Intake Manifolds for Dummies

plenum intake manifold

In the bad old days of eHow.com (before Leaf Group shoved most of the site's content into oddly named niches), contributors were forbidden to use Wikipedia as a source. We assume that's because Wikipedia had/has a poor reputation: is that the pot calling the kettle black, or what? Whatever the case, lots of contributors simply reworded the Wikipedia article for the topics whey didn't understand and then slapped a bogus reference on the article... much like Andrea Stein did for her ItStillRuns.com article, "What Is a Plenum on an Intake Manifold?"

We'll get the answer out of the way up front. The plenum, whether in your car's intake manifold or in your forced-air furnace, is the large, central chamber where all the tubing or ducts meet. The manifold is a collection of branching pipes or ducts that all meet at a central location: the plenum. It's as simple as that.

Stein (at the time publishing under the name Kobeszko) pretended to have used a book titled Engine Management: Advanced Timing (as if that has anything to do with the plenum of the intake manifold) and an online definition of the plenum to "answer" the question. That online definition said, in its entirety, "[U]sually a large cast alloy body which connects the throttle body or inlet tube to the cylinder head(s) or inlet manifold." From that tiny definition, Andrea supposedly harvested such information as,

1. "The intake manifold’s primary function is to transfer the air and fuel combustion mixture to the intake ports contained in each cylinder head."
2. "Intake manifolds contain runners, or tubes that extend to the cylinder head intake ports from the plenum."
3. "Intake manifold runners take advantage of the Helmholtz Resonance phenomenon..."

Strangely enough, the Wikipedia article on intake manifolds contains the following statements (in order):

1. "The primary function of the intake manifold is to evenly distribute the combustion mixture (or just air in a direct injection engine) to each intake port in the cylinder head(s). "
2. "Modern intake manifolds usually employ runners, individual tubes extending to each intake port on the cylinder head which emanate from a central volume or 'plenum' beneath the carburetor." [NOTE the definition of plenum contained therein...]
3. "The purpose of the runner is to take advantage of the Helmholtz resonance property of air."

Plagiarism, anyone? and, more to the point, nowhere in her post did Stein/Kobeszko actually say what a plenum is. Instead, our Dumbass of the Day blathered incessantly about what an intake manifold does; in the process making it pretty obvious that she had no idea what she was talking about. Feh.

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