OT: -Asymmetric Transfer and Exhaust in two-stroke engines

manolis · Jun 24, 2017

Hello all.

Here is an unconventional two-stroke (the PatATE) in comparison to a conventional two-stroke:

The main difference is that the exhaust port is now a "hybrid" port (the 4): at the end of the expansion the valve 7 connects the hubrid port with the exhaust passageway 5, and the exhaust starts the conventional way.

Later the valve 7 opens the transfer passageway 6 and seals the exhaust passageway 5; the exhaust continues through auxiliary (and "lower") exhaust ports 8; the transfer uses the conventional (symmetrical) transfer port 9 and the hybrid port 4.

Later the piston closes the conventional transfer port 9 and the auxiliary exhaust ports 8.

In the conventional two-stroke the exhaust remains open for several degrees (while the transfer is closed). In the PatATE the transfer continous (while the exhaust is closed). Regarding the operation of the engine, it looks like a significant difference.

Here are some more drawings / graphs:

For more: http://www.pattakon.com/pattakonPatATE.htm

Thanks
Manolis Pattakos

partsproduction · Jun 24, 2017

Have you made a working model?

Porschefix · Jun 24, 2017

I've had dealings with this sort of flapper valve idea. Good luck getting the thing to hold together. 2Cycle engines beat that problem by going to reed and/or rotary valves in the early 70's but reeds are pressure controlled. A timed flapper would have to open and close roughly 133 times a second at 8000 rpm. Interesting in theory but. . .
I like the adjustable chamber tuned exhaust system for max efficiency, forget the emissions compliance though.

DDoug · Jun 24, 2017

I really think McCulloch was ahead of their time:
Popular Science - Google Books

A 2 stoke with an oil sump (no oil in the gas)...Sort of like a Detroit Diesel.

If your design is typical 2 stroke with oil/gas going thru the crankcase,
I think the EPA won't allow it in the USA, one of your larger intended markets.

kustomizingkid · Jun 24, 2017

Lets talk about the new injected KTM's... now there is some new two stroke tech that I am excited about

CalG · Jun 24, 2017

Could the "Asymmetric port timing" be augmented with "clean" technology such as Honda's radical burn?

greenbuggy · Jun 24, 2017

kustomizingkid said:
Lets talk about the new injected KTM's... now there is some new two stroke tech that I am excited about

Also worth noting is Stihl's 4-Mix system which is a 2 stroke with valves. I have one of their BR600 backpack blowers and that thing works awesome, but I hear some people have problems with carbon (which I suspect is largely due to using shitty 2 stroke oil)

The functioning of the STIHL 4-MIX engine - YouTube

CalG · Jun 24, 2017

greenbuggy said:
Also worth noting is Stihl's 4-Mix system which is a 2 stroke with valves. I have one of their BR600 backpack blowers and that thing works awesome, but I hear some people have problems with carbon (which I suspect is largely due to using shitty 2 stroke oil)

The functioning of the STIHL 4-MIX engine - YouTube

, I'm confused, I counted FOUR strokes to the complete aspiration cycle. NOT TWO.

Just because an engine design makes use of the crank case pumping, does not change the "STROKE" designation.

4-MIX is fine, Two stroke is wrong. Count 'em.

CarbideBob · Jun 24, 2017

manolis said:
In the conventional two-stroke the exhaust remains open for several degrees (while the transfer is closed). In the PatATE the transfer continous (while the exhaust is closed). Regarding the operation of the engine, it looks like a significant difference.

The reality is not this simple.
While physically open the exhaust port in a two stoke is actually shut or can even become a input due to the reverse pressure wave created in the exhaust system from the reflected pulsations of each stoke.
The strength, duration and timing of this effective shutdown of the port are controlled by the design of the pipe.
Hence the name "tuned exhaust".
Sort of a reverse thing at lower pressures on the input side which is why reed and rotary valves help and one tunes length here also for differing rpm torque and hp needs.
Even the pipe length above the restriction or butterfly matters, note the unequal tube length on early BB Chevy fuel injection systems needed to compensate for the cylinder head design.

Very few things in the world are as straightforward as they look in CAD drawings.
This is probably the single biggest draw back to the use of CAD and computers now.
Everything seems easier or more perfect fitting than it actually is. One can draw two mating parts with zero corners and wonder why the real parts don't seat. The machinist then thinks the designer is not playing with a full deck.
I'll often see a special toolholder drawn with the screw hole on center. Nice in the perfect computer world, very bad in actual usage.

The action and flow inside a two or four stoke engine is a very complicated thing. The best of the best will spend a lifetime working on it and still admit to not quite understanding it fully.
Bob

CalG · Jun 24, 2017

To add to Bob's useful description, Can you imagine that IC engines can "breath" greater than 100% of the displaced volume.

Volumetric efficiency is easily pushing 140% on four cycle engines. I'm not sure where the two strokes left off....

Ram tuned and "on the pipe" are not just catchy phrases!

moonlight machine · Jun 24, 2017

greenbuggy said:
Also worth noting is Stihl's 4-Mix system which is a 2 stroke with valves. I have one of their BR600 backpack blowers and that thing works awesome, but I hear some people have problems with carbon (which I suspect is largely due to using shitty 2 stroke oil)

The functioning of the STIHL 4-MIX engine - YouTube

I just bought a Stihl string trimmer with the 4 mix engine, it kicks ass, for sure the most powerful string trimmer I have ever used. and the bump feed for the string works as well!

MattiJ · Jun 25, 2017

Good luck with that flapper valve on the exhaust side and high rpm's

History has seen gazillion of amazing motor inventions that just dont work in practice. Some of the 100 years old inventions are gaining new interest nowadays because some new materials and manuf. technologies have made those look like feasible (again).

Here would be one such "invention":
CSRV System - Coates International Ltd.
(The claims on website are totally nuts)

kustomizingkid · Jun 26, 2017

Even rotary engines... the single example of an off the wall design that has seen production fails the 100k mile+ test. There are lots of wild things you can build that just don't hold up.

DDoug · Jun 26, 2017

kustomizingkid said:
Even rotary engines... the single example of an off the wall design that has seen production fails the 100k mile+ test. There are lots of wild things you can build that just don't hold up.

Agreed, however, if a new design is half the weight, and get's 3x the mileage, but only goes to 5ok miles,
you just need to repair it sooner.
The fuel savings counteracts the longevity.

kustomizingkid · Jun 26, 2017

People are pissed that they have to do $600-$800 timing belts every 60-90K... good luck with that.

DDoug · Jun 26, 2017

kustomizingkid said:
People are pissed that they have to do $600-$800 timing belts every 60-90K... good luck with that.

Let's take a step back and look at the "bigger picture'

There are engines out there that go 1 million miles or more, before even opening them up.

They aren't lightweight, and they aren't "pushing the envelope" as far as fuel efficiency.

kustomizingkid · Jun 26, 2017

digger doug said:
Let's take a step back and look at the "bigger picture'

There are engines out there that go 1 million miles or more, before even opening them up.

They aren't lightweight, and they aren't "pushing the envelope" as far as fuel efficiency.

Cars are already maxing out efficiency, there isn't all that much on the table while meeting emission, crash standards, customer desires etc... there is a reason why gimmicks stay that way.

manolis · Jun 26, 2017

Hello all.

Thanks for your responses.

Instead of the flap valve, a rotary valve can be used for the control of the communication of the hybrid port(s) with the transfer and the exhaust passageways, say like:

In this PatATE design there are two hybrid ports arranged anti-diametrically on the cylinder liner.

Here they are shown the cylinder liner, the rotary valve and a slice from the top end of the casing:

The timing plot reminds “4-stroke” timing plots:

In the specific case, but not necessarily, the rotary valve rotates at crankshaft speed:

From another viewpoint:

Disassembled:

With the rotary valve revving at constant angular speed, the rev limit is set by the rest engine (piston – connecting rod – crankshaft – casing).

More at http://www.pattakon.com/pattakonPatATE.htm

Thanks
Manolis Pattakos

manolis · Jun 28, 2017

Hello all.

Two more animations of a PatATE with rotary vave:

and

Thanks
Manolis Pattakos

MattiJ · Jun 28, 2017

Nice animations.

Now lets add axial motion to the rotating sleeve valve and instead of rotating it 360 degree turns lets move it only something like 45-degree cyclical motion. That way we can use the rotating valve sleeve as a cylinder bore because piston rings wont get eaten by the timing ports anymore. Finally Add cylinders to make 2-row radial configuration.

Oops, we got 1930 era Bristol Hercules

OT: -Asymmetric Transfer and Exhaust in two-stroke engines

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