Beginning January 1, 2015 two new changes made to the Automatic Horsepower factoring System will go into effect. These two changes are described below and are further defined in the highlighted text found in the Automatic Horsepower Factoring System (AHFS) Explained document also shown below.

 “Mineshaft” Events

To decrease the potential for horsepower/index adjustments when favorable atmospheric (i.e. “mineshaft”) and/or track conditions may have contributed to extraordinary performance the NHRA has developed a system to protect the racers’ horsepower/indexes.

Competitor Requests

Per the requirements outlined below “only one request per competitor” will be strictly enforced. Additionally request for horsepower and/or index changes from competitors will only be reviewed annually, at the end of the year. Once a combination has received a horsepower increase it is not eligible for a decrease for three (3) years.

Automatic Horsepower Factoring System (AHFS) Explained

The AHFS is used to review and evaluate runs in Stock and Super Stock for possible horsepower adjustments. The review is conducted twice per racing season. The two reviews are compiled individually so the data is not cumulative. Runs included in the AHFS database are limited to final qualifying runs (Q data) and all elimination runs (E data) at all NHRA National, Sports National and LODRS events. (At events where class eliminations are run, all class elimination runs are included in the AHFS database. Only the first round of class is part of qualifying and therefore is part of the "Q" database.) The "Q" data and "E" data files are the official data gathered by the NHRA timing system and processed through the NHRA Information Technology department. NHRA "Q" data and "E" data are the only data files used for the AHFS. No runs made during National Opens, test and tune, time trials, or races within a race (i.e. Jegs Allstar eliminations, Stock / Super Stock Combos or other races that are not part of a season long points championship) are included in any review.

The first review period includes data from National and LODRS events 1 through 12 and the second period includes runs from events 13 through 24. The following procedure is used in reviewing run data:

Final qualifying, class eliminations, and elimination runs of 1.00 seconds or more, under the index, at NHRA National, Sports Nationals, and LODRS events will trigger an automatic review. (The combination must make at least two runs of 1.00 or quicker before a review is triggered to prevent a "one time fast run" from triggering the system.) In reviewing runs of 1.00 or more under the index, the database of runs for the engine combination being reviewed are put through three screenings as listed below. The screenings will look for an overall engine family average or class/engine average faster than 0.850-second under. Runs of .350 and slower are not included in calculating the engine or class/engine averages:

• Engine family average: The overall engine average for all cars, regardless of class, running the particular engine combination being reviewed are included in this screening.
• Class/engine average where engine is run: The class/engine average of the car running the specific combination in the class that triggered the review is studied.
• Body style and transmission type: Also considered in the above two screening processes are body style of the engine combination being reviewed and transmission type. Adjustments are only in effect for the specific car model being evaluated. The body style are generally classified by the OEM auto manufacturers' definition of "platform", i.e., the Camaro and Firebird body are both based on the same platform and therefore considered the same with regard to body-style classification. In some instances, however, more than one body style will trigger a review. With regards to transmission type, if the class average triggers the review, the adjustment would be for classes with the type of transmission triggering the change. However, if an engine family average triggers the review, the adjustment would be for all transmission types.

If either the engine family average or the class/engine average are found to be faster than 0.850-second under, a change will be initiated.
To more clearly illustrate how the AHFS program affects a given combination, the following is a hypothetical evaluation in Stock class for a 305-cubic-inch, 215 factory rated horsepower, fuel-injected Camaro during a review period:

Two K/SA Camaros running this combination ran 1.114- and 1.187- second under the index, triggering a review. As per the procedure outlined above, the overall engine average is analyzed first. Upon reviewing the engine average made by the 305/215/241 FI combination, 10 runs had been recorded (2 in K/SA and 8 in L/SA) with a total engine average of .845-second under. Because the overall engine average did not hit the required 0.850 under, the combination did not warrant a horsepower adjustment based on overall engine average.

The next step, per the procedure outlined above, is a class/engine review. The class of the car that actually triggered the review was K/SA. The class review revealed that K/SA had a class/engine average for the combination in question of 1.101-second under, therefore surpassing the 0.850-second-under requirement and signaling a horsepower adjustment for all 305/215/241 FI Camaros.

An important element to note and one most often misunderstood by racers is that although a K/SA Camaro affected the change, the L/SA 305/215/241 FI Camaros that run this combination also received a horsepower adjustment. The reason is that a specific combination can run in more than one class based on NHRA rules; therefore, all cars with the specific engine combination, transmission and body style will be affected.

To decrease the potential for horsepower/index adjustments when favorable atmospheric (i.e. “mineshaft”) and/or track conditions may have contributed to extraordinary performance the NHRA has developed a system to protect the racers’ horsepower/indexes. If at the conclusion of qualifying the first competitor in the bottom half of the field is -.850 seconds or more under the class index, the Q and E Data will not be used for the mid-year and year end reviews. This will only apply to qualified fields of 32 or more cars. Automatic changes due to runs of -1.20 or more under the respective index will still count at these events. At any event where the Factory Showdown is held, no runs by Showdown cars will be used in the mineshaft calculations.

Once the need for an adjustment is determined, the following sliding-scale formula, based on a percentage of horsepower, is used to calculate the horsepower increase:

Adjustments are rounded up to the nearest full horsepower even if the fraction is below 0.5 horsepower. As an example, 2.15 horsepower is rounded to 3 horsepower. The quickest run, by the combination being reviewed, is used to determine the adjustment percentage.

Runs of 1.200 or more under the index will be reviewed and adjusted Tuesday following the event. Runs at all NHRA National, Sports National, and LODRS events, including those at altitude factored race tracks, are included in the 1.200-second-or-more-under analysis. No runs made during National Opens, test and tune, time trials, or races within a race (i.e. Jegs Allstar eliminations, Stock / Super Stock Combos) are included in the 1.200-second-or-more-under review or adjustment.  This is done to better react to any out-of-line indexes or under-horsepowered combinations. Therefore, at all such events, a horsepower adjustment or index reduction will be initiated Tuesday following the event.

The decision to adjust horsepower or to reduce the index will be at the discretion of the NHRA Tech Department.

In addition to reviews resulting in a horsepower increase, a competitor can request (only one request per competitor, per review period.) a review for the purpose of a decrease in horsepower factor or index adjustment; the review is conducted once per racing season. The request must include eliminator, year, model, engine size, advertised horsepower, factored horsepower, and class; to be eligible. (NHRA AHFS Horsepower Request Form)

The screenings will look for an overall engine family average less than 0.550-seconds under. Runs of 0.100-second under and slower are not included in calculating the engine average:

In addition, the combination must NOT make two runs of 0.650 or quicker or any run 0.850 or quicker during the past two (2) review periods, for the review to continue. Once a combination receives a horsepower increase it is not eligible for a decrease for three (3) years.

Engine family average: The overall engine average for all cars, regardless of class, running the particular engine combination being reviewed is included in this screening. If the engine family average is found to be slower than 0.550-second under, a change will be initiated.

To more clearly illustrate how the AHFS program affects a given combination, the following is a hypothetical evaluation in Stock Eliminator for a 305 cubic-inch, 150 factory rated horsepower, carbureted Camaro during a review period:

A written request triggered a review by the committee. As per the procedure outlined above, there were NOT 2 runs 0.650-second or quicker preventing a review or ANY run 0.850-second or quicker preventing a review. The overall engine average is analyzed next. Upon reviewing the engine average made by the combination, 10 runs had been recorded (2 in I/SA and 8 in J/SA) with a total engine average of 0.535-second under. Because the overall engine average did not hit the required 0.550-second under, the combination proceeds with the evaluation.

Once the need for an adjustment is determined, the following sliding-scale formula, based on a percentage of horsepower, is used to calculate the horsepower decrease:

Adjustments are rounded up to the nearest full horsepower even if the fraction is below 0.5 horsepower. As an example, 2.15 horsepower is rounded to 3 horsepower. The quickest run, by the combination being reviewed, is used to determine the adjustment percentage. The decision to adjust horsepower or to increase the index will be at the discretion of the AHFS Committee.