What is engine runner?
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. The purpose of the runner is to take advantage of the Helmholtz resonance property of air.
How do variable intake runners work?
A variable intake can create two or more pressurized “hot spots”, increasing engine output. When the intake air speed is higher, the dynamic pressure pushing the air (and/or mixture) inside the engine is increased.
What are the runners in an intake manifold?
Intake Runners. A series of tubes or channels in the manifold distribute the air-fuel mixture from the plenum chamber to the individual cylinders; these are the “manifold runners.”. Carbureted engines need very straight runners, because the fuel droplets in the air don’t like to go around corners.
What’s the difference between short and long intake runners?
However, on some designs, and most notably some BMW applications, the simple control valve that switches the intake air path between the long and short runners has been replaced with a “scroll-like” device that can be rotated with a stepper motor to create an almost infinitely variable-length flow path to suit all engine speeds and loads.
How are intake runners connected to the plenum?
Intake runners are the actual tubes that channel intake air from a reservoir, known as a “plenum” to the intake ports. The image above shows a typical intake manifold, on which the runners connect to the plenum individually, as opposed to branching off from a single exit point as was usual on older manifolds.
How does the distance of the intake runner change?
In practice, the distance that the intake air is forced to travel around the device is roughly equivalent to the air flowing through a runner of the same length, so by altering the position of the “scroll” within the manifold, the distance the intake air has to travel can be varied through an almost infinite range.
Intake Runners. A series of tubes or channels in the manifold distribute the air-fuel mixture from the plenum chamber to the individual cylinders; these are the “manifold runners.”. Carbureted engines need very straight runners, because the fuel droplets in the air don’t like to go around corners.
Intake runners are the actual tubes that channel intake air from a reservoir, known as a “plenum” to the intake ports. The image above shows a typical intake manifold, on which the runners connect to the plenum individually, as opposed to branching off from a single exit point as was usual on older manifolds.
However, on some designs, and most notably some BMW applications, the simple control valve that switches the intake air path between the long and short runners has been replaced with a “scroll-like” device that can be rotated with a stepper motor to create an almost infinitely variable-length flow path to suit all engine speeds and loads.
In practice, the distance that the intake air is forced to travel around the device is roughly equivalent to the air flowing through a runner of the same length, so by altering the position of the “scroll” within the manifold, the distance the intake air has to travel can be varied through an almost infinite range.