How to Tune a Turbo Carb

Carburetors and turbochargers both require periodic adjustment.

Receiving gasoline from the fuel pump, the carburetor is responsible for mixing the gas with air before the fuel is sent to the piston combustion chambers in the engine. Turbochargers are essentially air pumps that “boost” the amount of air-fuel mixture reaching the pistons during acceleration, resulting in an increase in horsepower. To properly adjust a turbocharger-equipped engine, the carburetor setting must be adjusted to get the engine running as smoothly as possible before adjusting the boost on the turbo.

Things You'll Need

• Flat-head screwdriver
• Phillips screwdriver

Instructions

Carburetor Adjustment

1. Start the vehicle, and allow the engine to reach the normal operating temperature as indicated by the engine temperature gauge. If the vehicle does not have a temperature gauge, allow the engine to run for five minutes.

2. Locate the idle adjustment screw on the face of the throttle linkage assembly, attached to the side of the carburetor. Listen to the engine while turning the screw, in and out and one-eighth of a turn at a time with a flat-head screwdriver, until the engine is idling as smoothly as possible.

3. Identify the air-fuel mixture screw located at the base of the exterior of the carburetor throat. Adjust the fuel mixture by turning the screw one-eighth of a revolution at a time with the flat-head screwdriver until the engine is running smoothly.

Turbocharger Adjustment

1. Locate the wastegate adjustment screw on the turbocharger regulator valve, controlling the wastegate actuator rod that regulates the amount of boost pressure produced by the turbocharger.

2. Turn the wastegate adjustment screw on the turbo regulator valve counterclockwise with a Phillips screwdriver until the screw is backed all the way out and stops turning. Turn the screw back in, clockwise and half a revolution.

3. Drive the vehicle at highway speeds, going through several sudden acceleration cycles, until you get a feel for the amount of power being produced by the turbo. Continue fine-tuning the wastegate screw half a turn at a time until the engine is performing to your liking.

Tips & Warnings

• Having the boost on the turbo set too high can cause the vehicle to spin violently out of control. Master driving the vehicle at lower settings before increasing the boost.

References

• Haynes Repair Manual, Chevrolet and GMC Pickup; John Haynes
• Chilton's Ford Pick-Ups and Bronco 1987-96 Repair Manual; Jaffer Ahmad

Resources

• Street Racers: Turbo Chargers