Question, what does the sign “No engine brake…by city ordinance” mean on the highway?

Big Trucks have an engine brake. It is a device when turned on and the accelerator is released, a certain number of cylinders are turned off to reduce power of the engine and slow it down, thus an engine brake. This is designed to help save on the friction braking system and keep them from getting to hot and burning up. The engine brake is restricted in urban areas because it is loud. Every been sitting at an exit ramp from an interstate and heard the exhaust of a truck sound off….? That is the engine brake.

Brake Definition

No Engine Brake

Many large trucks (dumptrucks and the like) have an engine brake that can slow the truck down without wearing on the regular brakes. When the brake (usually called a jake brake) is engaged, it’s pretty noisy. You’ll typically see those signs in residential areas.

Ignore the signs. Brake in accordance to best practice and vehicle operating procedures. You are supposed to engine / transmission / jake brake to avoid having your brake pads and shoes from overheating and failing. If you arrive at a steep hill or decline, short stop or ramp that requires quick or continuous deceleration, use these alternate braking methods in combination with your pedal brake (but not your emergency brake unless absolutely necessary).

Refers to the jake break, which is a specialized braking system or “brake retarder” that employs the engine to brake.

It was used primarily to assist braking in hilly locations, but many truck drivers use it to compensate for bad technique or shoddy mufflers. It makes a loud sound.

This is not referring to the technique of engine braking that you would use in your car. It is a similar principle.

High rpms, steady speed, using the engine to slow you and not relying as much on the brakes. This is better for your fuel mileage, better for emissions and the environment and is smoother and better for your driving technique, passengers, and your brake system.

Go to http://www.ecodrive.org/The-golden-rules-of-ecodri… for more info on saving the world by saving your brakes.

Go to http://www.cga.ct.gov/2004/rpt/2004-R-0741.htm for more info on jake breaks.

jake brake…trucks use the engine to slow the truck…makes like a ratatatatatata sound as he slows. Its loud, annoying and disruptive in residential areas. Probably on a downhill area, although it can be anywhere.

JAKE BRAKE:

The Jake Brake or Jacobs Brake is a particular brand of engine brake manufactured and sold by Jacobs Vehicle Systems, Inc. While the term Jake Brake technically only describes Jake Brake brand engine brakes, it has become a genericized trademark and is often used to refer to engine brakes or compression release engine brakes in general, especially on large vehicles or heavy equipment. “Jake Brake” is a registered trademark of Jacobs Vehicle Systems, Inc.

An engine brake is a braking system used primarily on semi-trucks or other large vehicles that modifies engine valve operation to use engine compression to slow the vehicle. They are also known as compression release engine brakes.

When the accelerator is released on a truck, its forward momentum continues to turn the crankshaft and compress air inside the engine’s cylinders. When the crankshaft passes the top-dead-center position, the compressed air in the cylinder acts as a spring and pushes the piston back down the cylinder, returning the energy to the crankshaft and pushing the truck forward. Little of the energy absorbed by compressing the air is lost, so the engine does not effectively aid in slowing the truck. Of equal importance, even with zero accelerator input, there will be some trace introduction of diesel fuel (make and model dependant) which will still undergo combustion. Any power created from this will hinder efforts to decelerate. In a gasoline engine, some engine braking is provided during closed-throttle operation due to the work required to maintain intake manifold vacuum, the balance coming from internal friction of the engine itself. Diesel engines, however, are unthrottled and hence do not provide engine braking from throttling losses. A compression release engine brake uses an extra lobe on the camshaft to open a second exhaust valve at the top of the compression stroke. The stem of this valve telescopes during normal operation so the valve remains closed, but is locked at full length by a solenoid when the engine brake is engaged so that the valve opens as directed by the cam. This releases the compressed air in the cylinder preventing it from returning its energy back to the piston and accordingly, the vehicle.

The driver controls consist of an on/off switch and, sometimes, a multi-position switch that controls the number of cylinders on which the brake is active. When the compression release engine brake is turned on, it will activate when the driver releases the accelerator. There are also switches on the clutch and accelerator pedals that will deactivate the compression brake when the clutch is disengaged or the accelerator is pressed.

Compression release engine brakes may make a loud chattering or machine gun noise while being used, which has led many communities to ban them. There are signs on the side of some freeway offramps, or at municipal boundaries, that will say “No jake braking”, “Engine brakes restricted”, etc. These signs are referring to compression release engine brakes. This has led to special mufflers on trucks that also muffle the sound of the compression release engine brake. Also, some engines use a butterfly valve in the exhaust and/or stator travel beyond the normal operating range on the variable-geometry turbocharger to produce engine braking without the noise associated with a compression release engine brake.

Large trucks have what are called commonly called “jake brakes” … formally “Jacobs Brakes.” Some smaller vehicles used to have them too. (It is not simply shifting the transmission to use a lower gear.) Trucks fitted with a “jack brake” or engine assist braking system have a modified engine valve operation that uses the engine’s compression to slow the vehicle. They are also known as compression release engine brakes. The application of the braking system opens a valve whereby presurized exhaust is allowed to escape without going through the manifold, tailpipe and muffler. This releases the pressure on that end of the engine valves which otherwise cushion them and assist the engine in its operating cycle. By releasing the pressure, the engine’s valves have a lot more compression that slows the vehicle.

The reason they are prohibited within most city limits is because they are loud. It sounds like a big truck without a muffler or tail pipe.

Although all of this is true, but not for years, decades actually. around 1990 all semi-tractors have mutes preventing the noise. The reason you still see these signs, and even more so now, especially on declines, is due that some automatics (Toyota, BMW) are especially able to brake using downshifting (also called engine braking, but is really more of a transmission braking). However, brake lights do NOT come ON during this downshifting (with the exception of some high-end BMWs), and thus can cause accidental rear-ending of vehicles braking in this manner.

So the old signs stay up, just for different reasons.

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RE:

Question, what does the sign "No engine brake…by city ordinance" mean on the highway?

I don't know if that's the exact wording of the sign, but it says something like that on the signs on an area of the highway I drive on when going home. I've always wondered what that meant…..anyone else have a clue?