Calculation For Intake runner length? 1

[hvychvy81]

Hello all,

I'm currently working on an Individual Throttle body intake for my Car. I was wondering what to use to calculate the optimum runner length for the intake, before the throttle bodies. Better if there was a way to choose which Rpm the power would be coming on full. If anyone has any advice let me know... Thanks in advance, Stephen

 

[patprimmer]

The 80 to 90 deg is to do with valve timing starting the process and where the piston os when the reflected pulse arrives. You want it to arrive as the inlet flow is falling off, but the valve is still open, so you get that extra shoy of air before the valve closes.

Regards

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[MichaelPal]

an obvious answer pat...but that's what i needed

hahha

~Michael Pal

Pal's the name, FSAE race cars are my game.

Terps Racing

 

[oab]

The 80/90* depends on cam timings, and is used on engines at higher rpms. As the inertia of the shorter gas column can move faster..
The sonic wave starts at the inlet valve opening, travels to the end of the track, to reflect back as a positive wave, meets the piston 80/90* down the stroke. The closed pipe, reflects the positive wave back to the open end of the tract, a reversal takes place to reflect a negative wave back into the cylinder as the piston is slowing at BDC. The negative wave is reflected back from the piston, through the cylinder dropping the pressure to increase filling. The wave finally reflects back from the open end of the tract as a positive pressure, to increase the external pressure on the inlet gas to assist filling and prevent charge reversal.

Harvey.