HOT AND COLD


powertrains. At that time, extrapola- tion error was usually observed as 10-20 percent. However, the extrapolation error on electronically controlled powertrains is approximately three to five times more severe than the extrapolation error for mechanically controlled powertrains. With so much error in the test results for powertrain performance, we can have little confidence in how the vehicle will actu- ally respond to the extreme demands of desert warfare.


In addition, it is important to note that the error resulting from linear extrapolation is biased towards false failures. In other words, linear extrapolation will predict engine or transmission overheat on a vehi- cle that may have had no issue if actually tested at 120 degrees.


This is because linear extrapolation cannot account for control algorithms that might derate the engine power or increase powertrain cooling to lower key parameters such as engine oil temperature, engine coolant temperature and transmis- sion oil temperature. (See “What Is Engine Derate?” Page 78.)


SOLUTION FOR NONREPRESENTATIVE TEST CONDITIONS If you have ever attempted to adjust the thermostat in your home or workplace to your preferred setting, you have probably experienced the disruption in harmony with those individuals who are hypersen- sitive to changes in temperature. A battle over 70 degrees versus 72 degrees ensues. Electronically controlled powertrains know when the “thermostat” has been touched and they care. Linear extrapo- lation of key powertrain parameters such as engine oil temperature, engine coolant temperature and transmission oil temper- ature has too much error to be trusted during mobility-performance testing.


80 Army AL&T Magazine Fall 2022


TEMPERATURE TESTING


Extrapolation error of engine oil temperature during mobility performance testing at desert conditions. (Graphic by Steven Zielinski, GVSC)


UPFRONT PERSPECTIVE


The Palletized Loading System (M1074A1) in PEVEL for mobility performance testing at 120 degrees. Using the “oven” for actual ambient temperatures produces much more accurate results. (Photo by Stephen Roberts, GVSC)


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148