Friday, September 04, 2009

Testing Radar Detectors in the Sonora Desert

Radar detector manufacturers usually introduce new models at the Consumer Electronics Show, the huge trade show held in Las Vegas each January. But by the time these new models are flowing through the retail pipeline, summer has arrived at our Sonora Desert test sites.

There are better times to work there. Aside from venomous bark scorpions and Western Diamondback rattlers, summer days routinely hit 108 degrees. The overnight low temperature frequently hovers well above the 90-degree mark. Locals don't blink at those numbers, but when the thermometer resolutely creeps past 110, the difference is both palpable and as history shows, lethal. (The 2005 heat wave led to the deaths of 18 people, for example.) This year it's been hotter.

To test radar detectors we use three primary sites along rural desert highways in central and western Arizona. Our radar vehicle, a Ford Expedition 4WD, is parked at roadside and remains idling there for the day. Six to eight hours spent motionless in ambient temperatures ranging up to 116 degrees, with the air conditioning running flat out, places considerable thermal stress on a cooling system. The intercooled ATI D1SC ProCharger supercharger only adds to the heat load.

I've owned several new police vehicles and modified most of them—B4C Camaro, Mustang SSP, Crown Victoria Police Interceptors and Chevrolet Caprice 9C1s, among others--and I'm impressed by their bulletproof cooling systems. These include larger radiators, extra-capacity fans, and heat exchangers (coolers) for engine, transmission and power steering fluids. Also standard are additional front fascia air intakes and wide-open-throttle A/C cutoff switches. Any of these vehicles could be run at top speed for an hour and then parked nose-in to a block wall and left idling in 105-degree heat. Come back one hour later and fluid temperatures would still be within spec.

But even a police-package vehicle can't maintain those healthy fluid temperatures all day long. Inside, the first sign of distress is a steady rise in air temperature flowing from
the A/C vents. As the sun climbs higher, the pleasant 62-degree dash air rises in lockstep. Engine oil will nudge 235 degrees; the tranny fluid nearly as high. After three hours the A/C will be blowing warm air, with fluid temperatures dangerously elevated.

We can't afford that kind of heat buildup while testing. The vehicle has to sit there and cope with the brutal heat, reliably spinning the 250-amp Ohio Generator alternator and the A/C compressor, powering the radar gear and radios while keeping the operator cool.

To accomplish this we added a second engine oil cooler, a big liquid-to-air unit, plumbed inline with the stock liquid-to-liquid cooler and controlled by a thermostat to bring it online when the oil reaches 215 degrees. Two thermostatically-controlled, liquid-air transmission fluid coolers, taken from one-ton Ford commercial vans, were added to supplement the stock liquid-to-liquid cooler.

To improve airflow over the coolers and A/C condenser, a Denso two-speed electric radiator fan was added, also thermostatically-controlled. I trimmed away much of the splash guard along both sides of the engine block, letting hot engine compartment air exit behind the front wheels. The result is fluid temperatures that remain below 210 degrees F regardless of the hours spent idling.

But nothing can prevent the sun's rays from heating our dash-mounted radar units. The adhesive of the Velcro affixing their brackets to the IP turns liquid and flows in rivulets slowly down the dash. It's not unusual to have a radar shut down without warning, a design feature to protect it from dangerously overheating. Oven mittens are useful for prying them from the dash to hold in front of the A/C vents to cool, their metal surfaces routinely reaching a skin-blistering 185 degrees. The radar detectors get nearly as hot. But there's an upside: if a radar detector is prone to overheating, we're always the first to identify the problem.