Graph 5: Lug Down Test (Engine Speed, App1, Vehicle Speed, And Imp) - Navistar MaxxForce DT Diagnostic Manual

10.5. GRAPH 5: LUG DOWN TEST (ENGINE SPEED, APP1, VEHICLE SPEED, AND IMP)

1. Intake Manifold Pressure (IMP)
(psi) [Purple]
2. Engine speed (rpm) [Blue]
3. Vehicle speed (mph) [Red]
Figure 30 Graph 5: Lug Down Test (Engine Speed, APP1, Vehicle Speed, and IMP)
Graph Analysis:
This graph shows the Intake Manifold Pressure (IMP) signal value responding as designed. This test does not
give pass or fail results. It only allows the user to validate IMP signal value under load. Engine power band is
typically between 1300 to 1700 rpm with peak power occurring around 1600 rpm. Anything outside of this
power band drops boost and power significantly. Accelerator Pedal Position 1 (APP1) signal value must be
99.6% to successfully reach peak boost during this test. Low IMP can be the result of low Fuel Rail Pressure
(FRP), or high Turbocharger 1 Turbine Outlet Pressure (TC1TOP). Diagnose low FRP concerns first, high
TC1TOP concerns second, and low IMP concerns third.
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4. Engine load (percent) [Orange]
5. Accelerator Pedal Position 1
(APP1) (percent) [Green]
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