2-Stroke vs 4-Stroke - Page 5 - RC Groups
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Nov 03, 2015, 06:42 PM
Bellanca Kruesair
epoxyearl's Avatar
I paid $89 for a starter that would relieve some of my efforts to start the myriad of engines I have..... gas and glow, two and four stroke...

So as not to confuse the issue of whose engine doesn't need a starter,I treat them all equally.
I either turn the ignition switch 'on', or apply the glow starter battery, and bump the spinner with the starter.....and awaaaaay we go !

Neat little inventions, these starters.....
Latest blog entry: I'm a 'whiner'
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Nov 04, 2015, 10:37 AM
Methanol, The Cool Fuel !
Gary Cee's Avatar
Yes , very handy . Nice to know they aren't universally mandatory .
Jun 04, 2017, 04:01 AM
Registered User
Hi chaps , just a newly to this forum, well sort of , been reading it forever but only just registered. Just reading this discussion on 2 vs 4 strokes and I know many people (and myself included) assume 4 strokes are heavier than an equivalent size 2 stroke. Well I was curious so I did some weighing today. My OS 75 AX 2 stroke weighs 866 grams ready to go. My OS91 Surpass 4 stroke weighs....wait for it ....774 grams. So that blows that old chestnut out of the water. I was curious because I was tossing up which engine to use in my Hurricane and I naturally assumed the 91 would be heavier, so out of curiosity I weighed them.....any one else got some comparable 2/4 strokes to compare?
Jun 04, 2017, 04:53 AM
the great Gassif´er
True... but the 75 AX blasts the 91 FS for power by so much that the larger slower prop does not make up for it....
Jun 04, 2017, 07:36 AM
Now I have to land that thing?
PGregory's Avatar
Ray - Roughly, the equivalent 2s displacement is 0.7 times that of a 4s. Roughly, that, makes the .91 an equivalent for a .63 sized 2s.
1) Actual power/weight and 2) torque are key factors.

Good info, you added.
Jun 04, 2017, 08:47 AM
Methanol, The Cool Fuel !
Gary Cee's Avatar
Quote:
Originally Posted by Ray Melton
Hi chaps , just a newly to this forum, well sort of , been reading it forever but only just registered. Just reading this discussion on 2 vs 4 strokes and I know many people (and myself included) assume 4 strokes are heavier than an equivalent size 2 stroke. Well I was curious so I did some weighing today. My OS 75 AX 2 stroke weighs 866 grams ready to go. My OS91 Surpass 4 stroke weighs....wait for it ....774 grams. So that blows that old chestnut out of the water. I was curious because I was tossing up which engine to use in my Hurricane and I naturally assumed the 91 would be heavier, so out of curiosity I weighed them.....any one else got some comparable 2/4 strokes to compare?

I believe the YS 115 weighs in even less than the OS 91 (735 gram).

In the real world , with a scale plane like your Hurricane it may also pull the Hurricane a bit better too. Another plus is that the 4 stroke exhaust systems tend to be less bulky and less unsightly (lighter too) . In fact , even the older YS 91 may still be competitive here.

YS 4 strokes will often out power 2 stroke engines of the same size.
Jun 04, 2017, 08:54 AM
Closed Account
Quote:
Originally Posted by PGregory
Ray - Roughly, the equivalent 2s displacement is 0.7 times that of a 4s. Roughly, that, makes the .91 an equivalent for a .63 sized 2s.
1) Actual power/weight and 2) torque are key factors.

Good info, you added.
These days with the newer 4 strokes from OS and YS you really can't use a set formula like that. The best thing to do is take a look at the recommend prop size and operating rpm for each engine and compare. Example, my YS 115 will blow away any 2 stroke 1.2.



You also need to look at the model it's self and determine what would work best. Some airplanes will work better with a low rpm large prop while others a higher rpm small prop. There is much more to it then looking at a catalog or web pages for somewhat bogus HP figures.
Jun 04, 2017, 10:23 AM
Registered User
DGrant's Avatar
Something like this just came up the other day. Irregardless of the weight factor, I've been enjoying my newer generation OS four-strokes incredibly for the last few years, and haven't even ran any of my two-stroke engines...

I've found the four-strokes much cleaner running, much quieter and smoother as well... and they use a bigger prop.. less fuel apparently(stands to reason)... just many reasons I've came to like my four-strokes... more and more.

I replaced an older ASP 1.08 two-stroke with an OS 1.10 four-stroke a while back, and the difference was astonishing to me.... and the OS four-stroke was so much lighter then the ASP two-stroke.... it just made a world of difference, and clean-ups are a cinch..

I also have a few older generation Magnum four-strokes... which aren't as powerful as the newer offerings of OS, YS, and even Saito's I would imagine... but still they're rock solid runners, and very clean running as well.

Yep.. I don't know if I'll ever go back to two-stroke glow... there's really nothing on the market that I like anyway. I've got an OS .91FX sitting here too.. not sure if I want to even use it lately.
Jun 06, 2017, 08:50 AM
Methanol, The Cool Fuel !
Gary Cee's Avatar
Yep 800 Caterpillar horses work far differently than 800 Ferrari horses.

DGrant,

There will never be another 2 stroke in my hangar. I hear you !
Jun 06, 2017, 10:29 AM
AMA 537620
ChillPhatCat's Avatar
Quote:
Originally Posted by Ray Melton
Hi chaps , just a newly to this forum, well sort of , been reading it forever but only just registered. Just reading this discussion on 2 vs 4 strokes and I know many people (and myself included) assume 4 strokes are heavier than an equivalent size 2 stroke. Well I was curious so I did some weighing today. My OS 75 AX 2 stroke weighs 866 grams ready to go. My OS91 Surpass 4 stroke weighs....wait for it ....774 grams. So that blows that old chestnut out of the water. I was curious because I was tossing up which engine to use in my Hurricane and I naturally assumed the 91 would be heavier, so out of curiosity I weighed them.....any one else got some comparable 2/4 strokes to compare?
It's a very common misconception and it is very often wrong. I had a Magnum .61 4-stroke at one point, it weighed about 15.7 oz with muffler if memory serves... compare that to any .61 2-stroke on the market. I think you'll be hard pressed to find any .60 size 2-stroke that is that light.
Jun 06, 2017, 12:16 PM
Airfield Hermit
I'm sure I'm totally nuts on this one, but...

I've had planes that I wouldn't consider running with a 2-stroke, but then there were others that I not only ran a 2-stroke, but they were the bearing-less, red-headed step-child LA series of 2-strokes!

I'm not stuck on whether it runs in 2-cycles or four. I'll look at the important information, which is relative, depending on the airframe. For some, I just love having a larger prop and slower rpm. For others, cost comes into play. Behind door number three, is the all-important weight. Which things are important is handled on a case-by-case basis.

I wouldn't think of running my Kadet Sr. on anything but the .91 4-stroke OS. When I had my Lazy Tiger 51, it was a smaller airframe with a LOT of wing chord, so the 46LA worked PERFECTLY for my needs. Let the airframe, your wallet and the scales tell you what works best. My .02.
Jun 06, 2017, 01:20 PM
Methanol, The Cool Fuel !
Gary Cee's Avatar
My original Kadet Sr came from the first batch that Sig released. It is still with me.
The first powerplant was a lowly Saito 30 open rocker. The plane was 3 channel , taildragger. Covered with light weight EconoKote . Later on it got a Saito 50 and then on to a 62 Saito . Tht is the present engine and it is quite adequate.

In the meantime I also have a full blown, barn door aileron Kadet Sr.(My Avtar pic) That one uses an OS 91 Slurp-ass engine. Moves along very well .

No interest in two strokes at all for the last 30 plus years.
Jun 06, 2017, 02:05 PM
AMA 537620
ChillPhatCat's Avatar
The OS LA series are just about as good as the FP series... as they say the .40 FP was one of the best 25 sized engines ever made. The great thing about them is how incredibly light they are without all the extra casing and ball bearings and unneeded beefing up. They make less power for the displacement but make up for it with the weight savings... Much in the same way a 4-stroke does.
Jun 06, 2017, 07:10 PM
Airfield Hermit
Quote:
Originally Posted by ChillPhatCat
The OS LA series are just about as good as the FP series... as they say the .40 FP was one of the best 25 sized engines ever made. The great thing about them is how incredibly light they are without all the extra casing and ball bearings and unneeded beefing up. They make less power for the displacement but make up for it with the weight savings... Much in the same way a 4-stroke does.
Agreed! That's why they're great. Was going to put a 40LA in a Great Planes T-Craft (one in my avatar) but, gravity beat me to it. Always thought that if it had prop clearance, that engine would have been sweet. And, it didn't weigh any more than the .25 Magnum that was in there, which on a grass field, was part of the reason gravity grabbed it so firmly.
Jun 06, 2017, 07:14 PM
| Saitopunk |
Bunnyshooter223's Avatar
Quote:
Originally Posted by ChillPhatCat
The OS LA series are just about as good as the FP series... as they say the .40 FP was one of the best 25 sized engines ever made. The great thing about them is how incredibly light they are without all the extra casing and ball bearings and unneeded beefing up. They make less power for the displacement but make up for it with the weight savings... Much in the same way a 4-stroke does.
Hey, i think you're on to something there.
Bigger and slower rpm versus small fast and finicky...

I really would have preferred a larger 4-cycle Saito in my nitro rc car...
but was not up to the mods or cooling challenges. With the right gearing it could be fast enough to have fun yet be far more reliable and sound ...way better imo lol


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