Plenum Dimensions, Primary runners length ...???

[TiTiKo]

Hi i am looking for some help about the plenum ( cylinder plenum ), how i do determine the correct, perfect volume of the plenum, how do i improve the plenum performance, and how the length of the primary runners affect the power and torque curves?

[TiTiKo]

Hi i am looking for some help about the plenum ( cylinder plenum ), how i do determine the correct, perfect volume of the plenum, how do i improve the plenum performance, and how the length of the primary runners affect the power and torque curves?

[Sam Zimmerman]

For the plenum question, I attempt to make the specific impedance of the plenum perform similarly to the specific impedance of the runners around the RPM range of your torque peak. You can do this by plotting the impedances over one another and changing your plenum length and area and the area of the plenum inlet. This works well because the impedance of the plenum does not affect the impedance of the runners, although the opposite is not true.

For the runners, look up Helmuth Engleman's papers on the subject. There are several and they are useful and provide a simple analysis technique. For the record, I do not use Engleman's techniques but they are certainly valid. I prefer to plot the impedance along the entire length of the intake system.