How to Make a Stock Duramax Blow Smoke

by Walter Bourne

Some diesel trucks can produce enormous black clouds smoke from their exhaust pipes. The black smoke is caused by unburned fuel. Many methods can blow smoke from a stock Duramax diesel engine, which is common in GMC and Chevrolet vehicles. Most of those methods use the concept of reducing the air-fuel mixture within the motor.

Step 1

Reduce your diesel truck's air intake by partially obstructing the air intake with cloth or another object. This is the easiest but potentially the most harmful way to make a stock Duramax blow smoke. It causes the engine to overheat quickly and can lead to serious engine damage. Decreasing airflow decreases the air-fuel ratio in the exhaust and causes smoke.

Step 2

Neglect your truck. New trucks are designed not to blow smoke because the smoke is the result of wastefulness and subject to environmental restrictions, but dirty or improperly tuned diesel trucks blow smoke because their motor is not fuel-efficient. Smoke is caused by numerous factors, such as worn injectors, carbon buildup or faulty valve timing. That is why smoke is usually associated with older trucks.

Step 3

Accelerate quickly. Many trucks blow smoke with sudden full throttle because the turbo lags behind the increased fuel. Towing a heavy load in low gear furthers the effect. Try hitching your truck to a 5000 lb. payload, and drive it full throttle uphill.

Modify your truck. Several aftermarket parts are designed to increase smoke from a diesel engine. The most common and easiest to install aftermarket parts are chips that modify the air-fuel ratio, turbos that reduce boost in low gear and exhaust smoke kits.


  • Because new trucks are designed not to smoke, often it is easier to buy an older truck than to modify a new truck to smoke.


  • In many states, smoking exhausts are illegal. You could be fined and your vehicle impounded if you are caught with a smoking diesel vehicle.
  • Modifying timing, compression rates and fuel injection amounts can seriously damage an engine, including bursting the head gasket or studs.
  • Black smoke is sometimes attributed to slight increases in horsepower, but it is always attributed to reduced gas mileage and increased pollution.

Items you will need

  • Diesel truck with stock Duramax engine
  • Cloth or other object (optional)
  • Aftermarket parts (optional)

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