Many of the applications of flowbenches and the data that they provide are often set apart from normal data because of the mystique associated with flowbenches and flow testing. Engine component airflow data is easy to compare if you know how.
An air flowbench is essentially a device that measures the resistance of a test piece (cylinder head, manifold, carburetor, throttle body, exhaust systems, etc.) to flow air. Many different designs and models are on the market today that allow the user to compare flow results before and after changes in the flow path.
Flowbenches and airflow data have been part of the internal combustion engine development cycle for design, research and development for many years. Some of the first engine airflow studies (using some type of flow testing) date back 85 years. However, the study of engine airflow and flowbench information and the relationship to performance has only been commonplace in the racing industry for about the last 30 years.
The foundry process and the associated compromises actually controlled most early cylinder head and manifold designs. These manufacturing compromises drove most designs—not the technical aspects or specific airflow requirements.
When SuperFlow Corporation introduced the first portable flowbench in 1972) to the engine builders of the world, airflow science came to kitchen tables, shops, and garages everywhere. More elaborate and very complex benches had been around for some time when the first SuperFlow model was made available, but never in such an easy-to-use configuration. As market demand and understanding grew, many larger models were made available as racers everywhere began to compare flow information. Many thousands of benches are in use every day, and engine component airflow technology is growing rapidly.
The various test pressures in use in the field are interesting in that they were derived as a historical reference more than a technical requirement (see “Test Pressures and Comparing Flow Numbers”).
The first airflow benches in use at the Original Equipment Manufacturer (OEM) level were expensive, cumbersome, and complex machines that were applied in the late 1960s and early 1970s for some specific engine airflow development work. Oldsmobile and Pontiac used flowbench-guided designs early on; however, Chevrolet did not have a flowbench lab in use until the 1970s. American Motors used flowbench-guided cylinder head designs in the early 1970s as well. Chrysler adapted a flow lab from elements that were used in air filter work, and the lab was developed in parallel with their introduction of the 426 Hemi engine. The Ford Motor Company flow lab dates to the mid-1960s where they supported their winning Le Mans racing effort with their GT40 racing vehicles.
Some of the OEM, specialty-engine manufacturers, and professional race teams are now using Computational Fluid Dynamics (CFD) to assist in Computer-Aided Design (CAD) and flowbench driven designs. Many of the OEM have abandoned their in-house airflow benches and outsource much of their airflow development testing. As a result, some well-established shops using SuperFlow or other flowbenches around the country typically get involved in OEM development contracts because the programs are more cost and time effective.