SuperFlow AutoDyn, Руководство оператора

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Supplemental Information
Appendix A - Page 202
AppA General Testing Information.fm
If the flowbench investigation (surely you checked things out on a flowbench!) indicated that you
have parts that should make strong power but the dyno results are lower than expected, start by
looking at the air related information the dyno provides for the solution.
When measuring air flow, be aware that pulsations in the air flow, or in the fuel flow for that matter,
will cause errors in the reading. Each engine induction cycle causes a pulse in air flow. Because
the fan blades are not symmetrical to air flow for forward direction versus backward, pulsating air
flow will cause the turbine to read consistently high or low, depending on its design and the
frequency. At higher pulsation rates, this result tends to be very small. When running at lower
speeds, pulsations can cause significant errors.
For instance, a four cylinder engine running at full throttle at 1500 rpm will have substantial airflow
pulsations. The frequency is low enough that the flow rate can be in error by as much as 15%. The
solution is to add a dampening drum between the engine and the air flow sensor. The damping
drum should have a volume of 30 to 100 times the volume of the engine displacement. A 50 gallon
(200l) barrel can be hung from the ceiling, and connected to the engine with a 12-inch (30cm)
diameter flex tube. The air turbine is attached to the end of the damping drum and the pulsation
problem is minimized. This solution will work well on a 4, 6, or 8 cylinder engine.
Please note, the readings from SuperFlow flowbenches cannot be used to directly calibrate the air
flow turbines. The flowbench compares the flow through an orifice to the flow through the test item.
At sea level temperature and pressure, the air turbine and the flowbench readings will be the
same. At all other air densities, the flowbench flow will differ from the air turbine flow by the square-
root of air density. For this reason, it is recommended you send you air turbines to SuperFlow to be
recalibrated at least annually.
A.4 Flow Bench Correlation
It’s widely known that the internal combustion engine is an air pump. With that in mind, modifying
an engine design to maximize its air flow will generate more power. Using your SuperFlow
flowbench and dynamometer in tandem will produce a reliable testing team in your on-going
search for power.
When a cylinder head, intake manifold or head and manifold together are placed on the flowbench
for evaluation, the temptation must be resisted to automatically make all the holes larger for one
important reason: air flow is more dependent on the shape than it is on size. Air flow testing
becomes mandatory in order to precisely gauge the air flow capability of the components. What
“looks about right,” usually is not.
The complete intake system can be evaluated on the flowbench to indicate the level of power that
the system will produce. The maximum air flow at a test pressure of 25 inches of water multiplied
by 0.27 will estimate the horsepower (per cylinder) that the components can make. (When a test
pressure of 10 inches of water is used, the formula becomes the flowbench reading multiplied by
0.43). This number may shift slightly if the engine is not matched with the components or if the
engine is extremely efficient. This estimated power versus air flow number is a reliable indicator of
predicted performance.
Your flowbench can also produce a close estimate of the speed at which peak power will occur.
This determination is made by dividing 1266 by the displacement of one cylinder and then
multiplying the result by the maximum air flow measured at a test pressure of 25 inches of water.