ASTM 909 Standard Test Method for Supercharge Rating of Spark-Ignition Aviation Gasoline
1. Scope
1.1 This laboratory test method covers the quantitative determination of supercharge ratings of spark-ignition aviation gasoline. The sample fuel is tested using a standardized single cylinder, four-stroke cycle, indirect injected, liquid cooled, CFR engine run in accordance with a defined set of operating conditions.

1.2 The supercharge rating is calculated by linear interpolation of the knock limited power of the sample compared to the knock limited power of bracketing reference fuel blends.

1.3 The rating scale covers the range from 85 octane number to Isooctane + 6.0 mL TEL/U.S. gal.

1.4 The values of operating conditions are stated in SI units and are considered standard. The values in parentheses are the historical inch-pound units. The standardized CFR engine measurements and reference fuel concentrations continue to be in historical units.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Annex A1.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D2268 Test Method for Analysis of High-Purity n-Heptane and Isooctane by Capillary Gas Chromatography
D3237 Test Method for Lead in Gasoline by Atomic Absorption Spectroscopy
D3341 Test Method for Lead in Gasoline - Iodine Monochloride Method
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D5059 Test Methods for Lead in Gasoline by X-Ray Spectroscopy
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
E344 Terminology Relating to Thermometry and Hydrometry
E456 Terminology Relating to Quality and Statistics

2.2 CFR Engine Manuals:
CFR F-4 Form 846 Supercharge Method Aviation Gasoline Rating Unit Installation Manual
CFR F-4 Form 893 Supercharge Method Aviation Gasoline Rating Unit Operation & Maintenance

2.3 Energy Institute Standard:
IP 224/02 Determination of Low Lead Content of Light Petroleum Distillates by Dithizone Extraction and Colorimetric Method

2.4 ASTM Adjuncts:
Rating Data Sheet
Reference Fuel Framework Graphs

3. Terminology
3.1 Definitions:
3.1.1 accepted reference value, n - a value that serves as an agreed-upon reference for comparison, and which is derived as: (1) a theoretical or established value, based on scientific principles, or (2) an assigned or certified value, based on experimental work of some national or international organization, or (3) a consensus or certified value, based on collaborative experimental work under the auspices of a scientific or engineering group.
3.1.1.1 Discussion - In the context of this test method,
accepted reference value is understood to apply to the supercharge and octane number ratings of specific reference materials determined empirically under reproducibility conditions by the National Exchange Group or another recognized exchange testing organization.

3.1.2 brake mean effective pressure, n - for spark-ignition engines, the measure of engine power at the output shaft as typically measured by an absorption dynamometer or brake.

3.1.3 check fuel, n - for quality control testing, a spark-ignition engine fuel having a supercharge rating accepted reference value determined in accordance with Practice D6299 requirements for check standards using interlaboratory testing.

3.1.4 firing, n - for the CFR engine, operation of the CFR engine with fuel and ignition.

3.1.5 friction mean effective pressure, n - for spark-ignition engines, the measure of the difference between IMEP and BMEP or power absorbed in mechanical friction and any auxiliaries.

3.1.6 fuel-air ratio, n - mass ratio of fuel to air in the mixture delivered to the combustion chamber.

3.1.7 indicated mean effective pressure, n - for spark-ignition engines, the measure of engine power developed in the engine cylinder or combustion chamber.

3.1.8 intake manifold pressure, n - for supercharged engines, the positive pressure in the intake manifold.

3.1.9 knock-limited power curve, n - for supercharge method knock rating, the non-linear standard knock intensity characteristic of a primary reference fuel blend or a sample fuel, expressed as indicated mean effective pressures, over the range of fuel-air ratios from approximately 0.08 to approximately 0.12.

3.1.10 mean effective pressure, n - for internal combustion engines, the steady-state pressure which, if applied to the piston during the expansion stroke, is a function of the measured power.

3.1.11 octane number, n - for spark-ignition engine fuel, any one of several numerical indicators of resistance to knock obtained by comparison with reference fuels in standardized engine or vehicle tests.

3.1.12 power curve, n - for supercharge method knock rating, the characteristic power output, expressed as indicated mean effective pressure, over a range of fuel-air ratios from approximately 0.08 to approximately 0.12, when a supercharge test engine is operated on isooctane plus 6 ml of tetraethyllead per U.S. gallon under standard conditions at a constant intake manifold pressure of 40 in. of Hg (134.3 kPa) absolute.

3.1.13 primary reference fuels, n - for knock testing, volumetrically proportioned mixtures of isooctane with n-heptane, or blends of tetraethyllead in isooctane which define the supercharge rating scale.

3.1.14 quality control (QC) sample, n - for use in quality assurance programs to determine and monitor the precision and stability of a measurement system, a stable and homogeneous material having physical or chemical properties, or both, similar to those of typical samples tested by the analytical measurement system. The material is properly stored to ensure sample integrity, and is available in sufficient quantity for repeated, long-term testing.

3.1.15 reference fuel framework, n - for supercharge method knock rating, the graphic representation of the knock-limited power curves for the specified primary reference fuel blends of isooctane + n-heptane and isooctane + TEL (mL/U.S. gal) that defines the expected indicated mean effective pressure versus fuel-air ratio characteristics for supercharge test engines operating properly under standardized conditions.

3.1.16 repeatability conditions, n - conditions where independent test results are obtained with the same method on identical test items in the same laboratory by the same operator using the same equipment within short intervals of time.
3.1.16.1 Discussion - In the context of this method, a short time interval is understood to be the time for two back-to-back ratings because of the length of time required for each rating.

3.1.17 reproducibility conditions, n - conditions where test results are obtained with the same method on identical test items in different laboratories with different operators using different equipment.

3.1.18 standard knock intensity, n - for supercharge method knock testing, trace or light knock as determined by ear.
3.1.18.1 Discussion - Light knock intensity is a level definitely above the commonly defined least audible "trace knock"; it is the softest knock that the operator can definitely and repeatedly recognize by ear although it may not be audible on every combustion cycle (intermittent knock). The variations in knock intensity can occasionally include loud knocks and very light knocks. These variations can also change with mixture ratio; the steadiest knock typically occurring in the vicinity of 0.09 fuel-air ratio.

3.1.19 supercharge performance number, n - a numerical value arbitrarily assigned to the supercharge ratings above 100 ON.

3.1.20 supercharge rating, n - the numerical rating of the knock resistance of a fuel obtained by comparison of its knock-limited power with that of primary reference fuel blends when both are tested in a standard CFR engine operating under the conditions specified in this test method.

3.2 Abbreviations:
3.2.1 ARV - accepted reference value
3.2.2 ABDC - after bottom dead center
3.2.3 ATDC - after top dead center
3.2.4 BBDC - before bottom dead center
3.2.5 BMEP - break mean effective pressure
3.2.6 BTDC - before top dead center
3.2.7 C.R. - compression ratio
3.2.8 FMEP - friction mean effective pressure
3.2.9 IAT - intake air temperature
3.2.10 IMEP - indicated mean effective pressure
3.2.11 NEG - National Exchange Group
3.2.12 O.N. - octane number
3.2.13 PN - performance number
3.2.14 PRF - primary reference fuel
3.2.15 RTD - resistance thermometer device (Terminology E344) platinum type
3.2.16 TDC - top dead center
3.2.17 TEL - tetraethyllead
3.2.18 UV - ultra violet