Sometimes bigger is betterWritten by Nick Shultz | | email@example.com
While doing our research for the purchase of a new car, we can often find ourselves reading over detailed technical specifications. Along with other information, the vehicle manufacturers will supply technical data covering a vehicles maximum torque output and maximum horsepower and state those values at a given engine rotations per minute (rpm). Further, the vehicle manufacturers will supply the expected average fuel efficiency for the vehicle for both city and highway driving. Many new car buyers will not pay attention to any of the technical data provided except the miles per gallon (mpg) information.
As the miles begin to build up on a new vehicle, the consumer may become upset because they have never been able to consistently realize the manufacturers stated mpg averages. Consequently, many new car buyers believe that the mpg averages have been “padded” by the manufacturers in order to sell more cars. I can understand your reasoning, but I think it is much more likely that you simply did not buy the right vehicle for your needs or driving style.
If you frequently drive with several passengers, do a lot of in-city driving, primarily drive on the highway or frequently carry heavy loads or perhaps tow a trailer, then an understanding of some of the other technical information provided by the manufacturer could actually help to improve your overall fuel consumption and overall driving experience.
Torque is like a sprinter and can help get you up to speed fast. Horsepower is like a marathon runner and can help sustain speeds for long distances. There is a relationship (mathematically and physically) between the two, but a proper explanation of that relationship would take more space than this newspaper is willing to give me. Torque and horsepower are important units of measurement because they can allow us to save money on fuel all the while supplying sufficient power when we purchase the correct combination of the two for a particular task.
Let’s take any given vehicle that has at least two engine options available to us. One option is a four-cylinder engine with a stated 22 mpg/city and 28 mpg/highway fuel average. The same vehicle with a V-6 engine option gets a stated 20 mpg/city and 26 mpg/highway. You purchase the four-cylinder option because fuel mileage is a major concern for you. After driving the vehicle for a while you find that your overall fuel mileage average is 23 mpg for combined city and highway driving. You become upset because you thought you would get better fuel mileage with the four-cylinder engine option. The V-6 engine option may actually have allowed you to achieve a higher overall mpg fuel average. Or it may have equaled the fuel average of the four-cylinder engine all the while giving you better acceleration and performance.
The reasons for this fuel mileage advantage from the V-6 engine are torque and horsepower. Your particular driving style and the amount of work you perform with your vehicle may require, or benefit from, an increase in torque and horsepower.
Every additional pound of weight that your vehicle has to pull down the road requires more power. Adding even one more pound of weight increases the power requirement of your engine. Any resistance to the forward movement of your vehicle will adversely affect fuel efficiency as well. Increased vehicle speeds and wind speeds will increase overall drag and, therefore, decrease fuel efficiency.
The air conditioning system, when operating, requires more power. The headlights, when operating, require more power. The radio, the GPS, the electronic suspension system, the air bag system, the anti-lock brake system, they all use more power when operating. Many of those systems are operating whenever the car is turned on without our knowledge. There is a point at which a larger engine becomes more efficient than it’s smaller counterpart.
Driving habits have a great effect on efficiency and performance as well. The rate at which we accelerate our vehicles and how consistent we are at sustaining our speeds can adversely affect the fuel consumption of a given engine. Other factors are the type of transmission (sometimes referred to as the torque box), the size of the final drive assembly (differential) and the tire and wheel size. All can aid in fuel efficiency or all can adversely affect fuel efficiency depending on many variables.
Manual transmissions, when properly used, are more efficient than automatic transmissions. Larger wheels will generally lower engine rpm which equates to better fuel mileage. Higher final drive ratios are usually more efficient than lower final drive units. The more valves an engine has, the better it breathes. The better an engine breathes, the better it can sustain power and, therefore, the better the overall fuel efficiency.
There really is no “one size fits all” in the automotive business. An understanding of the mechanical variables that are in play during the operation of your vehicle can aid in your overall driving experience and fuel efficiency. Sometimes bigger is better.
Nick Shultz is an instructor of Automotive Technologies at Owens Community College. He is an arbitrator for the Better Business Bureau who specializes in cases involving the Ohio and Michigan Lemon laws. He is a certified master automotive technician by ASE, General Motors Corp. and Ford Motor Co. Shultz, a Toledo native, will take questions at firstname.lastname@example.org.