Difference between 2-stroke and 4-stroke.
 

I have heard of 2stroke, 4stroke, and gas engines. I know 2stroke engines are glow. My question is, are 4stroke engines glow also, or do they all run gas? I appreciate any and all information you guys have.

RE: Difference between 2-stroke and 4-stroke.
 

You have 2 stroke glow and 4 stroke glow, then you have 2 stroke gas and 4 stroke gas.

RE: Difference between 2-stroke and 4-stroke.
 

like one of these http://www3.towerhobbies.com/cgi-bin/wti0093p?&C=GCI ?
ya their glow

RE: Difference between 2-stroke and 4-stroke.
 

What about saito engines? What are they usually? Specifically a saito FA56?

RE: Difference between 2-stroke and 4-stroke.
 

All Saito engines are 4-strokes

most are glow, one is gas

The FA56 is glow

RE: Difference between 2-stroke and 4-stroke.
 

The Saito .56, like most Saito engines, is a 4-stroke glow engine. It runs on the same type of glow fuel as most other RC engines and uses a glow plug rather than a spark ignition system.

Saito does make a couple of larger 4-stroke engines that run on gasoline though. These are spark ignition engines that use an electronic ignition system with a spark plug just similar to mowers, motorcycles and cars.

2-strokes, 4-strokes, glow, gasoline and everything else all have their place. Everything offers some advantages and gives up others.

RE: Difference between 2-stroke and 4-stroke.
 

The Saito is a glow fueled engine.
4 strokers sound a little better but weigh more and COST MORE and are a little more complicated...more moving parts etc.
2 strokers have a better power to weight ratio often better throttle control, are simpler in basic design, simpler to trouble shoot and cost less.
The four strokes are said to be quieter but actually they just produce a less annoying note. Decibels usually run close. So if Noise Perception is important to keeping your field a four stroke is priceless.
RC engine quality in either one has never been better so enjoy!

RE: Difference between 2-stroke and 4-stroke.
 

Actually, 4-strokes have better throttle response, and although they cost more, you will save that in fuel savings in one season.

Also, 2-strokes turn more RPM, but 4-strokes have more power.

Think about it this way...

A Dirt Bike is a 2-stroke. A Harley is a 4-stroke.

RE: Difference between 2-stroke and 4-stroke.
 

I am looking to buy a used at-6 texan equiped with the saito FA56. Does this sound like it could pull this plane? the plane itself has a 61"wingspan, retracts, flaps.

RE: Difference between 2-stroke and 4-stroke.
 

The main difference between 2 stroke and 4 stroke engines when comparing them side by side with cubic inch size is 2 strokes are generally less cost, more powerful, fewer moving parts, more crash damage resistant, lighter, better selection of sizes to fit more models........

4 stroke model engines are engineering marvels, most brands and sizes can be matched up with a corresponding airframe to deliver either stupendous or "scale like" performance....whatever you want.

RE: Difference between 2-stroke and 4-stroke.
 

That sounds like it will fly it in a very scale mannor

RE: Difference between 2-stroke and 4-stroke.
 

You will be flying that one "on the wing". That is, you won't have a ton of power left over. It will however, fly fairly scale like. A lot depends on how it was built, how much it weighs. Hope it won't be your first plane, or you have someone with some experience help you.

RE: Difference between 2-stroke and 4-stroke.
 

Right.

All too often we see the "Four Strokes have more power & use less fuel" statements here.

In a direct comparison of identical displacement TWO STROKE engines produce more power, but they need to rev higher than four strokers to do so.

To equate power output, you most purchase a larger displacement four stroke engine. However since the four stroke engine produces more torque at a lower RPM, larger props CAN be swung with the larger sized engines. At equal displacements this is not necessarily true and is marketing hype.

By the time you move up to the larger four stroke size, fuel utilization is only marginally less for an equally performing four stroke engine.

However the four stroke engines sound so nice, and some are SO tolerant of mis-tuning ( Saitos ) that we tend to like them a lot.

Ultimately you can use whatever you wish to use for your plane.

RE: Difference between 2-stroke and 4-stroke.
 

Let's look at the numbers.

It is generally accepted that a plane with a 60-size 2-stroke would need a 90-size 4-stroke.

The OS 61FX has a displacement of .607 Cubic Inches
The OS 91 Surpass II has a displacement of .912 Cubic Inches

The 61 will run at approximately 11,500 RPM
The 91 will run at approximately 9,500 RPM

This means that for every rotation of the 61 it takes in .607ci of fuel/air mixture, or 6980.5ci per minute.
Meanwhile the 91 takes in .912ci of mixture every OTHER rotation, or 4332ci per minute.

6980.5 - 4332 = 2648.5

So the 91 is using less than 1/3 of what the 61 is using... AND this does not take into account the amount of fuel loss generated by a 2-stroke (For a 2-stroke to operate, the new mixture blows out the exhausted mixture and some of the new mixture is blown out along with it - which is one reason that 2-strokes slime your airplane so badly).

If you burn 3 gallons of fuel per month at $20/gallon, you will save $20 a month

Cost of a 61FX = $180
Cost of a 91S = $300

So in 6 months, the 4-stroke will have paid for itself, kept your airplane cleaner, made your airplane sound better, and in all probability, contributed to world peace. :D

So not even taking mixture loss into account, a 91 4-stroke burns about 1/3 less fuel that a 61 2-stroke, it swings a bigger prop, and it doesn't spit slime all over your plane.

RE: Difference between 2-stroke and 4-stroke.
 

In the real world that 1/3 less fuel translates to about 1/4 - 1/6 less fuel actually used.

In practice I find my four strokers are not saving me anything significant in terms of fuel usage over the 2 stroke engines I could have used in their place.

Not that there is anything wrong with four stroke engines ( I do like them ), but this is not the big factor that it seems made out to be.

When dealing with .40 - 1.20 sized planes cost savings are not significant.

Going larger things change, but by the time I hit 1.80 CU I'm buring up so much glow fuel on my four strokers, that I'm better off going to gas instead.

My 1.80 CU four strokers seem to go through a gallon and a half a day at the airfield at a minimum.

RE: Difference between 2-stroke and 4-stroke.
 

opjose, would that by chance be a Saito?

RE: Difference between 2-stroke and 4-stroke.
 

There used to be a british tv show that explained how mechanics of things work, and it had little corny cartoons with it too. It was my favorite show, and the one on IC engines was the best. I will always remember SUCK SQUASH BANG BLOW!

RE: Difference between 2-stroke and 4-stroke.
 

Saito's, Magnums, O.S.'s, etc.

I'm not talking about the sloberingly rich glow fuel consuming mis-tuned engines either.

I consider my Saito's "sippers" once they are properly tuned, compared to my larger Magnum's or even my OS four strokers of equal size.


Of course if I don't get at least eight flights a day on a particularly day, I've hauled out to the airfield, then it's a bad day!


As one person so humourosly put it.

"Isn't it aweful? All that glow fuel sitting in the jug, so sad. "


I'm not knocking four strokers. I think they are great, and thus far VERY reliable...

But two strokers also work fine particularly within the .40 - .90 sized plane range.


I'll also futher add, that on my Skybolts, a Tower Hobbies .75 2 stroker outperforms my O.S. FS .91 on an identical plane, and they both consume an almost identical amount of fuel on equally timed runs.

RE: Difference between 2-stroke and 4-stroke.
 

Then you might enjoy this Brett.

I got bored one day and created this GIF:

http://www.minnartist.com/RCU/grafix/OS91_700.gif

RE: Difference between 2-stroke and 4-stroke.
 

lol, thats really cool (better than the one on wikipedia) , make that w/ solidworks?

the 4 stroke/2 stroke debate will go on.
the way i look at is any plane that will fly the way i want it to with a .50 ci 2 stroke or smaller will get a 2 stroke.
any plane that needs more power than a .50 ci 2 stroke will get a 4 stroke.
their are exceptions, but thats how i usually do it

RE: Difference between 2-stroke and 4-stroke.
 

If you like the sound of corn grinders then 2 strokes are for you.. [X(]:D

RE: Difference between 2-stroke and 4-stroke.
 

Right clicked and saved! Would make a sweet avatar, thanks Minnflyer!

RE: Difference between 2-stroke and 4-stroke.
 

You'll never get the file small enough for an Avatar.

My engine choices are:

Depending on the plane, a 2 or 4-stroke for 40 - 60 size planes.

From 60 - 120, I go 4-stroke.

Above that, Gassers

RE: Difference between 2-stroke and 4-stroke.
 

i thought the same thing. need a animated gif editor though. dont have one at the moment

RE: Difference between 2-stroke and 4-stroke.
 

Ok, here it is small enough for an avatar:

http://www.minnartist.com/RCU/grafix/OS91A.gif

RE: Difference between 2-stroke and 4-stroke.
 

it still doesnt like it. says file is to large. the only thing i can think of is if you right click on it it says (size 6.92 kb, 8.00 kb on disk)
yay for a 40-60 sized 4 stroke lol

RE: Difference between 2-stroke and 4-stroke.
 

Now if we could only get one with the YS supercharging system displayed...:D

RE: Difference between 2-stroke and 4-stroke.
 

Old thread, but the debate is always fresh and fun ..... you guys left one important factor in choosing a 2-stroke of a smaller displacement than an equivalent but the needed 25% larger 4-stroke to get equal performance (as in SPEED, ultimately what we WANT!). And that is the weight savings in choosing a 2-stroke over the BIGGER4-stroke!

Point in fact - I have a BHModels "60 size" P-51 and so does a friend, they are identical in every way in the build, except the motors. I have a <font>SuperTigre</font><font> G75 in mine and he has a Saito 100FS in his. My 2-stroke P-51 blows his 4-Stroker into the weeds, over 16 MPHfaster on a police radar gun. His Saito runs sweet ... when it's not "being a woman" (finicky bit@#); while my 2-Stroke SuperTigre never so much as hicups ever. We both burn through a gallon os 15% Nitro in the same damn time. (so much for the less fuel usage of a 4-Stroke story)

I also think my P-51 sounds more like a Merlin-Packard V12 at full gallop than his Saito does, sputtering like an old Harley.

I used to race some Motocross back in the late 70's while in the USAF, I had </font>Husqvarna<font> 360(cc), which I still have and ride (and keep rebuilding), and I'll take that baby against a KTM500 4-Stroker any day and it will still blow it into the weeds as well, even though the KTM with todays technology is pretty damn light .... but still not as light as a fine Swed 2 stroker ... from the late 70's..
</font>

RE: Difference between 2-stroke and 4-stroke.
 

I found the hard way that 2C engines dont run too well inverted as the carb is upside down. In the case of 4C, the carb becomes right way up when the engine is inverted. Just what I observed

Ameyam

RE: Difference between 2-stroke and 4-stroke.
 

So when your 4C is upright, it's carb is upside down, thus wouldn't work "too well" by your logic, right? Wrong both ways. The only thing affected with any of them is the starting. And once you've got the plumbing right and figured out what they need for choking (some don't need it and work just excellently well, some do and don't work very well) they usually aren't much problem.

There have only been a few engines that are difficult to handle when their carbs point down. Most often, it's when they need manual choking to prime, and since 2 cycles usually have the carb in front, where you can reach the carb easily even if cowled. Only 4 cycles that need manual choking have a problem when their carbs point toward the earth and are inside cowls.

RE: Difference between 2-stroke and 4-stroke.
 

Actually, I and many other at my field have had problems with inverted 2C engines. It has got to do with starting but also with tuning. We found that it would rich at full tank and lean out as you go through the tank. On a 3D airplane, this was an issue.

Apparently others had the same problem. I couldnt keep that engine running at all. When I finally gave up, one of the more experienced members came up to me and told that he had the same issue with the same airplane. So much so that he does not buy airplanes with inverted engines. He takes them if the engine is at 45 or 90 Deg

Ameyam

RE: Difference between 2-stroke and 4-stroke.
 

Actually some of the newer 4 strokes have the same problem as most 2 strokes. Oversized carbs. Because they had less power older four strokes had smaller carbs, thus better fuel draw and throttle response. To get more power some have gone to larger carbs.

RE: Difference between 2-stroke and 4-stroke.
 

If you look at the relationship of the tank to the carb, you can usually solve those problems before you have them.

Why would a specific airplane "always" have the same problem? Think it might be the design? The tank too low or too high?

I very often use uniflow tank plumbing. However, with my H9 Corsair (engine at 9o'clock) I had a siphoning problem. Rerouted the lines and had a draw problem. Actually, it was a priming problem as the lines were not only empty but the carb could barely be finger choked. So I got re-did the plumbing to the usual arrangement. That airplane went from a "leaky" problem, to a "dry" problem, to no problem. The H9 Spitfire engine is straight down. When I was building it, the Corsair was in it's wet phase. The Spit wound up having the same problem as the Corsair when it had the same plumbing. And again as well. In both, that very large tank winds up with enough fuel head over the carb (90degree or inverted) to cause headaches.

Bottom line is that every 6 o'clock engine I've got starts and runs great. But since I like to have the option of uniflow, I usually don't go for 6 o'clock as 1st choice.

There was only one engine in 50+ years that I never got to run straight down. OS produced a 4cycle "lightweight" awhile back and it's downdraft carb was basically a guaranteed flooded engine producer when pointed toward the sky. They did advertise that it started great dry. The opposite was also true. It was a disaster to start wet. If it did, you might wind up sending it back for repairs. They did send me a new replacement. I ran it upright and put it back in the box. Someday I might try it side mounted or upright. Otherwise it stays in the box.

RE: Difference between 2-stroke and 4-stroke.
 

When in put a 4C 91FS in the same airplane, I did lower the tank to about the same level as the carb. The problems seemed to go away but I have flown it only one day since and I didnt go 3D with it.

Will again try it in a month and if it works, I will tell everyone what needs to be done. Its a Flip3D /UCS 60 clone from Phoenix and I know a number of people on the field have it because of the way it flies but dont fly it because the engine issues or because its tail has a reputation for falling off if it is not strengthened with fibreglass cloth. Picture attached was taken on a day when I couldnt fly it further because the tail wheel broke during a dead-stick landing

Ameyam

RE: Difference between 2-stroke and 4-stroke.
 

Exactly!

I run dozens of 2C and 4C engines inverted, and any problems tend to boil down to plumbing or mistuning.

Even tank height differences only affect starting when the engine is on the ground, usually due to minor fuel siphoning.