Well.......... Judging by the number of responses to what I thought was an innocent question, I guess personnal experience will have to answer this one. Thanks to all, though.

Wow, this thread really took off before I had a chance to respond.

daven,

I never claimed that a .52 (fifty-TWO, not .56) 4-stroke had 50% more power than a .46 2-stroke. You claimed that your .46 2-stroke can swing a 12x4 prop. I'm not arguing that point, because I've seen it done.

However, that 12x4 prop loads the engine down and drags the RPMs outside the optimum power range. Most .46 2-strokes can't swing a 12" prop at more than 10,000 to 11,000 RPM. Most .46 2-strokes are capable of producing much more power in the 12,500 to 14,000 range. You are not getting optimum power from the engine by loading it down so much.

Power is a function of torque and RPM. Given the same RPM, the engine that can swing more lumber has more power. At 10,000 RPM, the .52 4-stroke has the edge on power because it can swing a propeller with 50% more pitch. Because propeller load varies directly with pitch, 50% more pitch means 50% more power is required. Of course, this is all purely theoretical, and ignores many real world factors, much like the F-F-F-Four Stroke page does

That does it! Since we've been talking about 2 and 4 stroke engines and even throwing in Jetex and such, I feel we have neglected rockets (OK, solid AND liquid) and turbines as power plants. So they don't swing a 12 x 4 prop very well... So what! Talk about easy to adjust? - A solid fuel rocket gets lit and off it goes! Talk about fuel guzzling? - A liquid fuel rocket can drain a tank faster that you can fill it! Talk about complicated? - A turbine can make a grown man cry!

The preceding has nothing to do with the original question, but it seems to fit some of the logic pro and con each engine type. They're as good or bad as you feel about them and both 2 and 4 strokers give excellent results, now go junk all the 2's and get a REAL engine...

quint

being surrounded banshee like scream of the 2 strokers at flying fields all day I am quickly being swayed towards the 4 stroke method. I rather have a whippersnipper that looks the part, not just sounds it. *note : slight hint of sarcasm *

yes but that harley ; you could dink a passenger and still have the same top speed as without one. whereas on your japanese superbike you would lose say ~50ks (if you were game enough to try it) sort of like comparing a big block chrysler with a souped up mazda rotary and putting an engine block in the boot...

The 2 vs 4 stroke debate has always made me laugh, and I guess that is why I posted the link to the website.

In my opinion, the ONLY reason to run a 4 stroke is the sound. Either you like the sound, or your field has an issue with louder 2 stroke engines. That is my opinion, others would certainly disagree.

For Example

Cost of O.S. .46 FX Approx $115
Cost of Saito .72 Approx $225

Most would give the edge to the Saito .72 on a typical 40 sized plane. For an extra $110 I would sure hope so.

Now if you were to take a Sport Jett .46 Approx $220 and put it on the same plane, you would see a pretty dramatic difference. This engine will turn an apc 10x6 prop at close to 17,000 rpms and yet still idle around 2500. Throttle response is smooth, and transitions extremely well for a two stroke engine. The engine is True ABC constructed, and one of the finest American or foreign made engines you will ever see.

Probably not responsible of myself considering a legitimate question was asked.

Just stating my opinion from the other side of the fence.

Quote:

" and not one of them is 'WORTHLess".

I believe I said "GETTING TO BE Worthless"

Just a little play on words,but based far more on fact than fictional humor . Yes two strokes are getting to be WORTH LESS and sell for LESS than 4 strokes . People pay more for for four strokes because they not only sound better they also fly better in many applications and they look better too . They don't require the HUGE HEAVY UGLY mufflers 2 strokes are usually laden with . They FLY better because the plane can make use of the far more EFFFICIENT power.

Four strokes COST LESS to RUN in FUEL savings.

That is why an ever increasing percentage of new engine sales are four strokes and the 2 stroke share is diminishing. People see the advantages and are willing to spend more INITIALLY to enjoy them.
So it its not so funny when you have to take a hit ? Lighten up , a little ribbing works BOTH ways. Maybe it hurts more when it's based more in fact than F...f...f...fiction

I fly a Ultra Sport 60/OS 91 Surpass with a 13x9 APC prop. It turn 9400 rpm on 11.5% Cool Power. The motor is ever reliable, it has about 30 to 40 flights on it, yet I can't say I like flying it as well as my buddies Ultra Sport 60/ST 75. He also flies mine and he said it needs a 14 inch prop however the ground clearance is close when the tail goes up prior to take-off. This is my 1st 4s and I just can't catch the 4s fever. I tell every one I love the plane. I'm really not into engine sounds however I do like the 4s's smaller muffler and I really liked the the looks of this plane with a side mounted 4s engine. I'm really working at developing a likin for this ole plane.

Wow!

I couldn't help it, but to jump into this thread.

It seem as though we all have our own opinions, but to put down on something like that, it's so unprofessional.

Yes, four stroke does burn less fuel at a given displacement than two stroke, but to fly the same size plane (i.e. .40-.50), you would have to use alot bigger displacement four stroke to compensate for lack of power, and that bigger displacement would burn more fuel. Hmmm... I don't see an advantage here.

I can go on and on between 2 vs. 4 stroke comparison, but why...

Another thing is... opinions are like ass%&#@... everybody has one!

Sam

Still burn much less fuel, even with the larger displacement.

To harphunt's first post. It really depends on what plane you want to power and what kind of flying your wanting to do with it.
I use both 4 and 2 strokes. on my larger planes and aerobatic ones I use 4 strokes and on my smaller lighter fun fly planes I run 2 strokes.
If I need anything over a .90size engine on a plane, it will be a 4 stroke. "Exception- Just put a 91 on a 60 size midget mustang" That is the largest 2 stroke I will ever own.
engines I prefer are OSfx 2 strokes or YS 4 strokes. The power to weight ratio on these engines are excellent! A bit pricey but, if your putting it in a plane you spent three months building and have several hundred dollars in, better use a proven engine. I feel better about it any how.
Maybe that will help you a little.

Please note that The F-F-F-Four-Cycle Page had to be renamed The F-F-F-Four-Strokes Per Cycle Page after one of the posters in this thread chastised me for using the technically incorrect term Four-Cycle, thereby proving beyond all doubt that I am indeed an idiot. Since I can't possibly argue with that logic, at least I feel better knowing that I'm in pretty good company with the idiots at Briggs and Stratton, the Four-Cycle people. See for yourself:
http://www.briggsandstratton.com/

(Trivia note! Briggs and Stratton started and built their business making "2 Cycle" engines. It's on their web site!)

And now for your enjoyment, here's the most irate reply I've ever received to date about The F-F-F-Four-Strokes Per Cycle Page:
As for some of you in this thread, (and you know who you are........well, maybe you don't), I think the rest of us may have discovered some new runners up in the Most Humorless Modeler competition.

Thank You Daven and JohnBuckner for actually recognizing tongue in cheek humor when you see it!
(I'm afraid to post my reply to "d.d.", because some of these F-F-F-Four-Cycle F-F-F-Fanatics might take it serious!)

I don't understand the fuel consumption comments. My experience is totally the opposite. My little Saito 72 is one thirsty mutha. My Webra 1.20 just sips fuel. You have to compare fuel consumption based of static and dynamic thrust, and how well the engine behaves at part throttle settings. Since the venerable Saito mentioned above has gotten so much attention on this thread, I will submit that mine consumes about 0.8 oz per minute at mixed throttle settings including full, half, and quarter throttle. The airplane is a GP Extra .40 and I use a 13-6 prop. My Webra 1.20 consumes about 1.0 oz/ minute with a 16-8 propeller and an 11 pound airplane and identical flying style. It produces almost twice the thrust as the Saito. Other fellows at my field also complain about the fuel consumption of Saitos. On the other hand, there are about 20 OS FS91's at our field and they all get very good fuel economy. They run very nice too.

I best if you tested the Brake Specific Fuel Consumption of a population of 2 strokes vs 4 strokes, there would not be any statistically significant difference.

Oh, as a motorcyclist, the comments on this thread about them make me laugh.

What Steve said. Even with, say a .91 4 stroke replacing a .61 2 stroke, the fuel consumption is less. Been there, done that.

Price is a non-issue, essentially. If you are spending several hundred dollars on a scale, or near scale (built up or ARF), what's an extra 40 to 50 percent cost on a motor that will burn less fuel and probably last longer due to less RPM turned?

Of course the same argument could be extended to radios, servos, wheels/tires, ad infinitum. PCM or FM? Computer or standard? High torque, high speed, or standard $15 servos?

What do you want to spend? What's your style? I like to spend more whenever possible to buy a 4 stroke regardless of whether it's a scale or aerobatic plane. It's my style, and my choice based on years of messing with both types of motor.

Just starting out? Get a 2 stroke since it wont hurt quite so bad if you bury it in the dirt.

Actually Dave, we might have a good candidate for the "d-d-d-driest website humor award".

Seriously, we're talking Sahara here, man. Unless someone actually knows a person, dry humor is lost 99% of the time on the listener or reader. If possible, look at your page from the point of view of someone that does not know you and is completely unfamiliar with your humor, and you might see how it can be taken seriously by intelligent people with great senses of humor.

Oh, did I mention "Sahara" dry?

Based on the email feedback, I figure that about 5% of the RC population considers The F-F-F-Four Strokes Per Cycle Page to be the gospel truth......and another 5% of the RC population considers The F-F-F-Four Strokes Per Cycle Page to be the work of the devil.

I find it encouraging to know that the remaining 90% of the RC population is open minded enough to know that the 2 Stroke vs. 4 Stroke Debate is really nothing more than a crock of $#!+.

2 stroke or 4 stroke? It doesn't really matter! Just fly what makes YOU happy!

[QUOTE]Originally posted by Dave McDonald
2 Stroke vs. 4 Stroke Debate is really nothing more than a crock of $#!+.


Boy you can say that agine!


John

Dave,

I agree with you 100%. Fly what you like and enjoy!

Both engine design has it place and time, and use what works best for the application.
If you want slow flight and quiet sound, fly a four stroke, but if you power and speed, fly a two stroke.

To some, a four stroke might tickle them pink, but for me... nothing
make me smile like a 30,000 rpm racing engine screeming at my ears.

Sam

I will never refer to a FOUR STROKE as four stroke cycle engine, they have an intake stroke, a compression stroke, a combustion stroke and an exhaust stroke. Keep up the good work Mr. McDonald.

Why would any debate be a crock of $#!+? I prefer to think that the exchange of ideas, information, and opinions is a good thing.

That's what I miss most about r/c car racing. When you get 4 cars going wide open within 10 feet of each other turning 30,000 RPM, that is music to my ears!

The term four stroke cycle refers to the number of strokes required to complete one cycle. IE four strokes to a cycle . Yes the common vernacular is in error ,not altogether unusual It has been shortened over the years to 2 stroke or 4 stroke. Briggs and Stratton is (was) misusing the term when they refer(ed) to the 2 cycle engines they also made at one time , Right now many manufacturers are dropping two stroke cycle engines as they have been outlawed in many applications for failure to meet air and noise pollution standards. (More to follow). A few years ago ALL two stroke cycle outboards were nealy outlawed INCLUDING the older ones .