the clean two-stroke thread

[WilDun]

For clarity: swirl is a gas rotation around the longitudinal cylinder bore axis. Generating swirl would require tangentially-aimed ports, but I took great care in aiming all six of my transfer ducts radially, so I don't think there is any swirl in the FOS cylinder; at least I hope not.

Because of the curvature of just about every transfer duct there will be a tendency to fling the heavy petrol and oil droplets to the duct's outer walls. Lubricating the opposite gas movements in the boundary layer is an amusing thought, I must say Will. It's one of those things that I hadn't thought of until you pointed me at it .

Frits,
I find it difficult to get my message across in 'written only' conversations and so I tend to use 1000 words to describe even the simplest thing properly! so forgive me !

I guess you answered the question in the second part also, - I wasn't actually trying to describe swirl in the cylinder.
What I was meaning really was the 'centrifuge effect' (not swirl) caused by the curvature of the ports just before it enters the cylinder- obviously you get that in any curved duct (depending on the speed of the flow), but due to the fact that in your FOS system the opposing flows of the 'in and out' gasses would actually come in contact and the transfer flow (now in a in a vulnerable "stratified" ?? form) would be a sitting duck for being dragged into the exhaust especially the outer layers consisting of oil and petrol.

Regarding the situation in the cylinder ie in a normal Schnurle type engine, whatever flow type (either swirl or tumble) is being employed, it surely must be a confused and cramped situation! and there can be no escaping the fact that the two charges will mix!

Whereas in the OP engine, there is room for separation of the charges and even a puff of air in between them. as Neil suggested a long time ago!

So, in the case of OP, (using 'tumble flow') - Is there the possibility of a slower moving 'slug' of mixture, maintaining its integrity as it moves down the cylinder to push out the remaining exhaust gas without actually mixing with it?

And yes, my "statements/questions" could be seen as amusing of course (and I don't mind that at all) - but question is, can you see any validity in them?

[Flettner]

Probably combustion chamber shape and exhaust piston thermal control are the worst features of the OP uniflow.
Differential piston size, exhaust being smaller and with a flat top, means a reduction in surface area to absorb heat but ultimately a different piston makeup / design is needed also.In my single cylinder OP Im running E85, total fuel supply through the exhaust crankcase for best piston cooling I can get. Other end is just air at higher loads. Low load running fuel will be only from the cold end via TPI. So a a lot going on, computer will be busy.

In saying this my new engine has same size pistons, partly to do with the fact that if its cast as one continuous bore size its seen as a single cylinder as far as plating cost goes, as good a reason as any.

[WilDun]

Probably combustion chamber shape and exhaust piston thermal control are the worst features of the OP uniflow.

Have you abandoned the thought of using HCCI? - I had thought that it might've been a good way around poor CC shape! also I thought that overall combustion temperature would be lower (my understanding). - I guess HCCI is't completely developed as yet!?

Differential piston size, exhaust being smaller and with a flat top, means a reduction in surface area to absorb heat but ultimately a different piston makeup / design is needed also.In my single cylinder OP ..............

Not all that clear on the significance of the use of squish or not using squish - how does it affect keeping it 'clean' ?- opinion seems a bit varied on this!- could HCCI totally bypass this dilemma?

In saying this my new engine has same size pistons, partly to do with the fact that if its cast as one continuous bore size its seen as a single cylinder as far as plating cost goes, as good a reason as any.

Good reason! but will the combustion chamber shape be a big handicap (in your design?) I realize that the more over square the bore/stroke ratio, the worse the CC shape will become!

Having said all that, just have a look at a high performance four stroke engine - could the combustion area on that be called a good shape?

[Flettner]

Got to start somewhere, spark ignition initially. Three plugs too, or was it two and one glow plug, or one and two glowplugs. Or three compression intensifiers, or a radio active isotope that pops into combustion chamber at just the right time, or .... there are many possibilities, some more real than others.

All kidding aside, my first OP 100cc started out with just a single plug per cylinder. About 40 degrees advance to get it to run anywhere near normal. I fitted two model airplane glow plugs opposite the spark plugs in the combustion plate. Instant retard to 20 drgrees. So thats when I sat down and jolly well learnt to build my own DC CDI's, what I wanted was not available, in NZ and if it was I couldn't afford it anyway. Also intetesting to see the light carbon build up on this combustion plate down wind of the direction of swirl from the sparkplug. This engine just had six ports creating a swirl pattern. Pistons were same size with domes, so combustion chamber shape was ugly. Zenoa weed eater pistons.

[WilDun]

Got to start somewhere, spark ignition initially. ............This engine just had six ports creating a swirl pattern. Pistons were same size with domes, so combustion chamber shape was ugly. Zenoa weed eater pistons.

Just the same there was a lot of stuff you learnt from that experiment which you will know to avoid this time!

Yes there are a lot of different scenarios to investigate which points to the possibility of eventually finding some interesting innovation for the future.

That is more than you could do with present day layouts - in my opinion, only cosmetic and tiny changes possible anymore (ie after TPI of course!)
Although perhaps Ken's idea will prove me wrong! - but whatever, I think something drastic needs to be done!

[Flettner]

Probably the wrong place for this but,
Building the top crankcase pattern, shes got that lovely black number on again. Somehow have to fit a rotary disc valve housing to this. 3D modeling on the fly.

[ceci]

25 years ago they already worked on the same approach as me

[Flettner]

https://youtu.be/lHWsjeCznm0

Motobacane, 1974, electronic fuel injection. Injecting into the boost port.

[ceci]

I do not think that any type of injection will be superior to the electronic one, but for what reason there cannot be one less effective, but also more economical.
The whole world is not just Europe. North America or Australia

[Flettner]

Or New Zealand.

I still find it hard to believe mechanical can be cheaper. If you go to any car wreakers yard in the world you will find all the nessasery componentry to build your own TPI.
You might need to be a bit of an electronic wizard to make a car ecu do what you want but the hardware is already in there. Stuff sooo cheap its just being sent off for recycling or just trampled into the mud.

[WilDun]

The 'whole world' (as far as everyday common commuter motorcycles are concerned) is mainly SE Asia and India etc and the profits will come from there as well - these guys will still manage to adapt things to suit themselves for any purpose,whatever they are dished up though!!!

The two stroke still has a chance, but it needs to hurry, because time is fast running out so it'll have to be cheap to beat the dreaded four stroke and so needs to remain simple (and the two stroke still has the edge on simplicity, but not in clean running) - and yes, there is (surplus, well proven) electronic technology, turbos etc. around these days so we need to make use of it all, instead of trying to re-invent the old mechanically simple stuff!

[190mech]

I read an article in 'Motocross Action' some years back that stated EFI(4stroke) was cheaper to build than a carbed bike ,,as carbs have many small passages and precise dimensions,an EFI setup has an in tank pump/regulator,throttle body,injector,and program box..I know from reading here a piped racing 2stroke engine is hard to EFI,but there are quite a few examples of lower revving engines that work well with a simple EFI system..

[ceci]

https://youtu.be/lHWsjeCznm0

Motobacane, 1974, electronic fuel injection. Injecting into the boost port.

Sorry to forget about New Zealand, if I have bothered someone excuse me.

Motobecane OK, the patent for this system expired on 1992-05-06,
https://patents.google.com/patent/US...r=Eric+Jaulmes
because being free the technology was not used by other brands? using these the EV-6 injectors



Why is it that the TPI is more successful than Motobecane ?: the use of the EV-14 injector, since with the EV-1 it would not work.
The success of the TPI is in the way of using the injectors and not in what type of injector is

[ceci]

It must be recognized that regardless of functionality, the issue of electronics on the motorcycle is something very beautiful, from the times when the Game Boy was used until today when smartphones are used.
In addition to what I already mentioned with the topic GPS smart injection

[WilDun]

Why has HAUFEN started this thread and never been heard from since - is he no longer with us? ........... I have asked this twice before and there has been no reply - so third time lucky?