YZ 250 EFI

[Flettner]

One of three direct inlet ports, also feed the crank case at TDC (piston ported)


Pattern


Some sand cores


ready to pour



Three of these ports are the high pressure transfers aimed at the combustion chamber and the other three are water jacket inlets. Ring is just a feeder system to supply molten alloy evenly and not turbulent, cut off afterward.

[rsmith]

I'm trying to wrap my head around your port/flow description. Do you have a diagram? 

I am having a hard time understanding how the fuel charge is going to be prevented from short circuiting out the exhaust. If it swirls as it reaches the top of the combustion chamber as is desirable to keep the fuel in suspension isn't it going to come back down into the air stream headed out the exhaust ports?

--Ron.

[Flettner]

Cylinder lay out
 https://youtu.be/2p0dyPu7Gcs
https://youtu.be/dT4btNAmjz0
https://youtu.be/Hodd8oyiawk

This is an FOS concept, an earlier one I made. This is to test a sliding cylinder idea (and the FOS system)
In this concept, it uses an ordinary crankcase, all six transfers pump at the same time. relies heavily on exhaust pulse to help with the pumping as there is not much crank case compression. pipe does most of the work any way in a normal twostroke. If you don't believe me, take the pipe off your MX bike and see how it runs.
In my HCCI cylinder the six ports are divided up into three crank case transfers and three direct from atmosphere transfers. The idea is that the HCCI crank case pumping volume is smaller than the engines capacity (so pumps less), is high pressure (so will still pump where there is not enough blow down time at high RPM). The exhaust is restricted so as to maintain a positive back pressure coupled with the low volume high pressure transfer (from three ports) should restrict fuel from exciting the combustion chamber, any leakage to the exhaust should be via the direct to air transfers (air only). as the pressure in the exhaust rises so does the pulse energy, the sign wave will still go negative an help draw air from the open transfers. Hopefully this will happen under the fuel air trapped up in the combustion chamber, this will be over rich to account for the extra air delivered from below. Clear as mud? There are a lot of ifs and buts, I find this kind of suck it and see interesting as sometimes something unexpected throws up.   

[_X_]

man, my brain hurts...

[Flettner]

Mine too.

[rsmith]

Okay, I think I got it.  I am familiar with expansion chamber theory so no argument on it doing most of the scavenging work.

If I understand correctly you are saying that the exhaust pressure will be positive when the fuel charge is introduced and the fresh air charge will help hold the fuel charge above the exhaust ports when the exhaust pressure goes negative.

Yes? Maybe?

--Ron.

[Flettner]

That's the plan, but what actually happens will be interesting to find out. The under piston pumping volume will be important I think as also will be the back pressure control.

[bearorso]

Well, Flettner here has got a bit of light shone on him in the latest issue of VMX - Vintage Motocross & Dirt Bike Quarterly, issue #69.

It's on page 3, in the 'The Sweep Rider'. There's a couple of pictures of his handiwork, and, it even reveals his real name.......................

[rsmith]

I will have to order that issue.

Flettner (Uniflow) and this thread is a large part of why I bought this site and spent all the hours to get as much of the old content back as I could.

--Ron.