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The CG Machine

  Great home made building tool

2 stroke vs 4 stroke fuel

  Provided by "The Aircraft Proving Grounds"

Did You Know?

Question:  How high does the U-2 reconnaissance plane fly on mission flights?

Answer:  Most flights are flown at greater than 70,000 feet.

Safety Tips

PROPELLER SAFETY

A finger in the prop will produce pain and bleeding and can result in serious injury.  Here are a few things that can be done to prevent this:

1.   Never reach over or around a spinning prop. Move to the rear of your plane to   adjust the needle valve.

2.  Paint the tips of your prop white.  This will make it easier to see.  Remember to balance your prop after painting.

3.  If you start your engine by hand flipping, wear a heavy glove.

4.  Always have someone hold your plane when starting.  This will keep both hands free and provide a "safety crew" while starting your engine.

How To's

THE PINCH TEST

I f you pinch the fuel line and the engine speeds up, the mixture is on the rich side of the adjustment.  How much it speeds up indicates how close you are to a neutral adjustment.  If it speeds up a lot, you are rich.  If it speeds up just a little, you are just right.  If it doesn't speed up at all, you are little bit lean.  If it slows down, you are lean.

The pinch test temporarily starves the engine of fuel and is a reliable test for a too-lean condition.  At full throttle, quickly pinch the fuel supply line.  The engine should momentarily increase speed before starting to die.  If it starts to die immediately, then it is already too lean and should be adjusted.

There are two basic theories of exhaust design: the common one is to design a system that, at some point in the rpm band, the system will enhance power by matching the resonance of the exhaust pulse and therein creating a "suction" to help evacuate the cylinder. The second design is the anti-reversion type wherein there is a pulse dam built into the inside of the pipe so that the return pulse is cancelled at all rpms so that it doesn't block the exhaust flow.

The former promotes peak h.p. numbers, while the latter promotes broad torque and h.p. readings and has the additional effect of leaning the engine.

The anti-reversion headers I had on my old dragster years ago not only gave me more total power (up and down the rpm band), but really improved my throttle response. I was also able to run a larger carb than usual without the loss of bottom end power.

Usually an expansion chamber has the primary pipe extending into it for a short way and this gives the anti-reversion effect.

One other quick note: the primary pipe diameter gives you the basic rpm range of the power enhancement of the system and the length gives additional fine tuning around that primary point.