Engine Braking

[ChinMusic]

I’ve never driven a vehicle with a “Retarder” which I understand is a form of engine breaking. I’ve always use “down shifting” in other vehicles for taming long decents.



I’ve always seen the following sign and assumed it never applied to me.



I assume the ordinance is for noise reduction. When I use the Retarder on my RV I don’t hear any obnoxious noise, nor much noise at all.

Does the sign apply to me or just the Jake Brake ones that sound like a machine gun?

 

[RRR]

It is just a sign that the people that wrote the ordinance didn't know what they were talking about.

 

[jymbee]

It is just a sign that the people that wrote the ordinance didn't know what they were talking about.

Seems a logical attempt to reduce noise levels. What am I missing?

 

[Skookum]

I suppose it can mean multiple things based on your setup. In a lot of gas coaches, it's an aggressive downshifting profile for the automatic transmission when you let off the throttle or apply the service brakes. In a turbo diesel, it can mean using the turbo to create pressure to slow the engine, or activate an actual engine "Jake" brake.

What sign? I've never seen one, and if I did, I'd deny it.

Although not always the letter of the law, what I usually interpret that wording to mean is don't use one if you're running straight pipes. The Jake on our coach is well muffled so I use it as I see fit. Safe > legal.

 

[Onyrlef]

Seems a logical attempt to reduce noise levels. What am I missing?

Exactly, truckers like to be a pita on city streets unnecessarily using those loud as hell jake brakes. Especially in small towns like Jaspar Ala. the coal trucks would roll through at 2AM thinking it was funny waking everyone up slowing for a stoplight, until they started writing tickets.

 

[Onyrlef]

I’ve never driven a vehicle with a “Retarder” which I understand is a form of engine breaking. I’ve always use “down shifting” in other vehicles for taming long decents.

View attachment 171134

I’ve always seen the following sign and assumed it never applied to me.

View attachment 171135

I assume the ordinance is for noise reduction. When I use the Retarder on my RV I don’t hear any obnoxious noise, nor much noise at all.

Does the sign apply to me or just the Jake Brake ones that sound like a machine gun?

Just the jake brake.

 

[jymbee]

What sign? I've never seen one, and if I did, I'd deny it.

Ah, but you know what they say about ignorance of the law/ordinance!

"Honest officer...!!"

 

[Tulecreeper]

Seems a logical attempt to reduce noise levels. What am I missing?

I suppose it can mean multiple things based on your setup. In a lot of gas coaches, it's an aggressive downshifting profile for the automatic transmission when you let off the throttle or apply the service brakes. In a turbo diesel, it can mean using the turbo to create pressure to slow the engine, or activate an actual engine "Jake" brake.

What sign? I've never seen one, and if I did, I'd deny it.

Although not always the letter of the law, what I usually interpret that wording to mean is don't use one if you're running straight pipes. The Jake on our coach is well muffled so I use it as I see fit. Safe > legal.

You see those signs before entering pretty much any small town all over this area. I always interpreted it as meaning the actual roaring stuttering jake brake the big rigs use when going downhill. However, although there is hilly terrain, there are no areas within 40 miles of me with steep enough/long enough grades to warrant the use of one so I'm not sure why a trucker would even have theirs engaged. But they sometimes do, hence the sign.

 

[Utclmjmpr]

The "Jake Brake" was invented by Clessie Cummins,, after having a downhill runaway brake failure while driving a diesel truck.. After producing them for the trucking industry for a few years he sold all the rights to a man named Jacobs that was doing all the machine work for the production,, that is when they became "Jake Brakes:..>>>Dan ( It also saves on brake shoes at all the wheels.)

 

[CharlesinGA]

The OP may want to skip thru my dissertation and read the bottom paragraph and watch the short video, as I suspect this is the system they have.

No Engine Brake is the best possible term that cities can use for the sign. The object is to eliminate noise, specifically the loud popping noise that Jake/Jacobs (and other brands) of COMPRESSION braking make when they let up on the throttle. Some cities and towns post signs that specifically say No Jake Brake, and I suppose if you could prove in court that your compression braking system is made by someone other than Jacobs, you would be legal.......

Most smaller diesels, those used in pickups and medium duty trucks, are EXHAUST brakes, and they make very little to no noise.

Any kind of engine braking, be it compression, exhaust (both found on diesels) or simply the engine braking a gasoline engine gives you, will require either you, or the vehicles computer, to downshift the gears of the transmission for optimum effect.

Fords, such as the E350/450 chassis used on most Class C models have very effective gasoline engine braking. When in Tow/Haul, if you start a downgrade, accelerator released, you merely press the brake for a moment and the transmission downshifts. The gasoline engine is trying to suck air thru a virtually closed throttle plate and this creates resistance to the engine rotation. If the speed is still too high, you again tap the brake pedal and again the transmission downshifts, maintaining your speed.

Exhaust brakes work in much the same way on newer diesels. They even use the speed control to know what speed to maintain and will downshift and apply more exhaust braking (usually its about three stages of it) again maintaining your speed. The exhaust brake restricts the flow of exhaust out of the engine (a diesel does not have a throttle plate like a gasoline engine, so the exhaust brake is a similar alternative for a diesel engine.

A diesel does not have any significant natural engine braking, due to the lack of a throttle plate, and, while they have very high compression, it only occurs on every other up stroke of the piston and quickly turns into a power stroke. A compression brake basically turns the diesel engine into an air compressor, with every stroke of the piston generating maximum compression before it is released in the loud/objectional popping you hear from class 8 trucks.

For older diesels, such as my 5.9L Cummins, I installed an aftermarket PacBrake brand system that is a butterfly that closes off the exhaust, when the engines computer determines that the 1) accelerator is fully released, and 2) the engine is at 900 rpm or more -or- when the engine is below 170°F the brake operates right down to idle speed. Cummins made provisions in the computer for operating an exhaust brake, but did not actually manufacture or provide the exhaust brake, leaving that to third parties. It is for me to turn it on, and then select the correct gear to provide the speed I want to hold on the downgrade, usually 5th or possibly 4th (6 speed trans)

This is the kit that I installed

When I find some decent short videos on different types of exhaust brakes that show how they work, I will add them.

An Allison transmission retarder is a totally different animal, built into the transmission, it uses transmission fluid in a chamber on the output shaft, with vanes, to create resistance to rotation. The Allison video explains it pretty well. The retarder is an option on the Allison 3000 series transmissions.

Charles

 

[KFX450RXC]

Our engine exhaust brake is awesome on my new F450. Ford has come a long way. I ignore those signs because my truck's exhaust brake noise isn't noticeable.

In fact, many people are of the opinion that using your engine exhaust brake will actually prolong the life of your turbo. It's been known to keep it much cleaner than running without.

 

[Larry N.]

Exhaust brakes work in much the same way on newer diesels.

The "engine brake" on my 2016 Newmar Ventana (Cummins 360HP) was a VGT, Variable Geometry Turbine (exhaust), it automatically shifted into 2nd gear when engaged (unless the computer said it was too fast, but it was still selected on the Allison), and it wasn't nearly as effective as the compression brake (two stage, 3 cyl and 6 cyl) on the Beaver I had (it initially selected 4th gear), though it certainly helped. For example, I still had to use a lot of braking coming down Rabbit Ears Pass westbound in the Ventana. To a somewhat lesser extent I still needed brakes westbound out of the Eisenhower Tunnel to Silverthorne.

Of course it wasn't nearly as noisy as the Beaver one, either. BTW, there is a No Engine Brake sign on I-25 southbound just before you get to Raton, coming down from Raton Pass, where it's still steep enough that I'd use one anyway.

 

[John From Detroit]

There are a few different 'Retarder' systems of which the Jake brake is quite possibly the LOUDEST.. Some you don't really hear..
All ICE vehicles use engine braking Any time you let your lead foot off the gas they are using engine braking.. So the"No Engine Braking" signs are.... Well Let's just say a good lawyer woudl have fun.

 

[Onyrlef]

However, although there is hilly terrain, there are no areas within 40 miles of me with steep enough/long enough grades to warrant the use of one so I'm not sure why a trucker would even have theirs engaged. But they sometimes do, hence the sign.

For the same reason C students put thrush mufflers on p/u trucks, it's loud and attracts attention. Even when that lady in the lane next to them in the ultra quiet ev Bolt with two kids in car seats and groceries in the trunk would kick his ass in a quarter mile.

 

[Gary RV_Wizard]

I assume the ordinance is for noise reduction. When I use the Retarder on my RV I don’t hear any obnoxious noise, nor much noise at all.

Does the sign apply to me or just the Jake Brake ones that sound like a machine gun?

I think "No harm, no foul" applies here. If your engine braking doesn't make any noticeable noise, nobody is going to report you are breaking (braking?) the law. And if you run into a nitpicker LEO, you have a perfect excuse - you have a "retarder" rather than an "engine brake". If it is indeed an Allison Retarder, it is NOT at all an engine brake, though it accomplishes the same end. But modern "Jacobs Engine Brakes" don't make that loud brrraaaat noise anyway.

Note that allowing a gas engine vehicle to slow due to engine compression could also be termed "engine braking". Especially if you downshifted. Engine braking is inherent in any gas engine. But few, if any, local noise ordinances define it that way.

 

[Joezeppy]

I use the exhaust brake feature on my RAM for fun sometimes - interesting to see how it holds the hills and even loses speed going downhill in some cases. Love it when I'm towing the 5th wheel. Last year, we came home from Cooperstown, NY north into the town of Mohawk with a fairly significant grade - I was impressed after leaving the brake check area that it held the truck and trailer right at 45 MPH the whole way down the hill.

 

[Ray-IN]

If I remember correctly an Allison transmission retarder works by changing internal valve positions.
Years ago there was an electromagentic driveline retarder that worked by creating a very strong magnet in a ring around the driveshaft, that itself was a permanent magnet. The two opposing magnets created the retard action and while doing so became quite hot. That design didn't last long for that reason.

 

[jymbee]

However, although there is hilly terrain, there are no areas within 40 miles of me with steep enough/long enough grades to warrant the use of one so I'm not sure why a trucker would even have theirs engaged. But they sometimes do, hence the sign.

"Why" being the question.

Seems hills don't have much to do with these ordinances, rather "no braking" signs are posted where the speed limit drops as you enter a town. Like the town next to where we are now and the speed limit drops from 75 MPH to 55 MPH as you get to the town limits:

 

[CharlesinGA]

Full disclosure, I own 88 shares of Allison (ALSN) which has gained almost 39% since I bought it, about three years ago if I recall. Ok investment I suppose.

Allison has a number of interesting and useful videos on Youtube. If you have a large diesel pusher with an Allison 3000 or 4000 you may find this video useful. It is on the operation of the shifter and covers extracting codes, fluid level, etc. Its 20 minutes long, so beware.

This is a decent overview of the Allison 1000-3000 internals, not too boring and does show the retarder function and operation at 9:10 in the video.

This is how an Allison 3000 internals go roundy-round. Very involved but good animation. They do show the retarder turbine but do not discuss it. Skip this if you are sleepy or easily bored!!!!

 

[Ray-IN]

Those videos are great, however they apply to the latest version-5. My 1999 Allison 3000_RV version-3 I think, shift pad is not like that and does not have many of those features.