I'm a born 2 stroke guy. I have just bought my first Saito. It's a 72. I guess I have yet to see the performance I've heard of. I'm going to check valves and re-tune the needles. I'm not giving up on Saito, but my next project is either going to be a 91FX with a Jett Muffler or a Saito 100. The Saito is 4 ounces lighter. The 91 seems to make about 2000 RPM more at top end. I rarely have trouble tuning a 2 stroke purely by ear. The 4 stroke seems a bit touchier to get right. No doubt once it's tuned and valves are set, it will give little trouble, but will the power be there? The new plane (with the 91 or 100) is going to be a GP G-202 46 kit. I'm sure I can build it below 6.5 pounds with either engine. My prop choice will be a 15x6 or 14x6 APC depending on the engines preference. Somebody convince me to go one way or the other. I'm not looking for an engine bashing thread, but I need good and bad. Also, what do you think about running Wildcat 20/20 4 stroke fuel in a 91FX?

IMO the Saito .72 wont give you what your looking for in that Giles. I had one and it had a .91FX in it and it was OK......

Plane is too big to really perform on a .72
Saito 1.00? Yes.

Anyone who know me on here knows what a big Saito .72 fan I am. I am no way bashing that engine.

And you are correct in your statement about tuning a 4 cycle by ear. To do it right, you need a tach.

Sorry, I wasn't too clear. The 72 is on a totally different plane. I mentioned it because it's my only 4 stroke experience, and it's not all that great. I have a tach, but little idea what to shoot for. I tried to get it to the peak rpm, and then back off a few hundred rpm. I guess I just need to give it time to start to seem right. I expected 9500 to 10000 rpm and got more like 8600 to 8800. For the Giles, the only engines in the heap are the 91FX and the Saito 100. I can get the 91 with a Jett muffler for $265 and I can get a Saito 100 for $260. Both are new engines. I'd expect 11000+ rpm (based on the Jett engineering numbers) with a 14x6 on the 91. I don't see any reason to believe the Saito 100 would break 9800 (based on Horizon's numbers). I believe the 91FX will do about 10000 (maybe 9800) on a 15x6. The Saito looks capable of barely 9000. Reliability and performance are the only factors with a $5 price difference.

tailtwiser, here are some RPM figures you might be interest in.

Saito91 15/16 bryon fuel. Here in Memphis, TN. Temps were in mid 60's. These were taken last week. Motor is broke in.

14x4W APC 10,800(Peak) I fly it at 10,400

15x4W APC 9,100 (Peak) I fly it at 8,800

I know the Saito 91 and 100 are 2 differant motors but, Maybe this will help.

I have read that the 100 will give you about 400 more RPM than the 91.

Hopes this helps.

*deleted*

That sure sounds like the 91 FX will out perform it on top end by quite a bit. Jett says a stock muffler 91FX will do about 10,700 rpm with a 14x8 APC. Their muffler brings the rpm to 11,500. Does anybody have 91FX numbers that say it will not?

You will not see outstanding performance numbers when looking at the specs of a motor...#1 you will never be running the motor at those numbers...#2 those numbers don't give best performance and can be interpreted different ways.

The 4 strokes have much more power throughout the range of throttle than the 2 strokes....the 2 strokes on make good power at the top end when running all out.

The 4 strokes have torque in the middle of the throttle band.

Another thing with only one exception the YS 140DZ (fuel Injected motor) cube for cube the 2 strokes will beat the 4 strokes at full throttle. SO


a 72 as you mentioned will not compete with a .61 or .70 2 stroke....but will have about the same weight and top end power of a strong I mean strong 46-50 size 2 stroke.

In fact the plane flying on the 72 will have more power because of the performance in the middle of the throttle band.


Another thing you can't look at a specific prop and rpms to determine power. Props are different and the 4 strokes like bigger props because of the power and grunt in the middle of the throttle.

Also you don't want the 4 strokes turning those high RPMS above 10K they work harder and get better when running down in the 8800-9500 rpm range.

The 2 strokes running in the rpm range don't make power because they get their performance from RPMs...the 4 strokes have it in the grunt category. Take for example an old tractor and a sports car.....the tractor could pull down a building but never hit 100mph.....


One other thing you will find is that the 4 strokes will respond to nitro much better than the 2 strokes. I never run below 20% nitro in the 4 strokes...reason is they run cooler and breathe better...Also the motors really perform as you up the nitro.

Type of Fuel is another issue.....I know there are big loyalties in the fuel department. I would caution you to try a few different ones....and see what you think. Last year I was testing the YS 140DZ and tried almost every fuel I could get my hands on....Wild Cat, Powermaster, Magnum, Cool Power, Excaliber, and so on...I tried all different blends from the 20/20's to pattern to 2 stroke, to you name it....what I settle on for peak performance reliable idle and cool running was the Cool Power 30% Heli Performance fuel. This is the same fuel that Saito recommends for their motors.

I bet if you look at running some of this fuel the performance will come....also as you up the nitro the needle valve becomes less sensitive and because the more nitro the richer the needle is set to get the mixture right.....the more oil flows and the cooler the motor becomes.

I know that Power Master has come up with a new Low Viscosity fuel similar to the Cool Power Heli and now Cool Power is making this same fuel in a 20%.....My guess is conservative but running a stock 20/20 fuel of any brand and then going to the 20% Heli Cool Power the results were over 10% in the performance and then going up to 30% the results were in the 20%+ range.....


The 4 strokes are not for everyone and every application but in the plane you are looking at the the Saito 100 on some 30% cool power heli is what I would run.



Good Luck
Troy Newman
Team JR

Im' running the 91FX on a Calypso. With a standard muffler it turns a 13/10 APC 10200 and a 13/8 3 blade Master at 10400 tuned for flight. With a Ultrathrust muffler it turns the 13/10 at 10800 and the 13/8 3 blade Master at 11400, again tuned for flight. This is on 15% nitro.

I sure do agree with the 30% low viscosity heli fuel in the Satos. I just can't stand the 27 dollar price tag for every day sport flying. But it does make a nice engine really, really nice.

I have to ditto this post... for the dollar difference in the 4-stroke vs a 2 stoke and then top it off with having to use higher nitro just to make it produce.... well I think thats why I have stuck withe 2 strokes. Outside of the enormous pipes you have to use they are pretty user friendly. Not mention much less maintanance... now some of you 4 strokers will disagree and say once they are set there is little maintanance and I wont disagree there. But I can take a 2 stroke apart and put it back together in less then a 1/3 the time of a 4 stroke.

SO.... now if I can adjust the fribulator valve and open the buffolator port just a little and decrease the net intenal drag a little bit.... just maybe I can get the torque of a 4 stroke.

Okay, I'll put in my $.02.
If I want throttle response but power isn't the biggest issue I go with a 4 stroke. If the throttle response isn't critical I prefer the 2 stroke. 3d type maneuvering is the primary time I want really crisp throttle response. My biggest headache with a 4 stroker is I can't hear it running. I want to hear my engine all the time I'm flying. I have a Saito 91 in a GP Super Sportster and it's the sweetest flying plane but I can never hear the thing. I grew up hearing these things scream and it just doesn't seem right being so quiet.
Later,,,basmmntdweller

I had the same plane till a battery messed up, what a great plane. In mine i had a 75 supertiger w/ a slime line pits muff.

I could do vertical snaps as high as i wanted, flat spin, invert flat spins just what ever you wanted. If i had my choice i'd damn sure go w/ the 91 FX..... In my opinion i think you hate life if you go with the 4 stroke....

I have a YS91 with a 15x6 prop on 20/20 fuel. It spins the prop at 10,400. Runs super smooth and sounds great. I'm never going back to 2 cycle again!

Rick

Yes some folks are driven by price and the fuel is more expensive I will grant you that.


Others are driven by performance and I like performance...the noise is an issue and throttle response and torque in the middle of the throttle ban is what I demand from a motor....


Its not a case of spend more money on fuel just to get it to run right...........


That's not the issue you wanted to see the motor really shine......then stick some nitro in it.

hey its different strokes for different folks....I prefer the reliable and consistent response and performance from the 4 stroke motors....In my opinion they make what I do easier....

I tried the 2 stroke pattern motors and saw the difference in my flying. The 4 stroke allowed me to stick the throttle where I wanted it and not try to anticipate the spool up and spool down of the motor and not have to anticipate it my my flying style either.....just stick it where you need it...if you need a little more then give it a little more....a little less and so on.....The more linear response is an advantage to me.....That why I use it.


The Saito motors are great for the same types of power response as the YS 4 strokes.

For sport motors I actually prefer 4 strokes now....they run better and give me more pleasure flying.


You can run them on any fuel you like as long as your happy with its performance....If your looking for more out of them then nitro will foot the bill.....unlike 2 strokes...


So try it its only 1 gallon of fuel...and if you live in Denver I give you a tank or 2 to see how you like it first!



Troy Newman

If you guys are spending $27 a gallon for fuel, you are getting fleeced. I run 30% high performance heli fuel by cool power in my YS 91fz. price is only 18.99 here in Tucson. 20% cool power is 14.99 byron 20% ys fuel 14.99

First, Let me thank veryone for speaking up. Next,let me let you in on my flying style. All I can say,is that it is a pretty agressive sport aerobatic, folllowed by a bit of 3D. I don't hover for 4 minutes at a time, nor do I beat the crap out of a plane all day. Even on the ground I recognize the linear performance of the 4 stroke, but remenber 2 strokes are what I'm familiar with. I have no problem with givng 2/3 open barrel to get 1/2 of available power. NOT THAT I THINK THAT'S BEST! I fly whatever the plane needs.

Fuel wise (locally) my choices are Cool Power, Omega, and Wildcat.

YS engines are easily the best, but not an option. $$$

tnewman-I'm not picking, I really liked what you said, just please elaborate.

basmntdweller- you may have hit my problem too.
My biggest headache with a 4 stroker is I can't hear it running. I want to hear my engine all the time I'm flying. I have a Saito 91 in a GP Super Sportster and it's the sweetest flying plane but I can never hear the thing. I grew up hearing these things scream and it just doesn't seem right being so quiet.
Any body got a comment.. Other than "Get over it!".

weatherly-In mine i had a 75 supertiger w/ a slime line pits muff.
I could do vertical snaps as high as i wanted, flat spin, invert flat spins just what ever you wanted. If i had my choice i'd damn sure go w/ the 91 FX..... In my opinion i think you hate life if you go with the 4 stroke....

CRAP! Did I mention I had a ST 75 (with a slimline) in the basement? Now the 91 is still winning based on familiarity.

tnewman-That's not the issue you wanted to see the motor really shine......then stick some nitro in it.

I like that comment alot. Saitos do well with 30%

I appreciate this comment the most so far.

I need explanation:
tnewmwn-Also you don't want the 4 strokes turning those high RPMS above 10K they work harder and get better when running down in the 8800-9500 rpm range
??? A 15x6 at a certain rpm equals a 15x6 at a certain rpm, right? Please see what I said about barrel opening vs RPM.

Another thing you can't look at a specific prop and rpms to determine power. Props are different and the 4 strokes like bigger props because of the power and grunt in the middle of the throttle.
15x6 is all I intend to do.

Not to pick, just I'm looking for the best 19 to 24 ounce power package. That's it! As of today, I do not have access to a cold fusion electric motor, so I've got to look elsewhere. At 10% to 20% nitro what can be done? Remember, I want an aerobatic plane (6.5 pounds), with a 14 to 15 inch prop, and reliable ( and quick) throllte response. I'd like the most static thrust I can get, with the two prior priorities addressed.

So,
14(or 15)x6 APC on a Saito 100?
14(or 15)x6 APC on an O.S. 91 FX?
Any other input?

Let me just chime in here for a minute. Tailtwister, you say YS are the best but not an option due to cost... I was going to suggest that you get a YS91FZ. To put it mildly, this engine has BALLS! And I run mine on 15% Cool Power, at 12 bucks a gallon. At that rate, you will more than cover the cost of the engine with your first 4 gallons of fuel. And after that, your fuel is still way cheaper than what you'd have to put in that Saito.

TailTwister,

You have been given some excellent arguments in favor of four-bangers by some very knowledgeable folks. But, judging from your last post, it seems to me you have your mind already made up in favor of a two-stroke. Hey, that's okay.

If you're looking for best power-to-weight, get a two-stroke. If you're looking for least maintenance, get a two-stroke. If you're looking for noise, get a two-stroke. If you're using a pipe on a two-stroke, have fun tuning it.

There is more to four-strokes than simple apple/orange comparisons. Four-strokes have an ambiance, an aura of cool, if you will. Those who are simply interested in price/performance would not understand.

Steve

*deleted*

Steve, I am leaning towards the 91, but just before this thread was started, I had convinced myself to go with the 100. I was sitting here with the credit card in hand and I read the top RPM figures from the 2 engines. I did not expect to find an almost 2,000 RPM difference. I spent some time thinking about it, and that's when I got really mixed up. At this point, if you handed me one of each for free and said "just pick one already", I'd still lean towards the 100. It's lighter, quieter, and probably likes the 15 inch prop better than the 91 does. I'm just trying to get some "convincing" going on so that I can part with the money. I was all set until the 72 I bought came up a bit shy.

I'll look at the YS again. That's a good point about using lower nitro fuel and the savings involved. I do recall that they are a bit heavier than the Saito too. I've heard about headaches associated with setting up the high pressure fuel system too. I'll look again.

YS 91 26.6 ounces @ $325. For the Saito I had intended to use Wildcat 20/20 fuel A $18 per gallon. Saving $6 per gallon means I break even around 11 gallons. That's about a season of flying for me. I probably would still run the 20/20 in the new engine because I still would need it for another plane. I actually had in my head that they cost a bit more than that. I can't imagine anyone saying they would pick the Saito over a YS unless it was based on price. Am I wrong? Any truth to the set up headaches I've heard rumor of?

$299.99 at Chief! Even better!

I have a YS91AC (the forerunner to the FZ) This thing ran straight out of the box on 15% Cool Power. I adjusted the needle valve slightly rich for the first 4 or 5 tanks, then brought it to just under peak, and I haven't touched a thing on that engine ever since. Here are some videos of it in action on my Skybolt. The Skybolt is a heavy plane for it's size (90-120 4-stroke) I haven't weighed it lately, as it is about 10 years old (so add the extra weight of all the repairs and oil-soaked wood) plus, to add to the weight, it has a smoke system.

You tell me if this is a sweet engine!

Videos are here:
http://12.31.143.32
Note: on the last video, the engine sounds sick. This is an audio problem with the tape and NOT how the engine really sounds.

Can you give prop and RPMs? It doesn't have to be exact, just not exagerated.

Thanks,

I can't tell you the RPMs but the prop is a Graupner, and I believe it is a 14x6.
BTW, many people here know that I am not the type of person to care about things like props. I'll throw anything that works on a 2 stroke, BUT! Graupner is (IMHO) the ONLY prop for a 4 stroke!