Boost pressure: what a pound of boost adds
At sea level each psi of boost packs in about 6.8% more air before heat. 15 psi gives a pressure ratio of 2.02, but compression heat takes a large share back.
Drag racing classes: from bracket racing to Top Fuel
How drag racing is organised: heads-up pro classes like Top Fuel and Pro Stock, versus bracket racing with a dial-in, handicap start and breakout rule.
Eighth mile or quarter mile: how the two distances compare
A quarter mile is 1,320 ft (402.3 m) and an eighth is 660 ft (201.2 m). Why the eighth-mile ET is not half, and the 1.55 to 1.57 rule for converting it.
Weight transfer: why a car squats at the launch
Accelerating moves load from front to rear: ΔW = m·a·h ÷ L. For a 1,500 kg car at 1 g that is 278 kg, which helps rear-drive and hurts front-drive.
The 60-foot time: why the first 18 metres decide a run
The first 60 feet (18.29 m) are 4.5% of a quarter mile, yet a slow launch is carried to every later line. A 2.0 s 60-foot time means about 0.93 g on average.
Racing for pink slips: where the name came from
A pink slip is the ownership paper for a car. Racing for pink slips meant the loser handed over the title and the car. Here is where the term comes from.
Turbo or supercharger: two ways to force air in
Both pack more air into the cylinders. At 1 bar of boost the absolute pressure doubles, 1.013 to 2.013 bar, but the air heats up, so an intercooler matters.
Why drag racers do a burnout before every run
A burnout heats the tyres and cleans the tread. Worked example: raising grip from 0.8 to 1.0 cuts a 3,000 lb car's 60-foot time from 2.80 s to 2.44 s.
Power-to-weight ratio: why a lighter car runs quicker
Quarter-mile time scales with the cube root of weight per horsepower, so 10% less weight is only about 3.4% quicker. Worked examples with the Hale/Fox formulas.
The Christmas tree: pro tree and sportsman tree starts
A sportsman tree runs three ambers 0.5 s apart, then green. A pro tree lights all three together, then green 0.4 s later. Here is how R/T reads on each.
When to shift: why the best shift point is past peak torque
Shift where wheel force in the next gear equals wheel force in this one. In an example engine that is 6,898 rpm, 1,900 rpm past peak torque.
Horsepower and torque: how to read a dyno chart
Horsepower is torque times rpm divided by 5,252, so the two curves always cross at 5,252 rpm. An example engine shows what each line means for acceleration.
Launch RPM: between wheelspin and bogging down
A launch is limited by grip, not power. Worked example: 3,000 lb, 50% on the rear tyres, grip of 1.0 gives 0.625 g and a 2.44 s 60-foot time; spin costs 0.36 s.
Gear ratios and final drive: what gearing does to a quarter mile
Final drive multiplies every gear. A 4.10 instead of 3.42 gives 20% more force at the wheels but cuts road speed at any revs by 17%, and can run out of revs.
Reading a drag racing time slip: reaction time, ET and trap speed
A time slip splits one pass into reaction time, incremental ETs and speeds. ET does not include your reaction, so the quicker car can still lose the race.