Below is a quote from Blair taken from a technical publication I was reading.

"These data coincide well with Blair who describes the fact that for loop scavenged engines“the majority of the scavenging
flow is concentrated around the BDC period, and very little occurs in the latter third of the scavenging period as the crankcase
pressure has decayed considerably”.

I have thought about this before and even mention my ideas before but never got any replies so I thought this time I would provide some crude drawings I doctored up to better explain my idea.

The idea is to have a chamber attached to the crank case that has a variable volume that is controlled mechanically or electro mechanically, the variable volume chambers volume would increase as the crank case is filling.

The chambers volume would decrease as required to boost cylinder filling.


I think the variable volume chamber would work best if it was computer controlled, maybe make use of a crank sensor so you could map and change the rate of the variable volme chamber filling and discharging, the computer might also need to be attached to other things like coolant temp, RPM (guess that can be taken from crank sensor) exhaust temp crank case pressure?

pics taken form http://www.sandwizards.com/twostroke.htm and modified by me.

Hoser, would'nt it be better to have the chamber shaped like a taper so that the pressure builds up and helps tp propell it forward, like the exhaust expansion shape?

I didnt draw it wide or big but their is a piston pushing the blue mixture into the Engine so a taper cylinder would not work, I follow what your saying tho, the size, shape of the variable volume chamber will all have to be engineered, so will all the controls that drive it, I think the volume will have to be controlled (high speed stepping motor (( Internal Combustion Engine ? ))) as the RPM changes to keep emissions in check, you don't want bunch of unburned air/fuel dumping into the exhaust this is what the tree hugger's are bitching about, you also don't want to drop your exhaust pipe temps.

My first thoughts on this was part of the crank case bulging in and out to vary the volume, further thoughts I think a cylinder and piston would be better, easier to engineer, the boost from the variable volume chamber would have the same affect as a turbo or supercharger but it would not be stuffing or increasing the crank case pressures until the current crank case pressure dropped, it would also be a fine control and incremental .

could use the crankshaft output or pulley side to operate the pump, after all the pump doesnt have to be actually attached to the Engine, it just has to be plumbed to the Engine. you could run a small sprocket(or large)(like a timing belt) off of one side of the crankshaft and just work out the timing to get it pump another piston.

you could go so far as to get a little weedwacker motor (( Internal Combustion Engine ? )) and use it to pump the air into the big motor (( Internal Combustion Engine ? ))(figure it would be small could mount just about anywhere. change the piston ring type and use the sparkplug hole to feed the pressure into the big motor (( Internal Combustion Engine ? )).

Wouldn't a supercharger be doing essentially the same thing?? Using an Engine driven pump to force more air into the Engine to improve its effeciancy.

You don't see too many superchargers on two stroke gas engines, though there are a bunch of turbo guys out there. Lots of issues with tuning or maintaining the tune in cold weather.

Superchargers and turbos are ban from most racing.


This would activate "the latter third of the scavenging period"

Now think about how you could control it, use a computer and stepping motor (( Internal Combustion Engine ? )) , you could vary and time the volume chamber to fill and dump as required or optimize it (map) to work best at different RPM's and Engine loads? Perhaps use a stepping motor (( Internal Combustion Engine ? )) to drive the piston in the HVVC ?

How about making some head mods, add two or three valves to the head like used on a 4 stroke, have them computer controlled and solenoid actuated, now you run some external ducts from the HVVC to them,
the extra flow could be used for cylinder savaging or after the piston was covering the ports use it to further fill the cylinder.

I think with testing you could also improve emissions with this setup.

Doesn't a 2-cylinder 2-stroke do the same thing as what you're trying to achieve - better scavenging?

No

On a 2 cylinder or more 2 cycle Engine the crank cases are not common like on a 4 stroke Engine, each one is sealed and separated from the other.

Cool, that I never knew. I never had the opportunity to take a multi-cylinder 2-stroke apart.

[
Now think about how you could control it, use a computer and stepping motor (( Internal Combustion Engine ? )) , you could vary and time the volume chamber to fill and dump as required or optimize it (map) to work best at different RPM's and Engine loads? Perhaps use a stepping motor (( Internal Combustion Engine ? )) to drive the piston in the HVVC ?

How about making some head mods, add two or three valves to the head like used on a 4 stroke, have them computer controlled and solenoid actuated, now you run some external ducts from the HVVC to them,
the extra flow could be used for cylinder savaging or after the piston was covering the ports use it to further fill the cylinder.

I think with testing you could also improve emissions with this setup.[/quote]

A stepping motor (( Internal Combustion Engine ? )) would be to slow for the Engine rpm. You would nee to use an actuator solenoid that would be pwm (pulse width modulated). An IPR valve off a HEUI type fuel system would be ideal. This would give you instantanous response if need be. To control this you would need a TPS, MAP, CMP or CKP, and a pressure transducer to measure the pressure in the bottom end of the Engine. Run these inputs to an ecm and data log with it and write your own program for it.

Ok it seems this idea has already been discussed in the past, 1935 to be exact in .A.C.A.Technical Memorandum No. 776 you can download and read here http://naca.larc.nasa.gov/search.jsp click on the NACA then search for two-stroke engines a A discussion of the several types of two-stroke-cycle engines will come up.

Its worth the read.

I still think computer controlled would have many benefits and this old idea would be worth revisiting.

Ok I give up how do I find v. Schnurlc's patents numbers 51I102 and 520834

Hey LEE your better and looking them up than me?

any updates on this?