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Stratocharging???

Started by celliott, December 13, 2009, 10:53:13 AM

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celliott

I have seen this new technology mentioned in a few other threads, but I am unsure as to what this is.  I am curious, could someone explain to me what stratocharging is?
Thanks
Chris Elliott

Clark 666C cable skidder
Husqvarna and Jonsered pro saws
265rx clearing saw
Professional maple tubing installer and maple sugaring worker, part time logger

Tom

When you get the answer to your question, perhaps someone can answer this one too.
The B-47 Stratojet/Stratobomber, B-52 Stratofortress, KC-97 Stratotanker and the C-97 Stratofreighter were designed to carry and supplement Atomic bomb delivery for the United States Air Force Strategic Air Command and flew at 40,000 feet or above.  It wasn't named for the j35 engines, which were turbocharged, so, did it get it's classification for it's ability to fly in the stratosphere, or from its designated command post, The Strategic Air Command?

Komatsu's two stroke Strato Engine appears to be a scavenger with a valve on the scavenging port to keep from releasing as much unburned (scavenged) fuel through the exhaust port as designs without the valve.  This link describes the design and shows pictures.
http://www.zenoah.net/tech/image/XE23.pdf

ladylake

A strato engine shoots a charge of fresh air into the cylinder that chases the exhaust out and when the intake charge comes in more of it stays in the cylinder rather than going out the exhaust port.     Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

celliott

So its a cleaner running engine, but I am guessing if this was better technology, it would of been put to use already.  This in efforts to satisfy EPA regs. isnt it?
Chris Elliott

Clark 666C cable skidder
Husqvarna and Jonsered pro saws
265rx clearing saw
Professional maple tubing installer and maple sugaring worker, part time logger

Rocky_J

Yes, the newest engines are all about meeting clean air regulations. Maybe the next generation will reach new levels of power to weight but the current new models are heavier and slower than the ones they replace. Sort of like when automobiles went to fuel injection in the 80's. For now I've stocked up on a few extra 372's and I will also invest in a couple extra Stihl 200T's before they are replaced.

ladylake

 I've been hearing the strato model use less gas, are heavy and have fair power.  Hopefully they'll come out with a direct injection saw that cures the emissions and doesn't weigh a lot.   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

celliott

Does anyone now how the fuel injected saws are developing? any news of these?
Chris Elliott

Clark 666C cable skidder
Husqvarna and Jonsered pro saws
265rx clearing saw
Professional maple tubing installer and maple sugaring worker, part time logger

Log Hogger

The new stratocharged Stihl MS 362 certainly wasn't ruined by the EPA:

MS 361:  59.0 cc, 4.4 hp, 12.3 lbs
MS 362:  59.0 cc, 4.6 hp, 13.0 lbs

The 362 is also reported to have a fatter power band and to burn significantly less fuel, traits common to engines employing stratified charge technology. 

WoodChucker81

The 441 is a strato saw and it screams.  I've run enough 440's/044's and the 441 is right there with them as far as cut times.

Some just have a hard time accepting "the new".

I can't wait for an MS461 and an MS661.   8)   ;D

sharkey

Stratocharging is a different way to scavenge a two stroke engine using filtered air that does not contain fuel. 

If you follow the design of a two stroke engine, it is scavenged (recharged for the next power stroke) through the flow of 'charge' which is transferred from the crankcase through transfer ports up to the combustion chamber at the top of the cylinder. 

As the piston moves down in its stroke it displaces the fresh charge that is trapped in the crankcase.  This fresh charge is piped up through the transfer ports and pushes any remaining exhaust out of the combustion chamber.

Because the fresh 'charge' has fuel and oil in it, some is lost out through the exhaust port during the scavenging process before the piston can trap it for the next power stroke.  This process allows some unburned hydrocarbons into the air, although not much, but this is what the EPA is concerned about. 

Stratocharged scavenging uses a small puff of filtered fresh air, rather than charge, to push out any remainder of exhaust that hangs in the cylinder.  Some designs hold this filtered air in a dished out portion of the piston sidewall or skirt, whereas others have small reed valves at the top of their transfer ports.  You will be able to recognize this style of engine by looking at the intake.  The carb will appear to look like it has two barrels, and does, but only the lower barrel gets fuel.   

As far as fuel injection goes, Husky has an 'Autotune' carb design out that uses a voltage to read air and fuel mixtures.  Its not doing real well in inititial testing.   

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