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Single vs twin cyliner engines

Old 05-10-2010, 07:31 AM
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Default Single vs twin cyliner engines

I am looking at trying my hand at a plane with a twin cylinder four stroke. I am keen on using the Saito FA100 twin for a plane.

But what 2 stroke or single cylinder four stroke would that engine be equivalent to in terms of power? Is there a rule of thumb you can use to compare single vs twin cylinder engines?

Old 05-10-2010, 07:42 AM
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Default RE: Single vs twin cyliner engines

G'day I only have one twin cylinder engine flying at the moment though I own two. The one I have recently flown is a Saito 90TS. It is in a Goldberg Anniversary Cub and it is using the same prop and is doing about the same revs at my Saito 72. It is smoother, easier to start but otherwise is very similar to my 72. The sound at idle is amazing and that alone is worth the price if admission. And the crackle in the simple pipe exhausts is very nice too.

It does not drop cylinders and I do not have any on board glow system. I use 10% nitro, 20 % oil (5 castor, 15 synthetic) and a 13 x 6 APC prop. Highly recommended.

Mike in Oz
Old 05-10-2010, 08:47 AM
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Default RE: Single vs twin cyliner engines

Hello; I have one of those 100 twins, but I have never had it in the air. I have run it on a stand to get it by that "drops a cylinder" phase; and have found that it'll turn a 13
x6 prop just like a Saito 80. Actually the 80 can rev a bit higher then the 100 twin, but it's so close that it's not worth argueing about. Of course, you know about the big weight penalty. I just wanted a twin, and though I knew about the 180 vs. 360 crankshaft and all that that brings, but beyond 2500 rpm., they sound the same, and run the same, so the difference is in appearance is what I wanted.

There will always be people who want to be a bit different, nothing wrong with that.
Old 05-10-2010, 09:31 AM
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Default RE: Single vs twin cyliner engines

Figure 75 percent displacement is equivalent power. So a 100T would be roughly equivalent to 75 regular 4-stroke. They weigh more as well.
Old 05-10-2010, 05:07 PM
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Default RE: Single vs twin cyliner engines

I have a Magumn 160 twin in an Ultimate running spark ign, no cylinder drop out. I have Satios 80 and 90 mkII's but not fitted to aircraft.

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Old 05-10-2010, 10:37 PM
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Default RE: Single vs twin cyliner engines

We were doing some thrust compairisons today at the field. One of our guys picked up a Saito 90 twin and he was able to top out just shy of 6 lbs static thrust on it. I've got a a Saito 45, so he mounted it on his test stand and it brought in 3 lbs static thrust. Really close to a 1 to 1 for a cui to cui compairson. I'm in the process of cleaning up a never run O.S 120ft Gemini twin. The orginal grease really dried and caked up. I've spent about 5 hours with it in a tub of glow fuel in a heated Ultrasonic cleaner. Ifinally got the main bearing to turn freely, It was dragging the ball cage, not letting the balls roll. We'll get some data on it later. It's not my engine, so I don't know when.

I've got a couple other twins though, an O.S 300 FT Gemini, and an older Tartan 45CC twin. I've yet to run either, but the O.S. 300 has a spark conversion on it, still running glow fuel. When I saw it run the last time before I aquired it, it seemed to tick over at under 1K rpm, forever on idle and it realy flew well.


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