1/5 scale supercharger

[kur]

I'm not going to tell anybody to go out and buy a supercharger for their redcat or baja, but I can tell you that the physics says a supercharger can work on a two stroke engine.

The people who disagree will always say the same thing. The intake and exhaust ports are open at the same time so you can't build and pressure in the combustion chamber..

But what people fail to realize is that it takes time for air to move. Also, a supercharger will be pushing pre-compressed air into the crank case. Once the more dense air/fuel mixture enters the combustion chamber, it will have to push the exhaust gases out of the exhaust port to fill the combustion chamber. That keeps the the pressure up.. a simple way to put it is squeezing air against air.. combine that with the sonic blow back of a tuned pipe, and the result will be a more dense air/fuel mixture being trapped and burned in the combustion chamber.

Of course some of that pressure will bleed off through the exhaust port, but not all of it.

Common sense says that pressure will be equal everywhere inside a container. But that is only static pressure. The air directly in front of your fan in the living room is more dense than the air across the room, even though there is no exhaust valve keeping it confined in front of your fan.

Pressure moves in waves. Waves that happen to travel at speeds slow enough that a piston cycling 8,000 to 20,000 times per minute can trap.

I'm not saying it would be easy or even feasible to supercharge a 30cc single piston engine, but it is certainly possible.

 

[Deluge]

Anything is possible, of course. Tuning it would be a nightmare, though. Yeah, you could slap a supercharger on a 30cc, but it won't be worth a damn if you're lean seizing cylinders left and right.

 

[RampageHopUps]

Its not possible.

 

[Guest]

A good tuned pipe would work far better than the supercharger. However, they would not work together.

 

[Shiny]

I've been considering a supercharger for the stock 30cc by redcat. I've read so many negative posts regarding the actual advantages. And several people quote the same thing over and over and over. "The physics this and the physics that". And "you can't super charge a two stroke" my cousin's daddy's sisters boyfriend said so. Fact, you can supercharge a two stroke. Detroit 671,471,371. built by GM came asperated in three ways. There are many configurations of that motor. Also, if you wanted even more power you could order a turbo/supercharged version. Facts;Detroit 671 is a two stroke. Fact; 671 Detroit was a very reliable engine. Fact. It performed much better than the naturally aspirated version. Fact; the engine was bullet proof but loud. Fact; you could run the engine in both directions with an oil pump mod.. Fact; the supercharged 671 is being used in an array of applications today right now, and the engine is over. 40 years old. So if a supercharger and a turbo work on a v6 two stroke why won't it run on a 30cc?

Fact that engine had exhaust valves

http://en.wikipedia.org/wiki/Detroit_Diesel_Series_71

 

[kur]

I'm going to try to explain this as simply as I can without having to resort to hand drawing a picture of what I'm talking about..

Imagine air flowing into the combustion chamber, and then right back out through the exhaust port. Imagine that flow of air as individual molecules flowing through the combustion chamber. A naturally aspirated engine relies on vacuum to pull the air into the crank case and then pressure to push it up into the combustion chamber. so, evacuating exhaust gases are pulling (vacuum) the new air into the combustion chamber as well. Vacuum creates low pressure, It spreads the molocules out thinner, low pressure air is less dense air, less dense air makes less power. This means that on a 30cc engine, you will only have 25cc of air in the combustion chamber at any one moment as the air flows through the open ports. When the piston rises and blocks the ports, it cuts off a section of that air flow, the 25cc of air, compresses it and ignites it, etc..

now if we force air into the crank case under high pressure, rather than letting the engine just ssuck it in, the molecules are packed in tighter, creating more dense air to begin with. The exiting exhaust gases are no longer pulling the fresh air in because the higher pressure fresh air is now pushing the exhaust gases out. More molecules are now flowing through the combustion chamber at any one moment. When the piston closes the ports, there are more molecules trapped in the combustion chamber. Now the 30cc engine has 35cc of air to compress and burn. So more power.

Think of it like a freeway. Cars are flowing through all the time. If you block off a mile long stretch (like closing the ports on an engine) at midnight and count the cars, you will have much less than if you did the same thing at rush hour. Sure, at first the freeway is open (like the exhaust port) but that doesn't mean that no matter how many cars are driving in, the same amount is driving out. Air molecules work the same way. If you push enough in, they can't get out of their own way fast enough to let the same number out. Pressure is built and more molecules get trapped the the combustion chamber when the ports close.

It's all about cutting out a section of the air flow. If your air flow is more dense, you will have a more dense section cut out.

Hope that helps.. if not I just might draw a picture.. lol

 

[RampageHopUps]