ARMY AL&T
Testing took place at the GVSC Propul- sion Systems Laboratory and the Power Energy Vehicle Environmental Labora- tory (PEVEL). In the laboratory setting, the ambient temperatures were controlled to produce representative environments matching the vehicle’s upper ambient temperature specification (120 degrees). Performance data was then compared on the same test setup at the same operating point while at a lower ambient tempera- ture (80-90 degrees).
From this test data, the linear extrapolation method described in Army test operating procedures (Test Operations Procedure 2-2-607 “Cooling Systems [Automo- tive])” was then applied to measurements of engine oil temperature. Tis provided a set of actual results at desert operating conditions (120 degrees) and an extrapo- lated set.
With a set of results from actual ambient temperatures and a set from extrapolated temperatures, we could calculate the error introduced by the prediction of extrapola- tion. Based on this test data, extrapolation of engine oil temperature was 65 percent to 116 percent off from the actual measure- ment. Te electronic controls prevented the powertrain from overheating even though linear extrapolation said it would.
For example, with that 65 percent error, linear-extrapolation-predicted engine oil temperature was 270 degrees when it was actually 250. Tis is a huge change consid- ering a vehicle will pass or fail mobility performance testing at the proving ground by crossing the threshold by 1 degree.
In the past, the Army has led many inves- tigations such as Yuma Proving Ground Report No. 221 and No. 135 into the impact of extrapolation error. Tis series of studies occurred back in the 1970s and only studied mechanically controlled
HIGH TEST
A self-propelled howitzer (M109A7) in PEVEL for mobility performance testing at 120 degrees. The types of tests conducted at the vehicle laboratory on tactical and combat ground vehicles are many. The influence of ambient temperature varies. (Photo by Steven Zielinski, GVSC)
DYNO LAB
The Power Energy Vehicle Environmental Laboratory (PEVEL) Environmental and Dynamometer Laboratory has the capability to test every tactical or combat vehicle at top speed but standing still. (Photo by Stephen Roberts, GVSC)
https://asc.ar my.mil
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