2 stroke compared to 4 stroke
 

Hi All'

Been flyin 2 strokes for about 2 years now and have just aquiered a couple of 4 strokes. I'm confused as to the power comparisons between the two type engines. Is there a chart or some formula you use to compare 2 and 4 stroke engines. For example: If I have a 2 stroke .61 and want to convert the plane to a 4 stroke, how do I know what size 4 stroke I will need. This just an example. What I would like is to have a complete comparison chart for future use.

Thanks
Tom

RE: 2 stroke compared to 4 stroke
 

A lot depends on the specific engine, but I generally say:

40 - 46 (2-stroke) = 52 - 70 (4-stroke)

55 - 65 = 91 - 100

75 - 90 = 110 -125

Larger than that, Gasoline

RE: 2 stroke compared to 4 stroke
 

I don't know of a chart, but 2 strokes are generally more powerful than 4 strokes of the same size. Each type produces a different kind of power in different ways. A 4 stroke will typically give power quicker without having to build up rpms. They are also good for pulling, such as vertical lines.

There are exceptions, of course.

RE: 2 stroke compared to 4 stroke
 

Minn has you going down the right road. For me I think a 33% increase is about right. So 90 x 1.33=120.

david

RE: 2 stroke compared to 4 stroke
 

Wow, no one is going to argue with 3 moderators! They have it right. But I'd also add that a 1.8 fourstroke pretty much equals a 1.2 two stroker. That would be my preference before switching to gas.

RE: 2 stroke compared to 4 stroke
 

From a practical point, when you get to big 4 strokes, the cost of fuel becomes an issue for me. A Saito 180 is pretty thirsty. That is why I am converting it to gasoline.

There are so many small gassers out there now, that a big 4 stroke just does not make sense for me, although I love the sound!

I am playing with several 4 stroke Ryobi gassers, and am looking for a Stihl 4-Mix for converting.

Sincerely, Richard

RE: 2 stroke compared to 4 stroke
 

Since when??? :D

RE: 2 stroke compared to 4 stroke
 

what is there to argue with, they stated it pretty much correctly.

RE: 2 stroke compared to 4 stroke
 

The world needs cheaper glow fuel. Or cheaper Saito gassers.

RE: 2 stroke compared to 4 stroke
 

YS is the best of both worlds IMO. You can get pretty good RPM's with more torque.
In YS land, a 1.40 4-stroke = a 1.20 2-stroke.

RE: 2 stroke compared to 4 stroke
 

When should we expect to see a YS gasser? I have not even heard of a conversion. Of course all of the silicone rubber parts would have to be changed. And/or we need to see cheaper YS engines.

Sincerely, Richard

RE: 2 stroke compared to 4 stroke
 

If you never own a YS, you'll never know the true value of them. They really are superior to all the rest both in power and value.

YS63 is the same power as a Saito 82
YS1.10 is just a bit more power than a Saito 1.25
YS1.40 is just a bit more power than a Saito 1.80
I own all these engines and have compared the numbers and thrust.

All that said, when you compare the power/weight ratio, they are much closer.
I give the edge on fuel economy to YS for doing it with less displacement.

RE: 2 stroke compared to 4 stroke
 

No argument there, I have rebuilt a few YS for a friend of mine, and they are indeed a fine machine. My question was when should we expect a gasser from them. Nitro based glow fuel is a diminishing resource, I think, and I think YS likes a little nitro in their fuel, not so?

Sincerely, Richard

RE: 2 stroke compared to 4 stroke
 

Most all of my engines run just fine off of zero percentage of nitromethane fuel. So I don't really need any nitro in the glow fuel.
Nitromethane is mostly a USA only kind of thing anyway. Everyone outside of the USA is running zero nitro or model diesel fuel or gasoline (petrol) of course.

RE: 2 stroke compared to 4 stroke
 

I wouldn't expect a gasser from them. It would give us less power in a heavier package.

RE: 2 stroke compared to 4 stroke
 

Yes, much closer. But the saito 82 weighs less than the YS 63. So, saito has better power-to-weight ratio. Now that might change with the new YS 70

RE: 2 stroke compared to 4 stroke
 

On my scale, with mufflers they are within a tenth of an ounce. That's the same to me.

RE: 2 stroke compared to 4 stroke
 

Ummmm, we are getting off track here.......

Let's post comparisons between the 2 types of engines. A lot of readers can get something out of it if we do.

RE: 2 stroke compared to 4 stroke
 

The main problem with the YS175 gassie is cooling for the current engine weight. Power I hear is about that of their 160 glow but the cooling is ineffective. The engine would need to be beefier to serve as heat sink and weight kills these things before they even start. Competitors in Pattern and Scale hate weight

It's been in the works for at least a year that I am aware. It may be at least another year or two before it is ready for market. Expect to pay through the nose too. I'd guess at least a grand. If it trully works right, it would be worth it.

The major issue I have with 4 strokes has always been maintenance, to go along with the every day running of the thing. The average competitor that runs a YS170 for example will burn about 1200$ annually in fuel and maintenance

Somebody mentioned sound quality. Unsurpassed in my opinion particularly a well tuned YS170 with a Hatori exhaust system. BTW- a gas version of the engine should have very similar sound quality. Forget the sound you know from your average DA gasser. Actually, if you ran a 30cc 2 stroke gassie on pipe, it would sound practically the same as a 26-30cc glow engine on pipe.....very quiet and smooth sounding. I am currently running both and know first hand

Torquewise, it has no equal, 2 stroke or 4 stroke, in this displacement size. Maybe a Moki 210 puts out more ponies at top end, but nothing right now beats the low end grunt of the 170

RE: 2 stroke compared to 4 stroke
 

uhm........i run electric rite now and am new to the hobby all together but there are a couple of things out of VERY many that i dont understand that may be appropriate to ask in this thread.The first thing is, why is there glow or nitro at all? Why is everything not 2 stroke, 4 stroke or diesel? Its 2010-why dont we have little turbo charged diesels flying around sounding like mini Peterbuilts?yea i know, crazy-but regular gas 4 stroke 2 cylinder engines isnt-i just dont understand the whole nitro thing i guess-and it seems like all the other countries are allways ahead of us on fuel and energy 

RE: 2 stroke compared to 4 stroke
 

in the old days it used to be you had to double the Cubic centmeters to be =.

A lot depends on the plane and overall performance you are looking for.

I will tell you that in the Saito engines that there is certain ones to buy like why buy a .91 when the 125 is close to the same weight. of the saito's

i will only buy the 40, 82, 125 or the 220.

no reason to buy the 1.80 when the 220 puts out more and is the same weight.


most four strokes dont like to turn much past 10,000 as a general rule. I have turned some of the saitos past 12,000 though in the air.

the saito 40 is 10.5 ouncs
from the 56 to the 82 there is only 1.5 ounces difference so why buy the smaller ones the 82 is almost as strong as the 91. the 91 is only 2.3 ounces more than the 82. the next engine of choice is the 125 with a weight of 21.9 ounces only 3.5 ounces more than the 91. So kinda see what i am talking about with my choices on which of the saito 4 strokes to buy.

saito 40 on most 30 size planes and smaller
saito 82 on small to med size 45-55 size planes
saito 125 on large 45- med size 120 planes
saito220 on large 120 size to 30 cc planes


If need more power can run more nitro. i have run all my saitos on 45% with no problems

RE: 2 stroke compared to 4 stroke
 

With the DLE 20 out pulling the saito 125 glow I see no reason not to go to gas for everything that size. Another option!!!!

RE: 2 stroke compared to 4 stroke
 

Not sure where your numbers came from but a bare Saito 2.20 is 6 oz. heavier than a 1.80 and with exhaust, it's 7oz. heavier.
A Saito .91 is the same weight as a 100. The 125 is 2 oz. heavier.

RE: 2 stroke compared to 4 stroke
 

2 stroke gas is not a viable replacement for 4 stroke glow. Sound and smell definitely count for something.

RE: 2 stroke compared to 4 stroke
 

To hit a few points mention above. I am not going to pay $500 for a 2.20 Saito. Makes no sense to me. The DLE20 looks like a nice unit and it will out pull a Saito 1.25. It also weighs 3-4 ounces more and that is not counting the ignition box and assuming you are using one battery. Finally maintenance on a 4 stroke issue. I may have to adjust the valve a couple times a year, but I go months at a time without adjusting the needles.

David

RE: 2 stroke compared to 4 stroke
 

I haven't seen a DLE20cc close up yet but sounds very interesting. Just don't know how much is hype and how much is truth, and who is doing the telling. About 90% of what you hear on some of these threads is pure, and unadulterated Bovine Skat

I converted all of my 140-180 glow 2 strokes to the SAP 30cc (180) gassie 2 stroke on pipe just about 1 year ago. Never had the need to look back. Flew alot over the spring and summer and burned around 10 gallons of gasoline, 14 ozs at a time. A tank lasts around 20 minutes and that's alot of flight time.

Ran 4 strokes maybe 8 years ago, YS120 and 140. Nice engines but anemic compared to 2 stroke of equal displacement. The present day YS170 is the sole exception, making gobs of useful power but running 30% nitro most of the time. That fuel has become very pricy and the engine often uses 24 ozs per flight. The cost differential per flight is something like 20X compared to 2 stroke gasoline

RE: 2 stroke compared to 4 stroke
 

For a comparison that has a lot of examples all one needs to do is look at the old FAI F3A engines. These engines were held to a 10cc displacement for the two cycle and 20 cc for the four cycle. Now all one has to do is look at the record book to see that even with 200% advantage the four cycle engine was hard pressed to beat the 2 cycle for a myriad of reasons. So for aircraft that were/are critically judged the two cycle is the superior set up for our toys unless one give the four cycle an inordinate displacement advantage. Now in this example both engine types were competition engine. For the sport pilot the formula might not be the same.

All the best,

Konrad

RE: 2 stroke compared to 4 stroke
 

And where are the 10cc engines in pattern today? Even the SPA is dominated by 15cc four strokes

RE: 2 stroke compared to 4 stroke
 

Here in Australia most of the guys run 5 to 10% nitro in their glow fuel. At least at the club where I fly that is the case. We've got some New Zealand guys over here and they said the same thing about nitro use there.

Model diesel fuel (1/3rd kerosene, 1/3rd ether, 1/3rd castor oil) is quite rare here, and prohibitively expensive. That wasn't the case in the 80s and before but now ether is very difficult to purchase. Petrol (gasoline) models are quite popular but most guys run either 2 stroke or 4 stroke models with nitro quite common.

RE: 2 stroke compared to 4 stroke
 

Funny, I cant get the local hobby shop to stock anything LESS than 10% nitro. Irun some european engines and would like to get low nitro fuel quick and easy.

RE: 2 stroke compared to 4 stroke
 

My 1.25 is about as maintenance free as a gasser. It doesn't have to be tuned much when broken in, so no big deal there. I am one of those who likes the small job of adjusting valve lash.:)

RE: 2 stroke compared to 4 stroke
 

I agree with the above with the exception of a .52 4-stroke engine. I'd equate them to a 25 to 32 sized two-stroke engine. I have always used .70 4-strokes in place of a .46 2-stroke.

RE: 2 stroke compared to 4 stroke
 

My saito .40 flies .25 2-stroke sized planes like a bat out of hell.

RE: 2 stroke compared to 4 stroke
 

mike yes i know the 125 is 2.3 ounces more in weight but why buy a 91,100,115 when all four are with in 2 ounces of each other.

Why buy a 56, 62, or 72 when the 82 is very close in weight.

Also mike the 91 is lighter than the 100 by about .7 ounces.

my point is if getting a saito get the most power per weight, buy the 40, 82, 125 and 180 over the 150. yes the 220 is 7 ounces more but alot more engine over the 180.

wy8e said it best yes back in the day of early four strokes the two strokes where king, but pattern has change to flying slower and ata more consistent speed through the pattern big props do that.

The new YS 70 is very close if not beating the 60 two strokes with regular muffler. It will turn an 12x8 APC at just over 12,000

My saito 125's will spin a 14x10 APC over 11,000
saito 40 spins APC12x4 at 11,400 on 30%

RE: 2 stroke compared to 4 stroke
 

And modern pattern is dominated by 25cc two strokes. When the weight reach's max the trend is toward two strokes. If a little lighter then a four stroke.

RE: 2 stroke compared to 4 stroke
 

There was a time I would have agreed with you, but I've got an OS 52 which I have used in several 40 size planes that was MORE than enough power!

RE: 2 stroke compared to 4 stroke
 

I have made a comparison among the recommendations for 2 and 4 stroke for several of the ARF's and kits commercialized by Tower Hobbies.
The rate is about 30% more displacement up for an equivalent 4-stroke.

In this case: 0.52 / 1.3 = 0.40

Since you guys have plenty of experience with these engines, let me know of any inaccuracies you believe my chart may show.

RE: 2 stroke compared to 4 stroke
 

Depends on how big your 40 size plane is; I had a Phoenix Decathlon with an OS46; my buddy built the same plane and used a Magnum .52. This plane calls for .46 2 stroke or .52-70 4 strokes, and weighed just over 6 lbs. I never thought the .46 was a powerhouse in this plane, but the .52 will barely do a loop with it, not for lack of trying props or anything else on the .52.

RE: 2 stroke compared to 4 stroke
 

Looks really good to me.

I don't know as much as these guys, but here's what comes to my mind:

I have 3 4-stroke engines, and I use them in 3D planes and 1 nostalgic style model. I prefer 2-strokes for general sport and high speed flying. Last year a guy at our club was hell-bent on getting max speed in his Shoestring and kept leaning out his Saito and overheating it. I think that if he wanted more speed, he should have used a 2-stroke.

I don't think adjusting the valve lash is a pain, just do it once and you will have no trouble at all. As said before, if you never have to fiddle with the needles, adjusting the valve lash once a year is a big plus (I know some guys who have never adjusted the valve lash on their engines and they still run ok).

When comparing the weights of 2 vs. 4 stroke engines, make sure the numbers include the muffler. The 2-stroke mufflers are big, fat, heavy, and ugly compared to the 4-stoke mufflers.

Despite the 30% difference in displacement to power the same model: 40 2-stroke vs. 52 4-stroke, 50 2-stroke vs. 70 4-stroke, etc... you will still get much better fuel economy with a 4-stroke.

Generally, 4-strokes are much quiter than 2-stroke nitros, and much quiter than the gassers. If people put the same muffler and noise restrictions on gassers as they did on the nitros, the gassers might not look as attractive.

Ok, I've said too much already. The three moderators can straighten me out now.

RE: 2 stroke compared to 4 stroke
 

You're right about the Magnum 52. I put one on my Sig Rascal in place of a 40 2-stroke and it barely has enough power. The Rascal is even lighter than the Decathlon, I think. I did it to make the plane more "nostalgic".