Grib, that certainly makes sense by having a low pressure condition in
the crankcase giving the crank and pistons less air to push around.
Hence, more net torque output.
As a historical note, BSA motorcycles back in the '50s did serious
development to timed breathers on single and twin cylinder racing
engines to get a lower-than-atmospheric pressure in the crankcase, to
net more power. This was significant with one or two big pistons
pumping in the small crankcase of a 350 or 500cc engine.
The BSA Twin that won the '54 Daytona 200 event had this feature. It was
NOT easy to whip Harley in that era but they managed to that time.
A late friend of mine, Roland Pike, was Development Engineer at BSA
then, and in recalling the occasion he said they had some headaches
during practice because the low pressure in the crankcase was sucking
oil mist in the tiny breather hose for the magneto points cover, which
was located down at the exit point for the case breather hose, and the
mag seal was leaking air into the case, and pulling oil up the mag
breather hose, which was fouling the mag points! A story only an
engineer would enjoy. Bill
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