2020 Weight Calculation

In an effort to continuously test and evolve our ruleset, we will be implementing a temporary rule change for the 2020 season regarding our power-to-weight calculation.

Our NASA Rocky Mountain Chapter is creating a local rule addendum to their ST6 class, and this change allows us to align with those local addendums in order to be more appropriately placed among their run-groups and sessions.

To calculate your vehicle’s new minimum weight please obtain your “average HP” using the method below, this is taken from NASA’s ST rules classification.

Step 1:
– Obtain the following sixteen data points from the dyno’s 50 RPM data export numeric RPM/HP table printout:
– Horsepower at: 250 rpm, 500 rpm, 750 rpm, 1000 rpm, 1250rpm, 1500 rpm, 1750 rpm, 2000 rpm greater than Max HP rpm
– Horsepower at: 250 rpm, 500 rpm, 750 rpm, 1000 rpm, 1250 rpm, 1500 rpm, 1750 rpm, 2000 rpm less than Max HP rpm
(If any of the above data points at higher RPM than Max HP RPM do not exist due to redline, then those potential data points will not be used in the calculation of Avg HP.)

Step 2:
– For vehicles with a redline greater than 7000 rpm: The seven (7) highest data points of the above sixteen(16) will be used in the calculation below:
Avg HP = (Max HP + (sum of the seven highest data points)) / 8

– For vehicles with a redline between 6000-7000 rpm: The five (5) highest data points of the above sixteen will be used in the calculation below:
Avg HP = (Max HP + (sum of the five highest data points)) / 6

Step 3:
Once you have your avg HP number, there is a weight modification factor based on the weights listed below. Once you know your cars weight, add the modification factor to 16.0
less than 2250lbs = 0.5
less than 2450 = 0.4
less than 2550 = 0.3
less than 2650 = 0.2

For example, my car weighs ~2350 with me in it, so I would take a .4 factor, so my power-to-weight ratio is 16.4

Then, multiply that number, (16.4 for me) with your average HP, and you now have your official, minimum-race-weight.

I’ve taken a general look at some of our existing car dynos and compared the old ruleset and the new 2020 ruleset, most cars are left mostly unchanged, such as Weston and Andrew. The biggest changes are to cars that had High TQ can now run at a lower weight, and cars that had a High Hp+low tq number gain some weight.

– We will also be lifting the 2200lb minimum weight threshold from the ruleset to better allow our low HP cars to remain competitive against the higher HP cars.


Front4 Co-Director #02 Blue 1992 Acura Integra

One thought on “2020 Weight Calculation”

  1. Please note that this a temporary measure for 2020, in an effort to be accommodating of a wider variety of cars, and more compatible with our NASA classing. Any intentional violations will not be tolerated, and we may return to the traditional Minimum Weight Rules if this generosity becomes a problem. Violators may also be tarred and feathered.

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