Air Injection System: Operation

1982 Porsche 928 Automatic TransSECTION Operation

The action of the air pump causes fresh air to be drawn in through the air intake filter. Here it is cleaned of excess dirt and foreign particles before it enters the air pump. In the air pump the air is pressurized and pushed on to the diverter valve.

Fig 1: Schematic of Porsche Air Injection System (924 Model Application Shown)
G09323292Courtesy of PORSCHE CARS NORTH AMERICA, INC.

The diverter valve acts as a pressure protection valve. If too much exhaust gas backpressure (or other system pressure) occurs, the diverter valve will dump the air pump air off to the atmosphere or to the air cleaner (depending on application). This protects the air pump from working against excessive system pressure.

Under normal conditions, the air flows through the diverter valve and on to the check valve. This is a one-way flow control valve. It will prevent a backfire flame from passing back into the air pump system. Passed the check valve, normal air will flow into the exhaust ports through a passage system in the exhaust manifold.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.