conforms to astm standards

  • D2699 Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel
  • D2700 Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel
  • D2885 Test Method for Determination of Octane Number of Spark-Ignition Fuels by On-Line Direct Comparison Technique

 

Three ways to find Octane Number:

  • Bracketing - Equilibrium Fuel Level (Procedure A)
  • Bracketing - Dynamic Fuel Level (Procedure B), also known as the Falling Level Method
  • Compression Ratio (Procedure C)

WHAT IS THE FALLING LEVEL METHOD?

The ESD Octane Analyzer Systems employ the well-known and proven Falling Level (Dynamic Fuel Level) Method for determining the octane number of a fuel sample. This method is documented in ASTM D2699 - Standard Method for Research Octane Number of Spark-Ignition Engine Fuel (Procedure B), ASTM D2700 - Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel (Procedure B) and, by reference, in ASTM D2885 - Determination of Octane Number of Spark-Ignition Engine Fuels by On-Line Direct Comparison Technique.

With the Falling Level Method, a specifically designed and calibrated fuel supply bowl is filled and is allowed to empty as the CFR test engine runs. The bowl design is such that a test cycle on any fuel sample can be completed in a reasonable amount of time while ensuring that a consistent and repeatable range of fuel mixtures are delivered to the engine without the need for intervention by the operator.

As the liquid level in the supply bowl fails, the rate of fuel supplied to the engine decreases and the fuel / air ratio changes. The knock intensity of the engine is measured continuously over the range of fuel / air ratios. In a properly calibrated system, this is characterized by a light knock condition, through a peak knock measurement and then back to a light knock.

By comparing the peak knock intensity level of the unknown sample with that of the known reference fuels, a simple straight-line interpolation reveals the octane number of the unknown fuel.

The peak knock intensity level of fuels with known octane numbers higher and lower than the sample fuel are plotted in a straight-line graph. The sample's octane number can then be determined by the position of its measured peak knock intensity along this plotted curve. The Falling Level Method has been statistically proven and accepted by the ASTM as a valid octane number determination procedure.

The Falling Level Method (Procedure B) differs from Procedure A - Bracketing Method only in that the fuel / air ratio is not adjusted by the operator; this function is accomplished automatically by the falling level of the fuel in the bowl.