Some engine help please.
 

Guys I bought a .40 through .60 Aeroworks Edge 540T, I was going to buy the O.S. .75AX but I herd that its not that great. Some guys said to get the .91FX and just use throttle management. First of, whats the difference between the FX's and the AX's? Second, whats the deal with the .75AX's? Third, do you think the .91 is going to be way over kill? Guys any help would be greatly appreciated, im a lil rusty in the glow fuel area. And please dont say, "buy a 4 stroke". I had a Saito .72 and couldnt stand it, never could get it to run decent, so 4 strokes is out the question. Thanks for any help guys. Oh and im going to order this engine this week.

RE: Some engine help please.
 

I don't think a .91 on a .60 size plane is overkill at all! Around here, that is pretty much standard practice.

On a downline, you DO have to use a little descretion and throttle management, so you don't rip the wings off, but that will be true of the .75 also.

As to the difference between the FX and the AX versions, the AX has an angled high speed needle valve, a new shape to the cylinder, and a new style muffler (which I don't like at all, but that is just personal preference...). The AX version also comes with a $50 higher price tag!

RE: Some engine help please.
 

The AX engine are newer in design than the FX. The 91 FX has been discontinued The new engine is the 95AX

http://www3.towerhobbies.com/cgi-bin...LXXMU4&P=7

RE: Some engine help please.
 

I just checked Tower, they still sell the .91FX. The .91FX ways less than the .95AX and the .91 is (if I spell this rite, lol) scherley ported. Im prolly gonna get the .91 I hope its not gonna be to much though. The plane says .40 through .60 in 2 strokes and im gonna put a .91 Man thats a lil big. Just gonna have to be easy with the throttle. Guys im not gonna have to buy a perry pump are glow assist for this thing rite?

RE: Some engine help please.
 

I own two .75's they work GREAT!!!

With the AX series, OS put the needle back on the carburetor body.

RE: Some engine help please.
 

Get a 4 stroke!!!!:D

RE: Some engine help please.
 

Y should I get a 4 stroke?

RE: Some engine help please.
 

There's nothing wrong with the new AX series. The carbs are an improvement especially with the HS needle back on the carb where it belongs. The engines seem to run cooler and seem to last much longer except the bearings need to be replaced at the same intervals as the FX. I wish OS would LOSE THE CHEAP STEEL CAGED BEARINGS, what do they save, 20 cents a unit their cost?

I would run the old 46 FX hard for a summer and the power would be down so I'd hand it off to the fist kid I saw for his trainer, still stronger than a LA right?
Then I'd pick up a fresh one for next season.
I now run a few 55AXs and it's been a few years and no power loss, they must have done something different to the piston or nickle plating.

The AX series engines make their power at a little lower rpm the other engines in their size, just adjust the prop size accordingly.

As to the suggested prop sizes in the manual .....are they kidding?

RE: Some engine help please.
 

Guys I just dont know what to do. I whant the plane to have plenty off power and everything, but a .91 just sounds kinda big. I have a .46AX and love it, I dont see anything wrong with the AX series except that there a lil mor exspensive. Now on the other hand, having a .91 on it is going to give some serious unlimited vertical. I definately like lots off power, just not so much were I have to start adding tons of tail weight either. Just gonna have to think some more I guess.

RE: Some engine help please.
 

Quote:

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ORIGINAL: Moki 1.8

...The .91FX ways less than the .95AX and the .91FX is (if I spell this right, lol) scherley ported. I'm prolly gonna get the .91

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Moki,


I believe you probably meant Schnürle ported (Schneurle - if it must be typed only in English ASCII characters).

Nearly all two-stroke engines sold anywhere today have schnürle porting + a boost port; both above OS engines included.

The classic schnürle porting arrangement includes only the two rearward angled side-ports.
The upward angled boost-port, at the rear, is there to add even more power.

The orientation of the ports is to the exhaust port; not to the engine itself. I.e. if the exhaust is to the side, the boost-port is on the other side and the schnürle ports are at the front and the rear of the cylinder.

Other, less common porting methods are TST - Travasi Super-Tigre, baffle-piston (loop-scavenged) and the Cox two-port... There are others too, such as PDP (Perry Directional Porting), that goes with baffle-piston and TST...

EDIT: Typo.

RE: Some engine help please.
 

Moki,

Let me tell you about my experience. I have a similar frame to yours. I have a GP Giles 202 that is for 0.46 to 0.60 2-stroke or 0.70 to 0.90 4-strokes. After flying the airplane with a 0.61-FX, I decided to upgrade the engine to a 0.90 engine. I ended up installing an SK-90 2-stroke with APX 14x6, 10,000 RPM max. SK-90 is a $100.00 engine. The Giles' dry weight is 6-lb and 15-oz. I balanced the model without adding lead.

The airplane flyes straight level at 1/2 stick having a decent vertical momemtum if I do not add power. The extra power gives you unlimited power to perform any aerobatic you want including big loops and long verticals. The key is throttle management. At the end, I could not be happier with the power my Giles has. I have plenty of power for performing anythig I want. The 12-oz tank gives me 10-minutes for aerobatics with about 1/5 of tank spare fuel in case I need to delay my landing. Yes, I could have installed a 4-stroke, but I prefer 2-strokes for their simplicity of operation, maintenance, and cost.

By the way, I built this Giles from a kit. I checked everything in the firewall to support this kind of power.

Hope it helps.

RE: Some engine help please.
 

Thanks for all the replys guys. Im definately not going to buy a 4 stroke. Alot has changed in the last couple days. The lil edge 540 that I ordered from aeroworks was on back order for 8 weeks, so I canceled that and ordered the .60-.90 Aeroworks Extra 260. So a .75AX is out the question now, to power this plane im going to use the .91FX. Well yesterday I went visit a buddy at his flying field, he was flying a Great Planes Extra300s with a Brisson 40cc engine, man that thing was bad to the bone. And now I want the exact same set up. So, with all that being said, im going to try and get rid of the lil Extra when it comes in. I have it for sale on this sight, im gonna sell it for the same price I paid, but i'll ship for free. Basicly saving the buyer $24.95. Once the UPS guy drops it off, i'll just turn around and ship directly to the buyer. I wont even open the box. Guys spread the word for me. But if it doesnt sell, im gonna go ahead and build it. My future wife wants to buy me a plane for christmas, well I know what she can buy lol.

RE: Some engine help please.
 

Post removed by myself. While this post was not edited by the moderator, it has become my policy to remove my posts to threads that have been edited without my permission and particularly without good reason. I will not be part of a discussion forum that does not allow discussion.

RE: Some engine help please.
 

Thats incorrect, Loop scavenged is a group of porting types that include schneurle porting. Usually original schneurle, and the more modern variants. What they call loop porting in the model world is reall cross flow porting. These names are from the pattern the flow makes when looking at the engine from the top looking down.

Opps, I see Bill had a similar post! Well I gues there are at least two who police improper scavenging names.

RE: Some engine help please.
 

Bill,


You are basically right, but the baffle piston design has been called 'loop scavenged' (in model magazines), because the intake flow loops to the top of the cylinder; and does not run across, directly to the exhaust...

RE: Some engine help please.
 

That's not a loop, its a U shape.

RE: Some engine help please.
 

Quote:

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ORIGINAL: Sport_Pilot

That's not a loop, its a U shape.

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Hugh,


A 'loop' does not necessarily cross its own path at the bottom...

For example, a loop in garments and canvas tents, is just a 'U' shaped part, which 'catches' on another part, hook, button, Etc..


In pattern it should be called another name, maybe, but anything shaped like an upright, or an inverted 'U' is a loop...

A cross-flow head in auto engines, has the intake on one side and the exhaust on the other.
Some other heads, which have both the intake and the exhaust on the same side, are not 'cross-flow'...

That's besides the point, however...

RE: Some engine help please.
 

Let me help you out here Dar :D. How about we call it an omega Ω scavenged engine :D. Feel free to copyright the name :D.

RE: Some engine help please.
 

Quote:

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ORIGINAL: downunder

Let me help you out here Dar :D. How about we call it an omega Ω scavenged engine :D. Feel free to copyright the name :D.

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Why, thank you, Brian!

But I think I will stay with my current nomenclature...


A 'baffle piston', 'cross-flow' engine, is no less 'loop-scavenged' than is a Schnürle ported engine...
In fact, it is even more so.

The term used in model magazines (RCM and MAN) is the term I prefer.
So, as far as I am concerned; a loop-scavenged engine has a baffle piston and a Schnürle ported engine is just that.


There's no need to translate. When one says an engine is 'Schnürle ported', there's no need to also describe how the exhaust gasses are scavenged...

RE: Some engine help please.
 

Dar a baffled cross flow engine goes from the intake port to the exhaust port. U shaped from the side. From the top it makes a straight line. When looking at loop port engines from the top the flow mkes too loops as below. See example below.

RE: Some engine help please.
 

Post removed by myself. I will not allow my posts to be cropped indiscriminately and without good cause.

Bill

RE: Some engine help please.
 

Hugh,


This drawing you posted does not portray much, I must say...

First of all, it is a five-port engine; not a Schnürle ported engine.
Also, the flow within the cylinder is three dimensional; not flat...

Let's call the exhaust side of the cylinder 'the front' and the opposite side will be 'the rear' of the cylinder...
If the drawing is as viewed from above; and the two ports nearer to the exhaust are the Schnürle ports, they seem to flow up and then then to the rear and then down, eventually flowing toward the exhaust under where the flow begins...

This cannot be. The drawn loop is reversed the the actual flow.
Schnürle ports flow to the rear, in and up, toward the rear of the combustion chamber and then the flow loops back through the combustion chamber, toward the front and down along the exhaust side of the cylinder.
The flow does not cross the place where it begins and flows over its beginning; not under.

RE: Some engine help please.
 

It is a loop ported engine because the flow loops as shown in the diagram, the flow acutally crosses. Our modern type model engines are also not true Schnürle ported engines with the ports at each side and a boost port across from the exhaust. If you take away the two righmost ports of this design it woudl be a true Schnürle ported engine and thus is closer to the original than most model engines. You tried to use a 2 dimensional model when you tried to say it looped when viewed from the side, but that is actually upside down U shaped. So IMO a 2D diagram from the top is more than appropriate.

If seen from the side the flow would be up in a spiral then sharply down toward the exhaust from near the top.