Section 14 - Engine Testing - Group 14 Engine Dynamometer - Install Engine (14-01) M11 Page 14-23 Intake Air Temperature Control The use of a remote aftercooler is mandatory whenever a Cummins CAC engine is attached to an engine dyna- mometer for the purpose of engine run-in, performance testing and engine diagnostics. Do not attempt to run a Cummins CAC engine without any means of controlling the intake manifold air temperature. Service tool, Part No. 3823978, utilizes twin Big Cam III aftercooler assemblies arranged for parallel air and water flow to cool the intake air to acceptable levels.
The parallel air flow circuit heat exchangers provide op- timum performance by delivering air to the intake mani- fold at temperatures no higher than 66°C [150°F], and with less than the maximum allowable intake air pressure drop (102 mm Hg [4 in Hg]). The remote aftercooler removes energy from the intake air which is compressed and heated by the turbocharger to temperatures as high as 210°C [410°F] then cooled to temperatures of 66°C [150°F] using city water at 16°C [60°F]. Water from a city tap line flows to the aftercoolers via a one inch I.D. neoprene hose. Testing has shown the 12 GPM city water flow is required (6 GPM per aftercooler core) to adequately cool the intake air.
A typical garden hose is not suitable for this flow due to the excessive restriction. A low restriction ball type or gate valve is suitable for the operation provided the required flow rates are obtained. Water returns to the drain or reservoir from the after- coolers via a one inch I.D. hose. A low restriction gate valve or ball valve must be placed on the drain line(s) to allow regulation of the water flow through the aftercoolers. This enables one to maintain optimum intake air tem- perature during the test or run-in procedure.
The condensate that will develop, as the intake air is cooled in the remote aftercooler, is allowed to drain at all times through a hole at the bottom of the tubular steel manifold between the aftercoolers. This fitting must re- main unobstructed throughout each use of the after- coolers. NOTE: Some air flow will escape through the condensate drain opening, but it is insignificant compared to the total air flow.