Generally a plenum volume of approximately 80% of engine capacity for naturally aspirated engines and 150% of engine capacity for turbocharged engines works best.
But I have seen as much as 220% of engine volume used in high hp / high boost turbocharged applications, in that one case a 140% engine volume plenum lost top-end power in comparison to the 220% one, I would not say that the "150% is best" is written in stone..
When I was road racing we did a lot testing on plenums and here are some of my experiences.
The plenum can be tuned for lower rpm torque peak (helmholtz). But the effects can diminish with long duration cams.
Larger plenum volume:
Pushes resonant frequency (and tuning rpm) lower down the rpm range.
Top end power increases due to better cylinder to cylinder distribution and larger reflected wave amplitude.
Throttle response can decrease with larger plenum if no changes are made to engine inertia (with throttle before plenum).
Current N/A and turbo designs use main plenum with what I call an "air knife" feeding into it along the length of the plenum. Air knife can be a divergent flat cone or a tapered cone along the length of the plenum.
Resonant frequency of plenum can be sensitive to plenum shape and plenum excitation can be influenced by runner spacing.
