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Two Stroke Engine

05/18/2012 10:04 AM

Two stroke engine is not popular due to 1. cross flow problem in scavenging causing fuel loss, 2. Lub Oil consumption. If you use air blower and direct fuel injection, there is no more fuel loss to scavenging, also since the crankcase is not used to pump air, same lubrication method as 4 stroke engine can be used. So , why is it not done, 2 stroke engine has 2x power and simpler.

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#1

Re: Two stroke Engine

05/18/2012 11:00 AM

Large two-stroke engines, including diesels, normally use a sump lubrication system similar to four-stroke engines. The cylinder must still be pressurized, but this is not done from the crankcase, but by an ancillary supercharger. (pasted from Wikipedia)

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#3
In reply to #1

Re: Two stroke Engine

05/18/2012 2:03 PM

Exactly my question, why not petrol engine made this way, since direct injection is possible now. You can have double the power, zero valve and zero cam shaft.

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#7
In reply to #3

Re: Two stroke Engine

05/18/2012 3:04 PM

Has been worked on can't make EPA ratings.

http://www.allpar.com/neon/stroke.html

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#22
In reply to #7

Re: Two stroke Engine

05/20/2012 10:46 AM

oop! I missed your post. Good link!

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#2

Re: Two stroke Engine

05/18/2012 11:40 AM

Are you just trying to get lyn kicked off the forum?

The failure rate is 100%

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#4
In reply to #2

Re: Two stroke Engine

05/18/2012 2:25 PM

Agitating the cauldron?

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#5
In reply to #2

Re: Two stroke Engine

05/18/2012 2:29 PM

You certainly can't kick Lyn off the forum, he had the keyboard permanently glued to his fingers !

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#6
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Re: Two stroke Engine

05/18/2012 2:43 PM

He just can't stop helping people.

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#8

Re: Two Stroke Engine

05/18/2012 3:11 PM
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#13
In reply to #8

Re: Two Stroke Engine

05/18/2012 8:53 PM

I see it has already been done by Evinrude. It is strange why the big auto mfg don't make this simple change. The technology seems well proven and 2 stroke is a lot cheaper to manufacture .

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#20
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Re: Two Stroke Engine

05/20/2012 8:32 AM

In the US, our engines are under control of the EPA. They are not engineers, so we do the best we can under the rules.

edit: Basically repeating what tcmtech said.

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#23
In reply to #20

Re: Two Stroke Engine

05/20/2012 11:00 AM

I just checked Evinrude website. Their new E-TEC engine is not superior to Honda/Yamaha 4 stroke engine, on both power and weight. My guess is, Evinrude engine will lose out to normal 4 stroke on efficiency count, because the compression ratio is very low by today's standard.

My question is still there, if American auto maker not willing to do it, why also the Japanese and European not doing it?

Are there other deeper and hidden difficulties?

This article http://www.allpar.com/neon/stroke.html (from Ozzb post ) say the Direct Injection 2 stroke can't meet Nox standard due to lean burning, but now isn't those fanstastic VW TSI engine (18 km/Liter !) has lean burning technology? so it can be used for new 2 stroke engine problem.

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#9

Re: Two Stroke Engine

05/18/2012 4:35 PM

Oh, I think the two-stroke is here to stay. From Wiki:

The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is currently considered the largest reciprocating engine in the world... producing 109,000 brake horsepower (81,3 MW).

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#10

Re: Two Stroke Engine

05/18/2012 6:39 PM

It is interesting to note that most applications for two-strokes these days are either very small (chainsaws, strimmers, etc. for light-weight and simplicity), or very large, such as the above-mentioned two-stroke diesels (these actually go quite far back in engine history).

I was always fascinated by the stepped-piston two-stroke design since I first read about it in the mid/late 70s. Look up 'stepped-piston two-stroke' and you will see some interesting stuff (I seem to be having a problem with hyperlinks at the moment), from Wulf in particular. To me it always seemed to combine all the advantages of a two-stroke with all the advantages of a four-stroke, so I could never understand why it never took off.

Two things to note:

Decision-makers within the automotive industry tend to be very conservative. This is quite understandable when you look at the number of forward-thinking, innovative companies & ideas that have gone totally bust due to lack of public acceptance (usually down to poor marketing). This is, in fact, a huge subject into which I will not delve. Get it wrong and get the sack, or play safe, who will take the risk?

Two-Strokes have been pretty-much written-off these days, particularly in mid-sizes, due to experience with ineffinciency in the 60s/70s. At the same time, fuel-injection and turbocharging have advanced even more considerably.

I quite agree with you, why not more focus on two-strokes for motive power? The simple fact is that all the focus currently is on fuel-cells and hybrids, and quite rightly so. But I would also argue that the best partners in a hybrid system are generally overlooked. Four-stroke petrol (gasoline) engines ought to be on their way out, in favour of two-strokes, or (for hybrids in particular) gas-turbines.

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#16
In reply to #10

Re: Two Stroke Engine

05/19/2012 3:38 AM

With direct injection , basically all the advantages of 2 stroke can be had without the disadvantages of complex valve, cam shaft , higher friction, more bulk of the 4 stroke.

It seems to be just a simple change from 2 to 4 stroke, all the technologies are already there and proven, it is just very strange why all big auto companies not doing it.

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#17
In reply to #16

Re: Two Stroke Engine

05/19/2012 12:31 PM

Thats because the big auto manufactures would rather bow down to the environmentalists demands even if said demands have little to no rational, logical, or scientific thought/basis behind them.

Burning more fuel to go less distance in order to save the planet from internal combustion engine fuel combustion byproducts being high on the list of things we must do.

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#21
In reply to #17

Re: Two Stroke Engine

05/20/2012 10:19 AM

Well said. GA.

It is disheartening seeing efficiency (as MPG) slowly decline as the ability of auto makers to innovate and make improvement is overwhelmed by legislators ability to legislate 'solutions'.

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#11

Re: Two Stroke Engine

05/18/2012 7:21 PM

Look into EMD 567, 645, 710 medium speed engines. Is this what you are referring to? Due largely to the 2 stroke design, these generator packages are well known for there very fast response to changing load conditions as well as stand by to full load in only a matter of seconds.

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#12
In reply to #11

Re: Two Stroke Engine

05/18/2012 7:25 PM

Ooops now I see this is regarding petrol engines...

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#14

Re: Two Stroke Engine

05/19/2012 1:08 AM

How about noise levels(environmental pollution) of 2 stroke compared to 4 stroke?.

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#15

Re: Two Stroke Engine

05/19/2012 1:24 AM

i thing your wrong on alot of points. the main advantage of a 2 stroke is they have aprox. x2 the power of a four stroke with the same ci. theres no need for a camshaft, valves, timing chain or anything pertaing to air intake other than a carb and a set of reed valves. a 2 stroke hs a pressurized crankcase to lubricate the bearing with the gas/oil mixture along with completing the 2 stroke cycle.

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#18

Re: Two Stroke Engine

05/19/2012 8:18 PM

Nothing new under the sun. Orbital have done it for almost 20 years.

http://www.powerhousemuseum.com/australia_innovates/?behaviour=view_article&Section_id=1020&article_id=10041#

http://twostrokemotocross.com/2009/06/two-strokes-strike-back/

I still thing that a rotary engine would have far more advantages over any reciprocating engine, 2 or 4 stroke.

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#19
In reply to #18

Re: Two Stroke Engine

05/19/2012 10:59 PM

Everyone thought rotary engine is way to go. But rotary engine only looks good on paper, it has some inherent problems, namely efficiency and reliability as compared to reciprocating engine, so much so, Mazda has announced that they are stopping Rx8 production. rotary is dead for auto industry. Even after courageous Mazda slogged for half decade on research , Rotary engine can even come near Otto engine in efficiency and reliability. Mazda rightly see rotary has no future in auto industry , in the age of fuel efficiency. So, it seems 2 stroke with direct injection is the way to go.

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#25
In reply to #19

Re: Two Stroke Engine

05/21/2012 12:25 AM

Correction:

Even after courageous Mazda slogged for half decade century on research , Rotary engine can can't even come near Otto engine in efficiency and reliability.

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#24

Re: Two Stroke Engine

05/20/2012 11:17 PM

If your looking for simplicity go for 2 stroke,easy to operate and maintain.Most Super long stroke 2 stroke engine can burn most low grade cheap fuel more efficiently than 4 stroke.For marine application on large vessels you do not need costly gear box to reverse the propeller motion,the engine is reversible and producing high power at very low speed say 100 RPM maximum speed, hence reducing propeller slip get advantage.Loop scavenging is most efficient widely used than cross or loop scavenging.

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#26

Re: Two Stroke Engine

05/21/2012 8:36 AM

Try Flying behind a Rotax 447....

Lightweight and Powerful...

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#27
In reply to #26

Re: Two Stroke Engine

05/21/2012 9:20 AM

I owned a KAWA H1 ,500cc 3 cylinder two stroke piston port, and the power vrs weight of the bike was astounding. only problem with piston port vrs reed valve is the torque curve. Either you were trying to get it to go or trying to get it to stop. However when it was in the power band it was a thrilling rush.

Fuel efficient, not really.

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#28

Re: Two Stroke Engine

05/22/2012 4:47 PM

I'd advise not painting too broad a "stroke" with regard to rotaries. There are many factors which weighed in on the decision that Mazda evidently came to; most of which will never see the light of day for us to debate.

Wankel had a brilliant idea, which was only partially realized by Mazda in their development area. On that point, and just for fun, does anybody remember the Norton RC588?

Two cents'...

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#29
In reply to #28

Re: Two Stroke Engine

05/22/2012 5:21 PM

The Norton was a cracking little engine. Infinitely better than the Suzuki monstrosity that appeared around the same time. It's a shame we didn't see more of the Norton rotary, although I believe the new Norton factory was considering bringing it back for racing.

Felix Wankel did indeed have a brilliant idea, and quite a few companies over the years have made a fair stab at producing Wankel engines. It has one major problem that has proven very difficult to overcome, and this is the sealing of the sides and tips (and corners) of the rotor. This accounts for the relatively poor efficiency. If someone could crack this you'd have a world-beater.

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#30
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Re: Two Stroke Engine

05/22/2012 5:45 PM

Quite so.

Materials science is still moving forward; and not all of the geometries which the good Doctor elucidated have been fully explored.

I'll always have a soft spot for this ICE design

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#31
In reply to #29

Re: Two Stroke Engine

05/23/2012 4:42 AM

People in Mercedez Benz and GM and Ford realised years ago that Rotary engine has a few inherent technical problems which are difficult, you cant work against the principle of physics.

Mazda Rotary engine after 50 years R & D , only can manage 25 MPG (US) or less. So rotary is not for automobile, but more specialised field , such as air craft .

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#32
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Re: Two Stroke Engine

05/23/2012 6:34 AM

I once heard or read of a company that had supposedly cracked the sealing problem, but then heard no more of it, so obviously not true.

An offshoot of the Norton rotary engine program is a company called UAV Engines Ltd. They make small engines for unmanned aircraft. The Wankel engine should be ideally suited to this due to its simplicity and excellent power to weight ratio.

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#33

Re: Two Stroke Engine

05/23/2012 11:55 AM

Look at snowmobiles for the latest 2-stroke direct injection!

Polaris has 600cc and 800cc engines with direct injection, they work great!

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#34

Re: Two Stroke Engine

05/24/2012 10:45 AM

To preface, I'll state up front that I am not any sort of authority on Orbital's (XIHB?) engine structure. Nonetheless, I'd like to propose a couple of points for discussion concerning the viability of small Orbital (and conventional) two-stroke designs in high reliability settings.

First, in this type of design, there seems to be a remaining structural/tribological nut to be cracked with respect to the reciprocating assembly; unless, perhaps, ceramics or other high-temperature materials are chosen for the piston crown and upper ring areas. Having worked with small conventional designs, I have seen the results of the piston-based valving activity with respect to hot exhaust gas flow: Coking and burning of the affected areas on the piston assembly. This would seem to be a structurally-similar limitation with the proposed Orbital Combustion Process construct.

In extension, there is the issue of increased, asymmetrical ring wear over a period of continuous operation as the ring(s) are operationally passed back-and-forth across the transfer/inlet and exhaust ports.

I know that large, mature diesel designs seem to have addressed these durability limitations; but truly wonder whether or not those key design features can be successfully scaled down to a practical, simple, and efficient automobile/small engine setting.

Thoughts?

Have a great day, folks

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#35
In reply to #34

Re: Two Stroke Engine

05/25/2012 2:18 AM

My conclusion is: 2 stroke engine with direct fuel injection, with blower , solve the old problems of 2 stroke engine, has 2x power of 4 stroke , much simplified (no vlavle, no cam) and therefore cheaper and more relible, more efficient because no wastage of 2 stroke movement. Emission is same as 4 stroke.

It just puzzle me so much , all the technologies are, why non of the auto company is doing it ? All those reasons cited here are not so convincing.

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#36
In reply to #35

Re: Two Stroke Engine

05/27/2012 12:56 PM

"Emission is same as 4 stroke."

I don't believe that's possible. The exhaust gases begin exiting before BDC, and must be sufficiently evacuated quickly enough to reduce dilution of the fresh incoming air.

It's been a long time since I looked at this kind of stuff in any meaningful way, but I believe that results in larger quantities of "bad emissions", compared to 4-cycle engines. Catalytic converters can help, but there are practical limits.

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#37
In reply to #36

Re: Two Stroke Engine

05/27/2012 10:33 PM

'Reducing dilution of fresh incoming air' isn't a big concern for exhaust emissions.

In fact most 4-stroke engines on the road actively promote 'dilution of fresh incoming air' with exhaust gasses, via an EGR valve ostensibly to reduce pollution by inhibit the formation of oxides of nitrogen by lowering in-cylinder temperatures.

.

The problem with the traditional 2-cycle engine (compared to 4-cycle) is the amount of unburnt fuel and lubricating oil that ends up in the exhaust.

The OP raises a valid question since new designs have essentially removed those handicaps when compared to 4-stroke.

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#38
In reply to #37

Re: Two Stroke Engine

05/28/2012 1:10 AM

Modern 2 stroke has made improvements in some followings-

1. Uni-flow scavenging system more efficient than loop and close scavenging systems.Some engine are also fitted with VEC (variable exhaust valve closing control) hence improve p comp and p max

2.VIT (Variable Injection Timing) for better fuel consumption at part load,poor quality of fuel.

3.Liner lubrication is fitted with independent lubricator which control/meter the cylinder lube oil required.

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#39
In reply to #38

Re: Two Stroke Engine

05/28/2012 10:48 PM

Do you know which manufacturer manufactures these 2 stroke engine?

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#40
In reply to #39

Re: Two Stroke Engine

05/29/2012 12:13 AM

The Makers are Wartsilla:- for VEC ,Uniflow scavenging system, cylinder liner lubricator and MAN-B&W-: for VIT,VEC Uniflow scavenging system, cylinder liner lubricator,possibly Mistubishi and others

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