Glossary
Drag-racing terms in plain English
You do not need to be an engineer to use MotoQuant. This page explains every term the simulator uses. Anywhere on the site, a word with a dotted underline opens a short version of its definition here.
- Quarter-mile time
- How long the bike takes to cover a quarter mile (402 metres) from a standing start. Also called "ET" or elapsed time.
- Lower is quicker. A 150 cc commuter takes around 18 to 20 seconds, a 400 cc sport bike around 13 to 14 seconds, and a stock Hayabusa about 10 seconds.
- Finish-line speed
- How fast the bike is going when it crosses the quarter-mile finish line. Racers call it "trap speed".
- It shows top-end power. Your quarter-mile time also depends on the launch. A stock litre-class sport bike crosses the line at around 215 to 235 km/h.
- First 60 ft (launch)
- The time to cover the first 60 feet (about 18 metres). It shows how well the bike gets off the line.
- Every extra 0.1 s lost here is roughly 0.07 to 0.1 s lost over the whole quarter mile. A strong launch on a sport bike is about 1.6 to 1.9 seconds.
- Halfway (⅛ mile)
- The time and speed at the halfway point of the run: one eighth of a mile (201 metres).
- Many strips run eighth-mile races. The quarter-mile time is usually about 1.5 to 1.6 times the eighth-mile time.
- Splits
- Elapsed times recorded at set distances along the run, such as 60 ft, ⅛ mile and the full quarter mile.
- Comparing splits shows where a run was won or lost: a slow first split means a weak launch, a slow final split means a lack of top-end power.
- Launch RPM
- The engine speed you hold while you let the clutch out at the start. Too low bogs the bike, too high spins the rear tyre.
- The best value depends on the bike, the tyre and the surface. The race-day setup tool suggests one for your conditions.
- Two-step (launch control)
- A rev limiter that holds the engine at a fixed speed while you wait on the line, so every launch starts from the same RPM.
- You hold the throttle fully open, the limiter keeps the revs steady, and you release the clutch.
- Gearing (sprockets)
- How far the bike moves for each turn of the engine, set by the front and rear sprockets and the gearbox.
- Shorter gearing (a bigger rear sprocket or smaller front one) accelerates harder but runs out of speed sooner. Taller gearing does the opposite.
- Sprockets
- The toothed wheels that the chain runs over: a small one on the engine and a big one on the rear wheel.
- Changing the number of teeth on either one changes the gearing. One extra tooth on the rear sprocket makes the bike pull a little harder and top out a little lower.
- Air and altitude
- Hot, high or humid air is thinner, so the engine gets less oxygen and makes less power. This setting accounts for that.
- Engineers call it density altitude. The same bike can be a few tenths of a second slower on a hot day or at a high-altitude strip than on a cool day at sea level.
- Traction
- How much grip the rear tyre has on the road surface. When the engine asks for more than the grip allows, the tyre spins.
- Prepped drag strips have far more grip than ordinary roads. A wet or dusty surface can cost a lot of time because power is wasted as wheelspin.
- Wheelie
- When the front wheel lifts off the ground under hard acceleration. The bike loses time while the front is in the air.
- Wheelie bars, a longer swingarm and a lower rider position all help keep the front wheel down so the bike can use its full power.
- Cost per tenth of a second
- How many rupees you spend for each 0.1 second a part makes your bike quicker. Lower is better value.
- It is the price of the part divided by the tenths of a second it gains. A cheap air filter with a small gain can beat an expensive part with a big one.
- Instant estimate
- A very fast approximate answer calculated in your browser. It is close to the full simulation but not exact.
- Use it for quick what-if checks as you change things. Run the full simulation when you want exact splits, charts and a result you can save.
- Full simulation
- The complete, exact calculation that follows the bike millisecond by millisecond along the whole quarter mile.
- It takes a moment longer than the instant estimate and gives you the exact splits and speed-over-time charts. Only full-simulation results can be saved.
- Engine power change
- Make the engine stronger or weaker by a percentage. For example, +10% means 10% more power than stock.
- Use it to try a tune, an exhaust or a bigger engine before you buy anything. Negative values model a worn or restricted engine.
- Weight added or removed
- Change the bike weight in kilograms. Use a negative number to remove weight, such as a lighter battery or exhaust.
- A rule of thumb is that 10 kg lighter is worth roughly 0.1 to 0.15 seconds in the quarter mile, depending on the bike.
- Air resistance (Cd·A)
- How much the bike and rider push against the air. It is the drag coefficient (Cd) multiplied by the frontal area (A).
- It matters more the faster you go, because air resistance grows with the square of speed. A fairing and a tucked rider reduce it.
- Redline
- The highest engine speed the bike is allowed to run, in revolutions per minute. The engine changes gear or hits the limiter here.
- Most sport bikes shift up just before the redline in a drag race to stay where the engine makes the most power.
- Wheelspin (slip)
- How much faster the rear tyre is spinning than the bike is moving. A little slip is normal and gives the best grip.
- Too much slip burns power as smoke instead of pushing you forward. The simulator tracks it moment by moment.
- Build type
- What kind of parts you are willing to use: street-legal only, drag-strip prep, full race, or anything goes.
- Street-legal keeps the bike road-worthy. Drag-strip prep adds track-only parts. Full race and anything-goes allow engine modifications such as nitrous or a turbo.
- Stage 1 / 2 / 3 / 4
- A common way to describe how far a bike is modified: a higher stage means bigger changes and a bigger bill.
- Stage 1 is bolt-ons (exhaust, filter, tune). Stage 2 adds clutch and gearing work. Stage 3 and 4 go into serious engine work and are usually for track use only.
- Outlaw (no-limit) build
- A build with no rules and no budget cap: every compatible part is on the table, aiming only for the quickest time.
- It is the "what is the absolute best this bike can do?" answer. It is usually not street-legal and not cheap.
- Dyno
- A machine that measures how much power and twisting force an engine delivers at the rear wheel at each engine speed.
- The printed result is a dyno chart. You can upload one to My data so the simulator uses your engine instead of a typical one.
- Dragy
- A small GPS device that sits on your bike and records your real quarter-mile times and speeds.
- Upload a Dragy run to My data to compare what really happened with what the simulator predicted.
- Top speed
- The fastest the bike can go when it keeps accelerating until the air resistance matches the power.
- Some bikes are limited electronically, often to 299 km/h on the big sport bikes. The simulator can show it with or without the limiter.
Missing a term? Tell us on GitHub, or head back to the simulator.