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Saito vs OS - 11/18/2002 3:56:05 PM   
$ircra$halot


 

Posts: 256
Joined: 9/24/2002
Status: offline 		I have a Saito FA91s on a Goldberg Tiger 60 that has about 6 gallons of cool power 15% fuel run thru it. After reading some threads here a while back, I adjusted the valves, a little on the tight side, with the supplied feeler gauge, and have been happy with it's performance. That is untill recently. A new guy started flying at the same field I fly at, with an OS 91 surpass ll, on a plane called a Duster that I believe was kitted right here in Colo. Springs Co. His plane is bigger and heavier than mine, but it spanks me bad, speed wise. I tried some of his fuel, which is a custom blend 20% with 18% klotz and synthetic oil blend. While performance was noticeably better, it was nowhere near his performance. His will swing a 14x6 prop with authority. Mine a 13x6, a 14" prop will barely get the plane off the ground. Mind you we are at 6000' altitude. OK Question is is it possible I got the valves to tight, or are OS motors that powerfull? My owners manual says I should be able to swing a 14" prop no problem. Always glad to help if I can. This time it's me that needs the help. After that if we could address the moter question. Garry
       Post #: 1

Saito vs OS - 11/18/2002 6:48:47 PM   
Damnathius



Posts: 518
Joined: 9/28/2002
From: Lancaster, CA, USA
Status: offline 		I had the same problem with an OS 52. After a few hours of running, I set the lash "on the tight side". The engine still ran okay, and since I had it in a Cub it didn't see full throttle often. But still noticed it didn't want to wind up.

Deciding to get rid of the Cub, I pulled the motor and prepared it for storage. I checked the clearance on the valves, and they were quite tight with very little gap while cold.

I also had a Saito 91 on a GP 40 sized Extra that would really pull that plane around the sky. Valve clearance? Set with the supplied feeler gauge, and not on the tight side. I never ran a 14 on it, but did find that a 13/8 ran best.

Your Saito should keep up with the OS, but that also depends on the plane. Different airfoil, different design, different purpose. Heavier does not always mean slower. Isn't a "Duster" one of those high speed planes?

Hope this helps.

Dave

(in reply to $ircra$halot)
       Post #: 2

Saito vs OS - 11/18/2002 7:11:12 PM   
$ircra$halot


 

Posts: 256
Joined: 9/24/2002
Status: offline 		Greetings Damnathius: All I can really tell you is the Duster has a much thicker airfoil. This leads me to believe it would be slower. But design is not one of my better Virtues. I am going to re- adjust the valves using the method described by w8ye in another post and see what happens. It seems to me that one 91 should be simular in power to another. I know they won't be dead on, but there is no resembalance. like I mentioned in the original post, the instructions say it will turn a 14" prop. I'll see. I still love the engine for it's looks if nothing else. And it has been reliable. Thanks for the input. Please forgive spelling, just can't seem to do it, and the spell check is not working. Maybe the boss can figure it out. Time for zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz's Garry

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Saito vs OS - 11/22/2002 3:52:59 PM   
$ircra$halot


 

Posts: 256
Joined: 9/24/2002
Status: offline 		Valves readjusted, and still being shown up by the OS, any ideas why this motor does not even come close to the OS. Both are 91s. As stated in the original post it is very reliable. It just seems it should be at least close power wise. I don't think the duster the other guy is flying is really built for speed. He states that he knows the designer personally and the duster is just a sport plane. Any ideas? I can live with this, but if I don't have to...... Garry

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       Post #: 4

Saito vs OS - 11/22/2002 7:02:41 PM   
Hobbsy



Posts: 10683
Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: offline 		The only way to judge this fairly is with identical planes or identical props and a tach. Your Saito .91 should turn a 14x6 at about 9,500 rpm on 15% nitro.

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"I have gone faster backwards, upside down and on fire than most people have gone at all" Don Garlits

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       Post #: 5

Saito vs OS - 11/22/2002 8:25:50 PM   
bpu699


 

Posts: 180
Joined: 3/13/2002
From: racine , WI, USA
Status: offline 		saito 91 should have more power than the os. Mine turns an apc 14/8 on 15% byron with no difficulty....

What brand prop do you use? What does he use? Are your rpm's peaked-300?

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       Post #: 6

Saito vs OS - 11/23/2002 2:34:04 AM   
ShempHoward


 

Posts: 1147
Joined: 12/4/2001
From: San Francisco, CA, USA
Status: offline 		Running on the same fuel, prop and plug the OS 91 Surpass (any version) will outspin the Saito 91 by a few hundred RPM. Read the magazine tests and see for yourself although it will take you a bit of searching around. Over tightened valves will make a lot of difference so I suggest you readjust them asap. Also you can't make a fair comparison unless the engines are running on the exact same fuel, prop, plug and airframe to start.

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       Post #: 7

Saito vs OS - 11/23/2002 3:12:06 AM   
sdt22



Posts: 112
Joined: 8/3/2002
From: Tampa, Fl
Status: offline 		If it's bothering you that bad go pick up a gallon of 30% fuel. I had a significant gain in rpm (about 800) when I made the switch on my saito 72

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       Post #: 8

Saito vs OS - 11/23/2002 3:14:00 AM   
LQUAN


 

Posts: 101
Joined: 10/7/2002
From: El Monte, CA, USA
Status: offline 		I have always been using OS. I have 3 OS 4-stroke 91 II with pump. I recently bought a Saito FA91 because of the enticing lower price and less weight. After comparing both, I am not too happy with the FA91 when it comes to smothness. I get a couple hundreds rmp more out of the OS 91 on the same prop. I don't see much difference in performance when they are in the sky. I use OS F type glow plug and 15% nitro on both and I see that the FA91 hesitates more at less then 1/3 throttle. The OS91 seem too rev smoother. I think the FA91 vibrates more than the OS91 ... I am not so sure ... may be it is my imagination.

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LQ

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Saito vs OS - 11/23/2002 1:16:25 PM   
$ircra$halot


 

Posts: 256
Joined: 9/24/2002
Status: offline 		It sounds like we have a hung jury on this one. I am turning a 13x8 prop. my friend a 14x6 on the OS, MA props seem to give the best performence for both engines. Unfortunatly I lent my tach. to another friend and have not seen him to get it back yet. We both feel the Saito is lacking several hun. rpm compared to the OS useing the 13x8 MA Saito, 14x6 MA on the OS. BTW the props tested were MA and APC. I tried a 14x6 MA (off my friends engine) and was lucky to get off the ground. Both of us were useing the same fuel right out of the same jug, for comparison purposes. And an OS type F plug. Again without a tach. it's not a fair comparison. I adjusted the valves to .002 per w8ye Jim's specs. he seems to be one of many, that is in the know on these things. It did not seem to make a lot of diff. compared to the Saito specs. As I have stated before it is reliable, so if I need more power, I'll just have to buy a Binford, I mean OS, or a YS if I really feel the need, the need for speed. Of coarse a YS. shall require a raise of $. Thanks for all the input. Garry

< Message edited by $ircra$halot -- Nov 23 2002 8:31AM >

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       Post #: 10

Saito vs OS - 11/23/2002 11:10:44 PM   
outssider


 

Posts: 1107
Joined: 1/18/2002
Status: offline 		the saito 100 has made the saito 91 obsolete.....so why buy the saito 91 in the first place ?????

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       Post #: 11

Saito vs OS - 11/24/2002 2:50:01 AM   
LQUAN


 

Posts: 101
Joined: 10/7/2002
From: El Monte, CA, USA
Status: offline 		I realize that the FA100 made the FA91-S obsolete. They both will fit into the same engine mount. I bought the FA91 brand-new in a the box from a guy who just bought it and decided not needing anymore. I got it for $200. Not to mention they both will fit into the OS91 engine mount as well.

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LQ

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Saito vs OS - 11/24/2002 8:20:19 PM   
$ircra$halot


 

Posts: 256
Joined: 9/24/2002
Status: offline 		Hi outssider: I bought the 91 before the 100 came out, by about a month. Would'nt ya know. Garry

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       Post #: 13

Saito vs OS - 11/27/2002 6:31:46 PM   
fred685


 

Posts: 98
Joined: 1/25/2002
From: salem, VA, USA
Status: offline 		I did a lot of testing a few years ago between my OS, Saito and YS 91's. The YS outperformed both by a bunch, but weighed almost as much as a 120. The Saito and OS turned almost identical PRM's on all the props I tried that a 91 would normally use. Both engines ran flawless during the testing. The only prop I found a difference on was an APC 16-8. Too much for both engines, but I was only testing on the ground at this point. Both engines could turn it at the same RPM, although I don't remember what it was. The Saito took about 8 seconds to get this prop going at full RPM, the OS got it going in about 3 seconds. Now I'm not an engineer, but I think the engines were equal in horsepower, but the OS was stronger in torque to get the bigger prop up to speeed faster. So this lead me to believe the OS was better. Then I flew the engines and the Saito performed better in the air, although not by much. So what does all this mean? Means ground testing with a tach is worthless. Performance in the air is what counts, not what a tach says. Fuel used for the testing was S&W 25%, and the OS was a non-pumped version.

Fred

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       Post #: 14

Saito vs OS - 11/27/2002 8:11:21 PM