for someone thinking about a new plane and engine. other than cost, what are the pros and cons. I am thinking of a 40 or 60 size aerobatic (maybe 3-D) plane. Would like to hear comments about the differences between 2 cycle and 4 cycle.

bbell

Speaking in extreme generalities, two cycles:
Lower cost
Lighter weight
Louder
Higher RPMs
Happier with "smaller" props
Less fuel efficient

Four cycle:
Higher cost
Heavier
Quieter
Lower RPMs
Happier with "larger" props
More fuel efficient

From what I've seen, two strokes work best when you need lighter weight and higher prop speeds. Four strokes do better where you need more "pull" and a little extra weight is not a problem. Of course these are generalities, because there are two strokes that love big props and generate huge amounts of pull .

ditto.
Plus, four strokes sound cool!
You can't underestimate the "cool" factor--after all, this is a hobby, and hobbies are made to be cool!

hmmmmmm makes me want to get a 4 stroke now

Do what you want to do, the man was asking a question and we've answered him.

Yes! Do it.... you will be happy. They are great little machines and they do sound much cooler than 2-strokes.

However, that being said, be aware that the fuel economy advantage is marginal at best - in fact I'd argue that my Saito is less efficient than an equivalent 2-stroke. (Yes, the mixtures and valves are properly adjusted) Also, while 4-strokes have a more pleasant sound than 2-strokes, they are not quieter in my opinion. I think the 4-stroke sound caries farther than that of 2-strokes. We get more complaints from neighbors with our 4-strokes than with 2-strokes.

I'll now put on my flame suit.

4 Strokes do sound cool... and otherwise I can't argue with the above comments...

But be warned... You will need a much bigger 4 stroke than 2 because they tend to be a bit gutless power wise...

Matt

If this is for your first plane its easier to hear what is happening on 2 strokes because of the noise difference. 4 strokes don't sound much different between slow idle and full rpm so its difficult to adjust the carb properly without a tach. 2 strokes also have a much shorter break in period which means you can get flying sooner. 2 strokes are considered flyable after 3 or 4 tanks of fuel have been burned. With 4 strokes I have read where some consider that you are supposed to burn a gallon of fuel through a 4 stroke engine before you even mount it on the plane! Thats a lot of fuel and running time with out air time. Nuff said![8D]

The instructions on the most recent 4 stroke I put in service, an OS FS-30, said to run one or two tanks on the ground and then start flying. Obviously they also contained text about running it appropriately rich, but the point is the manufacturer specifically said to go ahead and fly. I think the gallon recommendation comes from people who a) are extremely cautious, b) need very high reliability imediately due to some special application such as racing or aerobatic competition, and/or c) have too much time (and money) on their hands.

For the average sport flier, those just boring holes in the sky, most engines can be put in service after just one or two tankfulls on the ground.

Which engine is the most dependable, longest life and least repairs. 2 cycle or 4 cycle. Is OS the leader in 4 cycle. Or, I'v seen a lot of post about Saito, are they the leaders. Cost will be a factor, it may dictate staying with 2 cycle, but I am considering a Hanger 9 Funtana 60, or a Hanger 9 Twist. I have an OS .61fx on my Alpha 60 trainer, so far it seems to be very reliable.
Almost everyone I'v talked to has given me advise the OS is the best (or I should say best in 2 cycles, have never asked about 4 cycle until now)

I am going to the Southeastern Model Show (Perry GA) this weekend, want to keep my eyes open for any good deals.

Thanks for all the information given so far.

bbell

Where do people come up with this stuff???

Fast, no offense, but get your hearing checked.

I have lousy hearing (I rarely hear ANYTHING my wife says ) but I still have NO problem tuning a 4-stroke "by ear".

In fact, I bought a tach a while back (just so I could take a picture of it showing the RPM of an engine I was reviewing) but I wouldn't even THINK of using it to tune an engine.

bbellfish, get yourself a 4-stroke - I like OS over saito, but it's a ford/chevy thing. Get a 70 for a 40 size plane or a 91 for a 60 size plane and you'll be as happy as a pig in slop.

hmmm interestion thread. i was looking for a 2 st. 61 to put on my stuka. but a 4 banger sure would sound sweet in a warbird? the price difference is quite abit. are the 4 st. longer lasting engines?

Buy good quality, break them in right, don't run them lean, give them adequate cooling, run them dry at the end of the day, and oil as needed, and either 2 stroke or 4 stroke are going to last a long time. In the end, a 2 stroke will probably last longer simply because it has less moving parts to wear out, but longetivity isn't an issue with the name brands. If you want to run it hard and put it away wet, go with a 2 stroke. If you view engines as investments and do a few little things to protect them, choose based on the application.

The other positive factor for a 4 stroke in this application is that the muffler is so much smaller.

With a 2 stroke you can mount the engine horizontal and use a pitts muffler, resulting in the engine cylinder sticking out of the cowl, mount the engine inverted, and have a big muffler hanging out the lower side of the cowl, or maybe mount the engine at an angle and have the muffler hanging out the bottom of the cowl. No matter what, for many planes (other than those with cowls big enough to enclose the entire engine), there's usually a huge hunk of metal sticking out of the side of the cowl.

You can mount a 4 stroke inverted, which means no cylinder sticking out the side of the cowl, and either let the stock muffler stick out (much smaller profile than a 2 cycle muffler), or run an extension pipe to route it out the rear of the cowl. Much cleaner look.

Mrbass, it's a shame not to put a 4-stroke on a warbird.

my thoughts exactly, but the price difference is so great. and there are many models. i know os makes a good 4 stroke. but what about magnum?, thunder tiger?, and saito. but i have heard that saito's are good but ill bet there pricey.

I've heard good things about the Magnum and TT 4 strokes. I bought a well used Magnum .81 a few weeks ago, but haven't had a chance to start it up. My understanding is that Magnum, TT and OS are generally heavier than Saito. Saitos are not usually any more expensive than OS 4 strokes. I have a Saito .91 which I am very pleased with. If I could afford it, I would have a 4 stroke in all my planes. They sound great!

-Scott

I've got to be one of the few guys that differs with most about the sound of a 4-stroke.

I agree that single cyl 4-strokes sound better than small 2-strokes, & work particularly well in scale light planes & planes that have radials in real life. They don't sound that great in a warbird that has a V-12 in real life (Mustang, Spit, P-40, P-39, P-38 etc.) There is too much single-cyl put-put-put sound that's not even close to a V-12. In my opinion, large 2-strokes (both gas & glo) have an exhaust note that is much closer to a V-12 warbird.

thats a good point britbrat, im used to flying a 2 st 46 and really have not paid any attention to larger size 2 st.. ill have to pay attention next time out at the field. but i have noticed that the 4 bangers do have a deeper tone. maybee not live a v12 but a bit more realistic than a 46 size 2st. anyway

MMMMMMMMM 4 strokes.....

Britbrat's got a point.... I think my P-39 soiunds pretty good with the ST in the nose. However, I wouldn't have anything but a 4 stroke in my FW 190.....

Andy

Hello!!!!
Other think that you have to keep in mind is that 4S engines runs better than 2S at low speeds, you will have less probabilities that your engine stop running in the air with a 4S

Have a nice day
Escipion

I am not a 4 stroke fan, so lets set the record straight and compare apples to apples. You take a 40 size engine and look at the manufactures prop specs they are just about even for 2 stroke compared to 4 stroke. And I'll guarntee the 2 stroke will out perform the 4 stroke. Don't tell me they pull a bigger prop cause they are always 52 size compared to a 40 2 stroke.

Minn, re: " Fast, no offense, but get your hearing checked."< Ouch!! I know my hearing isn't perfect so you don't need to tell me. The type of reply I give is based on what the guy posting is asking vs. his experience. Its been my experience that new guys have more trouble adjusting a 4 stroke than a 2 stroke. They tell me its because they don't hear much difference if any between 10,000 rpm and 12000 rpm. So its not just me! In this case a tach is much easier to tell what is happening. I use a tach and like it!!

same here.. my 2 stroke 25cc gas sounds WAY better then my saito .72. 4 strokes are nice, but I think the sound is too much like a 10 hp riding lawn mower. I prefer a nicely tuned 2 stroke (40 size or larger) or a gasser. (now annoying little 2 strokes (15's - 25's) at insane rpm's, that is another matter entirely!)

4 strokes typically have longer strokes, and produce less horsepower than 2 strokes (mainly due to the rpm's of 2 strokes), but produce much more torque. More torque means a larger prop can be turned--apples to apples, the same sized 4 st has more torque than a 2 st, which means it will turn a bigger prop. That is fact. If you don't like 4 st, then that is fine, you don't ever have to buy one, but don't come on here talking about stuff that you don't know anything about. i own both 2 and 4 st, and much prefer the 4 st anyday!