I have been googling this for 10 minutes and it seems the same to me. Are both methods not just using the air from the intake to add more resistance to the pistons and crankshaft?
In: Engineering
Engine braking has two possible mechanisms that may cause the engine to slow:
Resistance against pulling on a vacuum during downstroke.
Resistance against pushing gasses together during upstroke.
The problem is that if no valves open or close then a significant portion of the energy used to pull or push is given back to the engine during the next stroke (you pulled against a vacuum during intake, but now the vacuum is helping you during compression OR you compressed gas during compression but now it’s helping you push back down during power stroke).
A jake brake releases the energy that would otherwise go back in to the system. At the end of the compression stroke, the pressure is released from the combustion chamber via a valve so that:
The compressed gas doesn’t help the piston back down.
The valve may close again so that the piston pulls on a vacuum during power stroke.
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