What are the pro's and con's of 2 and 4 stroke engines?

Andrew

Two strokes are usually cheaper to buy than four strokes. They have less moving parts and are generally considered 'easier' for a person new to the hobby to operate.

Some, not all, two strokes run well at idle and full throttle but not so well at half throttle. My Thunder Tiger 61 never ran well at half throttle but my ASP 61 does.

All of my four strokes seem to run well at half throttle and all other settings.

My .61 two stroke burns more fuel in a 10 minute flight than my .91 four stroke. Many people believe the .61 two stroke and .91 four stroke are fairly equivalent in performance.

A totally subjective point; I think four strokes sound better than two strokes.

This isn't really an answer to the original question, but I wish I got into four strokes sooner than I did.

I guess the biggest advantage I see is the immediate throttle response, due to the higher torque of the 4 stroke. When you ask for power, you get it immediately instead of waiting for RPM to increase. There is less top-end power, but you can use a prop with a higher pitch so you don't need to go there.

The sound is great, it's really neat having a little engine with valves and stuff (i.e. the neat factor). My four stroke seems to make less of a mess than my 2 strokes, and seems to be quieter overall.

4-strokes:
Sound more scale-like
More fuel efficient
More torque - spin larger props

2-strokes:
Higher power:weight ratio
Higher rpms for more speed
Cheaper, simpler.<br type="_moz"/>

I'm with Joe, Ithink it's more of a cool factor!!!
Ihave heard this debated before at the field, we all know how that goes, the thinking was that the four strokes were developed because of the noise factor?? You be the judge.
They do throw a bigger prop, they do use less fuel, they do produce more torque and they do sound cooler.
Other then that Ihaven't noticed much difference in flight. There may be less engine snot on your plane at the end of the day?? Now that Ihave seen it mentioned that could be right? Maybe not?? Ihave never seen a Saito that didn't sling so much snot the plane wasn't dripping when it landed, Ihave one YS that is really snotty too but that could be where I have my muffle pipes exit??
Idon't know, Ithink it really could just be the cool factor?
What ever it is Ijust really like them and don't have any plans about changing any time soon.

Saitos: definitely messy.

YS: A little less messy than the Saitos and the most powerful of the bunch.

OS: Very clean, not quite as clean as a gasoline engine but not bad. Very little oil on the plane after a flight. They run very good too. Probably second only to YS in my opinion.

2 strokes: Nothing wrong with them at all. Definitely cost-effective. Just gotten to where I can't stand listening to them. Inever say never though. I may have one again for something one of these days.

All just my opinion of course, your experience/perception may vary.

Bottom line is fly what you like and have fun.

Got my hands on 2 different Magnum 4 strokes and neither was worth owning.

I'm in shock!!!!!!!!Jeff, say it isn't true!!!!
As to the two strokes Iwent over to the SK engines and have been very pleased with performance, price and sound. Irun the SK .91, they take a big prop, anything less then a 15 inch and it will run lean, low RPM engines with stump pulling torque and very quiet!! For 100 bucks I like them a bunch better then the OS these days but I try not to fly real fast planes so the low RPM is perfect for me.
Hot rodders need not buy!

I managed to get my Magnum 2 stokes to run well,,,,,,,,,,,,,with a Thunder Tiger carb.

I think that regarding the 'not cool' sound of a2 stroke.... a pitts muffler installed ina 2 strole can change the noise pretty nice... do not you think guys????

It is entirely subjective as to the sound of the engine being pleasing. I happen to like the sound of a screaming 2 stroke even if it doens't sound like a full size plane. To me it just sounds Fast!

i love the sound of a four stroke on a slow fly by, nothing will beat it, their torque, "coolness" factor, and idle/midrange sound

however when you just WOT a two stroke in the air and it starts screaming, man it sounds great.

Chuck, that's funny - it's been a week and I totally agree! I fired up the 120 two stroke today and immediately was disgusted by the sound (and of every other 2 stroke I heard today. Thankfully there were some 4 strokes and a gasser).

This is totally subjective. Both engines will fly a plane just fine.

Quiet is good. Noise does not equate to power.

Many clubs have restrictions on noise, rightfully so.. they could lose their flying privilieges by the locals.

Pattern events alsomonitor noise limits as do other sanctioned events.

Our club is one that has noise restrictions.The difference to members is you can fly a larger engine in a four stroke without a special muffler than a 2 stroke. A 120 two stroke can make a lot of noise with a stock muffler and is usually too loud to meet noise requirements, especially with certain props.

I think you hit it on the spot. I would also add that 4 strokes are more complicated and expensive. Also, they are heavier. I got rid of all dirty and oily nitros, and only fly electric or gas.

The only important thing is to remember is: The best powerplant is the one YOUlike:-)

Good luck

Gerry

2 strokes are cheaper and have more top end power.

4-stroke. once broken in run better, idle better, use alot less fuel, have loads more tourqe, low end. sounds cooler and are quieter.

One more difference worth mentioning. A four-stroke prop hitting your hand hurts a lot more that a two-stroke prop on a comparable engine. It's the torque. Best 4-stroke advice I ever got was never touch the prop with your hand.

I wouldn't go sticking my hand in a prop on a 2-stroke or an electric either. High speed spinning knife blades and human flesh &amp; bone just aren't a good combination.

No kidding, a chopOmatic is just something I try to avoid, I don't care what is powering it!!!
A Pitts muffler sure does change the sound of a two stroke, Ihave a couple of Bison mufflers that make my SKs sound different, mater of fact they are even quieter then my four strokes.
As to the type of engines I use?? As stated, what ever will fly my planes.
My gassers are a bit on the loud side but the mufflers are nothing but square cans with pipes sticking out to direct the exhaust away from the plane. Ihave one fellow I fly with that spent big money on cans for his big twin and it was the loudest plane I have been around, he changed the prop and the same plane is really pretty quiet now. Props make a big difference in the sound!
Ijust really like my four strokes and other then one of them they are pumpers so plane/tank set up is really easy, they don't care where you put the fuel tank.
And that cool factor!!!!

After one more day with my big 2-stroke I am ready to start selling off all my two strokes and replace with four strokes. I got spoiled, fast!! I have no problem giving up top end power for more torque and immediate throttle response. The amount of time I had to wait today to reach max power with my 120AX is stupid[:'(]. It's 2009, and when I want power, I want it NOW!!

And did anyone mention simply how much cooler four strokes are?![8D]

Me thinks Joe has a bad case of the YS spoiled!!!!

I just started flying my first 4-stroke - a Saito .62 on an Ultra Stick .40, otherwise I would have used a .46 2-stroke. On the US40, the engine is sidemounted. That puts the idle needle facing the bottom of the aircraft (but it would be the same on a 2-stroke). Makes setting the idle a bit more complicated but once it's properly tuned, you won't have to change it by much.

I'll dispute the 4-strokes are heavier than an equivalent 2-stroke. The stock muffler on a 2-stroke is really heavy. I also have a Sig 4*60 which the previous owner originally had an OS .61 FX with a bit of noseweight. Ifitted a Saito 1.00 and will have to add MORE noseweight.

Cost of the 4-stroke is over twice what a 2-stroke costs. They slobber up the airplane less than a 2-stroke, sound better, run well and use a LOT less fuel. I'm really liking Saito-powered Ultra Stick.

It's $240 for a two stroke 120AX without muffler vs $350 for a four stroke FZ110-S. That's 50% more money for a 10% smaller displacement engine.

BUT, the $110 may be worth the better running, lower fuel consumption, less noise, better sound, higher torque and the lower mess factor.

For anyone having both a 120S-E Surpass (864g w/o muffler, max 11000rpm) and a FZ110-S (730g, 13700 max rpm) , how do they compare for power, and consumption? Close?

I have the OS 1.20 FS pumper and the YS 1.10 and the YS is just way more power and lighter. As for the 1.20AX and the YS 1.10 go ahead and ask ga what he thinks, he is just starting to get into his YS. I think it took him maybe one flight to make up his mind. Idon't see him ever looking back again.
Ithink he stated he will make you a deal on a good almost new 1.20AX!!!
I'm not real sure about that?? What say you Joe??