ok,
Whats the differences? And please dont say 2 more strokes!
I know the mechanical differences, I'm talking performance difference...

I know that 4 strokes turn bigger props because of more torque but is there a benifit to one over the other?

For instance in an areobatic plane is it best to have a 2 stroke of 4 stroke and why?

I've always used 2 strokes but am thinking of buying a 4 stroke to put in my supersportster 40, just want to know what advantage it would have over a 2 stroke or vice-versa
Thanks!

In a nutshell......4 strokes get alot better fuel economy and they don't plaster your plane with fuel oil. Oh yea,and they don't make your plane sound like a flying weed eater. By the way, a good one (such as a Saito) will last you the rest of your life.
Dennis Flora
Red Bluff, ca
[email protected]

so theres not performance benefit of going with one over the other? If thats the case then I'll just stick with my 2 strokes...

Of course there can be a performance benefit. It all depends on the application you're intending. 4 strokes won't rev as high as a 2 stroke, but it will swing a larger prop due to having more available torque. Larger props are more efficeint than smaller props (more thrust per rotation). They're also less noisy (both larger props and 4 strokes).

One of the reasons so many of the pattern guys went to 4 strokes was that the larger props gave them more control over their speed on the down lines. It can act as a brake, slowing the plane.

If you want some more detailed and perhaps aggressive opinions, do a search in the engines forum.

2 big differences. A 4 stroke runs just fine inverted while a 2 stroke just doesn't like it. Even though the 4 stroke muffler is tiny compared to a 2 stroke the 4 stroke engine is much quieter. The biggest reason I see to get one is that a lot of sport planes have cowls that don't allow for the big 2 stroke mufflers and look ugly as heck if you do manage to carve enough matewrial out to make it work. 4 strokes have very small mufflers which are easier to adjust for. For example the Great Planes Ryan STA 1.20 ARF has a shape that is very poor for a top mounted 2 stroke engine. An inverted engine fits much better but doesn't work very well on 2 strokes. The 4 stroke will fit in inverted and the small muffler is easy to make room for.

I'm currently flying an LT-40 with an OS FX 46.

I am going to build (kit) a Sig 4*60 over the winter. The most recommended engine is a Saito .91 (4 stroke).

I just want to understand what I am going to need different for the 4 stroke engine.

I.e., Is the fuel different.
Does it need oil (and how does that work).

If there is some sort of FAQ or something out there, feel free to route me to it.

GB

The one thing you need (or should have, anyway) with a 4 stroke is a tachometer. With a 2 stroke you can set the needle easily by ear, but with a 4 stroke you can't.

Many people run synthetic oil fuels in 4 strokes, as the castor residue can build up on the valves. There's no added oil in the crankcase.

99grandT:
different strokes for different folks!!
there are planes that beg for a 4-s, with time you will know!!, first steps are fine with 2-s, they are less $, are o.k. with 5-10% nitro & are simple in general, maybe your first biplane will bring the 4-s to you or a 3D plane!... but it will come.
Gostbear:
4-s don´t need as much oil as 2-s but benefits with more nitro in general; they need valve adjustment every so often but is no big deal, just read the manual, I use 12% oil, 15% nitro but I have read that saito´s love nitro in high%.
enjoy!

I just built a 4*60 & put a Saito .91FS in it. I absolutely love the plane & the engine. This thing is so much more fun to fly than my trainer. The Saito sounds great & it has more than enough power. I have an OS .61FX in my trainer, but I don't think it would be near as much fun in the 4*.
I use Byron's 15% nitro & 16% oil. This works very well for me. There is a small % of Caster oil in it which gives me piece of mind. It stains the muffler a little, but I just clean it with Z-Best every now & then.

I fly a profile with a saito.91 (top cap) and the 4-stroke torque is amazing I have a 3.5 pound home built stick I put a saito .56 on again the torque of the bigger props makes em a joy to fly. The throttle responce is instananeous (sp?) the fuel economy much better.
The sound is much friendlier. I had a TT pro 46 on the stick before I put the saito on,I hardly ever flew it. With the saito it is turning into my everyday flier. The saito out performs the TT by a good margin. and idles ever so slow. All my 2 strokes are goin down the road. I much prefer the 4 strokes.
Give one a try..... you will see what I mean.
My .02
John

I had a 120 size super sportster I put the 150 saito on, flew awesome, the 150 would hover it no prob. (11 pound plane)
I cant imagine a SS without a 4 stroke.

this plane is made for a four stroke.

got the avatar pic instead

It seems like 4-strokes are easy to use.
Stick around the field a while and you may notice that 4-S guys spend a lot less time cranking the prop. It seems like a lot of 2-S engines are very hard to start.
My first RC engine was a 4-S .52 Magnum and it works very well.
I have a TT Pro .46 on order, so I'll soon find out if a 2-S is easier to break in etc.

The guy at my LHS said that he was surprised when he put a decible meter on a same size 2 stroke and 4 stroke engine and found that they were the same as far as noise level goes.

However, the 4 stroke has a lower frequency which makes is less annoying thus it is perceived as quieter.

. <-- (grain of salt)

"Stick around the field a while and you may notice that 4-S guys spend a lot less time cranking the prop. It seems like a lot of 2-S engines are very hard to start. "

I think this is mostly due to the fact that most people have some experience before they get a 4-stroke. Also on average 4-strokes are larger on the same airframe. Larger engines are easier to start. Traditionally 2 strokes are timed for higher revs, newer pattern type 2 strokes such as the OS 1.4 are made for lower revs and compete very well with the YS 4-strokes. I like both, the only problem I have with 4 strokes is the higher maintenance and short bearing life.

It's probably not just user experience, but a higher build standard in most 4-strokes. Unlike 2-strokes, you can't get a dirt cheap 4-stroke.

you get what you pay for!!!!

I'm not so sure, the .52 cost me $150 and then a few weeks later, it went on sale for $120 for a few months.

I wouldn't say that they always wear out bearings quicker. We have a a guy at our flying field that has on older OS 91 4-stroke (built even before the Surpass came out) that had somewhere between 400-500 flights on the bearings finally gave out. And then he spend $30 for replacements bearings and it runs like it's a new motor now. I would say he definately got his money's worth on that motor.

rlt55: well, magnuns are made in china!
try other countries 4-s, you will be happy.

What countries makes a 4-s that has a lower cost?
I'm very happy with my Magnum .52
If I can get a 4-s this good for less money, I'll order one today!

Rich<>