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
General engine braking, via letting off the throttle, just uses the drag of the engine to slow down. The valves still open and close at their normal timing. A Jake brake, or engine brake is only on diesel engines, and when you let off the throttle, instead of the valves opening in their normal sequence, an exhaust valve will be forced open right at the top of the compression stroke for a given cylinder, but before fuel is injected, and this will dump all of the compressed air out of that cylinder before it can produce any power. The engine uses some power to compress that air, but it doesn’t get any power from a combustion event, so it slows down even more.
Imagine blowing up a balloon, and letting the balloon push air back into your mouth, that’s similar to normal engine braking. Yeah, it took a little effort on your part to blow up the balloon, but when the balloon pushes back, you have air in your lungs. Now imagine every time you blew up the balloon, someone popped it with a needle. You’d have to take a whole new breath, and blow up a new balloon, and it would take a lot more effort from you. That’s kind of what a Jake brake does.
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