Turbo Charging a Saw

[timberwolf]

Seeing that any time the transfers are open the exaust is also open, I think a turbo on it's own would just end up blowing more out the exaust, at least without a pipe to keep stuffing it back in. Though it might help to overcome a overly restrictive carb/intake in certain cases.

the so called husky turbo system has less effect than the direction of the prevailing breeze. Taking the filter off and blowing in the carb while cutting would give more preasure.

And there is also the other word associated with turbo:

Detonation!

 

[Crofter]

I think that having the intake pressurised above atmospheric is definitive of supercharging. An exhaust driven device to pressurise the intake is technically a supercharger, but it became CUSTOMARY to call them turbochargers and direct coupled or belt driven devices superchargers or blowers as Glen says. A bit like whether it is a tomahto or a tomayto as long as you know it wont make apple pie!

 

[ehp]

Glens , I have to take my hat off to you , you are doing very well

 

[NeTree]

Crofter, you're correct.

Turbocharger is simply a shorthand way of saying "Turbine powered supercharger." ... where a supercharger (N2) is coupled to an exhaust-driven turbine (N1).

For a chainsaw, maybe one could adapt a coupla small model aircraft motors to the task?

 

[Al Smith]

Tough to do

Now this one,ponders some thought.In my wild way of thinking,you could possibely do it through a "window" in the piston,and having the intake much higher than the exhaust.However all theorys of loop scavaging,would not apply,in this case.Then,the question,how to get it started.How much over normal atmosphere,to run the pressure relief?I think a tuned pipe is much more simple.

 

[NeTree]

Simpler, sure... but not very creative.

After all, it's the builders who experiment with the outlandish that propogate tomorrow's engine technology.

Guys like EHP, Dozer, Greffard etc. pushing the power envelope are why we have 346XP's that can put out the same power as a saw ten times as heavy did 50 years ago.

(Not to mention the Cahoon's and Fales's and the like in regards to chain. While saw racing doesn't interest me so much as a sport, the knowledge gained in these events can be compared to Nascar and other auto racing advancing the horseless carriage!)

 

[Mange]

Would not a reed valved solve the intake porting problem?

 

[rmihalek]

Or a gear driven rotary exhaust valve that would allow the cylinder to be pressurized by the turbo without blowing all the charge through the exhaust port.

 

[Al Smith]

True story about the "cutting" edge,of design.Most improvements of design,on about anything,come from " sports" type things,from the people involved in it.Auto racing has given us many improvements,we enjoy today,in our autos .Outlaw bikers,were responsible for many motorcycle innovations .Who knows,perhaps the next improvement in saws,could come from one of these fine engine and chain builders .

 

[Crofter]

Losing charge out the exhaust is a big drawback of two stroke. The new breed (like 475) is working at controlling that, but every move from where we are seems heavier or more complicated. If we could have a closed oil base, separate powered air induction (where you could scavange with wild abandon) then inject the right amount of straight gas on the compression stroke. That would clean up the exhaust and reduce fuel consumption.

 

[glens]

Mike, they don't create a positive pressure in the airbox, so technically they don't supercharge.

 

[Kenskip1]

Here is my 11cents worth.We all have witnessed the leaf blowers ext in action. Now just suppose some mechanical genious mounted the blower to the clutch side of the saw. As the clutch enguages the blower would come into play. Now it should be rather simple to connect the out put side of the blower to the carb of the saw.MAny anomolies left on the table here.The bottom line is as the saw engine idles,it breaths normally.When the throttle is enguaged, the chain and the blower start to spin. The blower forces air into the carb. The carb will have to be richen up significently.Just my novice opinion, Ken

 

[ehp]

I guess the main reason for no turbo's is why would we spent all the money and not be able to race it cause turbos are not allowed and you would need a way to get it to cold start, sure you could use nitrous shotting it at the turbo blades to help it start with no lag but it would have alot of power . but all you are is putting more air into the motor, nitro methane does the samething, it has oxygen in the fuel , now a turbo may be easier to make run but nitro makes ever bit as much power and no more extra weight, it just maybe a little harder on the hair on your arm when it backfires

 

[glens]

They don't create positive, but they create less of a negative.

Do they?

 

[woodshop]

Found this on Madsens site, wonder what they mean by "true" turbocharging as opposed to what? Maybe true turbocharging is actually using exhaust to turn a turbine to force more combustion air, and "not true" would be the air injection kind of thing we are talking about here?

Dave

Madsens blurb:
At one time Madsen's was heavily into racing saws. We've played around with things such as "true" turbocharging and fuel injection as well as Nitro & Nitrous running saws. We keep a couple around so customers know we're knowledgeable about them, but due to increasing insurance costs and liability concerns we no longer produce them for customers.

 

[Lakeside53]

correct me me if I'm wrong (like you all wouldn't anyhow!) but Turbo-chargers use the exhaust gas to spin the turbine to compress the intake air, and SUPER-CHARGERS use a Power take off point (like belt or gear or whatever) to drive a turbine compressor...

Given the small CC and low'ish velocity of exhaust gas, it would be a lot easier to drive a small turbine from the crank than to intercept the exhaust gas stream etc... I.e. Super charge, not turbo-charge....

Sure would help get the HP up when cutting in Colorado... (at alltitude).

 

[woodshop]

Lakeside... catch is that exhaust gas is (relatively) free power, but supercharging using saws horsepower is not. It was always my understanding that in general, as engines got larger, superchargers got more efficient becacuse they could afford the power to spare for them. Smaller engines could not. The M-88 tank I drove in the Army had a huge V-12 1790 cu in engine, which did have 2 huge superchargers, one coming off each side of the crank. But again, that engine has the power to spare for them.

Dave

 

[rahtreelimbs]

When I was at the Paul Bunyun Festival in '97 a Husky rep explained that the Carb/Carb-box draws its air from the center of the flywheel. Since centrifugal force moves the debris to the outside of the flywheel this makes the center the "clean spot".


So "Air-Injection" may not be as the name implies!

 

[Lakeside53]

woodshop..

Probaby right, but I think that Turbo on small engines will suffer the same problem - there really isn't a big flow to play with and raising the the pressure is going to mess with the rest of the engine balance.

Maybe a small back pack scuba tank with a "press to inject air" button on the saw is all we need! Might help if those tough cuts! just kidding...

 

[Al Smith]

Aha,I just remembered The McCulloch BP model,was ,i n fact,internally supercharged,by the balancing piston .I wonder if Mike ever got his running .That model,was recalled because of design problems,but could have developed into something .If I can figure a good way to copy the micro fiche,I'll put it on the site,and the "great minds"can analize it.May be the answer.