Turbo!

[motorpsycho]

Two stroke engine can be turbo charged - snowmobiles for example http://www.tikka.se/default.asp?ID=80&menu_item=80

I am by no means an expert on this subject, but i the major difference is that snowmobile engines have reed valves, not transfer ports.
since the reed valve act like regular valve (such as in a 4 stroke) I could see how a turbo would work on one of these.
If you think abotu this as well, i have seen 2 stroke diesel engines with turbo's and superchargers together.
BUT, i think the major difference is the valve arrangemet, which allows you to actually build boost in the cylinders.

 

[motorpsycho]

That's one heck of a unique ride. And a unique crew. The bike ought to be as much fun to ride as it will be to watch it be ridden.

So turbo chargers are out? So I'm willing to bet some curious person will next ask, "What about a belt-driven centrifugal supercharger, shaped like the pistol-grip hair dryers of long ago?" I'll bet somebody will ask that....

no, but i've thought about making a dummy centrifugal super charger just for looks.
Or, maybe a small empty turbo case, bolted up to the intake, and then run the real exhaust through it just for the look.
hey, sometimes the look is all you need to make a point.

 

[Neon]

If it's not possible to turbo charge or super charge a two stroke. the maybe you can tell me why Jonsered, Husqvarna and Poulan have been doing it for years. It doesn't give a huge horsepower increase .1hp, It's not really a turbocharger. More like a low grade super charger, but is still forced induction. It's main claim to fame is to keep the air filter cleaner, but still manages to give a slight power boost. The saws certainly sound like something is going on, there is a massive whine that gets worse the more the revs increase.

 

[motorpsycho]

If it's not possible to turbo charge or super charge a two stroke. the maybe you can tell me why Jonsered, Husqvarna and Poulan have been doing it for years. It doesn't give a huge horsepower increase .1hp, It's not really a turbocharger. More like a low grade super charger, but is still forced induction. It's main claim to fame is to keep the air filter cleaner, but still manages to give a slight power boost. The saws certainly sound like something is going on, there is a massive whine that gets worse the more the revs increase.

yeah i know what you are talking about.
but really, on a 2 stroke such as these h.t. ones, a well tuned expansion chamber will give you the same results as if the engine had a turbo or a supercharger, and that would be at a fraction of the cost of a turbo or a supercharger.
when you have a well tuned pipe, as soon as the engine gets into it's peak working rpm range where the pipe is working, the rpms will just take off like crazy, just like they woudl with anything that builds boost pressure.
the whine you hear on those chainsaws may just be the chain.

 

[Neon]

The noise doesn't go away even when the chain is removed. Thought it might have been the auto chain oiler as well. With that gone it's still there. Also have a non-turbo Jonsered. I use it everyday. No whine at all just excellent cutting power. And yes an expansion chamber is still the easiest and cheapest way to go

 

[HeadSmess]

any two stroke engine, with the exception of the larger DIESEL engines, has transfer ports. regardless of whether the induction is via piston porting, reed valves, or disc/drum valves.

all twostrokes, excepting the diesels, use crankcase induction. it is a fundamental key to their operation.

i believe the "forced induction" mentioned with the chainsaws is to do with ventilating/cleaning the airfilter. simply raising the pressure in the air box, reducing the effort needed to suck air in through woodchips and sawdust and bar oil and sap and borer innards and index fingers is always going to improve performance. and blowing a breeze past a fiilter does something for keeping it cleaner than one that just sucks at debris all day...

more of a leafblower than a performance upgrade?


a tuned pipe, coupled with correctly shaped and TIMED ports is the ONLY way to go on 2 strokes.

the design of a 2stroke simply means that any method used to raise INTAKE presure, is useless. people have been working on them for over 100 years, thinking of how to make them run better. noone has yet thought of anything that works as effectively as a tuned pipe.


there is a fourstroke engine that completes ALL cycles in one revolution, intake compression power and exhaust... technically thats a twostroke... thought id throw that in just to confuse everyone

and to add to the confusion.... by using a tuned pipe in conjunction with some type of intake booster...ie a turbo... they could work. the pipe being there to squeeze everything back into the cylinder...so if the turbo pushed more out into the exhaust, the exhaust has more to push back in... and combined with reed valves that can open whilst the piston sweeps through bdc, unlike other port systems...

so ill change my statement and outright denial to " 2 strokes cannot be turbocharged EFFECTIVELY with the exception, possibly, of reed valved twostrokes combined with tuned pipes designed for such a system"

considering the effort required just to design a good pipe, and fabricate one... leave the turbo for the fourstrokers.

 

[Neon]

i believe the "forced induction" mentioned with the chainsaws is to do with ventilating/cleaning the airfilter. simply raising the pressure in the air box, reducing the effort needed to suck air in through woodchips and sawdust and bar oil and sap and borer innards and index fingers is always going to improve performance. and blowing a breeze past a fiilter does something for keeping it cleaner than one that just sucks at debris all day...

I believe i already had said that.

 

[HeadSmess]

If it's not possible to turbo charge or super charge a two stroke. the maybe you can tell me why Jonsered, Husqvarna and Poulan have been doing it for years. It doesn't give a huge horsepower increase .1hp, It's not really a turbocharger. More like a low grade super charger, but is still forced induction.It's main claim to fame is to keep the air filter cleaner, but still manages to give a slight power boost. The saws certainly sound like something is going on, there is a massive whine that gets worse the more the revs increase.

not exactly.... you call it a supercharger and forced induction.... mentioned the fame claim, but still called it a forced induction system, which it is not.

 

[Neon]

Ok, my bad. Sorry.

 

[machiasmort]

In a two-stroke, the exaust is the turbo. When balanced and tuned properly, engine hits given rpm (filling up the exaust pipe), this pressure pushes back on the top of the piston increasing the rpm of the motor, otherwise know as "power band".