indgroove

After reading various threads on 2 vs. 4 stroke. It seems that if one wants speed one should go for a 2 stroke. If one wants to pull vertical he should chose a 4 stroke.
Am I correct or is there more to it? (besides cost and sound)
Thanks,
Indgroove

Zippi

My Feedback: (10)

indgroove,

For the average weekend flyer it's just a matter of preference. The 4 strokes burn less fuel, swing a bigger prop, and sounds good, but cost more. Both 2 & 4 stroke engines have speed and power. If your a serious competitor then you may want to take a better look at what to run.

jay2000dakota

I would have to disagree, Speed and vertical pull is all the prop section. For example, a 15X10 is going to give a higher top speed but you will have less vertical performance, were as a 15X6 or 15X5 will have less top speed but perform better vertically (at least that how I understand it). As for the 2 or 4 stroke arguement. New 4 strokes are very light, they have alot more power then pervious generations and most importantly, they are reliable. Theres no more constant carb tuning, 4 stroke needle valves rarely need to be adjusted (once a year, if that), only after the break in period or if the prop is changed. For those reasons I will never own a 2 stroke again, but 4 strokes do have their downsides, they are more expensive and require more detailed care for breaking them in and winter storage. If this is your first 4 stroke make sure to read the manual about adjusting the carb and the break in procedure, I know no one reads the manual but 4 strokes are alittle different and its good to walk to path before you drive down it.

jay2000dakota

SAITO ALL THE WAY BOYS!

w8ye

My Feedback: (16)

What's a two stroke? That must be those engines I got rid of about 10 years ago?

I have Saito and OS Surpass. Are there other kinds of engines?

A four stroke can give you a pretty good show speed wise if it is set up for speed but I like their low end torque.

Jetdesign

My Feedback: (8)

Depends. If you're serious, there's YS. If you just want to play games, there's all the rest

ChuckW

Good question. I remember having something like that in the past but I'm all grown up now.

I'm kidding.

Yes, I do prefer a 4-stroke but there is nothing wrong with a good 2-stroke either (I own a few). Both can go fast and both can go vertical with the right prop selection. Sometimes the plane will dictate what engine to run depending on how much room there is in the engine area, available prop clearance, specific application, etc. Generally for sport flying though, use what you like.

Jester241

It's all a matter of which puts a bigger smile on your face. Its like do you like blonds(4-strokes) or brunettes(2-strokes) better? The only time you might want to use a 2-stroke instead of a 4-stroke is when its pretty cold out. Many guys will tell you 4-strokes dont like to idle to long in the cold because they dont produce alot of heat to keep the glow plug hot. You can(I always do regardless) use an onboard glow driver that helps ALOT,but they still can be alittle unreliable in the cold.

And I like blonds the best!!! Too bad blonds are harder on your wallet. [>:]

Stick 40

I have to agree with both, there is a place and plane for all engines and motors. I like my Saito's as much as the next, but my Enya .80 XF with the tuned pipe on my Sporster .60 is a blast!!!!

I have been having good luck with my Saito .56 in the cold, a little harder to start but idle seems alright.

indgroove

Thanks for every response. Since I am a intermediate pilot, I entend to fly through the winter. I want to get all the stick time I can. I dont want to lose what skill I have developed.

I am flying a Ultra Stick 40 and battle Axe through the cold months. They have 2 strokes in them.
I have 4 strokes on my Space Walker and 4 * 120. I have put thoses planes on standby until Spring.
If 2 strokes do better in the cold, then that settles it for me.
I am thinking of adding another ultra stick 60 or a 4* 60. and using it this winter too.

I want to have 2 planes ready to fly at all times. When I crashed my kadet, (lost it in the sun) I didn't have anything to fly until I got the Spacewalker (6 weeks later). Of course I lost all confidence when landing so I bought a used (& cheap) Ultra Stick 40 to practice with . Now I am much better than I was 3 months ago.

thanks again to all and to this forum!!!
Indgroove

Rcpilot

My Feedback: (78)

4 stroke DO NOT swing a bigger prop. Thats a MYTH.

Let's take your 91 size engine, for example. Most guys would run a 14-6 prop on a .91 engine. 2 stroke or 4 stroke... both engines run the same prop.

How about a 120 size engine? Same prop again. 15-8 or 15-10.

The DIFFERENCE is the 4 stroke will only turn the prop around the 8000-10,000RPM range while the 2 stroke is going to turn it a few thousand higher RPM.

Guys like to talk about torque on a 4 stroke. 3D fliers like to tell you a 4 stroke will rev faster. REALLY? [:-] Anybody ever set a .91 Super Tiger (2 stroke) against a 91 Saito (4 stroke) with the same prop and tached them both from idle to wide open? I'll bet you dollars to donuts the difference is immeasurable.

4 strokes just sound cool and look cool and cost more money. They DO NOT out perform the 2 stroke in ANY FASHION except fuel economy.

Slats!

My Feedback: (1)

In simplistic terms can anyone confirm the conversion of a 2 stroke to 4 stroke size wise (just simple rule of thumb without the disadvantages and advantages).

To get the same power in a 45 (2 stroke) you would need a what size in a four stroke

60 (2 stroke) = what size four stroke

90 (2 Stroke) = what size four stroke

Rcpilot

My Feedback: (78)

45 (2 stroke) = 60-65 size 4 stroke

60 (2 stroke) = 90 size 4 stroke

90 (2 Stroke) = 120 size 4 stroke

But thats not really an accurate comparison. The 90 size 2 stroke and 4 stroke will BOTH turn the same prop. The 4 stroke just turns it at less RPM because they make less HP.

Slats!

My Feedback: (1)

Thats great I know there are 1000 ways to look at this just wanted some sort of bench mark as I am looking to convert 2 strokes to 4 strokes. Thanks

Slats!

My Feedback: (1)

One last question is looking at the HP of the engines as a comparison useless.

ChuckW

I disagree on the HP thing. 4-strokes will almost always turn slower than a 2-stroke whether it is an RC engine, a string trimmer or a motorcycle. It has to do with the mechanics of the engine more than power output.

On the props, the 14x6 is just one example. Most .91 4-strokes will also happily turn a 14x8, a 15x6 or other various sizes. Even a smaller Saito .82 will spin the 14x6 just fine. The 4-strokes do have more torque and they have it at a lower RPM range. There are times when that is advantageous. Of course there are times when the higher RPM 2-stroke makes more sense for an application too. In fact you could make either engine work well for many applications with the right prop.

It is a little more complex than just looks, sound and cost.

Neither is necessarily better and both have their time and place. For general sport flying, pick what you like. For me that is usually a 4-stroke but a few 2-strokes are in my fleet as well.

ChuckW

YES

Each manufacturer measures them differently and the RPM range they are spec'd at is generally way beyond what most of us will ever see in the real world.

Take the OS .46-AX for example. It is an excellent 2-stroke and it is advertised as 1.65ps (approx 1.63HP) @ 16,000RPM. Some people might be seeing close to 16,000 with very specific set ups and specific applications such as racing. Most of us usually won't see over 12,000RPM or so out of that same engine though in general sport flying. The test is the real world and the particular engine in this example happens to do very well.

Rcpilot

My Feedback: (78)

Agreed, the 91 4 strokes will turn a 14-8 or even a 15-6. And so will the 2 stroke engine. You can overprop ANY engine if you aren't worried about RPMs.

My original point was simply to point out that when guys say 4 strokes have more torque .... thats a myth. Any given 2 stroke will ALWAYS turn the same size prop as the 4 stroke. And the 2 stroke will turn it faster. The 2 stroke wins every time. The idea that a 4 stroke somehow makes more torque because it fires every other revolution is absolutely not true.

ChuckW

Agreed 100%, if people use that logic it should actually make less torque. It tends to make more low end torque though because of higher cylinder pressure on the power stroke and that power stroke occurs for a longer duration of the crankshaft revolution than it does on a 2-stroke. Some of that is obviously negated by the less frequent power stroke on the 4-stroke engine. Things like camshaft profile and camshaft timing can also have an affect of course.

I agree that the power figures on identical displacement engines are likely equal or may even favor the 2-stroke but most people won't use say a .91 4-stroke on the same application as a .91 2-stroke. They'd put it where a .60 size 2-stroke would normally go.

Bottom line, both quality 2-strokes and 4-strokes work very well. Pick what you like and have fun.