Air Travel in an Intake 1

[racingvw92]

I keep hearing that there different ways to provide air and fuel to the engine. The idea I'm most intertested in is the idea of spinning the air inside the runner to mix with the fuel. I see all these fancy intakes and wounder if this is what they are doing or if there is something I don't know yet.

 

[SomptingGuy]

"Fancy" intakes are usually attempting to optimise tuning effects. If you want to see the ultimate fancy intake, take a look at Ferrari's amazing 3.6L V8.

 

[mattsooty]

When you say 'spinning the air inside the runner' I am assuming you mean around the axis of the runner, not the cylinder?

In most applications the actual air motion is imparted once in the cylinder. The runner does nothing more than provide some speed & direction of flow into the cylinder. However it can also be tuned to provide pressure waves to impart r massflow.

The main problem with all the clever air movement strategies is that they only really become meaningful over a limited operating range - for the rest of the time, unless variable, they are a compromise.

For example: -

At full load/high speed the action of squish forces charge away from the edges of the cylinder (the end gas locations). This serves to compress the charge within the cylinder and provide some degree of knock resistance by speeding up the burnrate.

However at idle/low speed light load the most useful charge motion is not squish but reverse tumble, whereby the small amount of charge is forced onto the spark plug position. The amount of motion provided by squish action at these engine speeds is small and the very geometry that usually provides this can cause quenching of the flamefront.

MS