[ARCHIVED THREAD] - Engine brakes? (Page 1 of 2)
Posted: 7/13/2009 7:59:08 PM EDT
| Are engine brakes on semis more effective at scrubing speed then hitting the brakes? If not, why the fuck do somany truckers use them? |
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It most definitely helps at slowing down, in addition, an engine brake prolongs the life of your brakes. Perhaps more importantly, unlike your service brakes, it doesn't fade with continuous use - which can be a life-saver on long downgrades. You can use it continuously, holding your service brakes in reserve for emergency stops. |
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WTF? Lazy Drivers who do not want to have to do gear changes?
NO, the Jake Brake will only slow the truck down to the speed the gear the truck is in allows the truck to go or you will Blow the heads off the engine red lining it!! On longer hills and such they are literally life savers!! You gear down to say 6 or 7th gear on a long mountain(this would be roughly 20-25MPH like most mountains require!) You have chices now, the engine can hold you back to that spped with periodic help from the service brakes OR.. You can rely entirely on the service brakes, glaze them over from thousands of degrees of heat and cause them to fail or catch fire and tehn go runaway over top of every car and through every house at the bottom of the mountain....... Your call, you want the truck behind you using a Jake Brake and having his service brakes totally operable to back it up if he needs to stop to prevent from killing your family? OR... Glaze those fuckers up right and roll right through several cars and buildings at the bottom of the hill with your family in one of them? People do not realize how much safer Jake Brakes make the highways by limiting speed of big rigs, especially the dumb fuckers who ban them in their towns and put their citizens at increased risk of disaster. The independents who run straight pipes to make it sound louder when they kick on ruined it for everybody, most muffled trucks the common bystander would never even know when the Jake Brake kicked on they would easily mistake it for down gearing the noise is so muffled. Are there drivers who use them un necesarily because they think it sounds cool? Yes! But... They also make controlling that truck easier and safer and therefore other highway users safer. BIG RIGS are NOT cars and do not drive like one, they need every advantage they can get or use to slow down and stop when they need to. Your car or Pickup truck weighs maybe one and half or two tons!! Thats is just the ENGINE in a Big rig!! Plus 60,000 plus in wieght can be in the typical van trailer and more than that on a flat bed. I leave you thinking about this.......At 65MPH it takes a fully loaded tractor trailer 698.5 ft. MINIMUM to stop completely just using the service brakes!! Now aren't you glad a lot of trucks have a engine bbrake to help with your family on the same roads? |
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Quoted: Are engine brakes on semis more effective at scrubing speed then hitting the brakes? If not, why the fuck do somany truckers use them? Friction brakes heat up under heavy use, and become ineffective. It also wears out the friction surface. It isn't more effective at scrubbing speed, but it is a better idea in many situations, just like in your car. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Not downshifting. Killing spark or whatever it's called on deisel motors to use the engine compression to slow the vehical. Sounds like the truck is cutting a massive fart. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Its kinda like that but on big trucks you have a switch that makes it happen by closing the exhaust ports ( or thats how im pretty sure they work) |
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WTF? Lazy Drivers who do not want to have to do gear changes? NO, the Jake Brake will only slow the truck down to the speed the gear the truck is in allows the truck to go or you will Blow the heads off the engine red lining it!! On longer hills and such they are literally life savers!! You gear down to say 6 or 7th gear on a long mountain(this would be roughly 20-25MPH like most mountains require!) You have chices now, the engine can hold you back to that spped with periodic help from the service brakes OR.. You can rely entirely on the service brakes, glaze them over from thousands of degrees of heat and cause them to fail or catch fire and tehn go runaway over top of every car and through every house at the bottom of the mountain....... Your call, you want the truck behind you using a Jake Brake and having his service brakes totally operable to back it up if he needs to stop to prevent from killing your family? OR... Glaze those fuckers up right and roll right through several cars and buildings at the bottom of the hill with your family in one of them? People do not realize how much safer Jake Brakes make the highways by limiting speed of big rigs, especially the dumb fuckers who ban them in their towns and put their citizens at increased risk of disaster. The independents who run straight pipes to make it sound louder when they kick on ruined it for everybody, most muffled trucks the common bystander would never even know when the Jake Brake kicked on they would easily mistake it for down gearing the noise is so muffled. Are there drivers who use them un necesarily because they think it sounds cool? Yes! But... They also make controlling that truck easier and safer and therefore other highway users safer. BIG RIGS are NOT cars and do not drive like one, they need every advantage they can get or use to slow down and stop when they need to. Your car or Pickup truck weighs maybe one and half or two tons!! Thats is just the ENGINE in a Big rig!! Plus 60,000 plus in wieght can be in the typical van trailer and more than that on a flat bed. I leave you thinking about this.......At 65MPH it takes a fully loaded tractor trailer 698.5 ft. MINIMUM to stop completely just using the service brakes!! Now aren't you glad a lot of trucks have a engine bbrake to help with your family on the same roads? Very well said. I think the people that bitch about the jakes should try driving a truck sometime just to find out what it is really like behind the wheel of one. |
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Quoted: Quoted: By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Not downshifting. Killing spark or whatever it's called on deisel motors to use the engine compression to slow the vehical. Sounds like the truck is cutting a massive fart. I don't think that diesel engines have the option of "sparking" since they don't have plugs. Maybe that isn't what you meant. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Its kinda like that but on big trucks you have a switch that makes it happen by closing the exhaust ports ( or thats how im pretty sure they work) The exhaust valves are opened at the end of the compression stroke just before the power stroke. |
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It most definitely helps at slowing down, in addition, an engine brake prolongs the life of your brakes. Perhaps more importantly, unlike your service brakes, it doesn't fade with continuous use - which can be a life-saver on long downgrades. You can use it continuously, holding your service brakes in reserve for emergency stops. This ! As a truck driver myself I use a jake all the time for hauling equipment up and down the highways and mountains of where I live in Northern Ca. hauling heavy equipment in to the job sites I work at , ie .. dozers, excavators, rollers, paddle scrapers.. The use of a jake is very beneficial to slowing down, using the gears also, but also maintaining a speed going down grades so you don't heat up your breaks so much and cause break fade . |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Not downshifting. Killing spark or whatever it's called on deisel motors to use the engine compression to slow the vehical. Sounds like the truck is cutting a massive fart. I don't think that diesel engines have the option of "sparking" since they don't have plugs. Maybe that isn't what you meant. I know they don't have sparkplugs. It was years ago when it was explained to me how they work. The jist of it that I got was that power was cut to half the engine and used the compression from the unfired cylinders to slow the motor. Still not sure how they do that with glow plugs though. If someone knows how a jake brake works, please let us 4 wheelers know. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Its kinda like that but on big trucks you have a switch that makes it happen by closing the exhaust ports ( or thats how im pretty sure they work) The exhaust valves are opened at the end of the compression stroke just before the power stroke. knew it had something to do with the exhaust valves just couldnt remember what |
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on big trucks you have a switch that makes it happen by closing the exhaust ports Yep, that's pretty much how they work. Basically, closing the exhaust valves (while still keeping the intake valves open) turns your engine into a huge air compressor. Air compressors soak up a lot of power, which helps slow the vehicle down. There's also an "exhaust retarder" version that uses a butterfly valve to pinch off the engine exhaust after it leaves the engine, rather than holding engine exhaust valves closed. The result is pretty much the same. |
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WTF? Lazy Drivers who do not want to have to do gear changes? NO, the Jake Brake will only slow the truck down to the speed the gear the truck is in allows the truck to go or you will Blow the heads off the engine red lining it!! On longer hills and such they are literally life savers!! You gear down to say 6 or 7th gear on a long mountain(this would be roughly 20-25MPH like most mountains require!) You have chices now, the engine can hold you back to that spped with periodic help from the service brakes OR.. You can rely entirely on the service brakes, glaze them over from thousands of degrees of heat and cause them to fail or catch fire and tehn go runaway over top of every car and through every house at the bottom of the mountain....... Your call, you want the truck behind you using a Jake Brake and having his service brakes totally operable to back it up if he needs to stop to prevent from killing your family? OR... Glaze those fuckers up right and roll right through several cars and buildings at the bottom of the hill with your family in one of them? People do not realize how much safer Jake Brakes make the highways by limiting speed of big rigs, especially the dumb fuckers who ban them in their towns and put their citizens at increased risk of disaster. The independents who run straight pipes to make it sound louder when they kick on ruined it for everybody, most muffled trucks the common bystander would never even know when the Jake Brake kicked on they would easily mistake it for down gearing the noise is so muffled. Are there drivers who use them un necesarily because they think it sounds cool? Yes! But... They also make controlling that truck easier and safer and therefore other highway users safer. BIG RIGS are NOT cars and do not drive like one, they need every advantage they can get or use to slow down and stop when they need to. Your car or Pickup truck weighs maybe one and half or two tons!! Thats is just the ENGINE in a Big rig!! Plus 60,000 plus in wieght can be in the typical van trailer and more than that on a flat bed. I leave you thinking about this.......At 65MPH it takes a fully loaded tractor trailer 698.5 ft. MINIMUM to stop completely just using the service brakes!! Now aren't you glad a lot of trucks have a engine bbrake to help with your family on the same roads? This is all well and good when you are going down a mountain, but what about when you are between stop signs in a small town on level road? Some drivers just like to make noise. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Not downshifting. Killing spark or whatever it's called on deisel motors to use the engine compression to slow the vehical. Sounds like the truck is cutting a massive fart. I don't think that diesel engines have the option of "sparking" since they don't have plugs. Maybe that isn't what you meant. I know they don't have sparkplugs. It was years ago when it was explained to me how they work. The jist of it that I got was that power was cut to half the engine and used the compression from the unfired cylinders to slow the motor. Still not sure how they do that with glow plugs though. If someone knows how a jake brake works, please let us 4 wheelers know. Sure. There are actually two kinds of engine "brakes". One is the Jake Brake, and the other is an exhaust brake which is not the same thing. The cylinder head of a Jake Brake engine has another exhaust valve which is activated by a solenoid when you lift off the accelerator pedal. You can turn it on and off with a switch if you don't want the Jake. The extra valve opens at or near TDC of the compression stroke to release the pressure so that it does not help to push the piston back down again, which slows the truck down. The engine is basically running with no compression. An Exhaust Brake shuts off the exhaust after the exhaust manifold which increases the back pressure and uses more energy to push the piston up to TDC on the exhaust stroke. The Jake Brake makes the cool popping sound and the exhaust brake makes a hissing sound as pressure is released through a pressure valve. |
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It turns the engine into a giant air compressor. It's the best auxiliary brake around.
At my Fire Dept, we have a lot of trucks with transmission output retarders. They use ATF to cause resistance to slow the vehicle, saving the brakes for more important stops. Problem is, it heats the ATF up too much, above 250ºF at times. An engine compression brake doesn't introduces a negligent amount of heat. |
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Are engine brakes on semis more effective at scrubing speed then hitting the brakes? If not, why the fuck do somany truckers use them? Since I'm apparently the resident expert on Jake Brakes, here's how it goes. Jake Brakes work great. They open the exhaust valve just as the piston reaches TDC, thus turning the engine into a giant aircompressor since there is no power stroke, thus, you have the drag of the compression stroke sans the resultant combustion stroke. The pop you hear is the cylinder pressure from TDC air being released into the exhaust manifold following the firng order. The faster the truck is going, the faster the reverb (obviously). The higher the horse power, the better jakes work. Most of the fleet trucks are fairly quiet. It's the hillbilly roadking chicken hauler cowboys with 8 - 10" straight pipes that ruin it for everybody else. With a factory exhaust you don't have that obnoxious reverb that echos for fucking miles. Do they work as well as the service brakes? IN an emergency stop situation. no. IN a long down hill grade. Yes. You can even use them while up shifting to save your clutch brake. You can even program them to control your cruise control speed. If you're really into heavy loads you can have a Jake Brake compression brake, a Jake Brake Dynatard (drive shaft mounted generator for dynamic braking action) and a Caterpillar Brake Saver (tourqe converter that runs off engine oil mounted between the fylwheel housing and bellhousing). Do they save wear and tear? Absolutely. Do they work? No question. Can they be obnoxious? Only when the factory exhaust has been tampered with. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Not downshifting. Killing spark or whatever it's called on deisel motors to use the engine compression to slow the vehical. Sounds like the truck is cutting a massive fart. I don't think that diesel engines have the option of "sparking" since they don't have plugs. Maybe that isn't what you meant. I know they don't have sparkplugs. It was years ago when it was explained to me how they work. The jist of it that I got was that power was cut to half the engine and used the compression from the unfired cylinders to slow the motor. Still not sure how they do that with glow plugs though. If someone knows how a jake brake works, please let us 4 wheelers know. Sure. There are actually two kinds of engine "brakes". One is the Jake Brake, and the other is an exhaust brake which is not the same thing. The cylinder head of a Jake Brake engine has another exhaust valve which is activated by a solenoid when you lift off the accelerator pedal. You can turn it on and off with a switch if you don't want the Jake. The extra valve opens at or near TDC of the compression stroke to release the pressure so that it does not help to push the piston back down again, which slows the truck down. The engine is basically running with no compression. An Exhaust Brake shuts off the exhaust after the exhaust manifold which increases the back pressure and uses more energy to push the piston up to TDC on the exhaust stroke. The Jake Brake makes the cool popping sound and the exhaust brake makes a hissing sound as pressure is released through a pressure valve. And which engine manufacturer is that? The only mod to the head is changing the non Jake (or Pac-Brake as the case may be) exhaust valve bridge out for the Jake bridge that has a platform for the Jake feet to act upon the valves. On the overhead cam engines you merely swap out the exhaust rocker arm and the injector rocker arm. |
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WTF? Lazy Drivers who do not want to have to do gear changes? NO, the Jake Brake will only slow the truck down to the speed the gear the truck is in allows the truck to go or you will Blow the heads off the engine red lining it!! On longer hills and such they are literally life savers!! You gear down to say 6 or 7th gear on a long mountain(this would be roughly 20-25MPH like most mountains require!) You have chices now, the engine can hold you back to that spped with periodic help from the service brakes OR.. You can rely entirely on the service brakes, glaze them over from thousands of degrees of heat and cause them to fail or catch fire and tehn go runaway over top of every car and through every house at the bottom of the mountain....... Your call, you want the truck behind you using a Jake Brake and having his service brakes totally operable to back it up if he needs to stop to prevent from killing your family? OR... Glaze those fuckers up right and roll right through several cars and buildings at the bottom of the hill with your family in one of them? People do not realize how much safer Jake Brakes make the highways by limiting speed of big rigs, especially the dumb fuckers who ban them in their towns and put their citizens at increased risk of disaster. The independents who run straight pipes to make it sound louder when they kick on ruined it for everybody, most muffled trucks the common bystander would never even know when the Jake Brake kicked on they would easily mistake it for down gearing the noise is so muffled. Are there drivers who use them un necesarily because they think it sounds cool? Yes! But... They also make controlling that truck easier and safer and therefore other highway users safer. BIG RIGS are NOT cars and do not drive like one, they need every advantage they can get or use to slow down and stop when they need to. Your car or Pickup truck weighs maybe one and half or two tons!! Thats is just the ENGINE in a Big rig!! Plus 60,000 plus in wieght can be in the typical van trailer and more than that on a flat bed. I leave you thinking about this.......At 65MPH it takes a fully loaded tractor trailer 698.5 ft. MINIMUM to stop completely just using the service brakes!! Now aren't you glad a lot of trucks have a engine bbrake to help with your family on the same roads? Oh yeah.....we had some guy in line at the asphalt plant who was waiting for his load. This tool would rev up his truck with jake on and then let off the throttle just to hear it gurgle back down to idle. He did it again, and again and again. He even pissed off the other super truckers in the que. Well as he was pulling under the hopper, the hopper operator accidently on purpose by accident opened it a little soon and dumped a line of hot ashpalt across his hood, windshield, cab protector (and rolled up tarp) oooopppsss. |
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What they need to do is make trucks like diesel trains. Use a smaller diesel generator in the place of the current engine and transmission. Slap a bank of ultracapacitors under the cab along with the control equipment. A couple large motors at the rear directly driving the wheels. Fuel tanks where they usually are. I wonder how fuel efficient such a system could be. Even if it got 20% better fuel economy, as long as the equipment didn't cost astronomically more than a standard truck... it could reduce the cost of shipping significantly, cuz heck, everything you buy at every store got there on a truck! |
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What they need to do is make trucks like diesel trains. Use a smaller diesel generator in the place of the current engine and transmission. Slap a bank of ultracapacitors under the cab along with the control equipment. A couple large motors at the rear directly driving the wheels. Fuel tanks where they usually are. I wonder how fuel efficient such a system could be. Even if it got 20% better fuel economy, as long as the equipment didn't cost astronomically more than a standard truck... it could reduce the cost of shipping significantly, cuz heck, everything you buy at every store got there on a truck! Caterpillar and Lieber already have that in off road mining trucks. Way way way too pricey for on highway trucks. And there would be no such thing as "a smaller diesel generator in place of the motor and trans". You would have the exact same size emgine. Horse power is horse power is Kilowatts. Lets say you had a 600 hp CAT C18 in a truck. If you want to move the same load with a geneset, you still rquire 600hp to turn the 400kw generator end. There is no way around it. The biggest advantage (and this is why CAT is experimenting with the idea) of the electric traction motors in on highway trucks is you can run the engine at a constant 1800rpm (60hz). What this allows you to do is build an engine that is emmissions compliant for ONE rpm, and not have to worry about all RPM ranges from 600rpm to 2100rpm. It doesn't sound like a big deal, but when the tier 6 or 7 emmission standards become the law of the land a constant speed engine is the only one that is going to pass. |
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EMD-You can even use them while up shifting to save your clutch brake. How will an engine brake save a clutch brake? Ever hear those guys who have the jake on red light to red light or going UP hill and shifting gears? Sometimes those guys are shifting w/o the clutch and using the Jake to slow down the engine and jam a gear as the rpm comes down and the gears synch (you can actually get pretty good at it, I tried it a few times, but when you miss it you get all kinds of grinding). We have a guy at work that only uses the clutch in first and reverse. Everything else is jake and shift. |
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EMD-You can even use them while up shifting to save your clutch brake. How will an engine brake save a clutch brake? Ever hear those guys who have the jake on red light to red light or going UP hill and shifting gears? Sometimes those guys are shifting w/o the clutch and using the Jake to slow down the engine and jam a gear as the rpm comes down and the gears synch (you can actually get pretty good at it, I tried it a few times, but when you miss it you get all kinds of grinding). We have a guy at work that only uses the clutch in first and reverse. Everything else is jake and shift. The only use for a clutch brake is to stop the trans input shaft. The only time you use it, is when the tractor is not moving. When you push the clutch pedal all the way down, you engage the clutch brake. The shifting you speak of has nothing to do with the engine brake, it is called floating. When you shift w/o the clutch pedal, you match the engine rpm to the next gear. It is very easy to do with a tractor, but kinda tricky in a car. I never use the clutch pedal in a tractor unless I am stopped. |
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....... You have chices now, the engine can hold you back to that spped with periodic help from the service brakes OR.. You can rely entirely on the service brakes, glaze them over from thousands of degrees of heat and cause them to fail or catch fire and tehn go runaway over top of every car and through every house at the bottom of the mountain....... This statement in particular. I don't drive trucks, but living in the mountains of Colorado I've discovered that there are two kinds of truckers; those who use engine braking down hills, and flaming wrecks on the side of the road. |
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You first have to understand that a Jake Brake is not 'engine braking' as you probably understand it. In summary, it turns the engine into an air compressor. The Jake system allows the engine to conduct a full compression stroke, then releases that compression before the what would have been your power stroke. Since the compressed air is vented, it's no longer there to 'help' the piston return to the bottom of the cylinder. Thus, it really magnifies the energy it takes to spin the engine. Diesels have such a high compression ratio, that it works really well.
Jakes shouldn't be banned because they are indeed a vital piece of gear in hilly areas. However, someone should design and implement an effective noise suppression system for the compression release. |
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By engine break do you mean down shifting so the friction in the engine slows you down? Because I do that in cars if i'm coming down a long hill. Its kinda like that but on big trucks you have a switch that makes it happen by closing the exhaust ports ( or thats how im pretty sure they work) Gas engines have throttle blades that when closed, creates an intake vacuum that provides engine braking. Diesels dont use throttle blades, so the exhaust brake creates exhaust backpressure needed to provide engine braking. Similar principle and effect, different part of the engine. |
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What they need to do is make trucks like diesel trains. Use a smaller diesel generator in the place of the current engine and transmission. Slap a bank of ultracapacitors under the cab along with the control equipment. A couple large motors at the rear directly driving the wheels. Fuel tanks where they usually are. I wonder how fuel efficient such a system could be. Even if it got 20% better fuel economy, as long as the equipment didn't cost astronomically more than a standard truck... it could reduce the cost of shipping significantly, cuz heck, everything you buy at every store got there on a truck! Caterpillar and Lieber already have that in off road mining trucks. Way way way too pricey for on highway trucks. And there would be no such thing as "a smaller diesel generator in place of the motor and trans". You would have the exact same size emgine. Horse power is horse power is Kilowatts. Lets say you had a 600 hp CAT C18 in a truck. If you want to move the same load with a geneset, you still rquire 600hp to turn the 400kw generator end. There is no way around it. The biggest advantage (and this is why CAT is experimenting with the idea) of the electric traction motors in on highway trucks is you can run the engine at a constant 1800rpm (60hz). What this allows you to do is build an engine that is emmissions compliant for ONE rpm, and not have to worry about all RPM ranges from 600rpm to 2100rpm. It doesn't sound like a big deal, but when the tier 6 or 7 emmission standards become the law of the land a constant speed engine is the only one that is going to pass. My understanding is that this is actually why Cummins is working on infinitely variable valve timing and and better injectors. They don't seem to be too worried. |
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EMD-You can even use them while up shifting to save your clutch brake. How will an engine brake save a clutch brake? Ever hear those guys who have the jake on red light to red light or going UP hill and shifting gears? Sometimes those guys are shifting w/o the clutch and using the Jake to slow down the engine and jam a gear as the rpm comes down and the gears synch (you can actually get pretty good at it, I tried it a few times, but when you miss it you get all kinds of grinding). We have a guy at work that only uses the clutch in first and reverse. Everything else is jake and shift. The only use for a clutch brake is to stop the trans input shaft. The only time you use it, is when the tractor is not moving. When you push the clutch pedal all the way down, you engage the clutch brake. The shifting you speak of has nothing to do with the engine brake, it is called floating. When you shift w/o the clutch pedal, you match the engine rpm to the next gear. It is very easy to do with a tractor, but kinda tricky in a car. I never use the clutch pedal in a tractor unless I am stopped. And what happens when the latest noob from the A B Tech truck driving school pushes the clutch pedal ALL the way to the floor while shifting???? It burns off the clutch material facing, or it wipes out the declutching mech inside some clutch brakes or it just shears the tabs off the clutch brake. I've spent enough time with a torch and my hands squeezed through the inspection hole of a Fuller to know. Further...shifting with the Jake slows the egine down enough (matching RPM to gear sooner) to shift quicker w/o the clutch or waiting for engine RPM to come down on it's own (for the impatient type drivers out there). Jakes will absolutely extend clutch brake life. Lots and lots of steering wheel holders out there and very few real drivers  .
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