Bench Racing Productions
Welcome to the FAQ page for Drag Racing Calculator, an iOS and Android app produced by Bench Racing Productions. If you have questions, you can email us.
Q: How accurate is this calculator?
A: This was built using Professor Geoffrey Fox's quarter mile equations published in 2001. His calculations were vetted against countless quarter mile slips and are considered to be the most accurate for determining quarter mile ET and trap speed.
There are many factors, however, that determine your actual ET, including driver capability, traction, weather conditions, transmission gearing, and altitude. I consider the most reliable calculation to be horsepower based on trap speed, as trap speeds tend to not be affected by traction and driver error issues as ETs are.
That said, this tool is for estimating your quarter mile ET, trap speed, and horsepower. It is not a substitute for going to the track or dyno.
Q: What is the difference between brake horsepower (BHP) and wheel horsepower (WHP)?
Brake horsepower (BHP) is the amount of power measured at the flywheel on an engine dyno. Wheel horsepower is the amount of power measured at the wheels on a chassis dyno (i.e., a roller dyno). WHP figures in drive train losses, therefore WHP readings will always be lower than BHP readings. I am using a standard correction factor of a 15% reduction for wheel horsepower, although the actual correction factor for each vehicle will be slightly different, depending on whether it's FWD, RWD, or AWD. AWD cars tend to have higher losses than FWD or RWD cars.
Most people who dyno their cars do so on a chassis dyno as it isn't practical to remove the engine to measure power, which is why I have included an option to perform calculations on WHP. You can access this on the settings menu by clicking on the blue gear icon.
Q: What is altitude correction and how does that affect my horsepower numbers and times?
The NHRA uses a standard correction factor for tracks that are 1200 feet above sea level or higher. The higher the altitude, the less power you make, thus the slower your ET and trap speeds will be. A car that runs 11.5 seconds in the quarter mile at sea level will run a full second slower at 3500 feet above sea level. I've built this correct factor into the app and have made it available in the settings menu, which you can get to by clicking the blue gear icon.
Q: Why is my car faster/slower/more powerful than the calculations I get from Drag Race Calculator indicate?
A: There are many factors that determine your actual ET and trap speed. These include driver capability (missed or less-than-optimal shifts), traction (slicks will always net a better ET than street tires), ambient temperature (you'll go faster in cold weather than in hot weather), and transmission gearing (lower gearing nets quicker ETs than taller gearing). This calculator cannot take into account all of these factors. Again, this tool is for estimating your quarter mile ET, trap speed, and horsepower. It is not a substitute for going to the track or dyno.
