Type of flying
 

From your previous posts, the only thing you are interested in is top speed on a 46 size AEROBATIC aircraft that wasn't meant to be flown at top speed.

If you want consistent aerobatics then the 4-stroke on this small of a plane would be the ideal setup.

I run a 100 Saito on a 60 size Kangke Extra 300s fueled with YS20/20 and sometimes on 15%Morgan fuel. My vertical is unlimited, and it will hover the plane around half throttle with a 15X6 APC.

Tuning is absoloutely not an issue. Tune it the same way you would a 2-stroke. You'll hear the RPMs drop if you go too lean and then back it to a rich setting, then go fly. Even though everyone will tell you that you can't tune a 4-stroke without a tach, they are wrong and you can. And man if you can't hear the rumble of a Saito 100, then you are DEAF.

Instant throttle up is where the 4-stroke beats the 2-stroke everytime. It hits its max very quickly, where the 2-stroke has to wind up to reach its max power.

It all boils down to what you want for your type of flying style.

I need convincing
 

From your previous posts, the only thing you are interested in is top speed on a 46 size AEROBATIC aircraft that wasn't meant to be flown at top speed.

Nope, try again. I do not want speed. When I set up a plane for aerobatics I choose a prop based on the operating range of an engine and what I want to do with it. Prop pitch has much more of an impact on speed than does top rpm when set up this way. I first choose the engine size based on weight. For this case I was trying to stay between 19 and 25 ounces. I choose the engine itself based on ability to do the job best. I choose the prop based on the intended style of flying. I have often bought much larger props and cut them down to get better low rpm performance from an engine. For example I might end up with a 17x6 wide blade cut down to 15x6. The blade will be quite wide once cut and generate plenty of static thrust. Also, the heavier blades will torque the plane better. But, the top speed will be a non-issue.

This, however, is a very good point:
Instant throttle up is where the 4-stroke beats the 2-stroke everytime. It hits its max very quickly, where the 2-stroke has to wind up to reach its max power.

I need convincing
 

YS 91FZ $279 at the Hobby Barn

I need convincing
 

Do yourself a favor... Check out Graupner Props!

http://www.hobby-lobby.com/grprop.htm

I need convincing
 

I used Graupners in my C/L days. I agree that the wide blade profile suits 4 strokes well. They would probably do well in a fun fly too. I guess I just got used to APC. My LHS has the Graupner 3 blades, but they have no 2 blades. I'll check out the pricing on line.

For $279 I may just have to try a YS. I assume that it has more gusto than a Saito 100? It's a bit heavier, but I guess I can handle that.

Anybody know for sure if (or when) YS has their 100 coming out?

I need convincing
 

Another nice thing about the YS is the pump. It allows me to keep my fuel tank back at the CG. Also, no flooding problems when fueling from a TEE connection.

I need convincing
 

MinnFlyer-
Please comment on how easy or hard the set up is. I've only talked to a couple of people regarding the YS and I've been told that they can be difficult to start with. I guess their comments were regarding the pressure system and fuel pump. Also what about tanks? Can I use a Great Planes tank at this pressure level? If not, what tank?

One other thing
 

If you go with the Saito, give it time to break in. This engine is amazing but it took a while to really show its potential.

Sorry if I was off the mark a little, but it seemed in your posts you were so concerned with max RPMs. If big props are what you want and the ability to rev them up quickly, then the Saito will outdo the 2-stroke.

You pick what you want, but I'm continually impressed with my Saito everytime I fly it. 30% heli fuel is not necessary. I've settled on 20/20, and see no difference between the 30 and 20% fuels. Like I said 15% Morgan is awesome too.

One other thing I have noticed with my Saito is that the fuel draw is more consistent than the 2 stroker. Without a pump my 91FX would lean out in high alpha without the aid of a pump. The Saito doesn't seem to suffer from this problem. My 160FX did the same thing.

Hope this helps you make your decision. Bottom line, get what you want.

I need convincing
 

I think this is one of those areas where people are afraid of the unknown. There's really nothing to setting up a YS. the only major difference is the pressure. There are two nipples in front of the engine. One draws fuel from the tank, (ANY standard tank) and the other goes to the tank vent. I have mine set up with a "T" fitting in each of the lines for fueling. These must be plugged or the pressure will escape from them.
Which brings up the next interesting point... When fueling, open the vent line first. You will hear a "PSHHHHHHHhhhhhh...." (Cool sound effects huh?) As the pressure releases. THEN you can open the feed line. If you open the feed line first, the pressure will push fuel out and you'll get your stand a little wet (We've all done it! LOL)

But that's it! There's really nothing to it. And the power is unreal!

I need convincing
 

Hello,

It looks like your 3 choices can be categorized as follows:

Saito FA-100, 15x6@9,800, 21 oz, $270:
As far as hearing, I can guarantee that you won't have a problem hearing the Saito 100. I have it on the UCD3D, and I can hear it well throughout the throttle range. That thing is considerably louder than the Saito 72 which I also have. Mine turns 15x6@9,500 on 10% fuel, which goes to tell you that you don't really need to buy premium nitro fuel. The 300~400 rpm increase doesn't justify the extra $10/gallon, especially considering you have more than enough for your .40 Giles.
Saito 100 won't idle too low reliably for the first 1/2 gallon, so on a small plane, that means the initial flights will have either hot landing or dead-sticks. Every plane that I have w/ new Saitos, I've had my share of dead-stick landing. Great ways to hone the landing skills...
Someone is selling this engine on Ebay, 1 per day. It usually ends up being $230.

YS 91 FZ, 15x6@10,400, 28 oz, $275:
Best power and throttle response, if you can balance the plane...

OS 91 FX, 14x6@11,000 15x6@10,400?? 24 oz, $200 - Tower discount - OS Gift Certificate + Jett Muffler cost
Although the 91 FX may swing the 15x6 at the same top rpm as YS 91, in practice, the throttle response will be too slow, about .5 second delay from idle to top end, my guesstimate. So you'd want the 14x6 if you were to go with the 91 FX. Besides, the plane is not that big, which does not beneficially justify the need of 15x6 prop.
Another thing, have you considered if the 2-stroke muffler will fit with the Gile? Will it hit the firewall?
I have an OS 1.60 FX, and I am not too impressed w/ its throttle response. I am not sure if the 91 FX is the same.

It seems to me that you will have more than enough power w/ any of these 3 engines. I'd be more concerned about weight. GP planes tend to balance right w/ the recommended engines, which means it should balance w/ a 46 FX, 16 oz? With the YS or FX, you probably need to put the servos and batteries at the tail.

Umm, regarding the Saito 72, I tached it using 14x5N @ 10,500. This might be enough for your Giles if it ends up 5 lb with the 72. This was not quite enough for the GP Extra 300S ARF, which weighed 6 lb. w/ the Saito 72.

I would go with the Saito 100, but you are not me. I hope you can make a decision which you won't later regret.

I need convincing
 

seanychen- Thanks for the breakdown numbers. I see the Giles balancing this way: I think with the rudder servo in the center of the plane it will balance the 46 FX. With the rudder servo in the tail (and battery to the rear), it seems like this option exists for the 91 4 strokers. I thought the Saito was a hair below 20 ounces, and the YS was just under 27? These are advertised numbers, but are they not reailty?

MinnFlyer- Does the YS not apply 6 to 9 pounds of pressure to the tank? Any tank will hold? I'd hate to hear a pop sound and then see fuel running out of the wing saddle...

I need convincing
 

Okay, I understand your hesitation now.

While I'm no newcomer to four strokes, I did put my first YS, a 91FZ, into service earlier this summer. I too had heard all the stories about all the tweaking, adjusting, etc., necessary to get one right. I'm here to tell you those stories are all BS; propagated either by people who don't know how to tune an engine or cannot follow instructions- or both.

I ran mine a few tanks on the bench, mounted it in the model and have been flying it with NO issues since. It has a down-draft air bleed carburetor, and you have to remember that the mixture screw works backwards (clockwise to richen), but I have adjusted that ONCE, and have touched the main needle a grand total of twice, in five months.

YS is great for cowled installations. You don't have to worry about T-junctions, those non-working fueling valves, etc. You have a fill line and a vent line. You uncap both, run fuel through the fill line until it comes out the vent, re-cap, prime, and crank. Since no fuel can enter the engine unless the crankshaft is turning, you don't worry about flooding the thing out while fueling. I have to use two hemostats on my Saito 150 in a 1/4 scale CAP to prevent sousing it. PITA.

I used to be a die-hard OS man. But since they caved in to the enviro-nazis with that preposterous new vent system which returns vented excess crankcase oil BACK into the fuel system (and the have the audacity to claim the engine is even more powerful and runs better!) I've basically written them off. Seen too many production corners cut lately, on ALL their engines.

I've been pleased with the Saito 150 (my first of that brand) too. So I think you would be okay with either the Saito 100 or YS 91. I have no clue which one is more powerful. But I'm running an APC 16x4W prop on the YS, and it is one hell of a stump-puller.

Steve

I need convincing
 

TailTwister--

I've run YS 2 strokes in the past and I've never had a problem with any tanks. I do wrap a layer or two of duct tape around the tank as a precaution, but I'm not even sure that it's necessary.

I just came back to flying after a few years away, and I got a U Can Do 3D with a YS91FZ. This is far and away the nicest engine I've ever owned. I'd buy another in a heartbeat. Absolutely great handling, it seems very uncritical on the needles, and hand starts easily for me. My U Can Do weighs around 7.7 lbs, and the 91FZ hauls it up like it's made of helium. The throttle response is superb.

In the past, I favored two strokes over four strokes, but the YS has changed my mind.

David

I need convincing
 

OK I'm convinced! I just ordered a YS 91 FZ. Boy, I hope this goes well.

Thanks to everyone for the info.

I need convincing
 

At the beginning of the thread you mentioned Wildcat 20/20 4 stroke fuel. I've only run Powermaster YS2020 in my engine so far, and it's been great for me. If the Wildcat has 20% oil content, and is all synthetic, you should be fine on it. The YS engines prefer synthetic to castor. Another thing... don't use regular after run oil in your YS, most are petroleum based and will attack the silicone parts in the regulator and lead to erratic behavior. Just make sure to run the engine dry at idle before you put it away at the end of a session.

Performance Specialties sell an after run oil that is compatible with YS engines, it's called "Ultra Oil"...

http://www.pspec.com/ultraoil.html

I haven't used it, but I haven't put my engine up for the winter yet. I'll probably get some before I do.

About props... I'm running an APC 16x4W on mine in the U Can Do, it's got tons of pull, and doesn't seem to be hurting for speed either. I haven't tried any other props yet, but I plan to get a Bambula 16x6 and maybe trim the tips a bit and see how that works out.

I think you're really going to like this engine.

David

I need convincing
 

For YSs I wrap the tank in straping tape. But you can still bust a seam on a cheap ARF tank though. You won't go wrong with any of the engines you've been considering. My YSs, Satos and both OS91FXs run great and have great throttle responce.

I need convincing
 

How is te YS 91's throttle response with the 16x4W? This prop gives me very slow throttle response on my Saito 100: going from idle to full takes about .75 second, and that's too slow for 3D flying. Just curious if the YS is better in this aspect.

I need convincing
 

I've never heard of that prop, what can you tell me? At least where to get a look at one...

I was figuring on an APC 15x6. Should I look more towards a 16x???

I need convincing
 

TailTwister,
I don't know the numbers, but as far as how much pressure is generated, let me just say that is a lot in relative terms. That is, When you run pressure from a regular engine, once you shutdown the engine, any pressure is immediately lost through the muffler. Not only does the YS claim to create more pressure, it is also a "closed system", so as Steve Campbell pointed out, fuel can't go in, and pressure can't leak out. At least, not until you open the vent. Then you get a slight rush of air (or fuel if you opened the wrong tube LOL). This escape of pressure is not something that we are used to hearing, so it SEEMS like a lot.
Do you need to wrap the tank in duct tape? I have been flying mine with the same Sullivan slant tank for two seasons with no problem. But this reminds me of that British passenger jet of the 50's called the "Comet" where after many repetitions of being pressurized and de-pressurized, they all started to explode. So, maybe before next season I will wrap it up just for good measure.

I need convincing
 

I'd be more concerned about losing a stopper? I'll for sure do the strapping tape. The website says 6 to 9 pounds of pressure on the tank. That's as much as a properly filled soccer ball. I usually put a bit of silicon glue around the stopper to eliminate all chance of a leak, but will a regular (Great Planes or Sullivan) tank hold?

I need convincing
 

TailTwister,

You'll probably do fine with the 15x6, I'm running the 16x4W, but I'm flying a bigger, heavier plane than the 46 size Giles.

If you want a look at Bambula Props, you can see them on RCShowcase's website, http://www.rcshowcase.com

Seanychen,

My YS's throttle response with the 16x4W APC seems a bit slow, but I'm still running rich (only six tanks or so run so far). Once I'm actually in a hover, throttle response seems instant, but there does seem to be a slight lag coming from idle, not like a transition issue, seems totally an inertia thing due to the weight of the prop. The 16x4W is definitely heavy. That's why I'm looking for a wood alternative.

David

I need convincing
 

Mine (sullivan tank) has held up so far. I also wrapped a little soft wire around each fuel line where it goes onto a nipple (IE at the engine, the check valve, the Tee fittings etc.). For filling, I'm not using fuel dots, (I didn't know about them at the time) when I bought the Tee fittings, they were in a package with several fittings including Tees, straight, 90 Degrees, etc. I cut two of the fittings so that one was straight, and one had a little 90 degree bend to it that way I can tell at a glance which one to open first (See pic) and I put a drop of CA in each to close them off. Also I use these to hold them on:
http://www2.towerhobbies.com/cgi-bin...1&I=LXD751&P=0

I don't know if they are necessary, but it doesn't hurt.

I need convincing
 

a bit heavier? I think the YS91 is a good 6-8 oz's heavier than the saito 100. I've had a YS91 and think that it's probably the best YS ever put out. It put's out the power of a normal 1.20 4stroke, but, it's almost as heavy.

I need convincing
 

I think the ad weight is 26.6 ounces. Yeah she's a brute, but I'm gonna give it a try. I may have to build the battery into the rudder...

I need convincing
 

Since you are putting 3 servos there already, how about the receiver, on/off switch at the tail as well? I mean, you have to have aileron extension cords: 2 to get the 2 aileron servos out of the wing, and 2 to connect from there to the receiver. Why not just make these two longer, and do away with the 3 extensions for the tail servos. Heck, also run the throttle servo from the tail to gain more tail weight. The pushrod is not that heavy... Top this off with the receiver antenna that goes from the tail to the front... Good luck!