Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Page 1 of 3 123 LastLast
Results 1 to 25 of 51

  1. #1
    Cogburn's Avatar
    Join Date
    Mar 2004
    Location
    Aurora, SD
    Posts
    256
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    Magnum .91FS!

    Just got done running in my new magnum .91fs. 150$ on sale at tower! Adjusted the valves and tried a few props. Here's what i'm getting!

    39'f , 30.15"pressure
    15% omega with 2% castor added

    11x9 apc 11600rpm 1.47hp
    12x8k ma 10650rpm 1.43hp
    14x6k ma 10250rpm 1.77hp
    Peaked
    HP from thrusthp
    These things must fall off fast after 10000rpm.

  2. #2

    Join Date
    May 2004
    Location
    tbilisi, GEORGIA
    Posts
    105
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    don't trust thrusthp calculator.
    I have same engine, running on 5%nitro and 18% castor
    here are some results

    MA 13X8k 8.3lb
    MA 13X8 3blade same, but more speed
    top flight 15X6 9.7 lb

  3. #3

    Join Date
    Oct 2002
    Location
    Chapel Hill, TN
    Posts
    1,107
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I dont touch the valves. I ran 2 tanks through my $149 tower motor too! I put a Master Airscrew 14x6 and pulled consistently 10,500 static. I put a 15x6 APC on it and pulled 8900. This is with Cool Power 30% Heli. This motor is a hog man, I love it.
    Where there is confusion, there is profit.
    AMA # 403098

  4. #4
    Moderator w8ye's Avatar
    Join Date
    Dec 2001
    Location
    Shelby, OH
    Posts
    37,013
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I ran mine a couple years ago and was 9500 with a 14-8 APC 1,100' @40F.

    It was stronger than my OS 91 Surpass I which was 9400 with a 14-6.

    Saito 80 was 9200 with a 14-6.

    All same day with Omega 10%
    Attended the CutFinger Institute of DirtNap University for years but never did graduate....
    Recipient, Mangledhand award August 2008
    Club Saito Member #7
    Original AMA #31261

  5. #5

    Join Date
    Oct 2002
    Location
    Chapel Hill, TN
    Posts
    1,107
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Now 3 gallons through my Magnum .91 for $149 on 30% Heli..... I spin an APC 15x6 at 10,000 even. This motor is incredible. Stronger than my newer .91 OS Max!!
    Where there is confusion, there is profit.
    AMA # 403098

  6. #6

    Join Date
    May 2004
    Location
    tbilisi, GEORGIA
    Posts
    105
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    thats joke yea? how can 91 magnum spit 15X6 on 10k? I can't believe. check thrust or recheck tchometer. if it'sso, lets god be with u. just wonderfull

  7. #7

    Join Date
    Oct 2002
    Location
    Chapel Hill, TN
    Posts
    1,107
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    It the 2nd one I have that turns a 15x4 or 6 at static 10,000. I have a Magnum tac and a Glow Bee tach. Both the same. The motor is screaming, I believe it. I will get some vid clips up soon. Take in mind, I run 30% nitro too... I run them rich, always run afterrun oil, and let the good times roll. Its 3D, So I dont need to wind them up, but they will!
    Where there is confusion, there is profit.
    AMA # 403098

  8. #8
    RCAddiction's Avatar
    Join Date
    Mar 2002
    Location
    Waxhaw, NC
    Posts
    1,006
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    14x6 APC 9900 rpm on Wildcat 15% full synthetic
    Lee

  9. #9
    Gringo Flyer's Avatar
    Join Date
    Jan 2004
    Location
    Formosa, ARGENTINA
    Posts
    2,370
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    HOw long after break in does it take to get to these rpmยดs

    I was breaking mine in yesterday and with a 14X6 MA prop and 10% fuel I was getting around 7500. It was super rich but I cant see another 2500 RPMยดs coming out of this engine.
    \"Courage is being scared to death...and saddling up anyway.\"---John Wayne

    Roll Tide Roll!!!!

  10. #10
    Gringo Flyer's Avatar
    Join Date
    Jan 2004
    Location
    Formosa, ARGENTINA
    Posts
    2,370
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I just looked through some tach readings on other four strokes and you guys are getting close to the same readings that guys are reporting on Saito 100.

    I just dont see how that is possible. Am I the only one not getting huge numbers on a Magnum 91?
    \"Courage is being scared to death...and saddling up anyway.\"---John Wayne

    Roll Tide Roll!!!!

  11. #11
    seanychen's Avatar
    Join Date
    Jul 2002
    Location
    Canton, MI
    Posts
    2,914
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    High nitro helps a lot in 4-stroke engines nowadays. Usually you can get 500+ rpm gain going from 15% nitro to 30% nitro.

    Having said that, the Saito 100 and Magnum 91 4-stroke differ in power by about 500 rpm on the same prop and same nitro. So I can believe that Magnum 91 on 30% nitro will catch up with Saito 100 on 15% nitro, if both use the same prop that's within comfortable range of the 91. However, running expensive 30% nitro fuel on a Magnum sort of defeats the benefit of Magnum's economy. I've found that 20/20 fuel is a good compromise between fuel cost and performance.

    Saito 100 will out-pull a 4-stroke 91 significantly when you go to larger prop, like APC 16x4W.
    E_Total = M*G*H + 1/2 M*V^2
    When H=0, all of airplane\'s velocity becomes crash energy!

  12. #12
    Sport_Pilot's Avatar
    Join Date
    Jan 2002
    Location
    Acworth, GA
    Posts
    13,316
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I think you will lose a couple of hundered Revs when it is over 80 degrees out. Anybody rememember what they were getting last summer?
    Glow Head Brotherhood #15

  13. #13
    Gringo Flyer's Avatar
    Join Date
    Jan 2004
    Location
    Formosa, ARGENTINA
    Posts
    2,370
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Over 80 degrees. We hardly fly when its under 95!
    \"Courage is being scared to death...and saddling up anyway.\"---John Wayne

    Roll Tide Roll!!!!

  14. #14
    akschu's Avatar
    Join Date
    Mar 2005
    Location
    , AK
    Posts
    417
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Magnum calls for no more than 15% nitro, so what happens when you run 30%? Are any of you running into detonation issues?

  15. #15

    Join Date
    Nov 2003
    Location
    Auckland, NEW ZEALAND
    Posts
    1,324
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    ORIGINAL: Gringo Volador

    I just looked through some tach readings on other four strokes and you guys are getting close to the same readings that guys are reporting on Saito 100.

    I just dont see how that is possible. Am I the only one not getting huge numbers on a Magnum 91?
    Gringo, I'm with you. Some of these numbers are just incredible. I bet some of these guys have got the special "one that got past QA" car that does 1000 mpg too.

    I mean...., one guys gets 10,000 with an "APC 15x4 or a 15x6". Well which one - or were they the same load?

    Also, 9500 with an APC 14x8 on 10% nitro. This is not only at least 600 rpm stronger than any OS, Saito or TT .91 I've ever tested (and I've tached a few now) but is more than 200 rpm stronger than my Saito FA100 can get on 20% nitro.

    I wish some guys would take more care when reporting rpms.

  16. #16

    Join Date
    Aug 2003
    Location
    La Mirada, CA
    Posts
    88
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I have 3 of these motors, two of which I regularly fly with Powermaster 20/20 fuel. I'm near enough to sea level and generally fly in typical Southern California 72 degree weather.

    One is in Funtana 40 spinning an APC 15x4W prop. Not sure of exact tach readings, but I do remember that it is reguarly right around 9900 - 10000 slightly rich (I always run rich for 3D stuff to keep it from leaning out in manuevers).

    However, my other one is in a Corsiar warbird. Looking for speed here, but I just don't seem to be getting a lot of love. For instance, a 13x9 prop only spins in the 8000 range which seems low. I've had to resort to running 12" props... right now I'm at a 12x11 that spins in the 9000 rpm range, and performance is decent for level flight but not a lot of thrust (as to be expected).

    I've tried everything... adjusted the valves (both tappet clearance and pulling the head to clean the seats) and even checked the cam timing.

    Perhaps I'm just expecting too much, but there seems to be a noticible power difference between the two motors. I certainly do not seem to be getting anywhere near the numbers being reported in this thread with that second motor...

  17. #17

    Join Date
    Nov 2003
    Location
    Auckland, NEW ZEALAND
    Posts
    1,324
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Endor, to see if your engines are performing up to par, try this: if you have an APC 13x8 handy, put this prop on and tach your peak reading on both your engines.

    If your engines are in the .91 four-stroke ballpark, you'll get mid to high nines. On the same day, on 10% nitro, I did this with a guy's TT .91 and another guy's Saito .91. They both got around 9800 rpm at sea level.

    Remember that from day to day, up to at least 200 rpm variation in readings can take place due to, among other things, temperature and humidity.

  18. #18

    Join Date
    Aug 2003
    Location
    La Mirada, CA
    Posts
    88
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Harry,

    Thanks for that tip. Some time ago I did try a 13x8 and seem to recall that it was only running in the mid-8000's on YS 20/20 fuel, but the motor was relatively new then and may not have been fully broken in. I'll grab that prop, a bit of my friend's 10% nitro fuel, and tach it out.

  19. #19

    Join Date
    Aug 2003
    Location
    La Mirada, CA
    Posts
    88
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    A follow-up...

    Ran an APC 13x8 on the Mag 91FS. With Powermaster 20/20 fuel it pulled right at 10k on a cool day (mid-60s).

    Wow, it must have finally broken in (it has about a gallon through it) because I do remember it not pulling anywhere near that RPM when the engine was newer.

    Thanks for that tip Harry, at least I know I'm in the ballpark with other motors.

  20. #20

    Join Date
    Nov 2003
    Location
    Auckland, NEW ZEALAND
    Posts
    1,324
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Endor,

    Thanks for the followup post. It sounds like she's a good strong engine and it should get even better with a few more hours up.

  21. #21

    Join Date
    Nov 2005
    Location
    Floroe, NORWAY
    Posts
    2,825
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    wow! I must say that some people are getting really impressive rpm`s out of this engine. Mine runs 10400 on dynathrust 13/6. 9200 on apc 14/6 and 8800 on master airskrew 13/8 k- series. I must be doing something wrong I guess. I run a 15/15 fuel.I`ve just installed a new liner and ring and set the valve clearances, so hopefully mine will run stronger than this when it`s fully broken in again.

  22. #22
    Cogburn's Avatar
    Join Date
    Mar 2004
    Location
    Aurora, SD
    Posts
    256
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    Here is an engine tuners calculator that might explain some of the RPM variations.
    http://www.wahiduddin.net/calc/calc_hp.htm

    [8D]

  23. #23
    Moderator w8ye's Avatar
    Join Date
    Dec 2001
    Location
    Shelby, OH
    Posts
    37,013
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I set the needles on a friends new Magnum 91 Four stroke last Thursday. It turned a 14-6 MAS at 9900 with Omega 15%. It was about 70 F outside.

    Enjoy,

    Jim
    Attended the CutFinger Institute of DirtNap University for years but never did graduate....
    Recipient, Mangledhand award August 2008
    Club Saito Member #7
    Original AMA #31261

  24. #24
    Gringo Flyer's Avatar
    Join Date
    Jan 2004
    Location
    Formosa, ARGENTINA
    Posts
    2,370
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    I see a lot of you guys are running 15% nitro in the magnum. I am running 5% and now that it is fully broken in I getting close to 10000 on a MA 14X6 .

    Mine has about 3 quarts of fuel through it.

    All that to say is that this engine runs just as well on low nitro so some of you guys could save a few bucks on fuel.
    \"Courage is being scared to death...and saddling up anyway.\"---John Wayne

    Roll Tide Roll!!!!

  25. #25
    Team_Monkey's Avatar
    Join Date
    Nov 2005
    Location
    Northeast, OH
    Posts
    117
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Magnum .91FS!

    To kick an old thread...

    Broke in my .91 yesterday. We're at about 700' above sea level and it was 60 deg. F. Spent all day running and cooling the engine. Granted it's still new with only maybe and hour of run time, but I was a bit disapointed in the RPM readings as they seem low. I have it on an Astro Hog so I'm not looking for speed I just want to be sure it's running right.

    I tried to run it mostly with good smoke for the break in but when I leaned it out, it maxed out at 9250 with a wood 14x6 break-in prop. Of course I would richen it for flight but I was checking the max a couple of times.

    Backing it off to 8900 to simulate a flight setting did not produce much smoke or goop on the wing. The manual says to fly with a smoke trail but I have to drop 600+ RPM to do that.

    I'm running 20% oil, 6% nitro home brew fuel. I mixed a few gallons for break-in of a couple engines.

    Oh, I'm running the McCoy Miracle 4stroke plug.


Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
All times are GMT -6. The time now is 11:02 PM.

SEO by vBSEO 3.6.1 ©2011, Crawlability, Inc.