How to Measure Exhaust Back Pressure

Written by mark o'brien
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A running gas or diesel engine produces a lot of exhaust and heat that needs to be removed from the engine to allow it to run properly. A blockage of exhaust in the engine can cause a back flow of exhaust into the engine, causing the vehicle to be sluggish. Some back pressure is needed in an engine and the catalytic converter and muffler provide that; too much back pressure, however, can cause problems. Measuring the back pressure is fairly easy and requires a few tools.

Skill level:
Moderately Easy

Things you need

  • Drill
  • 1/8-inch drill bit
  • 1/8-inch self-tapping screw
  • 15 psi pressure gauge

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  1. 1

    Position yourself underneath your vehicle. Center yourself under the exhaust pipe just behind the engine, but in front of the catalytic converter. The exhaust pipe coming from the bottom of the engine connects to the catalytic converter and then to the muffler out the back of your vehicle.

  2. 2

    Drill a hole in the base of the exhaust pipe that is in front of the catalytic converter.

  3. 3

    Screw the end of the 15 psi pressure gauge into the hole.

  4. 4

    Start the vehicle. Read the gauge. While the engine is idling a proper back pressure readout on the 15 psi pressure gauge should be between 1.5 and 2.75 psi. Shut off the vehicle.

  5. 5

    Unscrew the pressure gauge. Screw the 1/8-inch self-tapping screw into the hole you drilled in the exhaust pipe.

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