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Old 06-18-2019, 09:12 PM   #1
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What does "air to air" and "engine brake" mean?

I'm looking at a bus for sale and it lists:

Air to Air: Yes
Engine Brake: No

What do these refer to? Thanks!
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Old 06-18-2019, 09:26 PM   #2
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Probably air suspension, air brakes. It does not have a "jake brake" type system to use engine brake pressure to slow the motor.
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Old 06-19-2019, 12:40 AM   #3
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It may refer to the intercooler. poor description.
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Old 06-19-2019, 07:13 AM   #4
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A turbocharger intercooler is referred to as an air to air unit. An engine brake or Jake brake is an exhaust braking system equipped on big rigs and larger engines.
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Old 06-19-2019, 07:25 AM   #5
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Quote:
Originally Posted by kaivgrant View Post
I'm looking at a bus for sale and it lists:

Air to Air: Yes
Engine Brake: No

What do these refer to? Thanks!
air to air sounds like a charge air cooler to me.
And most school buses have no engine brake. Engine brake is a jake brake.
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Old 06-19-2019, 11:33 AM   #6
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Quote:
Originally Posted by kaivgrant View Post
I'm looking at a bus for sale and it lists:

Air to Air: Yes
Engine Brake: No

What do these refer to? Thanks!
Sorry, EastCoast, misread your post as someone else's the first time. I second EastCoastCB. Sounds like a turbocharged engine with an air-to-air intercooler. Some are water-to-air. Some more specific info on the bus in question would be helpful.

Engine brake is basically a setup that reduces engine power on certain cylinders, as with a rev limiter. This allows the driver to use the engine and transmission to slow the vehicle on hills, making it easier and safer to control, as overusing the brakes will cause them to overheat and fail. Nice to have, but not common on skoolies, I'm afraid, as most were not intended for mountain driving.

There are different types of auxiliary braking devices as well. Some solely use exhaust pressure, some are internal to the trans, others have an actual brake that clamps down on the crankshaft / balancer. Obviously the exhaust brake is the most common.
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Old 06-19-2019, 11:44 AM   #7
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Quote:
Originally Posted by kaivgrant View Post
I'm looking at a bus for sale and it lists:



Air to Air: Yes

Engine Brake: No



What do these refer to? Thanks!
—-//
When I was going through the air breaks diagrams, I read about the engine brake. I thought they were not allowed in everyday vehicles and especially in residential neighborhoods because of the loud noise it makes. But from what I recall it is to slow down the engine. I can’t see why a bus would have that, only big, huge equipment and rigs would need something of that caliber. Could it be a typo, maybe he meant to say air brakes?
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Old 06-19-2019, 11:54 AM   #8
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Originally Posted by Dèsirée View Post
—-//
When I was going through the air breaks diagrams, I read about the engine brake. I thought they were not allowed in everyday vehicles and especially in residential neighborhoods because of the loud noise it makes. But from what I recall it is to slow down the engine. I can’t see why a bus would have that, only big, huge equipment and rigs would need something of that caliber. Could it be a typo, maybe he meant to say air brakes?
Nope, doubt it's a typo. Engine brakes are an option on some commercial vehicles below Class 8. Engine brakes in and of themselves are not noisy. The ones you notice are straight-piped Billy BigRiggers that like to hear their engine over everything else. Every Class 8 truck built has had an engine brake for years, and none of them I drove were loud at all.

But as a driver of such trucks, for those who complain about loud engine brakes... They're not as loud as a loaded big rig crashing into your living room or running over your car. Most people who drive conventional vehicles have no clue how dangerous those trucks are, and when you pull out in front of them, we can either wake up the neighborhood with the engine brake, or we can run you over. Your choice.

Engine brakes are there to supplement the foundation brakes, and save them for when we REALLY need to stop, like your kid running out into the road after a ball, for example. They need a lot more space to stop and turn than you think. I would think most people on this site would have learned that by now, as most skoolies are in essence a medium-duty truck chassis with a bus body on it. Personally, I think the straight-piped growl of an exhaust brake helps to give a little extra warning that you just pulled out in front of something that's a lot bigger than you. Just my $0.02
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Old 06-19-2019, 12:23 PM   #9
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Quote:
Originally Posted by CHEESE_WAGON View Post
Nope, doubt it's a typo. Engine brakes are an option on some commercial vehicles below Class 8. Engine brakes in and of themselves are not noisy. The ones you notice are straight-piped Billy BigRiggers that like to hear their engine over everything else. Every Class 8 truck built has had an engine brake for years, and none of them I drove were loud at all.

But as a driver of such trucks, for those who complain about loud engine brakes... They're not as loud as a loaded big rig crashing into your living room or running over your car. Most people who drive conventional vehicles have no clue how dangerous those trucks are, and when you pull out in front of them, we can either wake up the neighborhood with the engine brake, or we can run you over. Your choice.

Engine brakes are there to supplement the foundation brakes, and save them for when we REALLY need to stop, like your kid running out into the road after a ball, for example. They need a lot more space to stop and turn than you think. I would think most people on this site would have learned that by now, as most skoolies are in essence a medium-duty truck chassis with a bus body on it. Personally, I think the straight-piped growl of an exhaust brake helps to give a little extra warning that you just pulled out in front of something that's a lot bigger than you. Just my $0.02
—-/
Quite an education I just got from cheese wagon... and worth a lot more than a silver dollar!
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Old 06-19-2019, 12:25 PM   #10
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—-/
Quite an education I just got from cheese wagon... and worth a lot more than a silver dollar!
Not to mention the only dime those trucks, or these skoolies for that matter, might be able to stop on, is the one in your pocket...
Your Braking Distance - OUR Braking Distance.jpg
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Old 06-19-2019, 12:30 PM   #11
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My little Isuzu turbo diesel has an exhaust brake. It is very effective above 30 mph but shuts off automatically below that speed. Basically, when the computer sees no throttle advance a vacuum driven slice valve in the exhaust pipe is activated blocking some exhaust flow. At the same time the diesel injectors are leaned out to prevent "blowing coal" upon acceleration--its sort of like stuffing a potato in the tail pipe.
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Old 06-19-2019, 12:45 PM   #12
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Originally Posted by CHEESE_WAGON View Post
But as a driver of such trucks, for those who complain about loud engine brakes... They're not as loud as a loaded big rig crashing into your living room or running over your car. Most people who drive conventional vehicles have no clue how dangerous those trucks are, and when you pull out in front of them, we can either wake up the neighborhood with the engine brake, or we can run you over. Your choice.




Just for clarification, did a quick check and it appears the Franklin driver was *NOT* the cause of this wreck, (s)he was rear-ended by another big truck causing a chain reaction. 4 semis and this pickup involved. The most I could fault for is not leaving enough room between vehicles, and given that the impact was hard enough to involve 3 big trucks leads me to think even another 50 feet of space would not have been enough.

Quote:
Originally Posted by CHEESE_WAGON View Post
Engine brakes are there to supplement the foundation brakes, and save them for when we REALLY need to stop, like your kid running out into the road after a ball, for example. They need a lot more space to stop and turn than you think. I would think most people on this site would have learned that by now, as most skoolies are in essence a medium-duty truck chassis with a bus body on it. Personally, I think the straight-piped growl of an exhaust brake helps to give a little extra warning that you just pulled out in front of something that's a lot bigger than you. Just my $0.02

It is for this reason (among others) I have a Grover fire truck air horn which will be installed. There's something satisfying about being able to yank on a lanyard and get their attention when someone does something stupid on the road - and a weak electric horn just doesn't convey the same message with the same intensity. I want people to *KNOW* something big and heavy is coming. Trains have loud horns because they can't swerve nor stop quickly. The horn isn't there simply to wake folks at night - it's there as a message that something really big and really heavy (and in some cases, really fast) is coming through whether you are in the path or not.
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Old 06-19-2019, 12:51 PM   #13
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Originally Posted by ol trunt View Post
My little Isuzu turbo diesel has an exhaust brake. It is very effective above 30 mph but shuts off automatically below that speed. Basically, when the computer sees no throttle advance a vacuum driven slice valve in the exhaust pipe is activated blocking some exhaust flow. At the same time the diesel injectors are leaned out to prevent "blowing coal" upon acceleration--its sort of like stuffing a potato in the tail pipe.
Jack
Exhaust brake that cancels itself above 30? Kinda defeats the purpose, doesn't it?
Quote:
Originally Posted by Brad_SwiftFur View Post
It is for this reason (among others) I have a Grover fire truck air horn which will be installed. There's something satisfying about being able to yank on a lanyard and get their attention when someone does something stupid on the road - and a weak electric horn just doesn't convey the same message with the same intensity. I want people to *KNOW* something big and heavy is coming. Trains have loud horns because they can't swerve nor stop quickly. The horn isn't there simply to wake folks at night - it's there as a message that something really big and really heavy (and in some cases, really fast) is coming through whether you are in the path or not.
Yup! Haven't driven a truck in over a year and I still drive people insane stopping at train crossings with the hazards on, especially driving Uber. Driving as I would with HazMat or passengers at all times has saved my life at least twice. Came up on a rail crossing with no signals. Stopped even though I didn't see any signs of a train. Sure enough, I look off to my right, here come those headlights out of the darkness. Same thing happened in broad daylight at a crossing that appeared abandoned.

Oh, and folks... Commercial passenger bus drivers are required by DOT rule to stop at all rail crossings, school bus drivers included. Not a bad habit to get into with a skoolie, if you aren't already. As I mentioned, it could save your investment, and more importantly, your life. Trains move faster and hit harder than you think, and it takes your skoolie longer to clear that crossing than you think, too. You don't ever want to mess with a locomotive or (any other vehicle that is bigger than you), you will lose.

The DOT procedure (for those interested in learning and practicing) with passenger buses is to turn on hazard flashers, come to a full stop, open doors, turn off any radios or other devices that can hinder hearing, and as the old saying goes, "Stop, Look, and Listen!"

The message here, though, folks, is that these systems don't exist to annoy, they exist to save lives. Don't blame the professional, blame the idiots that make it necessary.
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Old 06-19-2019, 01:12 PM   #14
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Exhaust brake that cancels itself above 30? Kinda defeats the purpose, doesn't it?
It is very EFFECTIVE above 30 mph but shuts off automatically below that speed.
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Old 06-19-2019, 01:22 PM   #15
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I've driven a truck or 2 on which the engine brakes shut off below a certain speed, 25-30 or so. I think the intent is to keep drivers from using them in residential areas and in town, where speeds are supposed to be slow anyway.
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Old 06-19-2019, 02:06 PM   #16
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Quote:
Originally Posted by Dèsirée View Post
—-//
When I was going through the air breaks diagrams, I read about the engine brake. I thought they were not allowed in everyday vehicles and especially in residential neighborhoods because of the loud noise it makes. But from what I recall it is to slow down the engine. I can’t see why a bus would have that, only big, huge equipment and rigs would need something of that caliber. Could it be a typo, maybe he meant to say air brakes?
REAL mountain buses have auxiliary braking systems. Only a scant few ever had jake brakes but many had retarders.
Its easy to overwhelm the brakes in the mountains so auxiliary braking is mandated in some areas.
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Old 06-19-2019, 03:02 PM   #17
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Originally Posted by Brad_SwiftFur View Post
I've driven a truck or 2 on which the engine brakes shut off below a certain speed, 25-30 or so. I think the intent is to keep drivers from using them in residential areas and in town, where speeds are supposed to be slow anyway.
Sound logic until Soccer Mom pulls out in front of you at 50 feet and closing.
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Old 06-19-2019, 05:58 PM   #18
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There are thousands of class 8 trucks without engine brakes Gene
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Old 06-19-2019, 06:01 PM   #19
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I've driven a truck or 2 on which the engine brakes shut off below a certain speed, 25-30 or so. I think the intent is to keep drivers from using them in residential areas and in town, where speeds are supposed to be slow anyway.
I think engine braking not as effective below 30mph and sulphur dioxide out put is above limits at low speeds. Gene
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Old 06-19-2019, 06:19 PM   #20
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There are thousands of class 8 trucks without engine brakes Gene
Oh, I'm aware of that. Just don't see many of them without some sort of auxiliary braking anymore. I've never driven one that didn't have one.
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