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

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

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.

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

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.

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

Since when???

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

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

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.

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

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.

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

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.

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

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

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

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.

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

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 

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

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!!!!

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.

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

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