A Dissertation On Ventilation
Extracted from another thread, this discussion was greeted with overwhelming disinterest.
Posting here, maybe connecting the crankcase to intake manifold vacuum is worth a look!
True Believers in the PVC valve mod sincerely think the results are one or more of the following:
* Increased power
* Reduced oil consumption
* Enhanced engine compression braking
* Better ring seating
* Improved fuel mileage
When asked HOW a check-valve in the crankcase breather hose creates these benefits, the responses are, well, vague.
Often, "crankcase vacuum" is cited as somehow responsible for these advantages yielded, although . . . no crankcase vacuum has ever been detected in normal engine operation.
Not surprising there's no vacuum, entirely, because . . . the crankcase ventilation line connects to the airbox at ESSENTIALLY ATMOSPHERIC PRESSURE, and the crankcase accumulates blow-by from the combustion chamber.
So, if crankcase vacuum is desirable, WHY NOT CONNECT THE CRANKCASE BREATHER LINE TO THE INTAKE MANIFOLD????????????
After all, our Positive Crankcase Ventilation automobiles have their crankcase vent lines connected to their intake manifolds, for goodness' sake! (CAVEAT: Positive Crankcase Ventilation's purpose is reducing emissions, pollution control; NOT performance enhancement, in automobiles.)
Connecting the crankcase vent line to the intake manifold (i.e., the rubber hose between the carburetor and the cylinder head, or even the cylinder head input stub) would provide the crankcase with the advantage of MANIFOLD VACUUM. (This notional modification is predicated on the supposition that crankcase vacuum is beneficial. A further note: Without value judgment concerning the justice and wisdom of any Clean Air Act, connecting the crankcase ventilation line to the intake manifold does NOT violate any such statute, as I fear the previously-proposed dump-tube ventilation of the crankcase to atmosphere would.)
CAUTION: If this modification is performed, a PCV valve MUST be installed in the crankcase ventilation line, for the same reason such a component exists on automobiles: To prevent an intake backfire from migrating to the crankcase, where flammable aerosols may ignite/explode. Further, manifold vacuum will modulate the effective open area of the valve; least when high manifold vacuum exists; greatest when low manifold vacuum is present.
Implementation technique? Off the top-of-my head, I thought perhaps a tubeless tire valve stem might be fitted through a hole in the intake manifold hose, then adapted to the crankcase ventilation line. Alternatively perhaps, one might tap into a carburetor vacuum port.
So, if crankcase vacuum is responsible for the claimed advantages of the PCV valve mod, wouldn't actual connection of the crankcase ventilation line to manifold vacuum enhance and increase crankcase vacuum?
Performing this notional mod would create a Positive Crankcase Ventilation system on a KLR, not unlike on every legal street automobile on the road today.
Postulation only in this post's thrust; comments encouraged and welcomed!