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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 LeMans 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 OEMs have abandoned their in-house airflow benches to 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.
7.2 Test Pressures and Comparing Flow Numbers
The necessity of flow number comparison is something anyone involved in flow testing must endure. Even
if the number comparison is made on the same components and flowbench, it is important to know how
to compare the numbers so the time and effort is worthwhile. The comparison process is necessary to
evaluate published numbers vs. your own developed flow numbers. The first principle you learn in flow
testing is that you must ask (or qualify) at what test pressure the flow numbers were recorded.
method. If you have flow numbers at a known test pressure and want to compare those numbers at a
different test pressure, it is easy to do. The formula is:
FlowAtFirstTestPressure
= FlowAtSecondTestPressure
X
SecondTestPressure
FirstTestPressure
As an example, if you have flow numbers at 10"H
2
O test pressure and would like to know what the flow
should be at 25"H
2
O test pressure, the formula is:
(25 ⁄ 10) = 1.58
So you would multiply the flow numbers taken at 10”H
2
O test pressure by 1.58 to see what the flow would
be at 25"H
2
O.
7.0 Flowbench Theory
