Saito FA-91S vs OS91FS?
Dave Tatosian
Now that Saito has caved their prices (at least for the next month or so)
down to where their FA-91S is the same price as an OS91FS, I'm interested
in opinions on which engine represents the better buy.
I've been flying with an OS91FS this season in a US60 and I've been
very pleased with its power and ease of use. I have no experience with Saito
engines - and don't know anyone that uses them (probably due to their
historically premium pricing).
The default would be to get another OS91FS, as I'm familiar with it, fuel
and parts are no problem, etc. But if the Saito is a clearly superior engine
I'm willing to give it a go.
This engine will be going into a CG Super Chipmunk to be built over the
winter. I've already decided it will be mounted inverted. With its hemi-head
I'm concerned that the Saito will *definitely* require on-board glow, whereas
with the OS engine there's some possibility that I can get away without -
we have a few inverted OS 4-strokes that don't have problems upside-down, just
stick an "F" plug in 'em, run 10% fuel, and they tick over just fine...
With regards to the Saito, I'm particularly interested in:
- ease of use (especially when mounted inverted)
- power
- weight
- parts availability
- fuel requirements
- quirks?
- does the Saito include a silencer?
Any and all input gratefully welcome (but try to keep the abject cheerleading
down a bit ;^)
Gentlemen: Start your keyboards!
Cheers!
/dave
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
<> Dave Tatosian tato...@eng.pko.dec.com <>
<> Digital Equipment Corp. Alpha Server Engineering <>
<> Parker Street Campus Maynard, Massachusetts <>
<> Charter Member of "Curmudgeons Unlimited" <>
<><><><><><><><><><><><> AMA 548313 <><><><><><><><><><><><>
Disclaimer: Opinion and content is mine alone, and unlikely
to be shared by my employer, etc...
Kwong Chu
I had a Saito 120-DP before, not exactly the size of the engine you have
question for. However, after experiencing an OS 91, I like the OS much
more than the Saito in terms of reliability and idling. 0.1 hp or $10
difference is not an issue, to me, in the 91 size class. Reliability
is! I don't want to mess with the engine in the field.
Kwong,
Waltham, MA.
Stephen
tato...@eng.pko.dec.com (Dave Tatosian) wrote:
>Now that Saito has caved their prices (at least for the next month or so)
>down to where their FA-91S is the same price as an OS91FS, I'm interested
>in opinions on which engine represents the better buy.
>I've been flying with an OS91FS this season in a US60 and I've been
>very pleased with its power and ease of use. I have no experience with Saito
>engines - and don't know anyone that uses them (probably due to their
>historically premium pricing).
>The default would be to get another OS91FS, as I'm familiar with it, fuel
>and parts are no problem, etc. But if the Saito is a clearly superior engine
>I'm willing to give it a go.
>This engine will be going into a CG Super Chipmunk to be built over the
>winter. I've already decided it will be mounted inverted. With its hemi-head
>I'm concerned that the Saito will *definitely* require on-board glow, whereas
>with the OS engine there's some possibility that I can get away without -
>we have a few inverted OS 4-strokes that don't have problems upside-down, just
>stick an "F" plug in 'em, run 10% fuel, and they tick over just fine...
<SNIP>
I am currently flying a Chipmunk with OS91 mounted 90 degrees. It has
plenty of power to do everything.
My experiences with Saito was on a 65 and it was quite a power house
as well. I did have problems getting a smooth idle (on a Piper Cub
mounted also at 90 degrees). Come to think of it, it never did idle
by itself. But almost every one of the Saito at our field will start
with one flip on the prop and sit there idle all day long, so it must
be my fuel or plug.
If I were to buy a new engine right now, I would definitely go with
OS. I believe their quality is more consistant and parts are much
easier to get than Saito. But for 91 I think the YS beats both hands
down.
I never did figure out what a Hemi head is? How can it affect the way
the glow plug works?
Stephen
Joe Finkelstine
Hi,
I own and run both 91 4 strokes you are asking about. Both engines are
very good and each one has its advantages. The Saito is the lightest of
the 2 by a long shot. The Saito 91 is lighter than several 60 2 strokes,
but it does have a little less power then the O.S. I've tested both
engines on the same APC prop, 10% cool power and the O.S. will run
between 500-800 rpm more on any given day I ran the test ( 4 different
days ). The O.S. creates more power, but at a higher rate. Both engines
will make any 60 size ship rip through the sky. I have read previous
comments about the Saito's being hard to get parts for, low quality,
etc. I am in disagreement with these comments. At my field ( Skymasters,
MI ) Saito's and O.S. 4 strokes abound with Saito's probably having the
edge in numbers. Getting parts is no different or harder then O.S. ,
both are available at our local hobby shops or mail order
Joe F.
Gordon_Jack
Dave Tatosian wrote:
>
> Now that Saito has caved their prices (at least for the next month or so)
> down to where their FA-91S is the same price as an OS91FS, I'm interested
> in opinions on which engine represents the better buy.
>
> I've been flying with an OS91FS this season in a US60 and I've been
> very pleased with its power and ease of use. I have no experience with Saito
> engines - and don't know anyone that uses them (probably due to their
> historically premium pricing).
>
> The default would be to get another OS91FS, as I'm familiar with it, fuel
> and parts are no problem, etc. But if the Saito is a clearly superior engine
> I'm willing to give it a go.
>
> This engine will be going into a CG Super Chipmunk to be built over the
> winter. I've already decided it will be mounted inverted. With its hemi-head
> I'm concerned that the Saito will *definitely* require on-board glow, whereas
> with the OS engine there's some possibility that I can get away without -
> we have a few inverted OS 4-strokes that don't have problems upside-down, just
> stick an "F" plug in 'em, run 10% fuel, and they tick over just fine...
>
>
> - ease of use (especially when mounted inverted)
> - power
> - weight
> - parts availability
> - fuel requirements
> - quirks?
> - does the Saito include a silencer?
>
> Any and all input gratefully welcome (but try to keep the abject cheerleading
> down a bit ;^)
>
> Gentlemen: Start your keyboards!
>
> Cheers!
>
> /dave
>
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
> <> Dave Tatosian tato...@eng.pko.dec.com <>
> <> Digital Equipment Corp. Alpha Server Engineering <>
> <> Parker Street Campus Maynard, Massachusetts <>
> <> Charter Member of "Curmudgeons Unlimited" <>
> <><><><><><><><><><><><> AMA 548313 <><><><><><><><><><><><>
> Disclaimer: Opinion and content is mine alone, and unlikely
> to be shared by my employer, etc...
Dave
I was going to recomend the YS 91 but if it is a CG Chipmunk you are
building better stick with the O.S. or Saito... The YS is a bit too
Much.
The YS 91is much better suited to a bit larger plane (Std 120) size and
for the flyer who expects exceptional reliability.
Gord
Douglas Bromley
I have an old Saito 65 that I bought beat up at an auction. After I put
new bearings in it, it runs great inverted in my Cap 21. A friend has one
in a Cub inverted with same result. The word at our club is that the
Saito's are work horses that last forever. Seems to be the case with me.
Also I hear that if money is not an issue the YS is the Cadillac (or
maybe I should say the Acura) of the 4-strokes. I am puzzling over the
same decision about OS vs. Saito but not because I am dissatisfied. Also,
I am tempted by the low price of the Thunder Tiger 91. Any thoughts about
that one?
Dave Tatosian
In article <56orjs$s...@news1.ni.net>, ste...@combridge.com (Stephen) wrote:
[anip]
>If I were to buy a new engine right now, I would definitely go with
>OS. I believe their quality is more consistant and parts are much
>easier to get than Saito. But for 91 I think the YS beats both hands
>down.
Stephen, are you basing the above on power alone, or ? I intentionally left
the YS91AC off my list due to the extra ~$100 it'd cost - and that the extra
thrust won't be needed for the 'Munk...
>I never did figure out what a Hemi head is? How can it affect the way
>the glow plug works?
"Hemi" is slang for hemispherical - and refers to the shape of the combustion
chamber. Non-"hemi" chambers are either cylindrical (flat topped) or wedge
shaped. Classic hemi designs are touted as providing more power from a number
of reasons (better intake and exhaust flows because of valve locations, better
spreading of flame front through the charge, etc).
I was speculating that there *might* be an attendant difference in the ability
to achieve a solid idle with a hemi because the plug sits in the center of the
"bowl" - which *might* be more prone to fuel puddling. Don't know/can't say -
which is why I asked...
Ed Cregger
Stephen wrote:
(snip)
> But for 91 I think the YS beats both hands down. (snip)
I finally got a YS.91AC and can tell you that comparing this engine to a
Saito .91 is like comparing apples and oranges. Yes, the YS does produce
more power, but - it is considerably heavier and larger than the Saito
.91, which is built in a much smaller frame. The Saito is nearly a
shoe-in for a model designed for a two-stroke sixty. The YS.91AC would
require a major redesign of a sixty sized model were it to be fitted
properly. Both are nice engines. I suspect that the OS.91 is probably
closer in size to the YS than the Saito.
>(snip) I never did figure out what a Hemi head is? How can it affect the way the glow plug works? (snip)
It doesn't. I would suspect a problem with fuel/adjustment/glow plug
selection or unrealistic expectations. Good luck in finding the
solution.
Ed Cregger
ecre...@water.waterw.com
Mark Orr
I have no actual experience with either engine, but the Saito is AAC
construction, has a 1 piece cylinder ass. and a 3 year warranty. If I were to
buy either as my first .91 engine, I would get the Saito.....Since you have an
OS, and you like it, it may be the way to go since you are already familiar
with it.....BUT variety is the spice of life.
Mark
Jon Earle
Joe Finkelstine <jfi...@eai.com> wrote:
>will make any 60 size ship rip through the sky. I have read previous
>comments about the Saito's being hard to get parts for, low quality,
>etc. I am in disagreement with these comments. At my field ( Skymasters,
Agreed. I used to happily own a Saito 65, and it was a darn fine
piece of craftmanship. One of the two best engines I've every owned.
Jon