Second Intake?

[JDMChris]

Someone told me today that he had an 1.8... and that after a certain amount of RPM, a second intake opens up.. Is he on crack or am i?

[SuperK]

the interior of your manifold generally has multiple "butterfly valves" that open or close shorter or longer intake runners to the cylinder heads loosely based on your RPM. For example, on some intakes, one butterfly valve opens up at 3750 rpm's, then a second opens up at 4250. so it could be considered a "intake in your intake" since it does adjust the length the air must travel to the cylinder head.

[Inodoro Pereyra]

open or close shorter or longer intake runners to the cylinder heads loosely based on your RPM.

Just a little correction: while K's concept is right, the VRIS valves don't change the length of the intake runners, but the length of the plenum. Otherwise, you'd need 12 butterfly valves, instead of 2.

Sooo...being the way the VRIS works, you can tell the guy he's wrong: K engines don't have 2 intakes. They have 3.

[Daninski]

Yes, the intake manifold is equipped with 3 chambers tuned to a specific resonant frequency. The computer dynamically switches between each resonant chamber to achieve the appropriate resonant frequency for the engine's rpm. This effect optimizes volumetric efficiency over a given rpm range to provide maximum torque over the entire rpm range. (plagerization at it's finest)