Instructions
Enter a vehicle by pressing the Y button on an Xbox 360 controller. You must be in a Triathalon race for the vehicle to have nitro. Watch for a bar to appear at the lower right of the screen to confirm the vehicle has nitro. Press the B button to activate your nitro.
Press the Triangle button on a PlayStation 3 controller to enter a vehicle. Watch for a bar to appear at the lower right of the screen. It indicates you are in a Triathalon race and your vehicle has nitro. Press the Circle button to activate your nitro.
Hold down the appropriate nitro button to continue to use your nitrous until it runs out. Wait for the nitrous to replenish, once the bar has been depleted. Look for orange flames coming from your vehicle's muffler and listen for a shrill noise from the car. These two signs indicate that your nitrous is ready for use again.