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I need help picking an engine

Old 10-08-2006, 09:16 PM
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k1s1h1
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Default I need help picking an engine

I am going to get the space walker II from horizon but I think I want to get a four stroke. The specs call for a 41 size 2 stroke and a 40-82 4 stroke. It seems like a large range on the 4 stroke. This is my second plane and i don't want to much engine then i can handle. What would be a good 4 stroke. And what are the advantages of a 4 stroke over a 2 stroke.
Old 10-08-2006, 09:24 PM
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jsn
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Default RE: I need help picking an engine

Saito 72 or 82 would be a good match... also an O.S. 70 or magnum 70... none of them will make the plane hard to handle. 4 strokes sound better on this type of plane IMHO... they also swing larger props that look better and have a smoother transition and throttle response. Either a 2 stroke or 4 stroke will fly this plane well... if cost is not a factor go 4 stroke hands down.

John
Old 10-08-2006, 09:30 PM
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Default RE: I need help picking an engine

magnum 52 four stroke will fly it all day long at 3/4 throttle or go with the evolution 46 2 stroke it will fly it all day at half throttle. i know this because here's mine
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Old 10-08-2006, 09:32 PM
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super tigre
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Default RE: I need help picking an engine

About a 70 4-stroke I think is about right, I have 2 os 4-strokes they work great and are very dependable.4-strokes can swing a larger prop and operate at lower rpms than 2-strokes.
AMA#511248
Steve
Old 10-08-2006, 09:39 PM
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Campy
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Default RE: I need help picking an engine

ORIGINAL: k1s1h1

I am going to get the space walker II from horizon but I think I want to get a four stroke. The specs call for a 41 size 2 stroke and a 40-82 4 stroke. It seems like a large range on the 4 stroke. This is my second plane and i don't want to much engine then i can handle. What would be a good 4 stroke. And what are the advantages of a 4 stroke over a 2 stroke.
I suggest the Saito 72. It is an excellent, troublefree, reliable engine. As with ANY 4 stroke, I STRONGLY recommend using a tachometer along with the manufacturer's breakin directions for a trouble free engine.

The 72 is a little over powered for the plane, however, that is why there is a throttle control. As long as you are not flying wide open (unless your skill level is up there ) you will have no problems.

4 strokes have been getting better in performance. A 72 will provide equivelant performance to a hot 46 or an average 61 2 stroke.

4 strokes are more fuel efficient than a 2 stroke. The size tank you can fly a 46 2 stroke on for 10 minutes, will normally fly a 72 4 stroke for 15 minutes or longer.

4 strokes have a more "realistic" sound than a 2 stroke, and while the db level of the exhaust may be the same as a 2 stroke, the 4 stroke is perceived (heard ) as being quieter because the exhaust is at a different pitch.

4 strokes NORMALLY are run about 9,500 - 10,000 rpm, while 2 strokes are NORMALLY run at rpms much higher. Because 4 strokes have a lot of torque, they can use larger props. While a 2 stroke prop is just "whipping up" the air, the 4 stroke is actually making use of the air. A prime example - a 46 2 stroke will run an 11x7 @ 12,000 rpm for a given speed, a 72 4 stroke will run a 13x6 @ 9,500 rpm for the same or slightly higher speed.

Hope this helps.
Old 10-08-2006, 09:47 PM
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Default RE: I need help picking an engine

nice campy well put
Old 10-08-2006, 09:48 PM
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Default RE: I need help picking an engine

heres a m.d.s. 2.1 compared to a evolution 46
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Old 10-08-2006, 09:52 PM
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Campgems
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Default RE: I need help picking an engine

I have a Magnum 52, Magnum 70, OS 52 and a Saito 45. I have flown both of the 52 in a Lanier Explorer 40 trainer and both were more power than needed. As the specs on the plane call for up to a 70 four stroke, I tried the Magnum 70 in it. I was just trying to do a bit of taxi runs without the wing, and jumping to 1/3 throttle about put the plane in the air without wings. I'm sure I could have pulled it off the ground at 3/4 throttle. Either of the 52 will do well for you. If you budget allows, go for the O.S. as there is a much shorter breakin period. It will idle at 1800 all day straight out of the box where the Magnum is back in the shop to try to get it to idle down reliabily. It doesn't like to play under 3000 rpm. It has had almost two gal through it, so I sent it back for a professional tune. I have no doubt though that it will be as good as the O.S. when this bug is worked out.

One more plus for the four stroke, I can fly it for four flights and only have to clean up the plane to put it back in the car. The 2 strokes leave the thing dripping with oil when it lands. I just put the Saito 45 into a plane I had an O. S. 40 two stroke in and will fly it tomorrow. I'll see if my theory holds.

Don
Old 10-08-2006, 09:53 PM
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k1s1h1
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Default RE: I need help picking an engine

Thanks yall have been really helpful I think I am going with the Saito 72. Horizon offers a combo with this engine for about $340.
Old 10-08-2006, 09:55 PM
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Default RE: I need help picking an engine

more bang for your buck i like that
Old 10-08-2006, 11:31 PM
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Default RE: I need help picking an engine

it depends on your flying style... a 52 is great for long spirited flying but nothing too crazy. a 70 will get you to a more aerobatic plane at speeds far exceeding scale. personally, i think a 52 is enough for something like a space walker but if you plan to get into aerobatics and will find yourself in the 40-size, the 70 will be a better choice as you'll be able to fit it into more aggressive planes. but if you're not on a budget, the O.S.52 is a gem of an engine.
Old 10-09-2006, 09:30 AM
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Default RE: I need help picking an engine

Another thing to be aware of with a 4 stroke - If the engine is not making smoke, it is too lean.
Old 10-09-2006, 01:00 PM
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B.L.E.
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Default RE: I need help picking an engine

The most common problem I see with 4-stroke engines, especially with planes that are stupid overpowered, is getting the engine's idle rpm slow enough to not taxi the plane on pavement. Four strokes have a hard time matching a 2-stroke's low idle rpm because they fire every other revolution and thus the glow plug has more time to cool off between firings. Also, when the throttle is closed, four-strokes have a very low effective compression ratio because the cylinder is only partially filled (a vacuum in other words) with air/fuel mix when the intake valve closes and the piston has to travel quite a ways up before the air in the cylinder is at atmospheric pressure and the compression can start.
Some people use an on-board glow igniter to solve the problem but the real key is to have the idle mixture perfect. Most everybody knows how to adjust the high speed needle but a lot of experienced flyers seem to be absolutely clueless about adjusting the low end and just live with thirsty planes that need "wing walkers" to hold them back before takeoff.
If you power it like a scale airplane, you can get away with an idle rpm that is 1/4 of the full throttle rpm. If you power it for ballistic verticle at full throttle, your idle needs to be 1/5 of the full throttle rpm or slower or you will need someone to hold the plane back for you on takeoff and will only be able to land by killing the engine.
Saitos come with the low speed needle set very rich. It should be left that way for the first couple of engine runs. The engine will be extremely thirsty at part throttle and the fuel tank will be empty in a matter of minutes. As you break in the engine, you need to gradually lean out the low end. If the idling engine revs up when you pinch the fuel line, your low speed needle is too rich.
Old 10-09-2006, 06:44 PM
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Default RE: I need help picking an engine

K1,
My opinion 4-stroke is the only way to go. The only other thing is don't be afraid to go to the top of the engine range. Here is why... LIMITS!!! The big vs the little saga... If you go small that's where it ends. If you go a little bigger that engine will apply to other airframes. As you already know this hobby is addicting. Furthermore if you plan to eventually grow into other planes it would be nice to have some single purchases instead of many. The 52 might be cheaper than an 80 but your most likely gonna buy that bad boy anyway. Remember you can't use the altitude above you, the runway behind you and the power in the engine you didn't choose!!!
Old 10-09-2006, 06:47 PM
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Default RE: I need help picking an engine

One of my flying buddys has that plane with a OS 70 surpass ,it has ample power but not over powered .I clocked the plane yesterday at about 60 MPH with a rich running engine .My self I wouldn't go less that a 70 sized engine for the main reason sooner or later your going to want a larger type engine as your flying skills get better .Good Luck
Old 10-09-2006, 06:52 PM
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Default RE: I need help picking an engine

don't forget the ys 63 very light and powerful
Old 10-09-2006, 08:27 PM
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Campgems
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Default RE: I need help picking an engine

Today confurmed my less cleanup theory. I flew the Saito 45 today for three flights and there was just a couple oil spots on the wing and none on the fuselage. With the 40 OS 2 stroke, I would have had to clean it after every flight.

On the idle issue. My Magnum 52 four stroke fell into this catagory. My O.S. 52 four stroke is just plane awesome at idle. It will putt along a 1800 all day and the when you jam the throttle, it jumps to life. Never had a stall or dead stick with it.

The Saito 45 is a different engine. I have never seen an engine that has such a wide range on the High Speed needle. The window is about 1 1/2 turns wide. I leaned it to day with a tach until it just started to drop. Richen it back to max and the keept going richer for just shy of 1 1/2 turns before it started to fall off a bit. I don't have the idle set really well yet, but it should only take one more day at the field with it before it is like the O.S. I'm guessing. I think my biggest problem on idle with it is servo related, not engine. I'll pull the servo an try it.

Bottom line, I would never buy another 2 stroke and might just sell off the one's I do have.

Don
Old 10-10-2006, 11:03 PM
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Default RE: I need help picking an engine

yes campgems.... you are another victim of fore stroke frenzy... buhahaha!
Old 10-10-2006, 11:12 PM
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Default RE: I need help picking an engine

I am hooked on them. The other day a guy was tuning up his 60 two stroke while I was trying to learn something from my instructor. What a racket. The little Saito 45 doesn't even have a muffler, just a straight pipe and it is quite. It went dead stick on the first flight and the only way I knew it was that it wouldn't answer the throttle. The whole world knows when a 40 two stroke quits, all the little animals start peeking out from what ever it was they were hiding behind.

Ok nuff 2 stroke basshing I guess.

Don
Old 10-11-2006, 09:21 AM
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Default RE: I need help picking an engine

Myself I like both the 2 and 4 stroke engines . Depends on what type of plane and flying I want to do ,dictates what engine I will use in it.

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