Hi guys,

I need some advice regarding engines. I am fairly new to pattern flying and have recently acquired a pattern plane. The trouble I have is that I am not sure what engine to buy. The requirements of this plane states 60 to 90 2-stroke.

Firstly I do not seem that there are any engines larger than 60 with a rear exhaust. Is there any?

I have also looked at 4-stroke engines, specifically the OS Surpass 90 with pump and the YS110. At this point I am all confused as there seem to be many disadvantages with 4-stroke engines i.e. weight and vibration to name a few. Some person also told me that the YS engine will only run properly with a 25+ percentage nitro, is this true? If this is true why does it not apply to the OS 4-strokes?

What is the main pro’s and con’s of 2-stroke vs. 4-stroke?

I guess that is enough for now, I would really appreciate it if some one could enlighten me regarding all these issues.

Thanks

Hi Weedfix

I think the first thing I would like to know is what pattern plane are we talking about? How much does it weigh?

IMO, I would get the YS110. The engine has more power than the others and a better throttle. As for the vibration, don't worry about it. If the model will let you soft mount the engine, do that. If the model doesn't allow for an easy/not expensive soft mount (a model that has a removable cowl. Eg. Swallow, etc) then hard mount the engine.

My advise for beginners is to buy the best engine and radio gear that you can afford. It can then be moved into other F3A planes as you get better at flying them. (or it is time for a new one)

As for the 25% fuel ....... I think it is a matter of opinion and how good you are at tuning your engine. I have successfully ran YS engines (91AC, 120FZ, AC, SC, 140FZ and L) on anything from 10% - 25% nitro. More nitro makes them a little easier to tune with a better idle. (That is not to say the idle on 10% is unreliable....it is!) I would run the YS110 on 15% nitro and see how is goes. Start with a 13-12 or 14-10 prop and go from there.

You will get a lot of pattern advise and opinions. This is one of them.

Cheers

Buzz

I flew pattern way back in "the old days" and for a long time you couldn't give me a 4-stroke.
I was sold on 2-strokes. But after starting pattern again after about a ten year layoff it didn't
take me but flying in one pattern contest to make me a convert. If you're serious about pattern
the 4-stroke is the way to go. The new ones are reliable, idle good, and have pulling power that
is unbelievable for all the vertical maneuvers in the new pattern schedules. I am just completing
a new CA Models Widebody that I planned on installing a MVVS .91 in but those plans have been
changed to a YS 1.10 4-stroke.

tommy s

The MVVS 61, 77 and 91 are apparently able to be converted to rear exhaust just by screwing off the cylinder and rotating it.
I use a Webra .80 Longstroke which is a very nice pattern engine but a little pricey. There's also some old OS RF's to be had second hand that you might consider. Super Tigre's X-61 rear exhaust is again available, at least in the UK.
You can also use a side-exhaust engine with a wrap-around or "swan-neck" header that you'll need to have custom made. www.justengines.co.uk makes those.

As others mention there's also 4-strokes, OS 91 with pump, YS 91/1.10 etc that can do the job although at a higher cost than the two-strokes.

Jon is correct about the MVVS. It is a powerhouse of an engine available as
a .61 , a .77, and a .91 all the same physical size and all can be run as side or
rear exhaust simply by turning the cylinder before you break it in. I have two
.77's and they both run great , very powerful with instant acceleration from idle
and they don't need a pump. I don't like the MVVS tuned pipe as I feel it is too
loud, too big , and too heavy. I am using an ES composites carbon fiber pipe
which is much quieter and produces more power , looks good too. The MVVS
engines also do not require high percentage nitro fuel to produce their power
in fact they recommend no more than 5%.They are my favorite 2-strokes.

tommy s

PS: I am still changing to a 4-stroke in my Widebody.

Thanks guys I appreciate all the help. Buzz Lightyear, here are the specs on the plane.
- Scorpio 60
- Wing Span: 1750 mm (69”)
- Weight: 4.1 Kg (9.2 LBS) (in box)

Ta

Weedfix

Is the plane suppose to weigh 4.1kg total? To be honest, I wouldn't stick anything smaller than a YS120 - 140 in it. I had an Adrenalin 90 with a YS140FZ in it....perfect! Took the gear out of it to put in another plane and when my back was turned, a mate put it in his car.....I have to get another one now. It weighs about the same as yours. It now has an OS91FX in it and it is not enough to fly F3A.

I guess it depends on your flying skills and budget?!

Get the best motor you can afford. It you are serious about flying pattern, make it an OS or YS. There are a lot of top pilots that can help you with them.

Cheers

Buzz

Weedfix

The fundamental difference between the OS and YS 4 strokes are that YS are 'supercharged', thus producing more horsepower and a sweet idle. They also do not require a pump, should you choose to mount your fuel tank amidships (to prevent trim changes as the tank drains).

I agree with Buzzlightyear in the nitro content issue. You don't necesserily need high nitro fuel. 15% will be adequate for a starting point. You can experiment with more nitro/differnt props as you clock up more practice time.

I personally run 20% for my YS 91. However, in my 2 metre ships I am running 1.40 2 stroke supertigres , with Perry pumps, swan neck headers and tuned pipes, running on only 10% nitro. If South Africa is like OZ, then nitro isn't cheap!

I would 'keep it simple' to start with. As you attend more pattern comps, you'll see all manner of set-ups. Ask questions and look around. No-one will mind, and most will only be too happy to help.

If you go with any of the powerplants mentioned above, you can't go too wrong. I think it's more important to be concerned about a nice clean and tight control set-up. Don't skimp on servos or connectors, and seal all control surface hinge gaps. You won't believe the difference this can make to your pattern flying.

Good luck and have fun.

Chunkylad

WeedFix, go MVVS .77 or .91, they are good engines. You can configure it as a rear exhaust
before break-in the engine. Forget YS engines. They must run on 30% nitro to get the power
and a reliable idle. I own a 91FZ that never ran properly. Too many problems with YS, I con-
sider they are not reliable engines.

I´ll just throw in my 2 cents worth. I go along with Chunkylad: control set up is just as important as engine sellection. I have a Desire 60, powered by 2 stroke OS 91FX, as my practise plane. I use JR 4131 coreless servos (on 6 volts), carbon rods and Dubro screw horns. As the man said, sealing those control surface hinge gaps makes does make all the difference. My 2 metre planes are great but a lightweight, well trimmed 60-90 sized plane is a joy to fly and still competitive up to advanced class.