By Guy Span
Published: November, 2004
Everyone knows about hybrids in these days of $2.60 per gallon gasoline. These not-so-thirsty smaller cars can get around 45 to 50 miles to the gallon and, under Governor Schwarzenegger, may be allowed with single-passenger occupancy in the HOV lanes, assuming California receives Federal approval. Virginia already allows this and sales of both Toyota and Honda hybrids have soared. These cars use a gasoline engine and electric battery to either assist from just the electric side or both electric and gas side, while charging the battery.
Some observers, such as Dr. Angus MacDonald, a local scientist who has experimented with a number of electric vehicles, feels that this crop of hybrids does too little and too much. “I don’t know this for a fact,” he said smiling slightly, “but I suspect these types of hybrids were designed to score the highest mileage on the EPA test.” According to the EPA web site, a car it tests is not actually driven, but is simulated at various torque levels to measure the exhaust content and from that, the probable mileage is concluded. In other words, just as the EPA warns, “Your actual results may vary.”
We found out that was true when we contacted a Prius owner who had recorded her mileage for a six-month period and the results were ugly. The average over six months was 41.2 MPG, including a mix of driving in the city and highway. This test ignored the on board computer analysis and simply used gallons of gas and odometer miles. According to the U.S. government’s EPA, there are a number of factors that affect mileage, including temperature (warm is better), tire pressure, distance driven, speed, and vehicle condition. Toyota has a few more including trips under six miles (warm-up factor) and also your driving style (fast acceleration, etc.).
The car was checked for all factors and the only one it failed was the under six-mile test, as the car was frequently driven less then that on trips to work. Thus, some of the poor mileage resulted from the short trips and the failure to warm the car all the way up. Note that it is difficult to warm up the car, because at rest it uses electricity only.
However, the car was also taken on a five-hour road trip, and the on board computer reported earning between 47 and 49 MPG (47 with the air conditioner on, 49 ventilators only). However, when adding in gasoline at the conclusion of the trip, the actual mileage turned out to be a little better than a Saturn at around 35 MPG. Other Prius owners report better results including one web site where the total MPG is hovering around 48 (but this site also reports a random disconnect between the computer and the actual results).
Other drivers have reported that Toyota recommends a careful driving style. If the driver were to use moderate acceleration, allow the car to slow going up hill (say 65 mph to 58 mph), drift down hill and other tactics, the results dramatically improve. We have known for a long time that speed and fuel consumption are linked. Bay Crossings tested a huge, inefficient 1989 Ford Country Squire wagon on a 279-mile trip on the Interstate (65 – 70 mph) and used nearly a full tank (23.6 gallons). The return trip by state routes (300 miles) at a maximum of 55 mph (including stop lights) only used a half a tank (12.2 gallons). The difference is significant as consumption goes from a worse than SUV 12 MPG on the Interstate to a nearly respectable 25 MPG on the state roads. It is clear from these tests why the national speed limit dropped to an unpopular 55 MPH during the previous oil crisis. It might be a solution for the present one.
Bay Crossings then asked Dr. MacDonald to describe a more useful hybrid. He said that all hybrids should specify the maximum range they can get while operating strictly as an electric vehicle (EV). For our current crop of hybrids, this distance can largely be measured in feet, not miles. He suggested an optimum range of around 20 miles for the battery portion alone and then the car would use a small (8 HP) high-speed diesel engine to charge the batteries and assist in propulsion.
Critics say that such hybrids would be too heavy, but Dr. MacDonald believes that their weight would be comparable to a medium horsepower gasoline engine and transmission. New Generation Electric Motors offers a high efficiency brushless DC motor (currently used in solar-powered racers). New Generation claims on their web site that if Toyota had used their motor, the Prius would have been more efficient.
Using eight rechargeable 6-volt golf cart batteries (400 lbs.), plus a 200 lb. high-speed diesel charger and two 60 lb. New Generation Motors does not create a significant weight load to reduce performance. Indeed, with this system, a car can be recharged using 110 volts at home or possibly at the work place. And, given that electric motors develop very high torque when starting, this car would not seem sluggish. Even better, it would resist the kind of consumption surge developed by poor driving techniques.
Dr. MacDonald concluded that today’s hybrids did better on the EPA tests than other cars, but for the extra $3,000 to $5,000 cost and added complexity, they were no bargain unless very carefully driven. He noted that anyone could improve their mileage by driving slower and easier and that might point to a short-term solution to air quality and gas consumption. But for a more practical solution, Dr. MacDonald noted that the hybrid must have more EV and less gas engine.
