AVDS-1790-2D Engine Dyno Testing

Automated Digital Run-In and Performance Testing of the AVDS-1790-2D Engine

Every AVDS-1790-2 Series Engine remanufactured by NSN Lookup is subjected to the US Army NMWR Run-In Procedure which lasts more than 16 hours and can take 4 days. After the Run-In sequence has been successfully completed, each Engine is calibrated and subjected to a Performance and Acceptance Test which qualifies the engine's performance for delivery in a battle-ready condition. This extensive testing procedure is required for every AVDS-1790-2D engine to ensure that the engine can be installed into a M48 Tank and used immediately at its full rated power without break-in and to ensure that no engine fails from "infant mortality" because of component failures or workmanship. Once an engine has been qualified by NSN Lookup it is delivered to the End User with a comprehensive warranty guarantee.



Dynamometer Test Equipment at NSN Lookup for AVDS-1790-2D Engines

NSN Lookup maintains several Computerized Digital Dyno Test Cells for engines that are built and remanufactured by NSN Lookup. The Test Cells are calibrated and certified at least every 30 days. The primary dyno test cells for AVDS-1790-2D engines are provided by SuperFlow. The Superflow test cells are water-brake test cells capable of testing up to 4000 LB-FT of Torque up to 6000 RPM. The test cells have a common infrastructure for the dynamometer water which includes 126,000 gallons of water storage, computerized water management for cleansing, flow and cooling as well as cooling towers backed by process chillers to enable 24/7 operation even at their full power potential. In addition to the fixed test cells, NSN Lookup also owns and operates fully-containerized engine test systems that can be deployed anywhere in the world and are self-contained. Each completely self-contained FCT system is capable of 3000 LB-FT of Torque up to 6000 RPM and can calibrate and test the AVDS-1790-2D engine at the End User even in remote locations. The FCT systems are designed and supplied to NSN Lookup by PowerTest Systems.


AVDS-1790-2D Dyno Test Cell

AVDS-1790-2D Dyno Mobile FCT Test System



Dynamometer Testing Procedure for AVDS-1790-2D Engines

NSN Lookup performs dynamometer testing of every AVDS-1790-2 engine it supplies. Each engine is first Run-In through a sequence of prescribed steps. After Run-In, a Performance Test is performed to ensure the performance and reliability of the engine. The detailed steps are published and regularly updated through the US Army publication NMWR-9-2815-220 and DMWR-2815-247. All performance testing is performed using the prescribed fuel of MIL-DTL-83133 (JP8) and lubricating oil of MIL-PRF-2104G, Type I, Grade 15W40. The results of the testing are stored permanently and a digital file is included with every AVDS-1790 for sale.


AVDS-1790-2D Run-In Dyno Sequence

Step # Duration (Mins) RPM Torque (lb-ft)
1 10 700 Warm Up (Ideal 140F Oil Temp)
2 15 1000 85
3 15 1400 440
4 20 1800 837
5 20 2200 1024
6 30 2400 1202
7 30 2400 Full-Rack Full-Load


If an air, oil or fuel leak is detected at any point in the run-in sequence, the engine must be cooled down by slowly decreasing the RPM to Idle and allowing the oil temperature to stabilize. The engine is then shut down, the leak repaired and the engine washed before warming the engine up again to its operating temperature of 140F minimum oil temperature and resuming the run-in at the step where the leak was detected. Using this dyno procedure each engine will be run-in for at least 3 hours before testing begins.



AVDS-1790-2D Dyno Adjustment Procedure

After the AVDS-1790-2 Engine has been successfully run-in using the Run-In Dyno Sequence, the engine is run further to allow for final adjustments to be made to calibrate the engine to its expected minimum and maximum operating limits. The test uses the Net Observed Torque of the calibrated digital dyno system which is corrected to the Corrected Net Observed Torque by applying correction factors using the SAE performance correction tables for the actual enviromental conditions of the test. The Correction Factor is the Air Inlet Temperature Factor x Barometric Air Pressure Correction Factor x Fuel Temperature Correction Factor. This correction factor almost always results in a lower Net Observed Torque than the Corrected Net Torque.

A correction is also applied to compensate for the power consumed by the cooling fans:

RPM BHP
2520 125.0
2400 108.0
2200 83.5
2000 62.5
1800 45.6
1600 32.0
1400 21.5
1200 13.5
1000 7.8
900 5.7


Adjustment Procedure:

Step # Duration (Mins) RPM Torque (lb-ft)
1 Check Power Ratings and adjust as necessary to the following:
735-780 CGBHP @ 2400 rpm
607-631 CGBHP @ 1800 rpm
2 Recheck Low Idle, 700-750 rpm
3 Check Adjust High Idle, 2600-2660 RPM
4 Stop engine. Leak check and repair as required
5 120 2400 Full-Rack Full-Load
6 Stop engine. Leak check and repair as required. Wash engine.
7 60 1800 Full-Rack Full-Load
8 60 5 min @ 2400 RPM, Full-Rack Full-Load 5 min @ 700-750 RPM, No-Load
9 Stop engine. Leak check and repair as required. Wash engine.
10 30 1400 Full-Rack Full-Load
11 120 2000 Full-Rack Full-Load
12 Stop engine. Leak check and repair as required. Wash engine.
13 30 0.5 min @ 2400 RPM, No-Load 0.5 min @ 700 RPM, No-Load
14 Stop engine. Review power ratings and make final pump adjustments at 1800 and 2400 RPM if necessary
15 Final Wash and Clean of engine.


If an air, oil or fuel leak is detected at any point in the adjustment sequence, the engine must be cooled down by slowly decreasing the RPM to Idle and allowing the oil temperature to stabilize. The engine is then shut down, the leak repaired and the engine washed before warming the engine up again to its operating temperature of 140F minimum oil temperature and resuming the run-in at the step where the leak was detected and repeating 30 minutes of the step where the leak was detected and the shut down sequence started. Using this dyno procedure each engine will be run for adjustment for at least 7 hours before acceptance testing begins.



AVDS-1790-2 Engine Operating Limits

During the Run-In and Performance Testing procedures, the following operating limits are observed at all times:

  • Maximum Oil Temperature (Oil Pan): 250F
  • Maximum Oil Temperature (At Oil Pump): 220F
  • Maximum Oil Pressure: 70 PSI
  • Minimum Oil Pressure (2400RPM): 40 PSI
  • Minimum Oil Pressure (700RPM): 15 PSI
  • Maximum Oil Consumption: 0.0075 pounds per brake horsepower hour (lbs/bhp-hr) at full-load
  • Maximum Fuel Consumption (2400RPM): 0.420 lbs/bhp-hr at full-rack full-load
  • Maximum Fuel Consumption (1800RPM): 0.400 lbs/bhp-hr at full-rack full-load
  • Maximum Exhaust Gas Temperature at Cylinder Head: 1250F
  • Maximum Exhaust Gas Temperature Variation between Cylinder Heads: 150F
  • Maximum Crankcase Blow-By (New Cylinders): 18 CFM
  • Maximum Crankcase Blow-By (Used Cylinders): 18 CFM
  • Minimum Induction Air Temperature: 60F
  • Maximum Induction Air Temperature: 100F
  • Minimum Fuel Temperature: 60F
  • Maximum Fuel Temperature: 100F
  • Minimum Fuel Pressure (at Injection Pump Inlet): 40 PSI
  • Turbo Boost Pressure: The Intake Manifold Air Pressure should be between 2.05 and 2.35 times the Turbo Inlet Pressure (Dry Barometer Reading). The Left and Right banks should not have a pressure difference greater than 4 Inches Hg



AVDS-1790-2D Exhaust Smoke Density Test

The maximum exhaust smoke density at full-load, when measured within one foot of the exhaust outlet, must not exceed the following conditions when using fuel conforming to MIL-DTL-83133 (JP8)::

Engine RPM Robert Bosch Smoke Meter #
1800 4.0 - 4.5
2000 3.7 - 4.2
2200 3.2 - 3.7
2400 3.0 - 3.5



AVDS-1790-2D Dyno Performance/Acceptance Test

Step # Duration (Mins) RPM Torque (lb-ft)
1 10 2400 Full-Rack Full-Load - 735-780 CGBHP
2 10 2200 Full-Rack Full-Load
3 10 2000 Full-Rack Full-Load
4 10 1800 Full-Rack Full-Load - 607-631 CGBHP


If repairs or adjustments are required during to meet the test requirements then the engine shall be warmed up again for 10 minutes until oil temperature is 140F and the adjustment test procedure is performed again before a subsequent acceptance test. The acceptance test requires the test cell operator to maintain the engine within its operating limits and within the exhaust smoke limits for the test to be deemed successful.

Subsequent to a successful performance test, the test cell operator will confirm the correct operation of all on-board electrical systems including the smoke generating system.

The performance test results are documented into the Final Inspection Record (FIR).