In class this week, the instructor attempted to describe for us the Jake Brake.Here's what I understood. He said that the Jake Brake on my engine (ISX 15) is called the Interbrake. It is built into the engine by Cummins and works by introducing fuel during the exhaust cycle of the cylinder movement and withholding fuel from the compression phase. In other words, instead of helping to propel the drive shaft forward during the compression phase, the engine applies pressure to the cylinder when it's in the exhaust phase effectively applying the same amount of force it would to propel the engine to effectively slow the engine. It's almost the same as reversing the current on an electric motor while it's in motion.He said that in the past, Jacobs made Jake Brakes that were bolted on to the engine and did the same thing, but these systems weren't muffled and in some cases, you could see flames shooting out of the exhaust. I'm assuming this was either a separate exhaust or fuel was introduced in the exhaust system somewhere down further.Other engine brakes restrict the exhaust to slow the engine but these systems are not as powerful as shooting fuel into the exhaust phase of the cylinder. Jacobs claims that their systems can produce as much braking power as the engine has horsepower. One of the confusing parts of this explanation is that every brake designed by Jacobs is considered to be a Jake Brake even though it may work differently.Is my understanding correct? Can anyone add to or help me correct this?

A true jake brake is electrical components, a toggle switch on the dash,a switch at the foot throttle. When the switch is on and the foot pedal is disengaged the electric solenoids in the rocker box hold the exhaust valves open, so the compression & heat isn't there to fire the fuel. Thus this is the noise you hear out the exhaust pipe. I never hear of flames coming out of the exhaust. Only back in the day when old timers would mix a ratio of gas to diesel in the winter, to prevent gel up.

yrusoslo wrote:A true jake brake is electrical components, a toggle switch on the dash,a switch at the foot throttle. When the switch is on and the foot pedal is disengaged the electric solenoids in the rocker box hold the exhaust valves open, so the compression & heat isn't there to fire the fuel. Thus this is the noise you hear out the exhaust pipe. I never hear of flames coming out of the exhaust. Only back in the day when old timers would mix a ratio of gas to diesel in the winter, to prevent gel up.I'm not sure I understand that at all. If the compression and heat isn't there to fire the fuel, isn't that simply called coasting? Your description sound like it would result in zero slowing power. Perhaps the exhaust valve is closed on the downstroke to create a vacuum? Where is the backwards braking power introduced at the engine?

The compression brake, originally called jake brake which a trademark, as mentioned, in the early days was added onto the heads of a cummins engine. As I understand it it reverses the action of the valves to turn the engine into a compressor ( not really that simple ) there may be a small amount of fuel introduced to keep the cylinders from running dry.I drove a 1962 Kenworth and we had one of the first 'jake' brakes installed. I could go down the g****vine grade with a 25 ton load and just touch the service brakes. Like I said in another post, this was the greatest invention ever for the heavy truck industry.

Thanks for bringing this up. I would also like to understand it, though I have never had a Diesel engine. Good old Wikipedia has an explanation that is helpful. https://en.m.wikipedia.org/wiki/Compression_release_engine_brake

I started to do some links but there are too many entries to do.Google "wiki diesel braking' and wiki retarder braking and wiki jake brake.There are some good simple descriptions.

What is a Jake Brake? | Good Sam Community

Harvey51
Explorer
Aug 09, 2015
Thanks for bringing this up. I would also like to understand it, though I have never had a Diesel engine. Good old Wikipedia has an explanation that is helpful. https://en.m.wikipedia.org/wiki/Compression_release_engine_brake
bigdog2
Explorer
Aug 09, 2015
The compression brake, originally called jake brake which a trademark, as mentioned, in the early days was added onto the heads of a cummins engine. As I understand it it reverses the action of the valves to turn the engine into a compressor ( not really that simple ) there may be a small amount of fuel introduced to keep the cylinders from running dry.
I drove a 1962 Kenworth and we had one of the first 'jake' brakes installed. I could go down the g****vine grade with a 25 ton load and just touch the service brakes. Like I said in another post, this was the greatest invention ever for the heavy truck industry.
holstein13
Explorer
Aug 09, 2015
yrusoslo wrote:
A true jake brake is electrical components, a toggle switch on the dash,a switch at the foot throttle. When the switch is on and the foot pedal is disengaged the electric solenoids in the rocker box hold the exhaust valves open, so the compression & heat isn't there to fire the fuel. Thus this is the noise you hear out the exhaust pipe. I never hear of flames coming out of the exhaust. Only back in the day when old timers would mix a ratio of gas to diesel in the winter, to prevent gel up.
I'm not sure I understand that at all. If the compression and heat isn't there to fire the fuel, isn't that simply called coasting? Your description sound like it would result in zero slowing power. Perhaps the exhaust valve is closed on the downstroke to create a vacuum? Where is the backwards braking power introduced at the engine?
yrusoslo
Explorer
Aug 09, 2015
A true jake brake is electrical components, a toggle switch on the dash,a switch at the foot throttle. When the switch is on and the foot pedal is disengaged the electric solenoids in the rocker box hold the exhaust valves open, so the compression & heat isn't there to fire the fuel. Thus this is the noise you hear out the exhaust pipe. I never hear of flames coming out of the exhaust. Only back in the day when old timers would mix a ratio of gas to diesel in the winter, to prevent gel up.

Forum Discussion

What is a Jake Brake?

About Motorhome Group

Related Content

Jake Brake

Jake vs Exhaust Brake

Jake Brake / Pac brake question

Exhaust or jake brake or neither?

Katy joins Jake