Before we begin today’s lesson, let’s take a look at some of the ELO’s and TLO’s that we will be discussing today. This lesson will be very brief as there isn’t very much detail that is NECESSARY. I emphasize necessary because, there are those that will argue with the point that there isn’t a reason to go into much detail about the drivetrain. For the purpose of this instructional period there is no purpose in delving into the depths and technicalities of drivetrains.
Enabling Learning Objectives:
1. Define Drivetrain, Give two (2) examples of a Drivetrain, and give a brief description of each drivetrain you listed and include their uses.
2. Define FR, FF, and AWD and describe the “tell-tale” characteristic behind each.
3. Describe one (1) advantage and disadvantage of the FR layout. (From a drivers perspective)
Terminal Learning Objectives:
No Terminal Learning Objectives are required for this lesson.
1. What is the FR layout and what other layouts exist.
The FR layout is system in which the engine (in the front) is powering the rear wheels.FR is an abbreviation standing for Front-Engine Rear-Wheel-Drive. This means that the engine rests between the front axels and passenger compartment while the power from the engine is delivered through your Drivetrain, or the system of rods, gears, and connectors that convert rotational movement of your engine to lateral movement of your car, to the rear axel which, in turn, rotates the rear wheels which moves your car forward.
This layout was widely used in both foreign and domestic markets from 1940-1990. For over fifty (50) years auto manufactures were convinced that FR was the way to go when making vehicles; mostly because they were easy to produce and required little maintenance when compared to the other drivetrains. Most auto manufactures today, will still produce one or two of their production vehicles with this style of layout. Most of these cars are classified as sports cars due to their handling characteristics.
Some of the immediate advantages of the FR layout are:
1. A noticeably increased engine efficiency rating. Without delving too deeply into drivetrains, FRs are known to be 10 to 15 percent more engine efficient that it’s direct competitor the FF.
2. Better acceleration. If you were to time a FR vs a FF with equivalent power specifications down a quarter mile track and in 0-60 time, you would notice that FRs are much better at transferring the power to the ground.
Some of the immediate disadvantages of the FR layout are:
1. Decreased gas milage. The drivetrain, simply put, has more parts in which to get rotating, this forces auto makers to increase the horsepower and torque ratings on the engines in order to compensate for this. More torque means more gas burned.
2. Inclimate weather handling is more dangerous in an FR car than with any other drivetrain. FR cars are susceptible to a condition called “oversteer” (which will be covered in the next lesson) in which your car turns more than the input was given. This creates the likelihood of a spin out in traffic.
Some examples of the FR layout are the Nissan 240sx, the Chevrolet Camaro, and Toyota Supra.
2. The FF Layout.
The next drivetrain that is seen very often is the FF or Front-Engine Front-Wheel-Drive layout. This simply means that the engine, like the FR, is nestled in front of the passenger compartment, however, because of the way FF has to work, the engine is rested almost directly on top of the front axels. FF’s are a new trend sweeping the automotive industry. Developers have noticed that, while the technology and maintenance required to build and keep this drivetrain running is higher, people have reported better gas mileage, improved inclimate weather handling, and an overall better sense of control with this particular layout.
The FF drivetrain is a relatively new one when considering the lifespan of the automotive industry. 1992 signifies the date in which front-wheel-drive vehicles became a mainstream and popular means of transportation. Companies such as Chevrolet, Dodge and Ford all began producing light-weight, economic FF vehicles and people began buying them like hot-cakes.
Some of the immediate advantages of the FF layout are:
1. Improved inclimate weather handling. If it’s wet, snowy, iced or just plain nasty outside, the FF drivetrain offers unrivaled handling and durability while driving. Even when pushing these vehicles beyond the safe driving margin, they still continue to out perform FRs under these conditions.
2. Better gas milage. The use of a transaxle, or transmission that links directly to an axel, means that there doesn’t have to be any “unnecessary parts” between the transmission and driving wheels. This creates a situation in which the engine doesn’t have to produce as much torque to move the driving wheels. Less torque means that your engine isn’t doing as much work. Less work means that your engine isn’t burning as much gas. The effects of this can be seen with the recent boom in the new high gas efficiency cars.
Examples of the FF layout can be seen with the Honda Civic, Ford Focus, and Toyota Prius.
Here’s something to think about: What if you could take all of the advantages of FRs and mix them together with the advantages of FF. You would have a machine that offers the best of both worlds right? Well, not exactly, but what you do have is a high performing machine that can do a lot without putting its operator in much danger. This fantasy machine is driven by a system called AWD or All-Wheel-Drive. This means that the engine is delivering power to all four of the wheels.
This is the newest and scarcer used technology amongst auto makers. You can see examples of AWD with vehicles like the Mitsubishi Lancer Evolution and Subaru Imprezza WRX. Both of these vehicles combine the qualities of FF cars and FR cars through a mechanism called a Variable Center Differential. This unit controls how much power is delivered to each wheel that is driving. This offers, from a performance stand point, several advantages. The most prevalent is handling. There’s an old saying “The Beauty of All Wheel Drive.” That stands true, to this day, there are very few FFs or FRs that can out handle an AWD vehicle. The same holds true for acceleration. It is known that if you take two drivers with equal skill and one is driving a FF or FR and the other is driving an AWD vehicle that the AWD will have a much better off-the-line response to throttle input. The only thing that hinders a lot of AWD system driven cars is the fact that they experience understeer, or the condition in which your car turns less than the steering input given, when making hard turns. This is a trait that can only be combated through driver skill.
As you can see there are many differing drivetrains to choose from in the world. If you are reading this, you most likely chose the FR which is a noble choice. By doing that, you’ve entered the realm of more experienced drivers and you have accepted the fact that you will have to be a little more careful in the rain, but when it comes to the track, with the right skill, you can out perform any other drivetrain in your class.