I'm still thinking/hoping my Craigslist OS 55 is gonna happen (the owner is in the middle of a move & is returning this week or next, when I hope we'll connect)...but I'm starting to look at options.

I'm seeing an awful lot of 4-strokes popping up, and especially at my LHS (not sure if that's cuz they're popular or if they're not selling ), so my questions are:

-Are these good for beginners? I guess I'm not really a beginner when it comes to engines...I have a lot of nitro rc truck experience...but I'd think other beginners would like to know about them, too.

-What are the pros & cons? I've heard fuel economy can be a LOT better, which would help offset the cost disadvantage...but what else? Finicky tuning? Quieter/louder?

-What's the 'conversion factor', i.e., what displacement would give me the same power as the OS 55ax?

-What brands do you like? OS vs. Saito? Are some of the offbrands good?

Speaking of offbrands...and getting back to 2-strokes...what would you recommend in a sub-$100 .50ish sized engine? JBA seems to have pretty decent reviews, so does Magnum? Thoughts? Alternatives?

Thanks, as always, to the best forum around!

In a nutshell, 4 strokes turn lower rpms but with more torque, meaning that you spin a higher pitch prop to make up the difference. The biggest flying difference you'll see is that if you're at 1/4 throttle and gun it, the 4 stroke engine will accelerate the plane immediately whereas the 2 stroke will be a touch slower because of the torque difference at the low end. Yes, fuel economy is better and 4 strokes are quieter and sound much more like a real airplane engine. As for care, 4 strokes aren't as obvious when you find the peak RPM, so it really helps to use a tachometer to tune them. It also lets you check your max rpm so you don't under prop it and float the valves. It's smart to check the valve clearance annually but that's not a difficult task. Sometimes you have to move your fuel tank because the carburetor height is different on a 4 stroke, which can cause fuel draw or siphoning problems.

For brand, OS and Saito both have their loyal followers and seem to be comparable in quality. I have a Magnum 4 stroke and so far am impressed with it. Thunder Tiger also has a good reputation with their 2 stroke engines (I have one and love it) so I'd expect their 4 stroke line to be good. As for lower priced 2 strokes, I'd say Thunder Tiger leads the pack for value while Magnum/ASP (same engines) are cheaper and still trustworthy.

Good advice jester could;nt have said it better.Although i only run saitos lots of people at the club are beginning to use thunder tiger and asp fourstrokes.Both brands very reliable and they make good power too.

Nutshell number two

If the used 55AX deals falls through go out and buy a new one that would be the best gift you could give yourself. Get your brain unwrapped around the attitude that its an engine, I gotta buy an old and cheap one.

The 55AX could not have been a better choice for that airplane and the mission you have in mind for it: Learning how to fly and learning how to operate our engines (they are not the same as the car engines not by a long shot).

Bear in mind not every one considers a fourstroke an upgrade, its all about the mission.

John

Normally, I'd never consider a used engine; you don't know what the sleeve's like, bearings, etc. But this one has only 5 flights on it after a proper break-in...so for $80, it's a remarkable deal (it's $170 new).

I've already stretched my budget w/the plane & the radio, so if there are good, reliable engines out there for $80-100 (or more for a 4-stroke that'll cut my fuel bills by 30-50%), I'll take a look.

Again, how do you compare/match up 2-strokes to 4 stroke equivalents? Does a .90 4s = .60 2s?

I totally agree with Johnbuckner, I would love to fly that plane with the .55AX. If money is a huge issue (I know it is for me) I have used
the Magnum .52 in a .40 sized edge and in my Great planes Reactor and it works great. Just make sure you break it in right and learn
to tune it right.

If I end up going 'all in'...I might as well (and might very well) go for the [link=http://www.jettengineering.com/]Jett Sport Jet .46[/link].

I actually asked for the Jett 'Hanger Sale' info to be sent to me, and it seems he's discontinuing the .46, so it's now 'only' $250.

Someone stop me!!!!![]

Comparing displacement, a 30-50% increase will give comparable horsepower. So a .56-.60 4s is comparable to a hot .40 2s, a .70 4s is comparable to a .46-.50 2s, etc. Which 4s you're talking about makes a significant difference too. Saitos and the newest OS's make the most horsepower for their size, so you don't quite have to go as big with them as you do with older OS's or one of the other brands. The weight will be close to the same too since 4s mufflers are much smaller than 2s mufflers are. All that said, it's not an apples to apples comparison. If you match horsepower, the peak will be at a much lower RPM so the plane will respond to the throttle differently. The 4s will pull the plane through maneuvers better and accelerate it better, while the 2s will generally make more overall speed.
To give you a real world impression, I just went from a .46 2s to a Magnum .52 4s in my Piper Cub. There is a definite drop in overall power on the top end, evidence by less top speed. But the throttle response is much more linear and it still pulls though big loops and hammerheads with authority. I like the feel better with the 4s, but I do have to manage the speed a little better and generally find myself flying at a higher throttle setting that I used to with a 2s engine.

Expecting a 30 to 40 percent savings in fuel by simply going to a four stroke engine is wishful thinking at best. This is not a viable expectation in the real world at all and its more likely you not experiance any measurable savings in the long run.

Four strokes are not an upgrade at all used in the wrong mission and primary flight training is one of them.


John

I had a Magnum 52 4Stroke on a Hanger 9 Cub with an 80" wingspan. I always felt that it was underpowered and didn't think the Magnum 4S developed as much power as an OS or Saito 4stroke engine.

I would stick to a 2 stroke myself. If really want to save fuel get a 20-25 sized plane. If you are like me when I learned to fly I went through a bunch of fuel just because I went flying 2-3 times a week.

Look at a Magnum 52 two strokefor less than a hundred bucks. I paid about $85 for the one I have. Its still new in the box and waiting on me to build a plane for it. I have a Krafty 60 kit just waiting to be built.

I look on Ebay for model stuff. I have bought two NIB engines off there for really low prices. AnOS FP25 and a TT 40 both for$40 each. An OS FP60 just sold for $55 IIRC a week ago. It was also new in the box. Lots of people are selling their glow fuel planes and motors and going all electric so motors aren't as valueable as they once were. That works for me. I have no interest in electric motors.

And don't turn your nose up at the plain bearing engines with thier air bleed carbs. They work just fine and are super easy to adjust. I sort of prefer them when can get a deal on them. And they sell cheap.

I started on a old O.S. 40 in a Goldberg Eagle Kit about 12 years ago. (First Glow Trainer I owned) 2-stroke glow engines require less maintenance and burn less fuel depending on what brand, and they are not hard to adjust once you have a little knowledge and background about them. They have more torque than the 4-stroke, however they are dependable equal to the 2-stroke- if the adjustments are correct and the proper glow plug is used.





I still use 2-strokes in most of my closed cowl aircraft, because they don't really need much maintenance, and there's a less chance of damaging my cowl from taking it off and on the fuse.

My 4-strokes do have that great sound, and have more power in the top end being able to swing a bigger prop than a 2-stroke of that same range of size. The only down side is I have to check the valves every year- 6 months of continued weekend flying, and they consume more glow fuel. It's wise to run 4-strokes a little on the rich side. Most of the time my valve adjustments stay at their recommended settings, but I have had the exhaust valve adustment tighten up from the heat and vibration. So it's good to check them once or twice a year.

I like my 4-stroke engines, and I love to tinker so I prefer 4-strokes most of the time.

My favorite 4-strokes are O.S. and Saito, and I like them equally.
My favorite 2-stroke is O.S. hands down. I do own a Super Tigre .51 Ringed, but I had a bad carb and replaced it with a Perry Carb, and changed the stock muffler for a Mac. Now my cheap engine is as dependable as any O.S. I have ever had after doing that. The only thing I don't like about the engine is the clearence between the prop and carb venturi, and I have to get a special boot on the fixed venturi if I want to put on a special air filter.

The engine I've had nothing but troubles with was the cheap Evolution Glow Engines. They work fine after a few years, but tend to start leaking from the gaskets, the low end needle valve likes to move under vibration, and they don't seem to have the same power that O.S. does of a engine that size. Plus they seem to like a lot of air hitting the cooling fins and doesn't take the heat very well in a enclosed cowl. A O.S. engine seems to take the heat better.

FS 52 is = to a .40TS
FS 61 is = to a .46TS
FS 91 is = to a .61TS
FS120 is= to a .91TS
FS150 is= to a 1.20TS

Approximate conversions from 4-stroke to 2-stroke.


Pete

Hi!
Hope you don't fly with just those few rubber bands

Ratshooter- I have that same plane and engine combo. I like that it's so scalelike. It had an Evolution up front originally. That's the first and last Evolution I ever expect to own. I got it free and still feel ripped off. I have to think about the wind I fly it in but I really do think it's fun to get up and tool around so slowly sometimes. It's a nice break from the Kaos that always comes with me but I'd also have to say the Cub is the most skill intensive plane I own, especially with the 4 stroke on it.

I hope no one does either![X(] No, it was just set up for a picture that evening. I usually used 12 or 14 rubber bands #64 if I remember right.

This is what it looked like before flight along side my Wing Dragon I once owned:




Pete