SuperFlow AutoDyn, Руководство оператора

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General Testing Information
Volume 3, 9/10/04
Appendix A - Page 203
This will lead to one final calculation regarding torque: peak torque will be achieved at
approximately 75 to 76 percent of the engine speed for peak power.
There are many factors to consider for these estimates to be accurate. Key among them is the
assumption that the engine’s components are matched or will be “tuned” correctly for maximum air
flow. If an engine has components to effectively operate mechanically at 7,500 rpm, but has air
flow capacity to turn 10,000 rpm for peak power, it may never make the trip to the finish line!
In addition, these formulas were derived for typical automotive 4-cycle V8 type gasoline powered,
normally aspirated engines. The formulas may not predict reasonable values for engines of
different configuration.
For additional information, refer to SuperFlow Flowbench manuals.
A.5 Oil Temperature Control
Every experienced dynamometer operator understands that oil temperature affects engine power.
For any extended testing,
an oil cooler is mandatory . When using an oil cooler, it is important to
note that the cooler can only control the temperature of the oil entering the engine. The
temperature of the oil exiting the engine is a function of the oil flow rate and engine heat rejection.
The typical flow rate for an automotive engine is approximately one gallon, (4 liters) of oil per
minute for each 1,000 rpm of engine speed. As oil passes through the engine, the oil temperature
will rise 20 to 60°F, (11 to 33°C), depending on power and speed. A rise of 60°F should be
considered the maximum for engine operation. A greater temperature difference means the oil is
either too thick or too thin at some point in the engine lubrication cycle. Industrial and race engine
designers try to limit the oil temperature difference through the engine to approximately 20°F,
(11°C), for minimum wear and block thermal distortions.
The oil temperature should be kept constant during an engine test. A variation of 10°F (6°C), can
change measured power by 1%. SuperFlow’s optional oil cooling system works with both wet and
dry sump oil systems. It is important that the engine oil pass through a filter before entering the oil
cooler. If your engine should fail during testing, the oil cooler can be contaminated and will be
difficult to clean.
A.6 Torque versus Speed
All 4-cycle engines running on gasoline without supercharging, tend to develop approximately the
same maximum torque per cubic inch of displacement. This number is approximately 1.35 to 1.55
lb-ft of torque per cubic inch of displacement. This can also be expressed as a BMEP of 200 to 230
psi.
Despite the best efforts of engine builders over the past 40 years, nothing has improved this
number appreciably. (Again, this number is valid only for 4-cycle engines without supercharging
running on gasoline, no matter what the size.)