runner length calculation

[seppen]

hi,

does anyone knows how too calculate precisely the runner length for the air intake, included the restrictor, plenum,...

I you need some more specs to answer, ask it...

thanks

Seppen

[seppen]

hi,

does anyone knows how too calculate precisely the runner length for the air intake, included the restrictor, plenum,...

I you need some more specs to answer, ask it...

thanks

Seppen

[Charlie]

Runner length can be estimated through resonance equations which can be found in any good engine's text (I like Winterbourne and Pearson for this stuff).

It can't be calculatec 'preecisely' without physical testing, or previous testing that you can use to correct your equations.

[Frank]

take the standard runner length and cross sectional area

use the same cross sectional area, and add 10%-15% to the runners

(half joking, half serious response)

[Sam Zimmerman]

You can not calculate precisely a runner length for your car, as Charlie said. Also, when analyzing your intake, the resonance frequency of your runner is not affected by anything upstream of it (i.e. the restrictor, plenum, throttle body, etc.) Everything upstream, however, is affected by your runner length. There are many ways to calculate runner lengths and you will be very close. Most of the ways are based off a guy named Helmuth Engelman. He has several papers on the subject and they are very good.

Once you get above the runners, all bets are off as far as cookbook methods go. Acoustically, the assumptions made in most papers are inadequate to cover the complex geometry of an intake system. It is very possible, though, to cause the plenum to be in anti-resonance while the runners are resonating, killing your torque curve.

In my humble opinion, their are two ways to attack the rest of your intake system, a cookbook approach and a good experiment design so you can make lots of modifications during your dyno time or a good understanding of acoustics and some simple tests in the acoustics lab. It all depends on how much time you have.