Bellmouthing ?

[B-Man]

What and how exactly does bellmouthing help intake systems ?

Does it increase velocity or flow ? Or does it help with consistant air distribution ?

Why 'tuned lenghth' bellmouth ends ? What does the 'tune' do ? Is it somehting to do with the pulse of the air flow ?

I know that these questions have probablly got 4 Uni subjects of theory behind them - But simple answers in B-Man speak would be appreciated.

Thanks,

[Roy]

The word tuned is thrown around a lot and i suspect used incorrectly in a lot of instances.

Some seem to use the word tuned when at best they mean equal length runners. Tuned typically refers to the acoustics of the inlet system, complete from throttle body to inlet valves.

It looks at the events inside the inlet plenum arising from the opening/closing of inlet valves and opening and shutting of throttle body etc. Typically the tuning of an inlet manifold impacts more on an engines torque characterisitcs then outright hp.

So by playing with length/diameter, injector placement/angle, no. of throttle bodies you can vary the design of the inlet plenum. You can also play with the type of throttle setup, forsaking the usual butterfly, and going for a barrel/flat slide etc (typically seen on bikes or race engines)

As for the bellmouths they attempt to promote airflow by radiusing the inlet of the runner, as a square edge would cause flow restricting turbulence.