hello guys,

I am new to gas engines I have a quick question. When i go to buy an ARFkit it only says what size nitro engine you should use but nothing about gas!for example 1.20 two stroke or 1.40 four stroke. How do i convert this to gas instead of nitro? lets say a 26cc? or maybe a 30cc? thanks!

You need to go about 10% higher with gasoline as a gasoline engine of the same displacement does not produce as much power as a nitro/alcohol engine. So for a 1.20 glow engine the equivalent gasoline engine would be 1.3 cubic inches. However, most gasoline engines are measured in cubic centimeters, not cubic inches. SO the conversion is:
1 cubic inch = 16.39 cc
So 1.2 glow == 1.3 gas = 1.3 cubic inches = 21.3 cc

It depends upon the hp of the gas engine your are considering and your type of flying ... for me, in general, I multiply the four-stroke value times 16.4. That will get you in the ball park anyway IMHO.

So a 1.20 four-stroke would be about 20cc gas. A 1.4 four-stroke would be about 26cc. A 1.6 four-stroke maybe a 30cc.

But consider the aircraft weight, too. You can get away with a smaller fuel tank which might equal out the weight increase due to the ignition and battery. Sometime you get lucky ... DLE-20 ends up being about 2 ounces lighter than a Saito 1.50 and produces about the same hp.

So there is no pat answer.

My 2 cents.

The "old" days had 1 cubic inch of gas engine for each 10 pounds of plane weight, but gas engines have become lighter than the saw conversions of yesteryear. That was for a "warbird" type power to weight ratio.

Useful gassers information here:

http://www.rcuniverse.com/forum/m_86...tm.htm#8673009

For equivalent displacements (cu.in. / c.c.):

http://www.rcuniverse.com/forum/fb.asp?m=10098109