Yes, double the engine-off braking capacity, and no, there is no noticeable difference in braking effort or effect. I've took some decent stabs at the brake pedal for testing purposes, and there seems to be no difference in braking ability. It'll still lock up the tires quite readily.
Here come the pictures!!
Parts needed: 3" PVC Pipe, 2 pipe caps, 1 threaded hose barb (brass)
Connection to vacuum line To the left is the check valve that prevents vacuum escaping when the engine is turned off. Then the T connector (3/8", 1/4", 3/8"). Use properly sized hose clamps and make sure there are no leaks. I'm going to replace the T with a brass unit when I next get to the hardware store. The plastic bit from the auto parts store is just too flimsy.
This thing is pretty big. It's zip-tied in place for now but I'd like to add some beefier pipe strapping that's screwed into place. It holds well right now, but it could be better.
The hose barb connection on the reservoir. I just drilled a hole in the end of the cap and threaded the hose barb in. (It's a 3/8" ID pipe thread used for water lines) If you drill the hole JUST big enough for the threads to get started, the brass pipe thread should cut its own threads into the PVC and make an air-tight seal. I'm sure I don't have to tell you, but make sure the inside of the pipe is CLEAN. Anything left inside here could potentially get sucked into the engine, or plug up the valve, causing your brake vacuum to leak out when you shut the engine off.
The car. Bone-stock base-model 1.5L 16-valve.
Blatant self-promotion. (53mpg is the average of my last two tanks)
