Turbo/super charging a 2 stroke.

[Kneejerk Bombas]

Why doesn't this work?

 

[Stihl 041 super]

what you mean

What do you mean. I supercharged my leafblower with the tube running off the blower tube. It didnot work very well because you could dump as much
fuel as you wanted into it and the revs wouldnot go up it would just get very
very hot. you could boil water in a spoon on the muffler. the only reason why
it wouldnot work because you couldnot feed it enough fuel to make a difference. But it would be a hog on fuel.

 

[Sylvatica]

Why doesn't this work?

It sure does work.

Two cycle GM-Detroit Diesels (series 53, 71, 92, 149) and GM electro-motive Diesels were blown, and turboed & blown. They were the performance Diesels from the end of WWII to the early 80's.

The Roots blower with an aftercooled turbo boost supplied charge intake and forced scavenging.

 

[ErrolC]

Several things to consider..as with 4strokes the overlap between intake and exh timing needs to be optimised..a 4 stroke has an induction stroke to allow time for the cylinder charge to be pressurise before the inlet valve closes for compression..a 2stroke does not have this luxury so the exh port/transfer port overlap has to be drastically altered and you still won't have positive pressure as the exh port is closed by the piston..2stroke diesels either have an exh valve in the head (with intake ports in the bottom of the cylinder skirt)..or they run slidding sleeve valves that are activated and timed from a camshaft/cranked arrangement which allows the intake ports to close after the exh ports..this is not possible with piston actuated cylinder ports.

If you supercharged a conventional 2stroke design you can get positive pressure in the cranckcase fine..but all the pressure does is blow more charge out through the exh port through the transfer phase..no advantage gained

 

[Al Smith]

The GM/Elecromotive diesel engines are in fact scavenging air diesels.The porting is entirely different than on a 2 cycle gasoline engine.All you are doing is boosting the air above atmospheric pressure,the fuel is injected in the cylinder and does not have to enter via the sealed crankcase as in a gasoline engine.Historically,the Cooper-Bessemer diesel was in operation much before GM and used a piston type pump for aspiration,instead of a Roots positive displacement blower.The idea does intrigue me about supercharging a 2 cycle gasoline engine.The only case I can think of would be the McCulloch BP model saw.Conceptually I think it would be possible,but I have not yet figured a practical way to retro fit an existing engine with one.

 

[McC]

Mike, you'll have some competition in the 50cc and under class at West Bend this year, and they will be supercharged. Mac BP1's, 44cc, 4.2hp, with balance piston that also acts as a supercharger by stuffing the crankcase on the upstroke. Your chain will be your advantage as the 2 we're bringing run round filed chisel. Hope to see you there.
Scott
Here's a link to Acres site for the BP1
http://www.acresinternet.com/cscc.n...378fb4451b521bbb88256b6100149cd3?OpenDocument

 

[shtoink]

Anyone know where to find some diagrams on how this principal works? I'd love to see more. My curriosisty is definately piqued.

*Edit*

I did find some information about turbocharged two stroke engines, but they were all diesle.

http://www.greencarcongress.com/2005/05/fev_developing_.html
http://www.bath.ac.uk/~ccsshb/12cyl/

It didn't help me much, but it was still interesting.

 

[CNYCountry]

Nitrous is a form of forced induction also:

http://www.madsens1.com/hotsaw.htm

The page says they did play with true turbocharging also...

 

[TimberPig]

Nitrous is a way of adding more oxygen to the air fuel mix rather than a true form of forced air induction. Turbocharging or supercharging aim to flow more air through the motor by packing more air/fuel mix into the chamber and burning it.

As to turbocharging a 2 stroke, it is actually fairly common in 2 stroke snowmobiles for people to mod their sleds up by turbo'ing them.

 

[Stihl 041 super]

ya

Ya because they have tuned exhaust's that act like a valve. Except they use
a resonance pulse or back pressure to push the air fuel mix that tries to flow out the exhaust port back into the combustion chamber. Most stock saws
dont come with that kind of exhaust.

 

[Sylvatica]

shtoink,
Aren't those pics of the assembly of that GIANT Sulzer marine Diesel awesome?! I've seen them before and I'm still amazed by that degree of engineering and power.

 

[shtoink]

Yeah! I was blown away by the sheer size. I hadn't ever thought about what drove those barges before, but after seeing them in mid construction it bring them into perspective. You just have to step WAY back to see it all.

Any other links to information on how the turbocharging of an ordinary 2 stroke? I'd love to see some of the inner working of that BP-1.

 

[ozflea]

Stihl 041 is right, yes other forms of turbocharging and supercharging have been tried but i suppose in the end the Tuned pipe is the answer as it pushes back excess fuel into the chamber before the piston closes the port, now if the pipe is setup correctly and the pulse wave is right great gains can be had.
Try running a Hotsaw with and without the tuned pipe and you'll understand where that power has been made.
Next the Tuned pipe is easier made and less weighty and can be finely adjusted and once set requires little maintance.
But understanding how and why true Tuned Pipes work is a bit of a black art and many will not devolge their secrets.
Don't blame them really as it takes a very knowledgeable person to get it just right and get you into the top competitors.
Just unbolting one off a motor bike and sticking onto your saw doesnt work as their characteristics are completely different.

Mc Bob.

Here's a formula to help those who know how try to work it out.

http://www.camaa.org/tpipe/TunedPipeDesign.html

 

[Stihl 041 super]

Want to know

If you want to know how to make a tuned pipe go to PSI,and Starting Line Products their the foremost designers in snowmobile racing pipes.

 

[Al Smith]

Now then,ye olde tuned pipe.My buddy,Louis Baughan was national #3 in points during one season in the glory days of 2 cycle kart racing.Hopped up Mac 101's, of course,about a dozen of them,with different porting,for different power curves,He designed by seat of the paints,so to speak,a tuned pipe arraignment whereby the main barrel was changeable in 1/4" increments.It worked very well for him.He could adjust his power band from around 7 thousand rpms up to about 14 thou,depending on the porting and race conditions.As a normal rule I do my own work but if I ever were to get into hot saws,he has already said he would build me a pipe.

 

[McC]

My cousin Paul owns the BP1's. He has a bare block and crank assembly. I'll see if he can bring them along next week so I can take some pics of it.
Scott

 

[ozflea]

Mc BP-1 Pics

This should take to another thread containing the pic's requires on the BP-1.

Mc Bob.

http://www.arboristsite.com/showthread.php?t=19072

 

[spacemule]

I just wonder how they start those behemoth ship engines.

 

[Stihl 041 super]

start

They start them with compressed air from huge compressors. Source Super Ships Discovery Channel.

 

[average joe]

Turbos work well on two strokes.

a 2stroke does not have this luxury so the exh port/transfer port overlap has to be drastically altered and you still won't have positive pressure as the exh port is closed by the piston.

A two stroke can be ported to have port overlap and also be ported so that after the exhaust port is closed the transfers can be still open. So a turbo will work just fine, provided the motor is ported properly.
Their are tons of blown snowmobiles around, btw.