The Heat’s on the Most Recent Models

Question: My brand-new Chevrolet seems to get hotter after sitting in the summer sun than some of my past cars. It’s white, like the others, so I don’t think the color has anything to do with it. Is GM using less insulation or something?--I.P.

Answer: The dog days of summer are here again, and modern car designs are indeed causing interiors to gain more solar heat than in the past. Modern aerodynamic designs feature sloping windows and greater total window area, which allows cars to heat up more in the summer sun. It is not uncommon for newer cars to reach interior temperatures of 138 degrees after sitting in the sun.

In part, that is why you are seeing so many motorists equipping their rear and side car windows with reflective film, which manufacturers of the product claim can cut solar heating by 35% to 65%. If that is true, it reduces the load on the air-conditioning system and keeps the car cooler with the air conditioning on. (California Highway Patrol asserts it is illegal to use film on windshields and front side windows.)

GM has an experimental station in Mesa, Ariz., to test how its mechanical systems and materials hold up in intense sunlight and desert heat. Jack Jacquette, director of the center, said the increase in glass surface area in recent years has led to a lot of research to find better ways to cool down cars.

The company is investigating better glass, which will help reflect heat without solar-reflective film. They are hoping that a chemical process in making the glass will help restrict heat waves from passing through the glass. Motorist comfort is not the only reason for the concern. Big loads on air-conditioning systems cut fuel economy.

“Extremes of temperature and humidity can impose a 20% penalty on fuel economy,” he said. “We are deeply involved in better understanding solar radiation and temperature effects.”

One related area involves the longevity of interior materials, particularly upholstery that is subject to serious damage from sunlight. “We are trying to perceive in a few months how materials will hold up in five or 10 years,” he said.

Separately, GM is using computerized models to help develop better air-conditioning systems. Using fluid mechanics borrowed from the aircraft industry, GM is trying to understand how an air conditioner can be optimized. The physical effects under study include examining the effects of air blowing from vents, the circulation of hot air masses inside the car, the heat transfer effects and the time it takes to cool down a boiling-hot car.

Q: A number of years ago, you wrote a column about how to adjust headlights. It worked great, but now I need to do it again and I never kept the column. Could you please give me the instructions again?--S.H.

A: Every state has a vehicle code that specifies how headlights must be aimed and where the headlights can be placed on the vehicle. These laws are complicated, and performing the adjustments to the letter of the law isn’t easy for an average motorist.

The code in California, for example, specifies that in a two-headlight system the intense portion of the light beam at a distance of 25 feet may not be higher than 5 inches below the lamp from which it comes. There are other regulations on stray light, fog lights and much else.

Garages with the proper equipment can perform this adjustment so that the light beams conform to that standard.

Many garages, though, use a mark on a wall, which may or may not be adequate. You could probably do just as well by carefully marking two sets of perpendicular lines on your garage door that correspond to your car’s headlight position. You’d then back up 25 feet and attempt to aim the headlight five inches below the center points of the lines.

Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.