WOT stands for Wide Open Throttle. It's the state when the accelerator pedal is pressed all the way down, the throttle body's butterfly valve is completely open, and the engine is receiving the maximum possible amount of air for combustion. This is a fundamental concept for understanding everything from acceleration tests to engine diagnostics and fuel economy.
When you perform a WOT run, the engine's computer (ECU) ignores signals from the oxygen sensors and shifts to a pre-programmed open-loop fuel map. This map delivers a richer air-fuel mixture to ensure maximum power and prevent engine knock, which is a primary reason why fuel efficiency drops significantly during WOT.
Understanding WOT is crucial for interpreting performance figures. For example, a vehicle's 0-60 mph time is always measured under WOT conditions. It's also a standard diagnostic procedure; mechanics use WOT to check for issues like misfires under high load or to test the fuel pump's ability to maintain pressure.
However, constant WOT driving is harsh on your vehicle. It increases engine wear, generates excessive heat, and leads to poor fuel mileage. It's best reserved for short bursts, like safe highway merging or performance testing.
| Aspect | Description | Typical Data/Measurement |
|---|
| Engine Mode | Switches to open-loop operation | Fuel mixture ignores oxygen sensor feedback |
| Air-Fuel Ratio | Runs richer for power and cooling | Approximately 12:1 to 13:1 (vs. 14.7:1 at cruise) |
| Purpose | Maximize power output | Measured in horsepower (hp) and torque (lb-ft) |
| Common Usage | Acceleration testing, diagnostics | 0-60 mph time, 1/4 mile time, top speed |
| Fuel Economy | Significantly decreases | Can be 80-90% lower than highway cruising efficiency |
| Engine Load | Maximum load condition | Manifold Absolute Pressure (MAP) sensor reads near atmospheric pressure |
