What are the differences between 2 stroke and 4 stroke engines in terms of...

-Power
-Fuel Consumption
-Noise level
-Ease of Use
-Quality


Just trying to know more about engines


Thanks!

Kev



edit: Grammar

4 strokes are more fuel efficient, less fuel on your plane, ease of use varies and don't know about the others.

dave trimmer

Kev, my opinion for what its worth

Power- A two stroke of the same displacement will deliver more power, and weigh less

Fuel Consumption - The four stroke uses way less fuel than the two stroke- A side benifit of this is less Goo on the airplane. Way less

Noise Level - the four stroke is quiter and has a much nicer sound

Ease of Use - Not much difference. Once you set the carb up correctly, just use it, same for both 2 and 4 strokes. The four stroke will require a valve adjustment once a year, depending on use. No big deal.

Quality - Again, not much difference overall.

Myself, I'm converting to four strokes where I can. I just like the cleaner burning and the sound.

Don

2strokes weigh less and produce more power. Lots less weight and lots more power.

Fuel economy differs in favor of the 4stroke but not enough that it actually is of any real value or concern.

They both sound about the same when muffled properly, but since the 4stroke won't turn the revs a 2stroke can, the 2stroke's prop noice tips the ballance.

4strokes are said to require higher nitro fuel to run well. My personal experience was the last 4stroke I bought ran like crap until I started using higher nitro. Since I don't normally run higher nitro fuel and had to buy some for that sucker, I'd consider the ease of use to be in favor of the 2strokes. That engine also was a pain in the plane when I tried to use it upside down. It's downdraft carburetor flooded like a rotten rowboat when trying to start it upside down. Turned it sideways and it ran ok. Ease of use says another one in favor of the 2strokes. I've never had a 2stroke that had a care which way it was mounted. Get the tank and plumbing right (as it was with that last 4stroke) and the 2strokes give zero problems.

I recently bought an OS4stroke70 for $180 from Tower. Recently I bought an OS91FX for $180 (actually was $160 with discount). One area LHS sells OS46AXs for $95. That's almost half the price of that 4stroke70. And they're about the same power.

I use an expensive glowplug in my 2strokes that Tower sells for $5 each when purchased in bulk. The good 4stroke glowplugs are something like $8 each when purchased in bulk. I've used about 3-4 fourstroke plugs in the last month. That was on one airplane that had the 4stroke in it. I've flown 4 or 5 other airplanes of my own in the last month. All were 2strokes and I've yet to replace a plug.

I greatly enjoyed the flight performance that Clipped Wing Cub had with the 4stoke on it. It was kewl how the big flatpitched prop would levitate the sucker on takeoffs. But for me, it wasn't worth the cost, frustration, and time.

Well the 2 strokes have um, 2 strokes and the 4 strokes have, well 4 strokes I guess. Everybody should own at least one 4 stroke just for the experience of it. Propping them right can be a challenge. When i bought my Saito 100 a couple years ago, I tried propping it for speed without going over the rpms limit. Did okay but was not use to the 4 stroke sound. Really threw me off. Since you associate speed whit a scream, and here I am cooking right along but the engine sounds like there is something wrong when its fine.

Really?! I thought a 2-stroke had 71 strokes and a 4-stroke had 723784728 strokes per cycle.

Thanks for the replies guys!

I also thought 4-stroke proiduced more torque than 2-strokes?

Ice,
See your learnin all the time, actually the four stroker has 723784729, but we will give you credit for tryin!!!

Actually this may sound (no pun) really stupid but its true, 2 vs 4 has a lot to do with your flying personallity!!! The stuff I fly, the way I fly, all that crap says 4-Stroker all day long for me!!! Just buy the 4 stroke you know you want to... All the cool kids will like you if you do...

One ting I didn't mention, a two stroke is way less expensive compaired to a four stroke, even in the same displacement.

Don

For the die hard 2 stroke fanatic:
http://mypage.yhti.net/~dmcdnld/4cycle.htm

For the die hard 4 stroke fanatic:
http://mypage.yhti.net/~dmcdnld/2cycle.htm

The rest of us wil continue to buy and fly what makes up happy.....no matter how many strokes it has.

One more question if you will...


What is the difference in noise level between a 2-stroke 0.46 engine and a 0.60 engine?


Is the .60 MUCH louder? Or just a little? Or even a subtle difference?

All the engines come with mufflers. The mfgs usually design the muffler to detract from the power as little as possible. Because of that, they almost always wind up with mufflers that produce the sound level that is the present standard. In other words, they all will wind up rating about the same db's on a meter.

The 4strokes all turn about the same rpm's. That is quite a bit slower than most 2strokes. Since the slower turning props make less noise, and prop noise is a considerable portion of the total noise, the 4strokes sound different and most people interpret that as quieter.

It's also impossible to categorize the noise level of "a 60" or "a 46" since there are dozens of each and some are simply louder than others in their own size, so there really is no answer. Other than that most are made to sound no louder than the current standard.

Comparing cats and dogs here. You'll never get the two camps to agree.

A four-stroke is about 75% less horsepowerful than a two-stroke of the same displacement. But that is at full RPM. A two stroke develops most of it's power at the top RPM. A four stroke has a much more even power curve. It has much more "low" and "middle" than a two. And, since it can spin a larger prop a four will accelerate a model better than a two; though it will probably still be behind in a quarter mile run. They weigh a bit more because of the added parts, but when you add in the relatively small and light spun aluminum muffer of a four vs the large, cast muffler of a two it narrows the difference some.

The larger prop will also give better braking effect at low RPM. That helps in landings and on pattern ships where they have to do the two downward legs of a square or diamond "loop" at the same speed as the upward legs.

So the best of all worlds is a GAS fueled two stroke swinging a really big prop.

It can come down to the type of muffler

Here is my take on it.

If you want SPEED, get a 2-stroke.

If you want POWER, get a 4-stroke.

Let's face it, there's a reason dirt-bikes use 2-strokes, and Harleys use 4-strokes

Personally, I have 2-stroke 46 - 52. Anything above that, I switch to 4-strokes (One big reason is for fuel economy)

The 4-strokes I have are 52's 70's 91's 110's and a 150. Anything above that, I go Gas

Two strokes can be very quiet. Use a good muffler, use vibration isolating soft mounts, and use larger or higher pitched props to keep the RPM down. I used to fly a .40 powered plane from the shores of the lake that I live close by. A neighbor actually mistook it for an electric plane because it was so quiet.

Four strokes can be quite loud if they aren't muffled well. If fact some of the loudest engines I have heard were four strokes. How loud can a four stroke engine be? To find out, I invite you to visit a NHRA sanctioned drag strip and stand close to the staging area as two nitro burning, supercharged rails drop the hammer as the christmas tree turns green. Back to model airplanes, if you really think the four strokes are so quiet, walk a mile away from the flying field and listen. You will still hear the four strokes after the sound of the two strokes has faded into the background.

Ding! Ding! Ding! We have a winner. The biggest difference I have found as far as performance of the two engine types is torque. If you get a OS .46 FX/AX and a Saito FA-82 you can swing a bigger prop on the Saito due to the increased torque. Everyone says the Two Strokes have more "horse power" but look at the numbers. On the Tower site an OS .46 AX puts out "Power Output: 1.65ps@16000 RPM" But I challenge you to tune this engine to spin 16,000 RPM with any prop you would actually use on this motor and expect it to live. I bet you will find yourself spinning closser to 11,000 to 12,000 RPM and who knows what the HP is at that RPM. Now practical aplication says fit a motor that fits your plane. Example. I have a Sig Something Extra and us an OS .46 FX even though a Saito FA-82 would probably be more fun I don't have the clearence for a bigger prop than the 12x4 Zinger on it. I am pretty much restricted to 3 point landings with this prop. I would have to hand launch with a 13x4 and 3 point it if I had the Saito 82. Hmm now I could get longer main gear but it would look silly.

Um, excuse me, but isn't a Saito .82 a much larger engine than a OS .46 . If you are going to compare two stroke torque to four stroke torque, shouldn't you compare the OS .46 to a four stroke that displaces approximately .46 cubic inches? Yes, the two stroke horsepower claims are highly inflated, that's because a lot of people make buying decisions based on the advertised numbers.
The torque needed to turn a prop is proportional to the RPM squared. Because of this, it actually takes more torque to turn a 10x6 at 14,000 rpm than it does to turn a 12x6 at 9000 rpm. Not understanding the exponential nature of prop load leads to the fallicy that 4 stroke engines make more torque than 2 stroke engines.

I chose these two engines because they are the common swap. You replace a .46 2 stroke with a 70-80 4 stroke not a .52. Look at every kit on the market and you will see the range of engines sudjested is comparable to my numbers above.

Buy what ever flips your trigger!

After all, it's just a hobby, not the end of the world......yet!

Only complaint I have right now is the price of fuel whether it be for a 2-stroke or a 4-stroke!

"Momma always told me, Stupid is what stupid does."

(Forrest Gump)

Ok lets compare 1.60 size
Is there a 1.60 2 stroke that can swing props like ys dz160 can and weighs less the 33 oz that might be without muffler it doesn't say so on the high side say 3 oz for muffler total 36oz out of the box ?

Just make sure it's a 1.60

I have a comment on the noise question.

Two strokes make a more annoying, higher pitched noise. Four strokes make a lower, more realistic, more agreeable noise (my opinion). However, the four stroke noise carries for a longer distance. Someone a quarter mile away from the field will probably hear the four storke louder than an equally powerful two stroke. Apparently the higher pitched sound is dissipated more rapidly as it travels through the air.

Our club was trying to secure a new field on state park land. We put on a demo flight for the homeowners organization at a nearby development. I stood at the development along with some of the homeowners. The club flew demo flights at the field site using both 2-strokes and 4-strokes. We could hardly hear the 2-strokes but the 4-strokes were very noticeable.

Hey, this thread got me to experiment. Why, because this topic must have at least five or six hundred threads about it and I haven't cared to experiment before? Well, this thread got a pretty good idea thrown out by someone with lots of experience, and I've just now got a 4stroke that'll easily compare with 2strokes I've got.

I got an OS70FL fourstroke. Turns out that OSMax worked long and hard to make it the same weight as their OS46AX twostroker. That's with mufflers on 'em both. They did things like make the backplate out of plastic. But both weigh almost the same in fighting trim.

The 70FL flew one of my airplanes great with a 13x6 prop. Unfortunately, the engine didn't run great while doing it. And it was lousy to start. So I'd swapped it out with a 46AX. And I was running that one with a 11.5x6 on that airplane. And about the only performance difference was that the twostroker took a bit more takeoff roll. And once in the air, the fourstroke didn't ever really pick up speed.

(I would suggest a very subtle but to me significant value to 4strokes. They make better engines for learning pilots because they have less range of speeds.)

Anyway.......

I decided to try the 46AX with a 13x6. It didn't really like it right away. It was really more my fault for not realizing that the needle was going to be lots more sensitive, but I didn't give it much of a test. Almost right away, I made up a 12.5x5 prop and gave it a try. It appeared to get the rpm's on step better, and had a bunch of fan area. Darned if the airplane didn't takeoff just about like it had with the 13x6/70FL. Either engine would basically "levitate" the airplane.

I'd say that as near as I got to a close comparison, that the 46AX showed about equal "torque" and better horsepower. It would accelerate the test airplane equal to what the 70FL did. I had to prop the 46AX out of it's normal envelope to get that, but it did it. And once in the air, the 46AX with less pitch and fan area had better vertical. I'm not sure why, but put it down to the extra speed the 46AX showed flying level. The 2stroke had about equal "pull" and faster airspeed.

Rule of thumb says that 1.5 is the comparison ratio. A 46size 2stroke would be equal to a 70size 4stroke. One and a half times 46 is 69.

I would hazard a bet that my 46AX (when propped to have close to the same fan area of the other engine) actually showed more torque/horsepower than the 70fl showed. And it's worth nothing to conjecture, but I'm fairly certain the 4stroke wouldn't have run if propped like a 45size.

One thing that does stand out to me about the differences, is that in the size airplanes I like the most (45size), there are very very few that have landing gear tall enough for me to run that 70fl with the prop I would certainly want to run.

What does any of this really matter? close to zip..............

Hey, you're from AG; I'm from Paso. Small world, eh?

Well, two strokes fire once every revolution, so they have more RPMs while four strokes fire once every other revolution, so they have more torque. Since four strokes fire once every other revolution, the fuel is burned more thoroughly, so they consume less fuel as less of ends up on the side of the plane. I guess four strokes also have a more scale like sound, although a two stroke 1.20 and a four stroke 1.80 sound about the same to me, but in the 40-60 size plane range, there is a noticeable difference in the sound. Four strokes sound more like a "buh-buh-buh-buh-buh-buh" while a two stroke sounds like a "mmmaaaaaaaaaaaaaaaaaaaaaaa"

Jeez, now we are comparing supercharged four stroke engines to un supercharged two strokes. But anyway, the OS 1.60 FX weighs 32.8 ounces without a muffler and the recommended props range from 16x12 to 18x10. It's maximum HP rpm is 8500. The stock muffler is 9.7 ounces but a much lighter muffler could probably be installed if you wanted an engine that is just as loud as the YS 1.60.
Also, this engine runs just fine on low nitro fuel, no YS 20/20 fuel needed or even desired.