I asked the same quesiton a few months ago, and someone pointed out what I missed- air does not flow smoothly into an engine.

The ads are correct in principle- a 'swirled' flow mixes air and fuel more efficiently and homogeneously, and burns better. All gas turbines (jet engines) and many straight- fuel burners (like boilers) have "swirl cups" (actual name) to impart a vortex to the fuel prior to being shot in a continuous atomized stream into the combustion chamber. A fouled swirl cup does significantly decrease performance.

The problem in an internal combustion engine is that neither the fuel nor the air flow continuously or straight into the cylinder. Both are squirted periodically through constrictions and turns and mixed afterwards in the cylinder... any vortex in the air would have been long since destroyed by the time it got to the cylinder.

Furthermore, the process is engineered to NOT have a fully homogeneous fuel-air mixture- there is a specific distribution achieved by the turbulent airflow to maximize the burn and extracted power for that engine's particular geometry, etc. A large part of the power/efficiency increases of the engine itself over the last 25 years has come from modeling and tweaking the exact combustion process with ever greater precision and detail. We've pretty much maxed out the 4-stroke Otto cycle itself for efficiency.

Net effect of "tornado" air flow: zero.