Active Standard: D7170 - 12a
Rationale for Change: The ballot is meant to meet the requirement in the method to maintain the correlation between D7170 and D613 as specified in A3.3. At the June 2012 Section B meeting a presentation was given on the agreement between the NEG D7170 data compared to D613 and how an updated equation could improve the correlation, during the meeting it was suggested that the original ILS data be added to the data set so this was done for this ballot item. The proposed equation has been modified based on 38 recent NEG sample data and the original ILS data with the exception of S4 that was removed after evidence was presented at Sub 1 that the sample had degraded. NEG sample D1078 was also added after the June meeting as it was a sample that extended the range of the data set. The equation was generated by using the ID and Cetane values from the ILS and the NEG samples along with the published precision statement of D7170 and D613 to calculate uncertainty; this aligns with the intent of the ballot only to update the equation. Following the same approach used with the original ILS data the D6708 spreadsheet was populated with the inverse of the DCN (1/DCN*100) and the Cetane values, this yielded the equation of 150.4*(1/ID)+5.3. The equation was then applied to the ID values and the resulting DCN values and the D613 results were entered into the D6708 spreadsheet to assess the equation. A presentation accompanies the ballot providing detail on the D6708 analysis of the new updated equation.
Keywordscetane number; derived cetane number; diesel performance; ignition characteristic; ignition delay;