to: bob@bobthecomputerguy.com (Robert Harris)
subject: pulse supercharger

 Consider a single cylinder engine with a conventional four stroke
overhead valve layout.  Assume an intake runner of volume of about
2x cylinder displacement.

 At the atmospheric end of the runner install a reed valve or shutter
mechanism.  Adjacent to the shutter install a small fuel injector and
a model airplane spark plug.

 During the intake stroke, the piston moves down with the intake valve
open, creating a depression in the inlet runner.  Air moves through the
shutter and down the runner.  Fuel is injected in the port near the valve.

 At some point - perhaps halfway through the inlet stroke - the small 
injector at the inlet of the runner injects some fuel.  Immediately
afterward the fuel is ignited by the small spark plug.  The fuel/air
charge blows the shutter closed and pressurizes the runner, shoving
the rest of the air in the intake runner into the cylinder under pressure.
The amount of air and pressure is determined by the amount of fuel
and the volume of the runner.

 The fuel/air mixture in the cylinder is not ignited by the pulse jet,
as the slug of dry air insulates the pulse combustion flame front from
the charge in the cylinder.  The byproducts of the pulse combustion
are carried into the cylinder on each succeeding intake stroke; as these
'inert' gases are the first into the cylinder on each intake stroke, some
may be passed directly to the exhaust system during the valve overlap
event.

 By varying the fuel quantity and timing we can vary the amount of boost
or turn it off entirely.  The shutter would add very little inlet
restriction when not in use; at part throttle it wouldn't matter and
at WOT you would assume you were under boost anyway.

 What we have here is a supercharger of any desired compression factor,
using no "supercharger" parts.  Alfa Romeo used reed valves in the intake
tracts of some of their engines in the late 1970s.  The additional fuel
injector is unremarkable.  The spark plug is odd, but it could be hidden
(or even disguised as a fuel injector) if stealth was desired.  Boost
is controllable directly by the ECU with spark and fuel events.  When not
in use, the only overhead is the shutter.

 "What do you mean, 'supercharger?'  Do you see a supercharger here?
I don't see no steenkeeng supercharger!  The intake runners always glow
like that."