What Is Engine Braking? What Is A Jake Brake?

I listen to you in order to practise my English. You speak very nice ! Thanks

Awesome explanation as always! It is amazing how much energy an engine uses when there is no combustion!

On our heavy haul trucks (pulling two mountain doubles), we had compression brakes (not a Jacob brake) and we had brake savers. The brake saver consisted of an extra compartment filled with engine oil. It was part of the engine and set at the back of the engine at the output shaft. When applied by switch or an extra "Johnny Bar", it would air activate a paddle that would drop down into the extra 3 gallons of engine oil. It slowed the truck down quite a bit in combination with the compression brake. We were hauling 500,000 lbs. gross on private roads. Just thought I'd share.

That's pretty close to how I explain how a Jake brake works. You flip the switch, witchcraft happens and then the truck sounds like a boss.

The "Jacobs" brake was invented by Clessie Cummins after he retired from Cummins Engine Co. He originally approached Cummins to use it, but they were not interested. So he went to Jacobs Manufacturing (The people that make Jacobs drill chucks) and they built the brake. The logo on the Jacobs brake is the same logo as on the drill chucks.

I wish more drivers wouod understand the concept of engine braking. On a flat surface, physics and engine braking constantly want the vehicle to slow down. Normal braking isnt always needed to slow a vehicle (and engine braking helps preserve your brake pads). When approaching a stop sign or red light, you can simply let off the gas and the vehicle will gradually slow down (this can also help gas mileage as the fuel injectors shut down under deceleration when throttle is closed). Using your regular brakes unnecessarily doesnt allow the injectors as long as idle period bc the engine revs drop faster vs engine braking. The injectors will turn on sooner as you approach engine idle speed. Being able to proactively downshift magnifies engine braking as youre able to reduce vehicle speed more aggressively thru gearing and youre allowing the injectors more idle time as the engine revs slowly come down from a higher rpm (from the lower gear you just downshifted too). The lower gear puts the engine at a higher rpm increasing that vacuum which in turn slows the vehicle down more quickly.

As a Truck Driver, thankyou, I can now explain HOW it turns my motor into a giant 14.5 litre 6 cyl air compressor.

So, a jake brake is when a semi truck goes down a hill and makes that loud HHHHHHHHHFAHFILUHAUIEGFBAJKGBALIUHV sound right?

The story of the Jake Brake is actually quite fascinating. It was not invented by Jacobs. The Jake Brake was independently invented by Clessy Cummins of the Cummins Engine Company and exclusively licensed to Jacobs. He was retired at the time, and he designed the valve system on paper at home, there by proving his brilliance as an engineer beyond any doubt. He wouldn't sell the patent to Cummins because of long standing bitterness about his pension and patent royalties.

Very good explanation of this. One thing to add though is with modern electronic diesel engines the 'control' solenoid is no longer needed as the engine computer is able to simply control an electric over oil solenoid to the exhaust valve to activate the system which gives much more precise control than the old master/slave type system of days past. Some modern engines even use the VG valve in the turbo to compound the engine braking using both back-pressure and compression combined together to often give the engine as much or more braking power than it has propulsion power depending on the engine spec for HP.

This is why im awake at 4am, when i actually should of went to sleep 23pm. Useful videos on your channel :)

False: a Jake brake is using your friend (Preferably Jake) as a brake by throwing him in front of the car :D It's simple physics, and is easy to do! The only problem is the maintenance cost :/

Dude, I had a pretty good idea of how automobiles worked before I found your videos, but you've given me a whole new level of understanding. Thanks for what you do man.

Was going to suggest you cover this topic, was interested to hear you explain it and you did not disappoint! Mint job

Thanks to Jake brakes I can drive in the Rocky mountains without catching my brakes on fire with my 80000 pound semi

This was a fantastic video as always. I love how you teach concepts that many people such as myself may not understand in ways that are easily understandable. I love this kind of stuff but am not a car guy, and the way you teach it makes it easy for anybody to understand. Keep up the great videos!!!!!!

In Europe, when I took my truck license, I was told there was also another engine brake system called "the retarder" which is a oil turbine based braking system connected to the engine output shaft or driveshaft

Thanks for this video! I never realized that "Jake Braking" was an actual thing. I thought it was just a term, rather than an actual mechanism.

Thank you so much for posting this. I was hoping you'd do one of these! Very informative.

Back in the 1970s when I was a college student in Los Angeles, I drove Crown school buses. These two and three-axle buses were powered by either Cummins or Detroit Diesel inline 6-cylinder engines with a five or ten-speed Fuller non-synchro transmission. I sometimes used the Jake Brake going uphill to catch an upshift especially first to second or second to third gears. The Jake brake would help decelerate the engine to catch the upshift. I was king of the road with that Detroit 6-71 when I hit that Jake brake.