than the pressure drop across the nozzles so each nozzle squirts about the same amount of water.

This is why turbos have such small intake ports, it helps with even flow distribution...

I guess that fact that I am a professional engineer with nearly 20 years designing manifolds for things ranging from fuel cell stacks to oilfield equipment should give me some authority in this discussion.

Disagree away.
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Last edited by unclebilly; 12-28-2014 at 07:43 AM..
Old 12-28-2014, 07:38 AM
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