What does it mean when someone says a car has a trap speed?

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When a vehicle has a trap speed it means that once you it that trap speed you can not go any faster.It just mean you can't go faster than what the vehicle is safe to handle.

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The trap speed is the measured "instantaneous" speed of the vehicle at some timing location, for instance at the end of a 1/4 mile run.

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The answer with the statement about "not being able to go any faster" is totally wrong. What they are refering to is called a "governor". On a mechanicaly controled fuel system, it would be a physical device that would limit how far the throttle could open. On computer controlled fuel systems, it could be done mechanicly or by programming a speed or throttle limit into the computer. I know for a fact that the computer on my truck will start cutting back fuel to the engine if it's speed reaches 93MPH.

The 2nd answer which refers to measuring an instantanious speed is correct. Specificly, the "trap" is a pair or series of photoeyes usually at the finishline of a drag strip. When the first light beam in the front of trap is broken it starts a timer that stops when the light beam in the back is broken. Simple math using the time on the timer and the length of the trap is used to calculate the speed the car was traveling at when it passed through the trap.

Trap speed shouldn't be mistaken for Elapsed Time or "ET". ET is exactly what it sounds like, the time elapsed in traveling a specific distance. Usually this is a 1/4 mile drag strip but some strips are 1/8th mile. A winner on a 1/4 mile strip might not be a winner on a 1/8th mile (and vice versa) because of differences in the car's top speed and how quickly it gets to that speed. The human equivalent would be compairing sprinters to distance runners.

Because drag races are decided based on Elapsed Time, it's completely possible for the losing car in a drag race to have a higher (better) trap speed than the winning car which crossed the finishline first.

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If you are referring to a certain feature in a car engine nowadays, in a way, statement #1 is true. Engines today are equipped with "fuel cut systems" or "speed-limiter systems" which if you reach a certain rpm, the "fuel cut valve" activates cutting its fuel supply. This is a safety feature to protect the engines and surely the one driving it- thus will prevent your car to increase its speed any further. However, there are aftermarket "electronic chips" that you can purchase to alter engine parameters for computerized engines if you want to "race-modify" your car.

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The third answer is right on. Specifically there are 3 sets of photocells/lights at the end of a drag strip. There is the set at the actual finish line 1/4 mile (1320 feet) from the start line (and itsphotocell/light). That wouldn't be enough to measure speed across the finish line. There is a photocell/light 66 feet before and 66 feet after the finish line so that the amount of time it takes to travel 132 feet can be measured. From that, speed can be calculated. That means one needs to keep "on the gas" 66 feet past the finish line if they want the highest possible speed in a drag race. In a drag race, the winner is the one who crosses the finish line first so speed isn't very important unless you are able to set a record or want maximum bragging rights.

First answer by ID0000000000. Last edit by Tanceymae. Contributor trust: 6 [recommend contributor]. Question popularity: 157 [recommend question]