Question 1

What is a correction factor in drag racing?

Accepted Answer

A correction factor (CF) normalizes current atmospheric conditions to a standard day of 60°F, 0% relative humidity, and 29.92 inHg barometric pressure. When CF is above 1.000, the air is less dense and cars run slower. When CF is below 1.000, air is denser and cars run faster. The NHRA formula is: CF = (29.235 / (Pb - Pv)) × sqrt((Tf + 460) / 519.67). NumberEdge Racing computes CF automatically and uses it to predict your ET.

Question 2

What is density altitude in drag racing?

Accepted Answer

Density altitude (DA) is the theoretical altitude at which the current air density would exist in the standard atmosphere. DA of 0 feet = sea-level standard density. Higher DA means thinner air, less power, and slower ETs. DA below 1,000 feet is good racing air; above 3,000 feet noticeably slows cars. NumberEdge Racing computes DA alongside correction factor, air density ratio, grains, vapor pressure, dew point, and wet bulb.

Question 3

How does weather affect drag racing performance?

Accepted Answer

Three variables control engine power: temperature (cooler = denser air = more oxygen), humidity (lower = less moisture displacing oxygen), and barometric pressure (higher = denser air). A 10°F temperature change can move a bracket car's ET by 0.03–0.08 seconds. In bracket racing, 0.01 seconds separates winning from breaking out. NumberEdge Racing tracks all atmospheric variables and predicts how they affect your specific car.

Question 4

What are grains in drag racing weather?

Accepted Answer

Grains (grains of moisture per pound of dry air) measure absolute water content. Unlike relative humidity, grains is a fixed measure of moisture displacing oxygen. Zero at 0% humidity, 120+ at 90°F/80% RH. Formula: Grains = 4354 × Pv / (Pb - Pv). Many experienced tuners prefer grains over relative humidity.

Question 5

How do I predict my ET from weather conditions?

Accepted Answer

Compute corrected ET for each run: Corrected ET = Actual ET / CF. Average your corrected ETs, multiply by current CF. Better: use linear regression of ET vs. CF from 5+ runs to capture your car's specific CF sensitivity. NumberEdge Racing automates this — logs runs with weather snapshots, learns your car's weather response, and predicts ET with a confidence interval.

Question 6

What is CF sensitivity in bracket racing?

Accepted Answer

CF sensitivity measures how much your car's ET changes per unit of CF change (seconds per 0.010 CF). Naturally aspirated cars: 0.08–0.12. Supercharged/turbocharged: 0.15–0.20+. Every car is different — generic calculators treat them the same. NumberEdge Racing learns your specific CF sensitivity from actual run data for more accurate predictions.

Question 7

What is the best drag racing weather app?

Accepted Answer

NumberEdge Racing is a free drag racing weather calculator and ET prediction tool. It computes CF, DA, ADR, grains, vapor pressure, dew point, and wet bulb. Unlike generic calculators, it logs runs, learns your car's CF sensitivity, predicts ET with confidence intervals, and recommends dial-ins based on breakout risk.

Question 8

What is vapor pressure in drag racing?

Accepted Answer

Vapor pressure is the partial pressure of water vapor in the air (inHg). It's how humidity reduces power: water vapor displaces oxygen in the intake charge. At 60°F/50% RH, Pv ≈ 0.26 inHg. At 90°F/80% RH, Pv ≈ 1.12 inHg — over 4x higher, significantly reducing available oxygen.