How to adjust the external wastegate on a turbo

Written by chris stevenson
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How to adjust the external wastegate on a turbo
Turbo boost can be adjusted at the external wastegate valve. (Jupiterimages/Photos.com/Getty Images)

An engine turbo charger produces extra horsepower and performance in an automobile engine. It does this by pressurising the intake air before it enters the engine for combustion. Rapidly spinning turbo blade fans compress the air, but in order to do so the compressor wheel needs to know how fast to turn and what pressure to deliver. The wastegate, mounted on the exhaust side of the turbo, controls the power boost, or pressure. The external turbo wastegate has an adjustment function which allows an increase or decrease in pressure.

Skill level:
Moderate

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Things you need

  • Owner's repair manual
  • Boost gauge kit (psi or bar-rated with vacuum line and adaptors)
  • Socket set
  • Ratchet wrench
  • Carburettor cleaner
  • Rags
  • Screwdrivers
  • Cotter pin puller
  • End wrenches (thin wall)

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Instructions

  1. 1

    Raise the hood of the vehicle and locate a vacuum line that enters the intake manifold. Refer to your owner's manual for a proper line that can be accessed easily. Pull the vacuum line loose and install a T-fitting to the hose, so that a boost gauge ties in the with the line and the other port of the boost gauge has a vacuum line that runs through your open window into the driver's passenger compartment.

  2. 2

    Drive the vehicle until it reaches normal operating temperature, typically 20 to 30 minutes. Find an expressway and bring the engine speed up to, or close to, 4,000rpm, according to the tachometer. Do not exceed the speed limit, but run the vehicle for a short duration at this speed and make a note of the boost gauge reading on the dial. Bring the vehicle back home, shut the engine off and place it in park or neutral with the emergency brake set.

  3. 3

    Raise the hood and locate the wastegate valve on your engine. Refer to your owner's manual for its location. It looks like a circular valve pod and attaches to the exhaust manifold. Use a rag and carburettor cleaner to clean the valve face off. Remove the air cleaner assembly box with a socket, if it impedes access to the wastegate valve. Use a screwdriver to loosen the cold air intake hose and push it aside.

  4. 4

    Locate the small retaining spring that holds the wastegate cover on. Use a cottar pin puller to catch the end of the spring and pull up and outward to remove it from its groove. It should slide out and pop free. Pull the wastegate cover off. Notice the locknut on the small shaft valve, with two flats underneath it. Use an end wrench to hold the flats steady while you use another end wrench to loosen and remove the locknut.

  5. 5

    Take the wrench you used to hold the flats steady and turn the flats shaft clockwise three full revolutions. This will adjust a spring underneath, inside the wastegate valve. Hold the flats steady with one wrench and screw the locknut back onto the valve threads. Tighten the locknut with another wrench. Place the wastegate cover back on and install the cover retaining spring by compressing it and fitting back into the housing groove. Make sure it snaps back into position, holding the cover firmly.

  6. 6

    Remove the boost kit T-fitting and refit the vacuum line on the intake manifold. Reconnect the air cleaner box and tighten the bolts with a socket. Refit the cold air intake hose on the air inlet and tighten the clamp with a screwdriver. Test drive the vehicle and note the change in the pressure bar reading. You should have at least a 2 psi boost, according to your dash gauge.

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