CARTRIDGE GP-TURBOCHARGER 1004095 - Caterpillar

All Turbocharged Truck EnginesMost types of air dryers lose some intake air from the turbocharger boost during the air compressor unloading cycle. This occurs because some of the intake air is wasted through the purge valve in the air dryer. This boost loss may be 1-7 in. of Hg and may result in marginal or less than minimum boost during a PAR test. Wheel horsepower may decrease slightly but its percentage of change is small.
If boost loss is a problem, first check all air compressor, air dryer and supply tank line connections. If no leakage is found, remove the air compressor inlet line from the intake manifold. Plug the manifold connection hole, and retest. If the boost performance increases, the customer has the option of adding a special discharge line pressure protection valve between the air dryer and air compressor. This valve, offered by Bendix HVS, eliminates boost loss during the compressor unloading cycle by maintaining boost pressure in the compressor discharge line ahead of the air dryer. (Bendix Bulletin PRO-8-13 describes the installation and use of this valve.)
Care should be taken in the installation of this valve. It is subjected to untreated delivery air from the air compressor, which could condense and freeze in the valve in winter operating conditions. This could result in air compressor damage. (It should also be serviced every 100,000 miles.)
The customer should weigh this risk against the small horsepower that is to be gained. Through field experience, the freeze-up problem is reduced (not eliminated) if the valve is installed either next to the engine and after the air compressor heat dissipation line or directly at the air dryer. The discharge line should constantly run downhill to the dryer to keep water from pooling in the valve.
The air dryer system is a customer's option. Most air dryers do result in a slight boost and horsepower loss. The customer must weigh the potential performance loss against the risks associated with the installation of a pressure protection valve.