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What Is an Accelerator Pedal?

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  • Written By: Mike Howells
  • Edited By: Michelle Arevalo
  • Last Modified Date: 24 August 2014
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An accelerator pedal is a device, used in many types of vehicles, that allows an operator to modulate engine power remotely. It is generally paired with a brake pedal, and sometimes a clutch, enabling a driver to control the speed of the vehicle almost exclusively with his feet. An accelerator pedal is typically connected to a throttle directly, either by cables or, electronically, to a computer that mechanically adjusts the throttle based on pedal input.

Beginning with the first engined vehicles, there has always been a need for the driver to adjust engine output in order to control speed. In gasoline-powered internal combustion engines, the accelerator pedal adjusts the amount of air allowed into the combustion chamber, with the corresponding supply of fuel being regulated by a carburetor or fuel injection. In early designs, the pedal itself was directly tied to a butterfly valve, located either in the carburetor itself or the throttle body, that could let more or less air in.

Many modern engines use a drive by wire system, in which there is no direct physical connection between the pedal and the throttle. Rather pedal pressure is translated by a computer, which regulates air intake in response to driver input, while maximizing efficiency. Detractors of this design claim the driver loses a degree of control when a computer is introduced into the equation, but car manufacturers contend technology has reached the point where there is no loss of what some people refer to as driver feel.

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The accelerator pedal of a diesel engine engine functions differently. Instead of controlling the flow of air, it adjusts the amount of fuel entering the combustion chamber. In a diesel engine, it is the compression of the fuel that causes it to ignite, as opposed to the introduction of air. Therefore there is no actual throttle. For the driver, however, the effect of pushing the pedal down is the same.

Accelerator pedal designs are almost always developed so that the pedal itself can be pushed down to the floor with the user's toe or upper portion of the foot, while the heel remains on the floor. This allows a much greater degree of control, as the ankle joint can modulate pressure rather than the hip joint, which would effectively be the case if the entire foot rested on the pedal. Designs are also usually much narrower compared to brake pedals, with the idea that the brake should be easier to find in case of an emergency.

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Discuss this Article

sunshined
Post 8

You can get a left foot accelerator pedal installed on a car if you don't have the use of your right leg.

This is usually installed to the left of the brake and allows someone to be able to operate a vehicle who wouldn't be able to otherwise.

My son has a friend who was injured in a four-wheeler accident. In order for him to be able to drive, he had to have something like this installed on his car.

When he starts the car, he has to push a button to activate the left accelerator pedal. If he doesn't push this button, then the right pedal is active. One of the safety features is that both pedals can never be active at the same time.

andee
Post 7

I think there have been quite a few improvements in the fuel system of cars over the years. I remember when you had to pump the accelerator pedal as you were starting the car to give it some gas.

If you did that today, you would probably flood the engine. We had an elderly neighbor growing up that didn't drive very often, but when she did, you could really hear her revving up her car.

She would sit there for what seemed like 10 minutes getting that car going. I could just picture her pumping that pedal for all she was worth.

Once it was going, she would very slowly back out of the driveway and head uptown. It always sounded like that car wasn't going to start or that she was going to flood it and she would have to start the process all over again.

SarahSon
Post 6

I really like the accelerator pedal I have in the car I am driving right now. My car has memory for such things as seats, mirrors, radio station and the accelerator pedal.

When I put my key in the ignition you can see the accelerator automatically move up to where I feel comfortable driving.

Since I am not very tall, having this accelerator pedal extension is wonderful. Before driving this car, I always felt like I had to have the seat too close just so I would be able to reach the accelerator.

Now every time I get in the car, all my settings are automatically set for me. When my husband puts his key in the ignition, you can see the accelerator pedal going back further, giving him the room he needs to drive.

julies
Post 5

@OeKc05 - My dad is in his 80's and is still active and drives all over the place. He grew up on the farm and has been driving cars and farm equipment since he was a young boy.

He uses his right foot for the accelerator and his left foot for the brake. I don't know if this is something he was taught or just started doing as soon as he started driving equipment.

After you do something for so long it just becomes habit, and it would probably be very hard for him to make a switch now.

I tried this a few times and it felt really weird. I felt like I didn't have much control and quickly went back to using my right foot for both the accelerator and the brake.

kylee07drg
Post 4

@orangey03 – My car is like yours. I have to apply a good amount of pressure to the accelerator pedal to get it to go anywhere.

That is why it is important that I wear the right kind of shoes while driving. I made the mistake of wearing flip-flops while driving to the mall one day, and one of them got stuck around the pedal.

I was switching quickly from the brake to the gas to speed out of the way of an oncoming car, and the sole of my flip-flop got stuck under the accelerator pedal. I had to quickly remove my foot from the shoe and press my bare foot on the brake to stop.

Now, I only wear shoes that are secured to my feet when I drive. This means sandals with straps and buckles in the summer and sneakers or boots in the winter.

OeKc05
Post 3

If you have been driving for many years, then it is highly unlikely you will ever get the gas pedal and the brake pedal confused. To me, it is just second nature to mash the pedal on the left to stop. I even find myself doing this to an invisible pedal while riding in the passenger seat sometimes when I panic!

So, I find it hard to understand how some elderly people have become confused and mashed the accelerator pedal, thinking it was the brake. I have heard many stories about elderly people crashing cars into buildings because they believed they were braking.

I may find that I was wrong someday. Who knows, maybe I will lose my memory a little as I age, as well. Right now, I just can't grasp how anyone could slam on the accelerator pedal to stop.

StarJo
Post 2

I prefer to use the cruise control button on my car, rather than keep my foot on the accelerator pedal for long distances. While driving to the beach last year, I noticed something about the cruise function.

I was cruising along at 60 mph, and I decided to speed up a little to pass the guy in front of me. I put my foot on the accelerator pedal to give it a little more gas, and I noticed that it was already partially pushed down, as though an invisible driver were mashing on it.

I always assumed the cruise control just bypassed the accelerator pedal, but it actually used it to get the desired speed. I was a little weirded out by this, and it made me hope that the pedal never gets stuck.

orangey03
Post 1

Accelerator pedals in different cars vary a lot in the amount of pressure you have to apply to them. Some you barely have to tap to get a reaction, while others, you have to really press.

My car's accelerator pedal is not terribly sensitive. This means that I have to apply a good bit of pressure to accelerate much.

However, my mother's accelerator pedal is so sensitive that just a light tap makes the car lunge forward. It is really weird to go from using my car to using hers, and I tend to make the car jump forward a few times before getting used to the difference in the pedals.

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