EFCO "Burn Right" technology

[Miles86]

I've been reading about EMAK-Efco's "burn right" 2 stroke fuel injection technology, it's very ingenious. It's found on their saws with the green "burn right" decal. Here's how it works:

There is a set of small ports above and below the main intake port. These two small ports are connects by a connector tube. There is a one way valve in the upper port valve body (like a reed valve). A fuel accumulation chamber is also in the valve body area. As the piston moves up, it opens the lower port and creates a vacuum in the connector tube (due to one way reed valve) and draws fuel into the accumulator chamber through a special passage in the intake manifold boot. (Main intake port still closed). As the piston reaches TDC and the power stroke starts the cylinder pressure is fed into the upper port and travels down into the connector tube throught the one way valve and bounces off the closed lower port (piston skirt).

The compression wave then travels back up the connector tube and atomizes the fuel in the accumulator chamber very finely and sprays this fuel into the combustion chamber as the regular transfer ports are also charging the cylinder with the fuel air mixture from the carb.

The carb mix is weaker (leaner) than normal, but that is offset by the fuel injection feature.

Due to the fine atomization, better fuel economy and lower emissions result. And the system needs no maintenance and has only 1 moving part. It uses a normal butterfly carb. That's very different from the strato-charging method.

 

[drkptt]

As the piston reaches TDC and the power stroke starts the cylinder pressure is fed into the upper port and travels down into the connector tube throught the one way valve and bounces off the closed lower port (piston skirt).

The upper (injector) port doesn't open until after the exhaust port opens (during blowdown). Doesn't go through the check valve, that's closed to prevent backflow into the carb. The hot cylinder gases start to vaporize fuel at this point.

The compression wave then travels back up the connector tube and atomizes the fuel in the accumulator chamber very finely and sprays this fuel into the combustion chamber as the regular transfer ports are also charging the cylinder with the fuel air mixture from the carb.

The carb mix is weaker (leaner) than normal, but that is offset by the fuel injection feature.

There's a lean mix from the carb into the crankcase only to provide lubrication using normal 50:1 pre-mixed fuel. If the engine had an oil metering system (like larger DFI 2-strokes) it would have only air in the crankcase/transfer ports.

It uses a normal butterfly carb.

It's a special carb; basically a 2-barrel with the bulk of the fuel going through the tiny upper throat. It has a separate throttle linked to the main butterfly through a cam.

 

[Miles86]

drkptt;

thanks for these clarifications, especially the carb, it "looks" from the outside like a regular cube carb, the differences must be internal?

 

[Chris-PA]

Gonna do an old thread revival rather than starting a new one - does anyone have any pictures of parts, links to documents, videos or other information on this system? It sounds interesting and I'd like to understand it better.

Also curious how the carb creates a richer mixture, as it appears to be a Walbro WT.

 

[Zombiechopper]

sounds like the bottom gets the short end of lube stick

 

[Chris-PA]

sounds like the bottom gets the short end of lube stick

I dunno - I guess if the fuel/air mixture going through the case is leaner then it gets a lower volume of oil per unit time going through there too, so maybe. Sounds like the richer mixture goes around the case, the opposite of the RedMax strato system where the mixture going through the case is the richer part. That's the kind of stuff I'd like to understand about it. Still seems interesting, and I'm still curious how a humble WT carb makes two distinct fuel/air mixtures.

 

[Franny K]

It is pretty confusing looking at the little brochure and the big brochure dated 2011 and the website. I don't see the burn right logo on any of the made in Italy "pro" grade chain saws. I see the burn right logo on the website for a MT 4100SP saw and the term "Compression Wave Injection technology." I see the burn right logo on the Honda powered four cycle trimmers as well. For what it is worth my PT 2700 pole saw came with the green burn right sticker on the power head though not in the catalog. Like elsewhere posted the carburetor has one round opening when viewed after the air filter is off. Looking at my parts sheet reading the above about upper and lower passages and seeing the four stroke ones I wonder if different designs might get the burn right logo. From the pictures in the parts sheets I see in the picture of the cylinder a small opening below the main opening on the MT4100sp and a miniature extra opening on the pt2700. With only one opening on the inlet pictured side of the manifold.

http://www.efcopower.com/sites/default/files/MT4100SP_IPL.pdf


If someone has a link to the parts sheets for some of the previous post stuff presumably elsewhere in the world versions things might make more sense.

Fran

 

[Chris-PA]

It is pretty confusing looking at the little brochure and the big brochure dated 2011 and the website. I don't see the burn right logo on any of the made in Italy "pro" grade chain saws. I see the burn right logo on the website for a MT 4100SP saw and the term "Compression Wave Injection technology." I see the burn right logo on the Honda powered four cycle trimmers as well. For what it is worth my PT 2700 pole saw came with the green burn right sticker on the power head though not in the catalog. Like elsewhere posted the carburetor has one round opening when viewed after the air filter is off. Looking at my parts sheet reading the above about upper and lower passages and seeing the four stroke ones I wonder if different designs might get the burn right logo. From the pictures in the parts sheets I see in the picture of the cylinder a small opening below the main opening on the MT4100sp and a miniature extra opening on the pt2700. With only one opening on the inlet pictured side of the manifold.

http://www.efcopower.com/sites/default/files/MT4100SP_IPL.pdf


If someone has a link to the parts sheets for some of the previous post stuff presumably elsewhere in the world versions things might make more sense.

Fran

Yeah, I tried looking at those IPLs too and couldn't see anything of interest.

 

[Miles86]

Hi-

Please look at this link for the detailed US Patent, (download the full document )

Fuel injection system for two-stroke internal combustion engines - EMAK S.p.A.

The Efco MT4100 is NOT compression wave despite the claims on the website.

The Efco MT4000 is the compression wave saw.

Here's a vid of the oleo-mac 4100 sister saw (orange):
http://www.youtube.com/watch?v=GQ9N8TkJQH0

 

[Franny K]

It is still frustrating. Either the drawing document is corrupted or my computer is. I found that model on Bailey's not on the efco website. http://www.baileysonline.com/PDF/Efco_MT_4000_parts.pdf is the parts sheet. The dual barrel carb stuff above in a previous post still seems not to hold true on this model.

Is that sound spec real? Husky for instance seems to post two numbers it is way quieter than my 132s and has more power per cc. http://www.baileysonline.com/PDF/efco_MT4000_specsheet.pdf

View attachment 277842

 

[Chris-PA]

It is still frustrating. Either the drawing document is corrupted or my computer is. I found that model on Bailey's not on the efco website. http://www.baileysonline.com/PDF/Efco_MT_4000_parts.pdf is the parts sheet. The dual barrel carb stuff above in a previous post still seems not to hold true on this model.

Is that sound spec real? Husky for instance seems to post two numbers it is way quieter than my 132s and has more power per cc. http://www.baileysonline.com/PDF/efco_MT4000_specsheet.pdf

View attachment 277842

Thanks for that link - this IPL at least shows something of the system. There is the external tube and some extra port drawn over the normal intake port as you highlighted, plus if you look at the carb item #31 is a piston pump that appears to be modulated/controlled by the throttle shaft. I suspect it is an "injector pump" running off of the impulse system that normally just runs the carb fuel pump. Maybe just pumps fuel through a controlled jet into the accumulator. This looks like the system that has been described.

Apparently some marketing genius has applied the "Burn Right" label to a lot of different stuff? None of the other IPLs I downloaded off the Efco site showed these parts.

 

[7sleeper]

The MT 4000 was the only saw with compression wave technology. It is something similar to direct injection. The german KWF site gave Emak a "Innovation prize" for the "direct injection technology" of the mt 4000 in 2006.
http://www.kwf-online.de/deutsch/information/fti/web_pdf/2006/060809.pdf
I cannot really tell you what's really behind it but there have already been multiple discussions with sawtroll on this and he always declines that there is something special behind it. The saw has long since been replaced by newer models. I assume that it has more to do with emission standards. If the product in question reaches the emission standard then "it burns right"!
As far as I have understood some models are special but others only have a cat mounted upfront. I have a gs 350 that has the burn right sticker but I accidently lost the cat insert. It still runs right though!

Actually ths is the saw that has convinced me of the quality of Emak/Efco/Oleo Mac products.

7

 

[Chris-PA]

There's clearly something to it. Broadly speaking the strategy is the same as the RedMax/Husky strato system - there are two paths for fuel and/or air to enter the cylinder. One path carries a lean (or no fuel) mixture and the other carries a rich mixture. The lean mix enters first to reduce the unburned fuel that goes out the exhaust and the rich mixture is brought in later.

This system seems fairly simple mechanically, but it puts the lean mix through the case which may be a lubrication issue. If indeed they are not using it on the newer saws that is not a good sign. Maybe there is some other reason.

 

[drkptt]

Carb part #31 is not a pump, though it's labeled as such. It's an assembly with a tapered pin that is coupled to the throttle shaft through a cam (labeled #10, 'lever slope'). It moves axially in its bore. It only moves with the main throttle; it does not pulsate while the engine is running at a steady speed. It is the throttle of the parallel air/fuel circuit that feeds the injection port. Almost all of the fuel goes through this circuit, which has a venturi of something like 2mm diameter, so the mixture is obviously extremely rich.

Bottom-end lubrication has never been a problem because what little gasoline there is in the crankcase vaporizes completely. There is no liquid gasoline acting as a solvent and diluting the oil.

Both CWI and the Redmax/Husky system are technically described as stratified scavenge/homogeneous combustion engines. The CWI system is significantly different in that exhaust gases are used to heat and vaporize the fuel and a compression wave generated by the opening of the injection port travels the length of the wave tube, reflects off the end, and returns to push fuel into the cylinder. The crankcase does not push the fuel into the chamber like conventional engines and the other strato systems. The length of the wave tube determines the timing of the injection and is optimized for the operating speed of the engine.

 

[Chris-PA]

Carb part #31 is not a pump, though it's labeled as such. It's an assembly with a tapered pin that is coupled to the throttle shaft through a cam (labeled #10, 'lever slope'). It moves axially in its bore. It only moves with the main throttle; it does not pulsate while the engine is running at a steady speed. It is the throttle of the parallel air/fuel circuit that feeds the injection port. Almost all of the fuel goes through this circuit, which has a venturi of something like 2mm diameter, so the mixture is obviously extremely rich.

Bottom-end lubrication has never been a problem because what little gasoline there is in the crankcase vaporizes completely. There is no liquid gasoline acting as a solvent and diluting the oil.

Both CWI and the Redmax/Husky system are technically described as stratified scavenge/homogeneous combustion engines. The CWI system is significantly different in that exhaust gases are used to heat and vaporize the fuel and a compression wave generated by the opening of the injection port travels the length of the wave tube, reflects off the end, and returns to push fuel into the cylinder. The crankcase does not push the fuel into the chamber like conventional engines and the other strato systems. The length of the wave tube determines the timing of the injection and is optimized for the operating speed of the engine.

Thanks - trying to figure out how things work from an IPL has its limitations! Do you know if they are designing this system into new saws?

 

[one.man.band]

drkptt..........is the "carb" device made by zama? or something similar?

though i read something about 2 barrels on thier site a while back.

-omb

 

[Saw Dr.]

There are quite a few of the newer stratos that have a divider plate in the carb. It only functions as a true strato when wide open. The side of the carb where the main nozzle is becomes the "fuel" side, and the other side is for air.