GB/T 503-1995 Determination of octane number of gasoline (Motor method)

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

GB/T 503-1995 specifies the determination of the Motor Octane Number of gasoline in a single-cylinder variable compression ratio engine, and this page summarizes its identity, scope, principle, apparatus, reference fuels, conditions, measurement sequence, calculation, precision and open points.

Evidence note: the 1995 edition has been abolished and was replaced by the 2016 edition on 2017-01-01; this page is an original compilation from the 45-page original of the same edition and is not the full standard text. Technical review is pending; dense tables, unit conversions and some annex formula queries are retained, and this page is not a basis for automatic table look-up, actual engine adjustment, product applicability or certificate values.

Identity and version: Original PDF pages 1, 45; official edition status and Announcement No. 8 of 2016. Number GB/T 503-1995, title Determination of octane number of gasoline (Motor method). The cover gives publication on 1995-12-21 and implementation on 1996-08-01; the printing date of August 1996 on the end page is not taken as the publication date. The official abolition record and the identity of the original are retained, and the old review record of continued validity is not used to override the abolished status.

Object of determination and scope: Original PDF pages 2, 6; scope and the restricted branch above 100. The scope of this edition covers automotive gasoline and spark-ignition aviation engine gasoline with an octane number below 100. Other engine types must meet the toluene fuel calibration conditions of the original text; applicability is not presumed directly from the name. The body also contains a specific branch for fuels above 100 and its operation, which cannot be expanded into a general scope for all gasolines/all engines.

Principle and indices: Original PDF pages 3–4; principle and definitions. Under the specified single-cylinder variable compression ratio engine and operating conditions, the knock response of the sample is compared with reference fuels to obtain the Motor Octane Number MON. MON is not the Research Octane Number RON or the aviation quality value MPN. The antiknock index coefficient of the same fuel requires the corresponding road test, and (RON+MON)/2 must not be treated as a general formula for all conditions.

Apparatus and reading system: Original PDF pages 3–5, 11–29; apparatus and table system. The original uses a CFR single-cylinder variable compression ratio engine, a knock measuring instrument, a cylinder height micrometer or a digital counter. The two types of height reading and the direction of atmospheric pressure correction are identified separately. The multi-altitude/throat condition tables are not all reconstructed, and this card does not provide automatic table look-up; candidate values must not be used to adjust an actual engine before the unit queries are resolved.

Reference and calibration fuels: Original PDF pages 2–4, 6, 32–33; reference fuels and calibration. The original covers isooctane, n-heptane, toluene calibration fuels and a specific leaded branch. The reference system below 100 and the system above 100 must not be mixed casually. The reference/calibration fuel tables are method information of this edition, not certified values of Origin products, blending permission or a sales correspondence. Hazards such as leaded materials must be managed under controlled safety data.

Samples and safety: Original PDF page 6, 9.21; sample handling and the safety boundary. The cold sample condition in the original is 2–10 °C, which is test preparation information for this method, not a product storage condition. Sampling, fuel handling and engine operation must be controlled; this learning card does not reproduce the complete leaded blending and start-up operating instructions. Storage, service life and batch values of specific products require the corresponding certificate.

Conditions and quality control: Original PDF pages 4–8; operating conditions and checks. Typical conditions of this edition include 900 ± 9 r/min, oil temperature 57 ± 8.5 °C, coolant temperature 100 ± 1.5 °C, intake air 38 ± 2.8 °C and mixture 149 ± 1.1 °C. Each condition has the branch restrictions of the original and cannot be assembled into an unconditional operating specification. Toluene calibration has time requirements and recalibration after a change of operator, shutdown or overhaul; full execution still requires the original text and controlled procedures.

Measurement sequence and valid records: Original PDF page 9, 13.6–13.10; valid readings. The interpolation method first brackets the sample response with two reference fuels whose octane numbers differ by no more than 2; record after stabilisation, and reverse the reference order on repetition. When the difference between the two sets of calculations is no more than 0.3 and the mean knock reading of the sample is 50 ± 5, process as two sets; if the difference between the first two sets is no more than 0.5, the third result lies between them and the mean knock reading of the sample is still within 50 ± 5, process as three sets. When the difference is greater than 0.5 or the third result does not lie between the first two, the original data must not be retained as a valid result.

Calculation and symbols: Original PDF pages 9–10, 13.11 and page 42, footnote to C1. The interpolation formula has been checked against the original figure on PDF page 9: X = [(b−c)/(b−a)] × (A−B) + B. A/B are the octane numbers of the high/low octane reference fuels; a/b the corresponding mean knock meter readings of the high/low references; c the mean reading of the sample. The valid record conditions of the original must be met before calculation, and this formula does not cover the compression ratio method or all branches above 100. The footnote to original Table C1, compression ratio = 6345/(1850 − counter reading units) + 1, has been checked against the original figure but does not replace full-table verification, and no calculator is released for the time being.

Precision and use boundaries: Original PDF pages 10–11, Chapter 16; repeatability and reproducibility. The original precision clauses are stated at the 95% confidence level. The repeatability of 0.3 applies only to the mean MON 85–90 of this edition and its same-laboratory conditions and cannot be extended to the whole range. The reproducibility table follows; points between table values are interpolated according to the original and not extrapolated; it is method precision information, not batch certificate uncertainty. Mean MON | Permissible reproducibility difference 80 | 1.2 85 | 0.9 90 | 1.1 95 | 1.1 99 | 1.5 100 | 1.1 105 | 1.8

Reporting and rounding: Original PDF page 10, 13.11.3/14.6/15; reporting and rounding. The result is reported as MON; the original retains three decimal places in the calculation and then applies its cited rounding requirement to form the final one decimal place; intermediate digits must not be taken as the reporting precision. The MPN conversion for aviation gasoline above 100 has a separate table, and the MON figure must not be labelled directly as MPN. The current versions of the cited rounding specifications have not been checked one by one.

Tables, annexes and completeness: Original PDF pages 1–45, continuous evidence; Annexes A–D. The printed body pages of the original run continuously from 1 to 43, cover and copyright pages making 45 pages in total; the page count does not mean that technical review of 45 pages has been passed. Annexes A/B/C/D were originally marked as supplementary items and are not rewritten into modern annex categories. Operating Tables 1–12, the B1/C1 conversion matrices and the D1 curves are not all rebuilt cell by cell; the checked Table 10 still requires a second check before publication, and this card cannot be called a complete table look-up tool.

Open points and items to be verified: Original PDF pages 5, 12, 15–16, 19–20, 22, 31, 38, 44; literal queries in the original. The conversion query between the original spark plug 0.51 ± 0.13 mm and the parenthetical 0.20 ± 0.005 in is retained; Table 2 high 85 count tolerance ±3.5 conflicts with ±35 in the body and in another table; the sign of the last term in the radical expression of Table 8, the B1 footnote, the D2.5 coefficient and the D3.2.1 unit conversion still require verification. Literal anomalies in dense tables such as 77.5/.745 and 79.3/542 are only registered, not corrected by trend or taken as valid calculated values. Partial scan ghosting is not guessed from OCR.

Customer Q&A and source: Original 45-page original and page-by-page segmented image evidence. Q: Can this 1995 page be replaced by the new edition? A: It cannot be replaced automatically; the number, year and purpose must be specified. Q: Can the repeatability of 0.3 be used as product uncertainty? A: No; method precision and the values and uncertainty of a specific batch certificate are verified separately. Q: Can this card be used directly for engine adjustment or table calculation? A: No; the complete matrices and the original unit/formula queries still await technical review, and the controlled original standard and procedures should be used. The source of this card is the original of the same edition of GB/T 503-1995, 45 pages in total; the original and the OCR are read-only and the scans are not published. Page-by-page facts and unresolved technical queries are listed separately; the historical edition is retained for reading, and current sample applicability or product relationships are not presumed.

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