2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

Hello all.

FW17 wrote:
“Didn't orbital come out with the air assisted fuel injector to resolve this problem?”

Yes. Several years ago.
A few 50cc 2-stroke scooters were in production (Piaggio, Aprilia, Peugeot) around 2000.
Thousands of articles were written about the great advantages of the Orbital 2-strokes.
Several millions were invested.
The “Great Expectation” proved not so great in practice and the investors’ money were lnvested...
No doubt, things are improved as compared to the conventional 2-strokes. But the problem is still not really solved.

Thanks
Manolis Pattakos

Not quite Manolis..

For example - see the Mercury 2T outboard 'Optimax' system that has run the Orbital DFI for years..

& the 2T mopeds built by Piaggio also continue using the Orbital DFI tech, don't they?

[manolis]

Hello Brian.

You write:
“In my experience, an engine maker will usually take notice of a credible and useful proposal presented in a professional manner, to the right person.”

Here is a “typical” response to a technical proposal:



It came from one of the biggest engine makers.

It is not too “fresh”, however it shows the “spirit”.

Several other reputable engine makers respond in a similar way.


The people composing / signing the letters are just doing their job: to protect the interests of the big company where they work.

I am not complaining.

However when an engineer or inventor asks my opinion, I tell him to try but not to be too optimistic about the result of its proposal to a big engine maker.

Thanks
Manolis Pattakos

[manolis]

Hello J.A.W.

You write:
“Not quite Manolis..

For example - see the Mercury 2T outboard 'Optimax' system that has run the Orbital DFI for years..

& the 2T mopeds built by Piaggio also continue using the Orbital DFI tech, don't they?”


We say the same thing.

The initial “Great Expectations” from the Orbital technology, i.e. to replace the 4-stroke engine in every application and size, proved totally wrong.

The very few and “marginal” applications are disproportional to the several millions of dollars invested to the “Orbital” technology, to the thousands of patents granted to Orbital, and to the thousands of relative articles written in the press worldwide.



The question is actually about the Rotax (Bombardier / Evinrude) E-TEC technology.

The 600 E-TEC and 800E-TEC engines (and now the 850E-TEC) are engines already in mass production: they are used in snowmobiles.

Why they never put such an engine on a motorcycle or on a car?
Any clue?



Back to the PatATeco.
This arrangement has 4-stroke lubrication and a scraper ring in the middle of the piston:



The middle-left and the right ports feed the cylinder with air during the scavenging

The middle-left port on the cylinder feeds also the space underside the piston crown with compressed air after the end of the scavenging.

The fuel is injected more than 90 crankshaft degrees before the BDC, though the middle-left cylinder port, towards the right half of the space underside the piston crown, wherein it evaporates into the air forming a rich mixture that waits the asymmetric transfer port (middle-right) to open.


The lubrication of the compression rings is unconventional and interesting:

Look at the lowest position of the second compression ring as it slides along the cylinder liner: it goes a little lower than the ports.

Then look at the highest position of the oil scraper ring as it slides along the cylinder liner: its path ends just below the ports.

This way when the piston is at its BDC the second compression ring abuts whereon, 180 crankshaft degrees earlier, the oil scraper ring was abutting and lubricating the cylinder liner.

I hope it is clearer now how it works

Thanks
Manolis Pattakos

[J.A.W.]

Here's one Manolis.. http://www.bikebound.com/2016/10/17/gatto-nero/

The issue for motorcycles is of course - not technical, actually its a marketing confidence thing.
In the UK, for example, you can still buy a new ( but 'ancient-tech') Jawa 2T motorcycle for road use..

Have you run that long-arm conrod set-up in metal - powered on a spintron - to view its actual motions at speed?

[Brian Coat]

Re: “typical” response to a technical proposal.

Yes.

Unfortunately, in my experience, I would guess 99% of unsolicited written proposals to engine makers get a 'stock letter' response like this.

[manolis]

Hello J.A.W.

You write:
“The issue for motorcycles is of course - not technical, actually its a marketing confidence thing.”

Let me doubt.

If the 2-stroke E-TEC engine of Rotax
is cheaper that an equivalent 4-stroke (I doubt),
is cleaner (not relative to other snowmobile or boat engines, but cleaner than the state-of-the-art 4-strokes),
is good at partial loads and along a wide rev range,
and is similarly reliable with the 4-strokes,
it would be in mass production motorcycles already.

In the Rotax they don’t use their E-TEC engines in aircrafts (they keep using their old tech 4-stroke boxers).


You also write:
“Have you run that long-arm conrod set-up in metal - powered on a spintron - to view its actual motions at speed?”

No.
I can’t see any issue.
The top end of the connecting rod runs actually unloaded. It just seals some piston ports receiving not significant load.

Thanks
Manolis Pattakos

[manolis]

Hello.

Here is another PatATeco version having four-stroke lubrication and crankcase scavenging:



The upward motion of the piston causes subpressure which suctions air into the intake manifold and into the crankcase through the reed valve and through the throttle valve at right.

After the TDC, the downward motion of the piston compresses the air trapped into the crankcase and into the intake manifold. With the ports open by the piston, compressed air from the intake manifold either scavenges the cylinder or enters inside the piston waiting the asymmetric transfer ports to open.

With the proper form of the air ducts, the oil droplets in the air exiting from the crankcase are collected and then return back into the oil pan, so that the air in the intake manifold near the cylinder ports remains rid of lubricant.

It reminds the "stratified charge" with the difference that here the "oiled air" in the crankcase remains away from the cylinder.

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

Thanks
Manolis Pattakos

[J.A.W.]

Hello J.A.W.

You write:
“The issue for motorcycles is of course - not technical, actually its a marketing confidence thing.”

Let me doubt.

If the 2-stroke E-TEC engine of Rotax
is cheaper that an equivalent 4-stroke (I doubt),
is cleaner (not relative to other snowmobile or boat engines, but cleaner than the state-of-the-art 4-strokes),
is good at partial loads and along a wide rev range,
and is similarly reliable with the 4-strokes,
it would be in mass production motorcycles already.

In the Rotax they don’t use their E-TEC engines in aircrafts (they keep using their old tech 4-stroke boxers).


Thanks
Manolis Pattakos

Hi Manolis,

As to your doubts, about Rotax aircraft, it must be a sales decision, since Hirth offer both carb & injection 2Ts...

http://www.hirth-engines.de/index.php/en/


BRP/Rotax also have marketing strategies about which arms offer what, 2T VS 4T.

Sea-Doo personal water craft only sell 4T, yet Evinrude marine outboards only sell 2T ( E-TEC).
Ski-Doo snow craft offer both 2T & 4T designs.

A Ski-Doo E-TEC engine with a motorcycle-type manual transmission has been shown as a tease,
but Canam, the BRP road vehicle arm has not produced 2 wheel motorcycles for many years.

Here's what Motocross Action magazine reckons, 2T VS 4T...

"Its no secret that 2Ts are cheaper to buy, less expensive to maintain,
simpler to work on, 20lbs lighter & are more powerful per cc than 4Ts"

http://www.motocrossactionmag.com/bike- ... e-kit-bike

They got more power out of that 300cc 2T than a Honda CRF 450 4T, & Manolis you can see how simple
that 2T top-end is compared to the cost & complexity in parts count - of a Honda high rpm OHC 4T.

That the 4T marketing propaganda ( more profit for makers/dealers) has extended politically into the area
of sports administration & emissions control/EPA governance ( with bans on 2Ts) can be compared
to the military arena, (which is exempt from such) , & where 2T basic advantages are still a primary value.

[FW17]

What are the beat options to close off the exhaust ports in the piston upstroke to aid pressure charging?

[J.A.W.]

What are the best options to close off the exhaust ports in the piston upstroke to aid pressure charging?

You could check with the aftermarket bolt-on turbos for snowmobile use, websites..
..but if you go back a couple of pages here & read the link given for the latest Ski-Doo 2T,
you'd see it features an ECU controlled exhaust port valve, so maybe it could be adapted, for your needs..

[FW17]

I as thinking more in terms of interchanging the exhaust and intake ports (intake port higher than exhaust) with a reed valve on the intake.

[J.A.W.]

I as thinking more in terms of interchanging the exhaust and intake ports (intake port higher than exhaust) with a reed valve on the intake.

Feel free to give a more detailed explanation FW17,
& duly inc' as to why the hot exhaust gases wouldn't jet out via that ( rapidly burned up) reed.

[FW17]

I as thinking more in terms of interchanging the exhaust and intake ports (intake port higher than exhaust) with a reed valve on the intake.

Feel free to give a more detailed explanation FW17,
& duly inc' as to why the hot exhaust gases wouldn't jet out via that ( rapidly burned up) reed.

The cylinder pressure towards bottom of stroke would be manageable to not blow off the reed. Yes, reed would need to be strengthened with more modern materials.

The system is going to be pressure charged with intake side with higher pressure than exhaust side.

[J.A.W.]

The cylinder pressure towards bottom of stroke would be manageable to not blow off the reed. Yes, reed would need to be strengthened with more modern materials.

The system is going to be pressure charged with intake side with higher pressure than exhaust side.

But if the inlet port is higher than the exhaust, it will blow out of there 1st.
& if the supercharger pressure is higher than the combustion gas pressure, what parts will do practical work?
Surely - you're not intent on suggesting a 'free energy'/perpetual motion machine...

[FW17]

I think you misunderstood

The intake will located above the exhaust but a form of non return valve will prevent the exhaust gas from blowing out through the intake

Once the exhaust port opens the pressure in cylinder will drop, once the intake pressure is higher than that of exhaust manifold the non return valve opens and air from intake manifold enters the cylinder.