Essentially, Pete was taking an academic approach to modeling induction systems and expanding on material originally presented in the Journal of American Physics and published in 1938, in addition to multiple other investigations since those early studies. By combining the effects of quarter-wave organ pipe tuning oscillation techniques with those involving Helmholtz resonators, Pete was able to configure multiple degree of freedom design capability. In simplified terms, this means his model produced single induction systems that enhance torque specifically at different engine speeds. Such systems enable parts designers (fabricators or modifiers) to configure intake (and exhaust) systems that target specific engine rpm. The method is sufficiently flexible to manipulate torque (v.e.) boosts that are intentionally separated or placed, relative to each other, over a range of engine speed. He's still doing that work, today.
From a hands-on perspective, Pete's approach included validation of the fact an intake or exhaust system will enhance torque output (relative to rpm) by encouraging a boost at a mean flow velocity of 240-260 feet/second. In this context, flow passages that incorporate a constant crossection will optimize their dynamics efficiency if significant mass is moving at this rate when such velocity is achieved, even though this notion may appear contrary to other tuning theories. Over time, Pete's ongoing research has added credibility to his approach, including favorable results from his earlier work with a variety of race teams, including Foyt and similar motorsports groups.
Quoting from Vorum, "In continuing work, I added specific time-average flow velocities that produce maximum scavenging and ram supercharge, when paired with Helmholtz-defined torque peaks. In the quarter-wave model, a designer considers the manifold runner length, one equation, one unknown." Pete's model contemplates the effects of multiple equations and unknowns, producing results that are more predictable to ultimate engine performance. Among them are cylinder volume, port length/area, mechanical compression ratio, valve timing, and target engine speeds where he wants a torque boost.
Further, it's possible to match intake and exhaust torque peaks relative to where you'd like them to relate to each other. Stated another way, you can individually tune intake and exhaust systems in an effort to manipulate a given torque curve for specific conditions. In the case of circle-track engines, this technique will allow tailoring an engine to accommodate track-specific gear combinations, for example. Pete says, "Engine performance is a balance of intake and exhaust pumping work, along with combustion heat release. If the pumping work is improved by good manifold design, the output of the engine can depend less on the combustion output." If you'd like to communicate with Pete, his email address is firstname.lastname@example.org.
Aside from the Vorum approach and utilizing concepts I was involved developing when he first contacted me, there's an additional approach you may want to consider. It includes the notion of separately tuning intake and exhaust systems that embodies an additional feature; multiple passage section areas. Here's a quick view of how this works.
If you agree that the 240-260 feet/second mean flow velocity condition occurs at peak volumetric efficiency (essentially peak torque), this approach can be used as a tool. For example, let's consider a single-cylinder engine. (You can also apply the idea to engines of multiple cylinders.) Suppose you size the inlet runner to reach this mean flow velocity at 2,500 rpm, thus producing a torque boost at that speed. Then adjust the section area of the exhaust passage to achieve this flow rate at 3,500 rpm. In a simplified fashion, you'll have broadened the effective torque range of the engine, compared to what you'd have if both peaks occurred at the same rpm.