Since his introduction to the internal workings of a two stroke engine 35 or more years ago the phrase Julian kept hearing most when talking to experts about how they work and increasing there performance was, "port area open time". The most recent occurrence was, "time related cross-section area" and "crank angle related cross-section area" which are the same but different.
He had the mathematical formulas to answer these questions but there are not enough buttons on this key board to show them here, he did have a scientific calculator and could have written a program to work it out for him, but he couldn't find anywhere in the formula where it asks for the pressure of the gasses going through the port.
He thought that the gas pressure would be crucial to working out any flow through a port, so somewhere in the formula should be port area, open time or crank angle and gas pressure.
It is because these pressures are so low and variable the performance of the engine can be improved dramatically by the addition of a tuned expansion chamber that will effectively draw the air mixture through the motor.
This is where some of his experience with the workings of a two stroke comes from, watching and helping well known and respected professional engine tuners working with factory parts, with Motocross World Championship Grand Prix teams such as Suzuki, Yamaha, Honda, Kawasaki and Husqvarna, chasing port heights up and down cylinders and exhaust dimensions in and out in order to improve the gas flows.
It didn't take him long to work out that although some improvements could be made to add power here or there the solution to the inefficiency problems, and to realize the actual achievable power, would not be found chasing the port timings up or down or fitting the right pipe.
He always had more success leaving the port timing alone and modifying the inlet side of the motor to allow more air flow through the motor and thereby improving efficiency.
This is where his ideas for a new design came from, to try and solve some of the efficiency and emission problems, that has led to the eventual granting of the patent.
The first thing he wanted to do was improve the displacement pumping effect in the crankcases for the induction phase of the cycle and to do this he needed to remove the connection of the cylinder to the crankcases by the transfer passages.
The negative pressure in the crankcases cannot begin until the transfer passages are closed by the piston, so up to 25% of the available effective stroke can be lost. This can be solved by using an external air pumping device but this still leaves the problem of scavenging the burnt gases out, and getting the fresh charge of air in, before the exhaust port closes and without the need for overhead cams and valves.
He was thinking that if you could introduce the gasses into the cylinder at a higher pressure than those coming out scavenging would be improved, as would the volumetric efficiency, and as the only aperture available in and out of the cylinder was the exhaust passage some way of separating the "new" from the "old" was required to prevent undue mixing.
If you consider the way this process is taking place in the current design by the fresh charge entering the cylinder, more by the pulse effect of the expansion chamber than the displacement effect of the downward movement of the piston, any pressure added to the fresh charge above that which this pulse effect generates would be an improvement.
Here we have the requirement for an external air pump, a problem already solved by design engineers involved in the development of the two stroke engine.
And this is where his new valve comes into play.
Air, from the external pump, at a greater pressure than the burnt gasses leaving the cylinder, is introduced into the cylinder, by the design of the valve surface and piston crown, this air could be directed under and behind the flow of the burnt gasses to prevent mixing.
Scavenging and charging the cylinder would be much improved over the present method.
As the air pressure entering through the valve is not dependant on crankshaft rotation it can be maintained until the exhaust port is closed. Along with the trapping effect of the piston this has the effect of "turbo charging" the cylinder ready for compression and the fuel to be introduced with an injection system.
Emissions would be improved because the fuel, without the oil, is added when the exhaust port is closed so there can be no loss to atmosphere.
Performance would be increased due to the more efficient scavenging and charging of the cylinder.
If the two stroke engine out performs it's four stroke equivalent even with the efficiency problems how would it compare working at it's best.?
This is really IMPORTANT and yet difficult bit to make any sense of, this is the link to the Patents that cover the ideas and designs you have been reading about.
Copy and paste this address into your browser and look at the complicated explanation !!
http://v3.espacenet.com/mypatentlist?F=4&LG=EN&CY=ep
If you have a interest, or would like some more information, in the development of the "Gadget" engine please send me an e mail.