Who doesn’t like watching cars doing big wheelies down the track? In most cases, it’d be the driver and his crew. Why? Well, as spectacular as they may be, uncontrolled wheelies can cost you valuable fractions of a second and potentially cause damage to the suspension and even the chassis.
Why do cars wheelie?
The best examples of big wheelies can be found on a drag strip, that’s because drag cars tend to have the right recipe for lifting the front end – big power and incredible grip through the tyres to the sticky racetrack.
When a drag car launches from the start line the rotational momentum of the rear wheels overcomes the weight of the car in front of the rear axle. The rear axle then acts as a pivot point forcing a weight transfer from the front to the rear. As the front end lifts, transferring even more weight rearwards, less and less force is required to lift the front it even higher.
How high the car lifts depends on several things: the power the engine makes at each RPM point, the weight of the car, the speed of the car, the suspension setup, the centre of gravity and the wheelie bar setup (if the car has them).
Controlling a wheelie
There are two ways of controlling a wheelie. The mechanical option is to fit “wheelie bars”. These are mounted directly on the rear end of the car and are height-adjusted to the amount of allowed lift. While this is a common sight on many drag cars, some classes do not allow them.
The second option is to control the front-end lift using an ECU with a Laser Ride Height Sensor.
How Does It Work?
Once mounted, the Haltech Laser Ride Height Sensor measures the distance from the sensor to the ground and feeds that information to the ECU. We can then set up a maximum lift distance and map the ignition and fuel against the front-end lift and the road speed.
To put it simply, when the front end lifts, the ECU will start cutting ignition or fuel or both. Once the front end comes down and makes contact with the ground the ECU restores the fuel and ignition to their original setting.
To prevent the front end from coming up again we can delay the return to the normal fuel/ignition map using the Timer function in the Torque Management setup. This will allow the car to settle, pick up speed and transfer some weight onto the front end.
We recommend mounting the sensor near the steering rack and between 3″ – 5″ from the ground at static ride height. However, your application may vary and require some adjustment.
The actual laser lens (red panel) needs to be pointing downwards and the wiring harness connection either to the right or to the left. Mounting the Laser Ride Height Sensor incorrectly can result in incorrect ride height readings and trigger an incorrect response from the ECU.
The Haltech Laser Ride Height Sensor comes pre-terminated with a DTM3 connector. If used with an HT-141376 (Elite 2500/2500T V8 Big Block/Small Block GM, Ford & Chrysler Terminated Engine Harness) then this sensor may be plugged directly into SPI4 on the engine bay harness with no modification.
With custom or universal wiring use the following pin-out:
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