The long butterfly runner ideas were first designed by Porsche engineers and found to actually provide a positive intake pressure that increased cylinder filling. Fiat also used them.
Turbulence is sometimes a good thing - particularly in an intake tract at the point where fuel injection and subsequent utility are concerned:
Effect of Turbulence in Intake Port of Mpi Engine on Fuel Transport Phenomena and Nonuniformity of Fuel/Air Mixing in Cylinder
Document Number: 900162
Date Published: February 1990
Author(s):
Jun Takemura - Mitsubishi Motors Corp.
Daisuke Sanbayashi - Mitsubishi Motors Corp.
Hiromitsu Ando - Mitsubishi Motors Corp.
Abstract:
Three zone mixture preparation model, assuming that fuel and air are distributed in three separate zones, fuel air and mixture zone, was proposed. Air Utilization Efficiency derived from the model was used to evaluate the mixing nonuniformity.
Effect of the large scale nonisotropic turbulence downstream of the dimple or edge in the intake port of MPI engine on the convective mass transfer from fuel film was clarified by the proposed nondimensional index, Local Sherwood Number. It was found that when the fuel is injected toward the wall where large scale turbulence exists, almost all of the fuel is seeded in the air passing the region at the beginning of the intake process, resulting in the time-resolved nonuniformity of the mixture strength at the intake valve.
Using the Air Utilization Efficiency, it was elucidated that time- resolved mixing nonuniformity at intake valves induces spatially nonuniform fuel/air distribution in the cylinder.
If you want to pay the price for a download, the entire technical paper can be obtained here:
SAE International Frank
