Designer's Corner 470

Auxiliary throttle control

If you're in a manual-transmission car stopped on a hillside, you'll need fancy footwork to avoid rolling backward when you try to move ahead. To deal with the problem, this throttle control uses a signal produced by a trigger-controlled potentiometer in the gearshift lever to open the car's throttle.

Within the shift lever, a trigger spring-loaded to the disengaged position is linked mechanically to a potentiometer. To operate the trigger, the driver first uses his or her thumb to press a spring-loaded safety-release button, which permits the trigger to move. Depressing the trigger then changes the potentiometer's voltage output in proportion to trigger movement. If the car has a carburetor, this signal causes the ECM to energize a small stepper motor coupled to the vehicle's throttle control. If the vehicle uses fuel injection, the ECM responds as though the foot-operated throttle control were calling for more power.

Michael R. Potis, JIT Engineering Services,Inc., 38162 Mt. Kisco Drive, Sterling Heights, MI 48310, 810-939-9435.

Quick-cooling AC

Designed to quickly lower the temperature in a hot car, this modified air-conditioning system worksas follows:

A pressurized refrigerant reservoir preserves refrigerant in liquid form after compressor shutdown. At start-up, the liquid refrigerant flows into the evaporator where it immediately absorbs heat. Conventional AC, by contrast, has no low-temperature refrigerant available at the evaporator during start-up.

In the winter, the system is also useful in speeding up windshield defogging.

Trenton Inc., 43244 Christy St., Fremont, CA 94538, (510) 490-9383.