When I first started in this hobby 4 years ago, I only used OS 2 stroke engines because they were great running engines for one. They were trouble free and easy to run. My first 4 stroke was a Saito 82 on my Twist and I haven't gone back to 2 strokes since. The power, reliability and particulary the sound of a 4 stroke is addicting. An occasional (once a year) 5 minute valve adjustment is all it takes to keep them running great. Today my fleet uses all Saito and OS 4 strokes and I can't foresee ever buying another 2 stroke engine again. This is of course just my opinion and preference.

yeah, but if you could get a 2 stroke that had 350ci, imagine how it would rpm and make power. it sure would sound cool too!

take this debate over to some of the dirtbike forums and see what happens. same answer as here, they each have their preferred application where one performs better than the other. my buddies and I had this debate on dirtbikes a couple years ago. we put my YZ250 (2 stroke) against his YZF 426 (4 stroke). at the end of the long track they were about even. I would lead some sections of the track and he would lead others, but in the end we were about even. i will tell ya that his bike made power as soon as you crack the throttle, and mine you gotta keep it up in the power band for it to make power. oh yeah, and he had a lot of cc's on me too.

There is a similar debate with street/track bikes. Everybody "knows" that four cylinder engines make peaky high rpm power and V-twins are better for low rpm torque and there are a lot of theorys as to why, most of them easily debunked.
My feeling is that four cylinder motorcycles are designed to satisfy a market that values peak horsepower even at the expense of low rpm tractibility. V-twins are designed to please a market that values "torque" (low and midrange throttle response and flat torque curve) even at the expense of maximum horsepower. Each market gets what it wants and the stereotype is reinforced.
Ride a Kawasaki ZRX1200 R or Suzuki Bandit 1200 and you will learn that fours can also make a lot of low rpm torque.

It's the same with model engines. Most 2-stroke engines are designed for maximum horsepower because that's what the 2 stroke market wants. Horsepower sell 2 strokes and most of the horsepower zealots never throttle down anyway so who cares about midrange? The maufacturers give the two stroke market what it wants and thus reinforce the 2- stroke stereotype.

Four stroke engines are designed for excellent midrange throttle control because that's what the 4 stroke market demands, and again, the stereotype is reinforced.

Can four stroke engines be high rpm screamers? Well that formula 1 car video I gave a link to in an earlier post certainly suggests so.

Can two stroke engines be designed for excellent low to midrange throttle response? Well, the motorcycles used for obseved trials where low rpm torque and throttle response if paramont are mostly 2-strokes. Most RC helicopters also use two stoke engines. Do you really want to try to hover a heli powered by an engine with a on/off switch for a throttle?

yeah...i'm a 4-stroke convert myself. i prefer the sound and the overal tractibility of the 4-stroke engines. i've loved my 32SX and 46FX but nothing beats my O.S. 30, 52, 70, 90, 120 and my YS 63 and Dingo. even my budget asp 61(?) wasn't bad. as you can see from my handle, i love four strokes.

I own a number of four strokes - a Saito .72, a Thunder Tiger F91-S, a Magnum RFS .52, and a Magnum RFS .70 and they're all really nice engines.

I have to admit to admiring the simplicity and reliability that my 2-strokes offer - 1 O.S. .46 FX, 2 O.S. .46 FXi, 1 Magnum XLS .52A, 1 GMS .47

As nice as the four strokes are, I doubt I'll ever get away from 2-strokes completely. They're cheap, they're easy, and they just work!

Not to argue a dead topic...but BLE, Barichello's Ferrari red lines at over 20,000rpm. So, yeah...it's a four stroke, but it's revving up higher than most people's two strokes do. Just think of how amazing that precision is. Also, both that car and the "four stroke powered retro rail" have almost unrestricted exhausts giving as much boost in performance as possible. Why do you think Harley's are so much louder than Civics? Exhausts!! They rev up way less, but have those big beefy exhausts. So...I'm just pointing out that rules of thumb apply to the vast majority of things. Also, R/C engines meant for reliability and fun aren't the same as engines costing hundreds of thousands of dollars with millions of dollars invested in designing them for absolute maximum power and minimum endurance. That's why (until recently) F1 had a one engine per race weekend limit on cars. Then they limited it to one engine every two until they made the engines V8's and increased it back to one per weekend. If not, I have no doubt that teams would have an engine each for practice, qualifying, and the race. I've owned one 4-stroke and 6 2-strokes. I crashed my Saito 100...a 280 dollar engine that cost me 160 in parts. It would've been over 200 for shipping the engine to and from HorizonHobby and the labor on it. I also buried a 46AX 8 inches in mud and over 3 feet of water. I pulled it apart and soaked it in WD40 for 3 days (first chance I had to get back to it) put it back together (i mean cylinder head, carburetor, and muffler ONLY) and it still started first flip. Now, I love my Saito to death (still waiting on the parts for it), and it intrigues me that it can turn such a huge prop with so little problem, but my AX has never given me anything but love and support!!

victor, i'm with you on that. 2 strokes are the more bang for the buck. 4 strokes are more like exotics. but at less than $200 for a smaller fourstroker, i'm happy i can still afford one or two exotics.

the 46FX was about the best engine i'd ever owned. the plane went in full throttle and planted itself three inches deep in hard dirt. shattered the piston, carb mount, needle, bent the crank and of course there were a few fins broken. no amount of soaking in WD40 could fix it :-) the rudder failed on a low high speed knife edge pass. scared the bejesus out of me.

i fly fourstrokes because i love them. they are temperamental, but that's just part of the hobby!

Many people prefer the sound of 4-strokes, and the ones I've seen are very reliable. Many would argue that they sound just fabulous. I prefer a 4-stroke glow engine over a big gasser, simply because the 4-stroke is quieter. I do believe that multi-cylinder engines are far superior to their single or twin-cylinder counterparts. I witnessed an OS Pegasus pulling a Christen Eagle, and it was just amazing how low that machine would idle. It was fantastically smooth at all settings, then engine did not miss a beat. It just amazes me that more people have not discovered what a radial, in line, or 4-cylinder 4-cycle has to offer.

As for budget. I do believe the new OS AX 2-strokes will give the best in reliability, simplicity, and output for the money. They are also very quiet and pleasant to listen to. I have had some very positive experiences so far with my 46 AX. Not only will it literally pull stumps, I have heard more than my share of electrics that are considerably louder. I am sure many other AX owners would agree. I have enjoyed mine so much, in fact, that I just recently purchased a 55 AX to add to my collection.

Will I get a 4-stroke? Maybe. But my preference will be for one with at least 3 cylinders.

NorfolkSouthern

Somebody's going to have to inform those TOC guys who fly big gassers that they are going to have to stop doing all those 3-D stunts with those planes, the big gas burning two strokes in those planes just don't have the throttle response to do 3-D. I said stop that!!! You're not supposed to be able to do that, you have a two stroke in that plane!!

Different stroke for different folks, lol. I usually let the airframe dictate which engine I use .

Well, I've got quite a few two strokes and just as many four strokes, and just recently a gas engine. I like all three quite a bit and like the variety. I like the sound of both two strokes as well as four strokes (not a big fan of the loud gasser though). I make the engine decision based on the plane.

LOL. The "big" 2-stroke gas engines "mimic" the smaller glow 4-strokes. They are swinging big, honkin props at 7,200 or 8,500 RPM top ends.

What torque does for you, in realistic flight situations, is give you a great mid-range. High RPM gives you lots of speed at top end, but high torque gives you low-end power and acceleration. Like driving around in second gear vs. fourth gear. It also gives you the ability to go up and down at approximately the same speed for IMAC and other pattern maneuvers.

I like 4 stokes because they sound better, but I really don't have any dislikes for either of them.

I flew nothing but two strokes after a bad experience with a saito .82 on my second airplane. i swore off 4 strokes and I was more than happy with my 2 strokes. Fast forward a year later when i have much more knowledge and experience with tuning glow engines and flying and now all i run is 4 strokes. I fly 3d almost exclusively and the four stroke wins in almost every 3d application. The spool up is what i really love. No matter how well a 2 stroke is tuned it will not transition like a well tuned four stroke. And I understand using 30% fuel is part of the reason why but that is one of the reasons I love using four strokes, 2 strokes just can't handle the high nitro as well. Some see 30% as a drawback because of price. With all this being said I don't think a four stroke is the right chioce for anyone's 1st or 2nd engine. They are not more difficult to tune but they do take practice to tune them right. Also some of them take quite a bit of break-in to perform like they should. Maintenance is another reason I would steer new pilots away from them. When you are learning to fly you have enough to worry about without trying to keep track of when you need to adjust your valves. Sorry about this rant and I'm sure some of you will disagree with me. This is just my opinion and I don't know everything.

OK. After reading through this interesting debate, I am thoroughly confused. I am buying a 66.5" P51-D. I will be using a Futaba 2.4 GHz 7C radio system and I am considering a Saito FA-91S or equivalent. I currently fly with a Magnum XLS .46 and have never had a problem. I have an 11x6 master airscrew on it and it runs excellent. It even survived a heck of a crash when I lost my first plane. Very durable indeed. What do you guys suggest for the warbird? I dont mind the noise of the 2s, but I hate the mess. Help me out.

fireflyer80: First, ask yourself which engine you like best. I can always build another kit, I can always get another ARF. They're cheap, take up a lot of space, and wear out quick. In fact, most airframes don't last through nearly as many flights as an engine and radio do. After you've decided which engine you like best, which has the most stuff to play with and sounds the greatest, then go with what ever plane is best suited for your engine (as per your preference, of course). I bought that OS 55 AX, just because I like its looks and I've had positive experiences with their 46 AX. I am sure I'll like the sound and performance too. I haven't found a barge for it to pull yet, but I will eventually.

NorfolkSouthern

in my Hangar-9 mustang which is about the same size I run a OS91 surpass its a fine engine for that size plane, a saito 91- 100 be a good size engine as well depending on the weight,for the lighter ARF mustangs 7-8lbs, the engine would be a great fit.
for a kit build like a Top Flight then a OS 120 or a saito125 might be a better choice since they tend to come in a bit heavy 10-12lbs.
my H-9 is a little over 8lbs

Thank's for the input guys. I was pretty much on the same track. Now it just boils down to making a choice. But, all of your arguments definately helped.