Ok, so I know this is probably a bad question coming from someone who has already done the EBPV/Exhaust Brake Switch Mod, but my wife is asking me what exactly the valve does and I can't give her a good explanation. I mean, I know it closes to aid in warm-up during cold weather, but what happens when it closes? Where does the exhaust go that causes it to help with warm-up? Why is it that when the valve is closed, it causes the truck to slow down like an exhaust brake? Thanks for helping me not sound like an idiot with the wife. I think she is worried that it will overheat the engine or something, even though I know from people on here who have used it that it won't, I just can't explain to her WHY.

Bob

 

The valve works much like a choke on a carb. With the valve closed, the exhaust is restricted down to almost nothing. This increases the backpressure in the motor, causing it to work harder and warm up faster. This is also why it slows the truck down- very little exhaust flow, high back pressure. It is a rudimentary exhaust brake.

 

Not an expert here...just using some logic to describe this...

The exhaust stroke of the piston is pushing air out the exhaust. However, when the EBPV valve is closed, the piston is pushing against the valve.

I'm also interested on how a Jake Brake compares with EBPV? If anyone has an animation/photo link..please post.

Jake

 

Jacobs-style engine retarders use the engine compression to work against itself.

The operation of a diesel engine lends itself to a very non-desireable trait....engine braking is pretty well non-existant. The problem is that the engine is always able to fill its' cylinders with air on the intake stroke. There is little restriction in the way to stop any incoming air into the engine.

As the piston approaches top dead center on the compression stroke, it compresses the air that was ingested. However on deceleration, instead of that air being used for work (making power), it is simply exerting the same force down on the piston that was exerted to previously compress it.

A "Jake" brake uses the compression stroke to slow the vehicle by releasing the compressed air at TDC.....making the engine work to compress the air, but not allowing the compressed air to push back on the piston on what would be the power stroke.

The exhaust brakes (butterfly valves) in the exhaust system create a restriction to airflow that backs up through the turbine housing, up-pipes, and exhaust manifolds. Since there is nowhere for the exhaust to go when the valve is closed and the piston is pushing out air against this restriction, then there is huge resistance to the piston coming up on the exhaust stroke.

Basically, they both work by creating a resistance to crankshaft rotation fed in by the drivetrain.

 

Subscribing

 

I found this while searching for an animation:

http://www.jakebrake.com/products/ho...rake-works.php

 

Cody's description makes pretty good sense to me. How does this action by the EBPV help warm the engine then? Just by trapping the warm exhaust gases and keeping them closer to the pistons?

 

Making the engine work harder. Nothing more.

 

In this case, "working harder" is accomplished by causing the engine to compress the exhaust gases to a higher pressure. Any time you compress a gas, the process generates heat. Furthermore, by slowing down the escape rate for the exhaust gases, their inherent high temperatures are sort of held in the engine just a tad longer than normal, so you really end up with two "heating up" (or, "working harder") actions by choking the EBPV:

- compressing the already hot gases, making them hotter, and
- holding these hotter gases in the engine slightly longer, and thereby transferring more heat into the block and other engine components (i.e. coolant).