Hi:

What is the difference between a 2 stroke and 4 stroke glow engines? Any advantage one has over the other?

Thanks
Chuck

A comparable (application in a given plane) four stroke is going to be about 40-50% larger in displacement than a 2 stroke. Therefore a .40 two stroke should be compared to a .52 - .60 four stroke.

Power: The two stroke is going to have more top end horsepower, the four stroke will have a broader usable power range. In other words if you are inclined to fly a plane at full throttle constantly, you might be better served by the two stroke. If you like to get good response from your plane at varying engine speeds, the four stroke is the way to go.

Fuel consumption: The two stroke pulls fuel ever two strokes, rather than ever four, so it will consume more fuel, on average.

Cost: The four stroke is going to cost you 50-100% more than two stroke.

this is a little off topic but how do the R/C rotary engines work? how do they get the timing right?

And just to muddy the water even more -- while the 2-stroke uses more fuel, per cc of displacement, the 4-stroke requires more nitro in the fuel -- which costs more. Your choice.

I disagree Britbrat. I run the same fuel in all my engines, Power Master with 10% nitro and 18% oil. Four strokes run just fine with it. The only four stroke that I know of that prefers higher nitro is the YS.

I'd say hgiles said it pretty well. If you use throttle and like good torque at the lower end of the rpm range, definitely a four stroke.
Dennis-

Same here our whole club burns the same fuel in either 2 or 4
storkes.. Well, we all use the same fuel since the club buys the
fuel in bulk and sells to the members at a two dollar savings..
We all use PowerMaster 15/18..
I like 4 strokes, for the low end torgue, less fuel consumption
and the sound.. But they do vibrate a little more, But should be
no problem... Altho I'm still breaking mufflers/pipe on my mag
91 on my 4*60... But I sent it in to be checked since the plane
looks sound.. Magnum also sent me a free muffler assy. when
I lost the last pipe.. And most at the field keeps telling me Mag.
will just send me a new engine??? I'll find out soon...

ChuckD, the main diff as it related to our planes is that 4S can turn larger props compared to a similar powered 2S. This is because 4S engines produce more torque at lower RPMs compared to a 2S. Take two 1HP engines. The 4S may produce the 1HP at 9KRPM, while the 2S may produce the 1HP at 14K RPM... both are 1HP engines. The 4S may have a 14x6 prop while the 2S would have a 10x5 prop (just as an example as the listed props work out to about 1HP at the example RPMs.) The advantage then is that 4S with the right propeller will product more static and low end thrust becasue they can swing larger diameter props, but speed suffers. Likewise, the 2S with the right prop will have poor thrust, but can produce higher speeds. In the above example, my Thrust calc is showing the 4S w/14x6 @9K produces 9.3lbs of thrust and has a top speed of 50MPH, and the 2S would produce 6.7lbs of thrust and a top speed of 70MPH. You can play games with props, like putting a very high pitch prop on a 4S to gain speed and putting a large very low pitch prop on a 2S to gain thrust. But IMO, you are better off matching the engine to your purpose. So, which engine offers the most advantage really depends on what plane we are talking about, or maybe more importantly, what type of performace you want out of the plane.

Think about motorcycles, The whiney little dirt bikes use 2-strokes (Rrring -ding-ding-ding) While the REAL bikes use 4-strokes!

Hey thank you all for the answers, that has got me clear about 2 vs 4 stroke so now I can set my sights on what I want to build!

Thanks
Chuck

Negative, I will assume you are speaking of a Wankle type engine. A rotary engine is a radial engine where the crankshaft is bolted to thefirewall and the engine spins (don't ask me why, it's a French idea, kinda figures). A wankle or a "rotary" engine is a horse of a completely different colour. It combines a two and four stroke in one engine. It has 2 ports just like a 2 stroke. But uses a four stroke cycle. It uses a triangular shaped rotor(or piston) in a roughly hourglass shaped combustion chamber. There is a shaft at the center that the rotor "wobbles around" and supplies the power. Each side of the rotor acts like a cylinder on a conventional engine. Intake ports and exhaust ports are directly above one another on opposite side of the glow plug. Fuel is drawn in and compressed in the upper half of the hourglass. At the other side across from the intake the fuel is ignited. As the rotor spins into the lower half the fuel burns and produces power. As the rotor tip sweeps by the exhaust port the spent fuel and exhaust is pushed out. Kinda simple but not. All you need is to see a diagram and it will be very clear how one works.

Having said that a rotory engine makes tremendous horsepower. The only limits on the engine are how fast you can spin it and how much fuel you can get in and out. They tend to run hotter than standard engines. And they are more delicate than standard engine technology. The rotor tip seals are a sore spot in the design. They are also fuel hogs. They love fuel. But for their size and weight only a gas turbine can make more power.

I hope this explains it for you.

Mark Shuman