Induction System Deposit Fuels Evaluation

Southwest Research Institute (SwRI) has developed a unique device to evaluate the tendency of motor gasolines to form induction system deposits. This compact analytical tool, known as the Induction System Deposit (ISD) Apparatus, simulates conditions in spark-ignition engines that cause deleterious deposits to form on hot metal surfaces such as the intake valve, manifold, and port areas. The Institute delivers complete, custom-fabricated systems for client operation or uses in-house systems to test fuels provided by the client.

Custom testing and screening programs include novel approaches such as:

• Screening base fuels or additive-treated fuels at temperatures ranging from 35 degrees Celsius to 400 degrees Celsius
  
  
• Exposing a material to first a base fuel and then an additive-treated fuel to determine how effectively additives remove deposits
  
  
• Studying the effect of crankcase oils on intake valve formation and how effectively additives prevent or remove oil-related deposits

The SwRI-developed Induction System Deposit Apparatus is compact and requires only a small amount of hood space. All controls are conveniently located on the front of the ISD apparatus.

During (ISD) tests, a measured amount of fuel is sprayed on a heated test bar. The bar is weighed before and after the test to determine the weight of the deposits. Correlating ISD test results with engine tests has shown severe test engine induction system fouling from fuels with ISD deposit levels higher than 2 mg/100 mL.

During testing, fuel is metered from a reservoir to a spray nozzle, where it is mixed with air and expelled in a flat spray pattern across three inches onto a heated, preweighed deposit-collecting tube. The increased weight associated with the deposit is the ISD index, reported in mg/100 mL.

A water cooling jacket prevents fuel vaporization within the spray nozzle to avoid erratic flow. Aluminum or stainless steel tubes, brought to test temperature by an interior heating rod, provide efficient heat transfer through the tube wall and permit accurate weighing to ± 0.1 mg.

A thermocouple inserted into the wall of each deposit tube measures the tube skin temperature, and the thermocouple side of the tube faces the spray nozzle. Tube and spray nozzle temperatures are displayed in digital readouts throughout the test. Testing of each 100-mL sample takes approximately one hour: 50 minutes for spraying the test fuel onto the deposit tube, followed by a 10-minute heat soak and cooling time. The complete operating procedure is described in Federal Test Method 500.1, and additional information is included in a manual provided with the system.

The apparatus includes all necessary control equipment, requiring only compressed air, cooling water, electrical power, and ventilation for operation.

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