ENGINE BRAKING How Semi Trucks Slow Down Without Brakes SCIENCE GARAGE
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Date: 2019-10-24
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Comments and reviews: 9
chris77777777ify
Jake brakes are only one component of modern trucks. In fact the jake brake will cause engine damage over long term use. Modern systems such as magnetic shaft retarders, butterfly exhaust valves & the most modern & most reliable, in new European trucks is the Voilth transmission water coolant driven brake retarder. The Voilth is guaranteed for the life of the transmission. Jake brakes in modern European trucks have been tuned down due to the superior Voilth Retarder. & the jake system does damage engines over long, long, long term use, so European manufactures have already tuned the Jake brake system down to avoid this engine wear. Voilth systems are really really good & one can use all day long without making too much noise & without causing un-necessary engine wear over the long run. Jake brakes has been a vital part in modern day heavy haulage, thanks Jacob.
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Jake brakes are only one component of modern trucks. In fact the jake brake will cause engine damage over long term use. Modern systems such as magnetic shaft retarders, butterfly exhaust valves & the most modern & most reliable, in new European trucks is the Voilth transmission water coolant driven brake retarder. The Voilth is guaranteed for the life of the transmission. Jake brakes in modern European trucks have been tuned down due to the superior Voilth Retarder. & the jake system does damage engines over long, long, long term use, so European manufactures have already tuned the Jake brake system down to avoid this engine wear. Voilth systems are really really good & one can use all day long without making too much noise & without causing un-necessary engine wear over the long run. Jake brakes has been a vital part in modern day heavy haulage, thanks Jacob.
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sac speed
wrong, wrong, it must be something that is taught in trade school or past down from mechanic to apprentice. No the engine doesn't slow down appreciably because of the air restriction/vacuum in the throttle/manifold, it slows down because of the compression stroke. This can be easily verified by fully opening the throttle whilst cruising down hill and killing the fuel or ignition or both(you'll need an old school car. The car will actually slow down more with WOT(because there is more air to compress) it ain't the 15 psi of atmospheric pressure that makes the motor slow down. Why people haven't tried this simple test for themselves before making disinformative videos, I don't know. Warning( dont try the WOT for too long without cutting the fuel or you will get an exhaust full of fuel and kboom when you hit the ignition again)
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wrong, wrong, it must be something that is taught in trade school or past down from mechanic to apprentice. No the engine doesn't slow down appreciably because of the air restriction/vacuum in the throttle/manifold, it slows down because of the compression stroke. This can be easily verified by fully opening the throttle whilst cruising down hill and killing the fuel or ignition or both(you'll need an old school car. The car will actually slow down more with WOT(because there is more air to compress) it ain't the 15 psi of atmospheric pressure that makes the motor slow down. Why people haven't tried this simple test for themselves before making disinformative videos, I don't know. Warning( dont try the WOT for too long without cutting the fuel or you will get an exhaust full of fuel and kboom when you hit the ignition again)
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02091992able
The original purpose of a Jake Brake was not to slow down the vehicle but to prevent the diesel engine from doing what is called a runaway which is a horrible event that can happen to a diesel engine which causes them to go out of control and often can lead to damage and destruction of the engine thrown rods though the block is a common effect. Stopping them is all a matter of luck and how fast you can move. First thing is to cut fuel but sometimes they will still run because they then begin to burn the engine's oil because of bad seals most times so in order to stop it you have to get to the air intakes and plug them with whatever you can find to cut off air to the engine. If your quick enough you can do this before any damage is done to the engine.
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The original purpose of a Jake Brake was not to slow down the vehicle but to prevent the diesel engine from doing what is called a runaway which is a horrible event that can happen to a diesel engine which causes them to go out of control and often can lead to damage and destruction of the engine thrown rods though the block is a common effect. Stopping them is all a matter of luck and how fast you can move. First thing is to cut fuel but sometimes they will still run because they then begin to burn the engine's oil because of bad seals most times so in order to stop it you have to get to the air intakes and plug them with whatever you can find to cut off air to the engine. If your quick enough you can do this before any damage is done to the engine.
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Gregory Lyan
I was taught in transmission school that automatics even older style ones also have kindof an engine/trans brake. If youre going downhill and your brakes fade you can slam the trans from OD or D into L2 or L1 and it will actually apply extra bands and clutch packs and the engine will rev up to a certain rpm. But will not go further because the throttle is closed. Thats when the torque converter will compensate and slow the vehicle. The atf is cooled right after it leaves the converter to the trans cooler. You will not damage it. Ive tried that even on the poor 700r4 gm. It grabs the rear end and you slow down quick. So many people have died losing brakes going down a mountain and not knowing this engineered function of an automatic
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I was taught in transmission school that automatics even older style ones also have kindof an engine/trans brake. If youre going downhill and your brakes fade you can slam the trans from OD or D into L2 or L1 and it will actually apply extra bands and clutch packs and the engine will rev up to a certain rpm. But will not go further because the throttle is closed. Thats when the torque converter will compensate and slow the vehicle. The atf is cooled right after it leaves the converter to the trans cooler. You will not damage it. Ive tried that even on the poor 700r4 gm. It grabs the rear end and you slow down quick. So many people have died losing brakes going down a mountain and not knowing this engineered function of an automatic
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Jay Em
A jake brake takes away the power stroke from the diesel engine which is a Compression Ignition type. The ignition or explosion otherwise suppose to happen is not happening because it does not meet the compression required for it to occur. Thus, there is no power coming from the engine even while the pistons are moving due to the kinetic energy of the truck. The pistons become passive and become a load with the whole engine as the tires on the road transmit the rotational force back to it with all the linkages. The popping sound is the external noise generated instead of the internal powerstroke. Thanks for your post. It is very informative and I enjoyed it a lot Cheers
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A jake brake takes away the power stroke from the diesel engine which is a Compression Ignition type. The ignition or explosion otherwise suppose to happen is not happening because it does not meet the compression required for it to occur. Thus, there is no power coming from the engine even while the pistons are moving due to the kinetic energy of the truck. The pistons become passive and become a load with the whole engine as the tires on the road transmit the rotational force back to it with all the linkages. The popping sound is the external noise generated instead of the internal powerstroke. Thanks for your post. It is very informative and I enjoyed it a lot Cheers
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02091992able
Not every big rig has a Jake brake some older Caterpillar engines could not mount a jake brake so they had to design their own device to do that for their engines they called it a brake saver which does the same thing as a Jake Brake but uses hydraulic pressure to operate which instead of a rumbling noise a jake brake does it just lets out a low pitch whine but can be a problem if set too high. Then Mack has what is called a Dynatard which is because Mack didn't have the rights to produce a Jake Brake for its engines it sounds often like a person farting. They also got a device called a power leash on newer engines.
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Not every big rig has a Jake brake some older Caterpillar engines could not mount a jake brake so they had to design their own device to do that for their engines they called it a brake saver which does the same thing as a Jake Brake but uses hydraulic pressure to operate which instead of a rumbling noise a jake brake does it just lets out a low pitch whine but can be a problem if set too high. Then Mack has what is called a Dynatard which is because Mack didn't have the rights to produce a Jake Brake for its engines it sounds often like a person farting. They also got a device called a power leash on newer engines.
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ruffnutz71
This guy missed the critical effect of the Jake braking system. He was correct in saying Jakes use the energy of compressing the air on the up ( compression ) stroke to slow the vehicle ( but that would have happened anyway ) what he didn't explain is by quickly dumping the compressed air ( which makes the iconic Jake brake noise) it causes the piston to now move down AGAINST 2 CLOSED VALVES without the former assistance of compressed air or the diesel bang, this creates a huge negative energy drag on the engines rotation which in turn creates the real braking effect from the Jake system
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This guy missed the critical effect of the Jake braking system. He was correct in saying Jakes use the energy of compressing the air on the up ( compression ) stroke to slow the vehicle ( but that would have happened anyway ) what he didn't explain is by quickly dumping the compressed air ( which makes the iconic Jake brake noise) it causes the piston to now move down AGAINST 2 CLOSED VALVES without the former assistance of compressed air or the diesel bang, this creates a huge negative energy drag on the engines rotation which in turn creates the real braking effect from the Jake system
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MrJeepin88
I had a teacher once that taught shop and electronics and he got on a rant one day about engines and he misinformed the whole class about how a jake brake worked. he said that engine stops and spins backwards I laughed so hard I about fell out of the seat. he said whats so funny I said that is not how it works. I said just think about your going 60 mph if your engine all of a sudden spins backwards theoretically youre going to lock up your tires and do a reverse burnout So I had to explain to the class how a jake brake worked that day
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I had a teacher once that taught shop and electronics and he got on a rant one day about engines and he misinformed the whole class about how a jake brake worked. he said that engine stops and spins backwards I laughed so hard I about fell out of the seat. he said whats so funny I said that is not how it works. I said just think about your going 60 mph if your engine all of a sudden spins backwards theoretically youre going to lock up your tires and do a reverse burnout So I had to explain to the class how a jake brake worked that day
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Crystal_Clear _
No, the draw of air restricted by the throttle body when closed is not at all what causes engine braking in a gasoline engine. Engine braking in a gasoline engine is caused by the removal of combustion at the top of the compression stroke. Meaning, because there is no combustible gases detonated to push the piston back down, the air being compressed as the cylinder reaches the top of the compression stroke is the restricting force slowing the vehicle. Durp.
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No, the draw of air restricted by the throttle body when closed is not at all what causes engine braking in a gasoline engine. Engine braking in a gasoline engine is caused by the removal of combustion at the top of the compression stroke. Meaning, because there is no combustible gases detonated to push the piston back down, the air being compressed as the cylinder reaches the top of the compression stroke is the restricting force slowing the vehicle. Durp.
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