tonywayne

Iv owned allot of 2 strokes and know them pretty well. iv heard that 2 strokes r more reliable and easier to operate. I'm interested in getting a 4 stroke. I do understand how a 4 stroke works and there more expensive but i just wanted to know the main differences between 4 and 2. Like power, fuel economy, ease of tuning, maintenance, crash resistance. anything that a long term 2 stroke person would need to know be for owning a 4 stroke.

Sport_Pilot

Hoo boy. I like four stroke for scale and two stroke for most everything else, however in some applications where wight is a consideration then a moden four stroke may be the best for the lighter weight of the newer engines thus more displacement and torque. Otherwise I think I will sit this one out, because this allways brings on a lot of meaningless arguments.

rainedave

My Feedback: (1)

As long as you pop with olive oil and don't overdo the salt[X(]

tonywayne

I dont want to start meaningless arguments. i just want to no the basic pros and cons of 4 and 2 stroke. Let me put this this way. 2 strokes r extremely simple and reliable in my opinion. What about 4 strokes?

Sandyt

Tony

There are many more moving parts in a 4 stroke engine, including a cam, pushrods, and valves. More parts = more complexity and probably a greater chance of some part failing. Maximum RPM must be kept within certain limits or engine damage will result. However, they actually work really well. You have to adjust the valves once in a while, but that is the only extra maintenance you need. They are difficult to lube with after-run oil, so many owners neglect this task.

Running wise, a 4 stroke will often provide a quicker throttle response than a 2 stroke. Depending on the application, this may not be a big deal. For all-out high speed horsepower, it is hard to beat a screaming 2 stroke with a tuned pipe, but for 3D type maneuvers, a 4 stroke is often better.

I happen to love the sound of a 4 stroke and therefore use them in most of my models. I also love to tinker with them, so any extra maintenance is OK too. My advice: buy one and try it.

Sandy T

Hobbsy

My Feedback: (102)

Sorry you got that loser answer, based on my own experience, fourstrokes deadstick far less often than two strokes. Once you get an ear for tuning a fourstroke and experience fourstroke flight you won't go back. There is plenty of help here and plenty of BS but it's easy to sort that out. I fly only FourStrokes and Diesels now a days and haven't had a twostroke glow off the ground in about 5 years. Making the jump is no biggy. You'll hear reasons why to buy every brand made and why to not buy some, if you have a fave, go for it.

tonywayne

Thanks guys. Thats said, what about brands and good values of 4 strokes. A few opinions on that and ill be happy and just my try my first 4 cycle.

Hobbsy

My Feedback: (102)

Well, I'm a Saito and Enya guy, I also have an OS .52 fourstroke that is a genuine jewel. Those are my picks.

rainedave

My Feedback: (1)

tonywayne, I'm not suggesting you're one of these people, but some - IMHO - tend to get too serious about stuff like this.

I own both, and for me it is strictly a matter of character. Some designs just look, sound and fly better with 4-strokes - again, my opinion - like a Cub for example. Other planes seem to look and sound absurd with 4-strokes, like a Curare, for example.

Sandyt is discussing performance which is also important to consider (I know, it's everything to a lot of people).

I would recommend you buy one and give it a try. You will see what I mean about how they have a character all their own. And that might lead you to build some new designs that you've may have overlooked in the past.

daveopam

My Feedback: (9)

I have both. I was a two stroke guy for 15 years. I still think they have there place. That being said a 4-stroke is less trouble than a 2-stroke. Less trouble= fewer dead sticks and less turning the needles. The valves do have to be set a few times a year. It's a 5-10 minute job. I have four Saitos. I started with a 72. I had to tune it with a tach until I got used to the sound. Now I can tune one by ear. However I rarely tune it. During the summer I never touch the needles. This time of year when the weather cools there is some temperature related adjustments. It seems like I tune my two strokes several times a day.
I mentioned Saito because that is what I have. OS and YS also make fine engines. I just would not suggest the YS for a first time 4-stroke user. Once they are set they are fine. They just seam to be a litle harder to set. If someone you fly with runs them then you would be fine. No body in our club runs one and help is 100 miles away for me. So I don't own one.

David

tonywayne

Great thread! Thanks alot gentlemen for you awesome opinions. But just one thing no ones mentioned yet. What about fuel economy between a 2 and 4 strk?

Hobbsy

My Feedback: (102)

When two engines make the same power, the configuration does not effect the fuel consumption much.

NM2K

My Feedback: (14)

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Two-strokes have a lower parts count. Some confuse this with simplicity. I can accept that.

However, when it comes to theory of operation and all of the "tricks" that must be learned for both types of engines, I see them as being equal. For the moment, let us limit this discussion to engines that draw their fuel via suction only.

As far as more reliable goes, once adjusted properly, it has been my experience that four-strokes tend to stay running more often than two-strokes. With that said, it is very, very close. So close that I wouldn't base a buying decision that placed reliability at the top of the requirements with either one type or the other. To me, it would come down to the actual manufacturer and model of the engine.

Four-strokes have more parts to wear out than two-strokes. This is obvious. Yet it has not been a significant factor in my years of operating both types of engines.

Two-strokes, of equal displacement, can swing as large a prop at better rpm than the majority of four-strokes of equal displacement. Yep, it has proven to be true, time and time again. You may have to do cartwheels and handstands in order to get it to happen (adjust nitro, glow plug, even port timing/size and cooling air flow), but it has proven to be true, at least to me.

Are four-strokes worth the additional cost? To me they are. To others they may not be be. My engine collection is half two and half four-strokes. I like them all.

rajul

My Feedback: (58)

4C engines have the ability to swing larger props, and that's an advantage for certain applications e.g. 3D flight. In terms of reliability, I think 2C and 4C are the same, given that proper operating procedures and maintenance are done. 4C engines require a little more adjustment on the valve gaps, which I do once a year. 4C also requires a little more safety precaution in preventing prop throwing (backfiring) by not overleaning the high end, and using double jam prop nuts. A tach is a must for tuning. Other nice things about a 4C is the "put-put" sound (unlike the high pitch 2C), and less mess to clean up after a day of flying. My ratio of 4C:2C engines is getting larger

rainedave

My Feedback: (1)

When I first started in r/c it was the cool factor that led me to buy a .91 Surpass. That was followed by a .40 and then a .70 Surpass, which was converted to CH ignition for a Lanzo Record Breaker (another story). They are a lot of fun to run and offer a nice change from 2-cycles. I like owning both. And I think each type has it's strong points and weaknesses, like anything else. Sometimes I need to have my ears split and get that ringing that throws off your equalibrium. It's also fun to listen to the purr of the 4-strokes. I've also noticed that the exhaust smells different from 4-strokes, which I like. *E-power folks are shaking their heads*

BTW, I just ran my old .40 Surpass this past weekend for the first time since 1992. I did check the valve clearance, but left in the original OS F glow plug. It still does around 11,000 with an APC 11x6 which is good for that engine. I plan to put it back in use and expect to get a lot more time out of it. And I wore out an Ace 4-40 with that thing.

I'd like to try a Saito. Especially since they have become so popular lately. I had a friend who had an old Enya .80. That was an impressive engine, too.

XJet

4-stroke pro's:

- they're quiet
- they're lighter for a given displacement
- they're sometimes ligher for a given power
- once set up, they're less problematic (ie: more tolerant of mixture etc).
- they can use more efficient props in slow planes(more thrust per HP)
- *some* (but not all) are more fuel-efficient than 2-strokes

4-stroke con's:
- they cost more to buy
- they do require regular (but not frequent) maintenance
- they do prefer a little more nitro than 2-strokes
- they're not so good in *fast* planes (inefficiencies of very coarse-pitched props)

that's just off the top of my head though.

I have four 4-stroke engines (2xSaito, 1xTT, 1x HP) and they're all wonderful engines -- each with its own personality, strengths and weaknesses.

I also have seven 2-stroke engines and *most* of them are great (the TigerShark is *useless* and I'm not so sure about the GMS -- it's worn out already and never ran that well). They are 3 x TT46Pro, 2 x ST90, 1 x GMS32 and 1 x TigerShark 56AR.

The problem is that I just *love* engines, no matter what type -- but, as they say "[a] different [number of] strokes for different folks"

However, I think that everyone should haev at least *one* 4-stroke -- just so they can experience the difference for themselves.

blw

My Feedback: (3)

The main advantage that I like is the more instantaneous power and more power at lower RPMs. I like to fly pattern and I don't really want a screaming 2 stroke for up lines, etc. You have to wait for a 2 stroke to rev up and put out power.

I have a couple of 2 strokes only because they are really good engines. If not for that, I would only have 4 strokes.

Kweasel

My Feedback: (29)

The performance equivalents between fourstroks and average sport twostrokes are very close these days. Beyond that its a matter of subject, pick whatever you like.

Sport_Pilot

My experiance is that four strokes dead stick more often than two strokes. Four strokes are less tolerant of inverted positions and I have had one occurance of a near dead stick from a broken rocker cradle. Other wise I think the dead stick issue when comparing the same quality of two strokes to four strokes (there are a lot more cheap two strokes out there) are the same.

Hobbsy

My Feedback: (102)

Any time a fourstroke deadsticks, the flight was began with the engine too lean. Most fourstrokes will tolerate a lot of too rich but zero too lean.

Sport_Pilot

Actually the opposite is true, however since four strokes are lighter for a given displacement in the smaller sizes, then that larger four stroke will indeed have more torque than the same weight but smaller displacement two stroke.

Opps! I was going to sit this out. Ok. I'm back in my seat.[sm=72_72.gif]

RVM

From what I've seen, currently, within glow engines, the best 4-strokes have a better power:weight than the best 2-strokes. Also, the fuel consumption can be a little better, and I have found that power is much more "instantaneous" with a 4-stroke than with a 2-stroke. Also, 4-strokes seem to run a lot smoother.

Sport_Pilot

Yeah. Sure. Whatever. Real smooth.[sm=spinnyeyes.gif]

Stoneweapon

I used the OS Max 70 Surpass, 91 Surpass, FS20 and FS60 in my models and tested the OS FS120 with pump, the older FS120, the Saito 90 twin and the Magnum XL FS52 on the bench.

They are a good choice if you want a light engine, which should operate around 10000 rpm. It is hard for a two stroke of the same weight to outperform a four stroke in this rpm range. Most likely the two stroke is heavier because he needs a bulky exhaust system and he will have problems to swing the same props with good transition. This can be solved if you use a "throttle muffler" for 3D applications with the two stroke but the aggressive response of a four stroke is difficult to beat.
If the desired rpm range is higher than 13000 the two strokes will probably do better.

A big advantage is that you don't need to think much about the exhaust system of a four stroke.
They perform very well with the simple stock muffler.

Normally there is no need to care about the displacement of your engine except you must observe competition rules.
If you just decide considering the power/weight ratio and other parameters which are important for your model you will often find that a four stroke is the best choice.

The reliability of every model engine depends on the user but I think the four strokes keep running a little longer if they have a few seconds of lean running in the air. This can be a deception because it is almost impossible to hear if they are too lean especially if they are airborne.
My FS70 and FS91 kept running until the tank was totally dry. There was no sign of getting lean when the tank was almost empty. They just switched off and that was it. Sometimes I wished that there would be at least a little sign of being low on fuel.

The run in process lasts a little longer than with the "ready out of the box" ABN 2-strokes because most of the four strokes are ringed engines but in return they last very long. The tendency to backfire will be reduced after a few running hours.

I would recommend a OS 52, 70 or 91 as a first four stroke. They are easy to start with a ordinary starter and it is impossible to hear bad things about them, exept the cracked valve springs a few years ago but this is not a problem if you by a new engine of the latest Surpass II series. The OS 4-strokes dont need much nitro. They run perfect with 10%.

scratchonly

I fly only 4S and the problems I have had are the same as for 2S; bad plugs, holes in fuel lines, tank location, dirt in fuel systems. I adjust my engines far less than my 2S flying friends who seem to be constantly trying to burn out their engines. I think after run oil is a must as you can't run the crankcase dry like a 2S.