Car Pedal System

[NewyorkKopter]

Hey, how are the gas, brake and clutch pedals linked to the engine, transmission, and brakes? I looked for diagrams on google but I couldn't find anything useful...



Basically, how are the pedals connected to the engine and brakes?

[curtis73]

Gas pedals are typically linked with a mechanical linkage of bars (old school), a cable (typical) or electronically driven with a servo.

Brakes use a master cylinder to pressurize fluid, the fluid is transferred through a tube to the wheels where it uses the pressure to squeeze pads against the brake rotors or drums. So, the brake pedal has a pushrod attached to it which pushes a piston into a bore. Usually the brake master cylinder is on the firewall just in front of the pedal.

Clutches can be mechanical using a series of linkage rods (old school) or a cable (rare) or more typically a master cylinder just like the brakes. The pedal pushes presure through a tube to the clutch where the pressure is used to release the clutch plate.

[GreyGoose006]

on new cars, the gas pedal isnt even directly linked to the engine at all (curtis mentioned this too)
it is wired to a computer that then sends the information to the engine computer.
the advantages of this system are that there is great control of wheelspin.

for example.
my uncle recently bought a dodge magnum.
one day last winter, i was over at his house and he mentioned that the gas pedal was electronic.
to prove it, he took me and the magnum out and floored the throttle (in ~4 inches of snow) and at first there was wheelspin, but after a half a second, the computer took over and limited the throttle and prevented wheelspin.
we drove around the block at 35 mph with him flooring the throttle the whole way.

this would not be possible in an old car with a mechanical connection.

[Moppie]

Originally Posted by GreyGoose006

this would not be possible in an old car with a mechanical connection.

Yes it would.

[NewyorkKopter]

oh true. But what about cars like the F40, and Mclaren F1? They had a mechanical connection right?

[NewyorkKopter]

oh true. But what about cars like the F40, and Mclaren F1? They had a mechanical connection right?

[curtis73]

To the best of my knowledge they had cables for the accelerator.

[GreyGoose006]

i meant that it would not be possible to only give the car part throttle when you had the gas pedal floored on a car with a throttle cable and no computers.
sorry for the confusion

[Moppie]

Originally Posted by GreyGoose006

i meant that it would not be possible to only give the car part throttle when you had the gas pedal floored on a car with a throttle cable and no computers.
sorry for the confusion

Its still possible.

But, I know what your talking about.

Your trying to say its very difficult to have very precise computer controlled throttle operation when there is a cable linkage between the pedal and the throttle body.

[GreyGoose006]

ok, i give up...

[NewyorkKopter]

lol, do you have any pics or diagrams of the cables connecting the pedals to the engine?

[GreyGoose006]

http://www.stu-offroad.com/engine/throttle/3.jpg
theres one from a jeep.

http://www.v8engines.com/Gallery%202...0-linkages.jpg
theres one from some car with a V8 and a carb

http://www.wilcoxengines.demon.co.uk/images/vaxinj2.jpg
and heres a modified setup for a Vauxhall with FI

on the jeep pic, i think the unhooked part is for the transmission, but i'm not sure. it could also be some kind of throttle position sensor.

[drunken monkey]

what he wants, is a pic of the entire cable set-up from pedal to engine/brakes.
come to think about it, what he really wants is for someone to show him how everything in a car works.

[GreyGoose006]

aha.

i neglected to add that once you leave the throttle cable in the pics, it is just a matter of attaching the other end to the gas pedal.

i'll draw a pic for the brakes.

[GreyGoose006]

its not to scale, and the abs computer should be at each wheel, but thats the idea.

any more questions?