Can you get better gas mileage with a different windshield? Who gets extra work when a transmission grows from five to six to seven to eight speeds? PPG maintains that their new Sungate windshield does, in fact, allow the car to get better gas mileage. And it is the development engineers who have a big headache when cars get transmissions with those extra speeds.

PPG's Sungate windshield glass has a special chemical layer that is infra-red (IR) reflective. They don't tell anyone what it is, but right now it is very effective. They are working on making it better with nanotechnology.

Sungate has been available for some time, but few manufacturers have delivered cars incorporating it here. In Europe, however, it is very popular -- even with economy cars. As it becomes more widely known here, however, PPG expects it to become more popular.

The U.S. Department of Energy's National Renewable Energy Laboratory (NREL) is working on new technologies that can be applied to reduce the temperature of vehicle interiors. This is very energy beneficial because if the interior can be made cooler, air conditioning doesn't have to be used as much, and that saves gas. NREL investigated Sungate technology in an enhanced version.

A normal windshield is two layers of glass with a layer of soft plastic between them. This is a "laminated glass" windshield. It is supposedly safer because the plastic sticks to the glass and keeps it in place when a person hits it in an accident. The Europeans have maintained, however, that a tempered glass windshield was better, though that would allow a person to fly through the windshield. The Europeans have agreed to the U.S. standards for laminated glass windshields, and people hitting them is much less of a problem these days with seat belts and air bags.

The Sungate windshield uses a coating stack of seven unique layers and is about 5.9 micro-inches thick. For reference a human hair is about 3500 micro-inches thick. The coating chemistry is the major, but not the only technology accounting for the IR reflection. They don't say what the other technology is, but it isn't optical.

Some glass technologies use adsorption of heat by the layer of material between the glass layers. This doesn’t work well because that heating then is radiated into the interior. NREL testing showed that Sungate EP (the second generation technology windshield) reflected some 97% of the IR energy. That sound really impressive because the IR portion of the spectrum accounts for the highest amount of solar energy. Fully 77% of the solar energy from all parts of the spectrum did penetrate through the windshield. The effect of the IR coating on the overall heat reductions in the NREL test car were not called out separately from the overall effects of that and several other heat-reduction technologies being tried. They included a PPG exterior coating that limits the amount of heat radiated into the interior from body panels and a parked-car ventilation system.

PPG demonstrated Sungate technology by using a split windshield with spotlights shining through a driver's side using a regular windshield and passenger side using a Sungate windshield. Using a remote temperature sensor, the difference in this rather unscientific demonstration was 30 degrees F. That means at least from the dashboard area, on a 100 degree day, the dash would be 70 degrees. That is a significant improvement.

As I stated before, this would reduce the use of air conditioning significantly. And using the air conditioner does reduce fuel economy. PPG did a study and found that in 2004, the amount of fuel consumed for light-duty vehicle air conditioning use in the U.S. was 7 billion gallons or 5.5% of the total amount used in these vehicles. PPG estimates that the Sungate windshield can increase fuel economy as much as 4%.

Given that fuel economy is a main driver in the selection of cars in Europe, this is why Sungate windshields are more common there. The price of fuel in Europe is several times higher than it is in the U.S. European manufacturers offer Sungate windshields as an option and market it as an inexpensive fuel-savings tool. Ford, for example, offers it as a $200 option on the Focus.

In the U.S. it is available on very few cars, just some Mercedes and BMW models. I don’t think either manufacturer even mentions it in their product information. General Motors, however, was the first manufacturer to use Sungate windshields. Less than 5% of the cars sold in the U.S. have them, but about 30% of them do in Europe. But it would seem that it makes more sense here than in Europe because the weather is hotter. In some areas of the U.S., drivers use their air conditioning system more than 80% of the time (like me!).

In the U.S., government standards require that windshields transmit a minimum of 70% of the light. The European standard is 75%. That means that the IR technology can be more aggressive in the U.S. It think you can look forward to a new technology windshield in your new car in the not too distant future.

What about those multi-speed transmissions? The gap in fuel economy and performance between cars with manual transmission and automatics has driven the development of automatics with more and more speeds. Today you can get many cars with six-speed automatics, Mercedes has a seven-speed, and Lexus an eight-speed. Those additional gears close the efficiency gap on manual transmissions and provide the opportunity for even more seamless gear changes as the result of smaller differences from one gear ratio to the next -- up or down.

One might think that with the design possibilities available to engineers with more speeds in the transmission, the calibration would be simpler. The real world, however, is that it is a more difficult task to choose the right gear more complex than ever.

Toyota points out that "as the number of gears increases, there can be multiple operating regions in which three or more different gear ratios could be used to deliver the power required to move the vehicle at a given speed." This is even more true with ever more sophisticated engine management systems that spread the torque over a wide rpm band. "The challenge is in picking one choice among several possible gears that best meets the driver's expectations for quiet, smooth, and powerful operation." When Toyota developed their eight-speed automatic for the new LS460, it turned out that huge task necessitated double the amount of track tuning compared to any previous Lexus product.

Also to improve efficiency, the newer automatics use freewheeling as little as possible, so shifting goes from clutch to clutch. General Motors found problems when they co-developed their new six-speed automatic with Ford. Also the complexity arose when they faced the requirement that the new six-speed unit had to be the same size as the four-speed automatic it would replace. The problem is that the clutch-to-clutch shifting requires a much more precise handoff from the outgoing gear to the incoming one -- far more difficult than a freewheeling transmission.

This became obvious when GM recognized that they missed their targets with their new transmission. Early deliveries -- including road test cars -- found that the transmission could get lost when the driver asked for enough power to require a downshift of more than one gear, then abruptly backed off the throttle. This confusing situation for the transmission was found in early deliveries of the Saturn Aura, for example. GM quickly rushed the engineering team to develop an improved calibration which was delivered just a couple of months after introduction.

Both Toyota and Mercedes have determined that it is much easier to control the transmission correctly if they integrate the engine controller with the transmission controller. That allows the transmission to receive much more data more quickly. This is rather easy for those manufacturers because they manufacture their own transmissions. It is more difficult for manufacturers who use the ZF six-speed or the Aisin six-speed. Those are OEM manufacturers and essentially make a "standard" transmission that gets sold to whatever manufacturer wants it. Of course they can specify what specific information the transmission needs to work correctly -- and what information it can send to the engine controller. Apparently ZF did a very good job at that because everyone thinks that the vehicles using the ZF transmission driver very well.

Mercedes, on the other hand, was very tight lipped about what data made their seven-speed transmission work very well. They acknowledged that they found integrating the engine and transmission controller was an advantage, but also said that there was a particular kind of data that made it work better.