I really want to get all the pro and con reactions to this idea, as well as some tips on how to implement parts of it. I talked to MPG Mike for about two hours last night, and he has about half dozen fairly simple mods that can improve both economy, and performance. All of them raise some concern that must be dealt with to keep things working in a healthy way.
One of those ideas, which I would like to try is to plumb the crank case breather cap so it builds vacuum inside the rank case. This will reduce some of the resistance to the pistons moving down on either the power stroke, or the intake stroke. According to Mike, the PCV valve will suck a vacuum into the crankcase if you seal up the breather. Hold on, don;t get upset till you hear the rest of it. It takes awhile for the vacuum to build up, and you must build in a small, controlable leak up top so you can adjust this vacuum to be no more than 6" of mercury so you do not suck your seals into the carnkcase thus creating massive oil leaks. It is a simple thing to put a check valve in the crank case breatherhose that allows pushing air out, but does now allow air in. I just realized as I am typing here, that this probably creates more of the vacuum than the PCV valve. So, here are the questions:
1. What problems do you foresee with this idea? Keep in mind he has done this many times, and I don;t want this to turn into an attack on MPGMike. I just want to explore the concept.
2. Can you imagine the hardware that would allow you to monitor the vacuum on the crankcase, and adjust it from the driver's seat? I know there are devices to control the boost on a turbo from the driver's seat by introducing a leak in the waste gate hose, or some such thing. I just cannot picture what kind of hardware could control this. Is there a valve that you could plug a vacuum hose into, that you could open and close to allow a controlled leak with a knob from inside the drivers compartment.
Mike talked about getting a needle valve from the line that controls the water flow to a refrigerator ice maker. I can't picture it, and I dont; know what I would be looking for.
3. And even cooler, is there a vacuum bleed down from one of the earlier emisions systems that would simply open after it hit 6" of mercury, and allowed a bleed to control the maximum vacuum inside the crank case. It seems as if there has got to be one of those small plastic canister devices that were about the size of a quarter that got inerted into the maze of vacuum lines in the early emmissions controls that were designed to hold vacuum up to a specified amount.
Mike says this is good for a 3 or 4 percent improvement in both performance and economy. It is small, but it is something, and tuning is mostly the accumulation of small things that ad up to a big thing. I know serious race cars run a vacuum pump to put a vacuum indside the crankcase, but their systems are elaborate, and expensive. This is the cheap way to get some improvement. I am hoping some good ideas will surface from this auspicious group of creative minds.
AFter I have played with this, I will report back, and let you know how it worked. Then it is on to the next idea, which I will share as well.
Sam