I was reading engine sizes on a kits' specs. It gave the nitro size as 1.20 or 1.80 or gas equivalent. My question is how do you figure out the gas equivalent(number of cc's)? Is there a formula of chart? I'm confused. I not at a point that I need to choose, but I planning a future project once I get good enough with my current trainer/skills.

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They would be about the same

The 120 equals a 20cc gas

The 180 equals 30 cc gas

There is a great article in the current issue ofModel Airplane Newson Nitro Methane. Some of the items covered are air/fuel mix ratios and they cover the pros and cons of each fuel setup. While Gasoline is the highest air/fuel ratio, it also will produce less heat and therfore lesspower on the same CU, or CC size that a glow engine would. Then comes the question of spark vs Glow and the pros and cons on that. I saw a thread not to long ago about a Glow/Gas setup and what was required. .

I've been asking myself that question over the last couple years, and Ithink itis a more complex answer thana simplecomparison ofcubic inches to Cubic Centemeters compairson. What all the factors are though is still unclear to me. I think that the bottom line thoughis that a gas engine usesless fuel than an equivlent size glow engine, and thatGas is about 20% the cost of glow fuel, it make them extremely easy onthe check book for fuel cost.

It's kind of interesting that model engines were all gasser on spark orginally andthen went to almost exclussively glow, and are now migrating back to their orgins. We've got one pilot at the field though that is a Diesel flyer. He hada new plane, his own design,that looked like an early low wing air racer, and was powered by an0.060 cuin diesel. Talk about air time. It sips fuel. He must have had a 15 minute fight on the little guy. He has previously flown a couple otherplanes, one is a 4*60with an O.S. 60 diesel conversion. They stink, they are messy, but they run very well andtheyare much easier on the pocket book for fuel cost. I'm kind of susprised that someone doesn't have a 50cc sizeone out.

Don

10 CC equals .60 2 stroke glow roughly

It takes roughly 1/3 to 1/2 more displacement in a gasoline powered engine to develop the same horsepower as the glow engine. So if the glow engine was 1.8 cubic inches (30 cc) then a gasoline engine of 40 to 45 cc would be very close in power.

The fuel energy is part of the reason, apart from the differences in heat content. It is all about the mass of the material that is being heated up and expanded. Running an engine on gasoline, there is a much lower mass of gas and air going through the engine to do work. With methanol, a much larger mass of fuel and air is doing the work. Partly, this is also why higher nitro fuel makes more power than low nitro fuel in glow engines as well. Nitro weighs more than methanol, and you can run a much higher mixture of fuel to air ratio.

I have both and they each have their issues. However, gas will have more vibration issues and require higher cost electronics, PCM receiver and metal gear servos etc. If you can stand the cost of the fuel glow is hard to beat, if you solve the RF and vibration issues gas is very economical. Glow fuel may be a little safer to handle and transport than gas. Both have their place, but even at the current prices I think glow is along way from dead.

I've been flying glow/gas RC since back in the 50's and I have only a few metal gear servos and no PCM recievers

How did we ever fly our gassers before we had PCM??? We set up the planes so our RXs didn't pick up the RF. Today I have three gassers in my fleet flying and only one of them is PCM, the other two are PPM. There are rules to follow when setting up anything and gassers have a couple you should never break, other then these little rules there isn't much difference in setting up a plane for gas or glow. Same equipment, servos and gear.

All good answers so far. I had never thought about diesel fuel. I guess maybe because of the lack of information. Does anybody know the setup for a diesel?

http://www.rcuniverse.com/forum/forumid_87/tt.htm

Well I am sure gas can be flown with standard servos and receivers, but the fact remains vibration is an issue with gas. Most guys with gas engines I know carry extra switches becasue of the failure rate due to the vibration. Ignition issues with a gas engine can drive you nuts, when everthing is right they are great. Most of the gas pilots I know will inspect for loose bolts etc after a few flights until everthing gets tightened, glued, lock-tited, until it stays put. Not to say glow doesn't require good maintence also, but vibration will kill a gas plane if maitenance and checking things out is not done often and thoroughly. MHO

Never had a switch failure either

8, I have had two now, once with one of those little switches that come with a flight pack, that was 10 or 12 years ago on my scratch built 40 size Fokker. The other one was last week on my CG Extra and it was one of the JR super switches. It didn't go out, just had dirt and general crud from the lake bed in it. A few shots of QD electrical cleaner and it's working again but is now an on and off switch for one of my gassers ignition.
This is just a wild guess but I am betting K3 has never owned or operated a gasser. Probably half the guys I fly with have gassers too and none of us bother bringing out anything in the way of a lot of spare anything. None of my planes I have flying at the moment are heavy vibrators, gas or glow?? Maybe I'm just lucky??

When I strip the parts out of an old plane I throw the switches away. I've read too many stories on here about how they go bad.

I also tie my connectors togehter with dental floss

I have a Fuji 43 EI and a Zenoah 23 mag. 16 gas and glow planes all flyable which I fly every year. My son and best friend have 6 gas planes between them and I help wrench for both of them, 3 DA 50's, Fuji and Zenoah. Get off your high horse.