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Os gt15!

Old 03-14-2014, 04:48 PM
  #76  
CustomPC
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I ran mine for the first time today and i have to say it's a sweet running engine.

It starts easily using my Align starter.
The carb seems to work great. and is very linear in performance like a glow engine and unlike any Walbro carbed engine I've ever owned.
It's also very quiet.
My prop was an APC 13x8 and I saw 10,300rpm at full throttle and a consistent idle around 2,000rpm.
Fuel used today is 91 Octane (RON) ethanol free gasoline with 30:1 Stihl HP mineral oil. I will be using that for the first 2 litres (1/2 gal) before i switch to the fully synthetic Stihl Ultra.
Old 03-14-2014, 05:47 PM
  #77  
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Ok guy's I played around a little more today first video is with a xoar 16x6 prop I got about 7800 rpm and had a head temperature of around 240 degrees. The second video I put the 14x6 Vess back on and was about 10000 rpm with the head temp around 230. I figured out when first hooking up the engine to the fuel I open the throttle all the way open and put my finger a the carb and it help pulled fuel up to the carb my tank and filter are way lower than the carb anyway. Today I fuel te tank up and I pinched the tank hose as I was filling and watched the fuel and air bubbles go threw the line turned ignition on and 1 flip of the prop and away it went no starter needed. The reason I fueled like this is because I drained the fuel tank the last time I ran it so it had air in the line and I wanted to see if I could start it without the starter and it did. I'M IMPRESSED WITH THIS ENGINE IT'S UNREAL!!!

https://www.youtube.com/watch?v=S-w0...ature=youtu.be

https://www.youtube.com/watch?v=g-on...ature=youtu.be
Old 03-23-2014, 06:33 PM
  #78  
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Originally Posted by erieqc View Post
The second video I put the 14x6 Vess back on and was about 10000 rpm...
Today I fuel te tank up and I pinched the tank hose as I was filling and watched the fuel and air bubbles go threw the line turned ignition on and 1 flip of the prop and away it went no starter needed. The reason I fueled like this is because I drained the fuel tank the last time I ran it so it had air in the line and I wanted to see if I could start it without the starter and it did.
I tried hand starting mine on the weekend after it had been sitting for a week with no fuel in the tank and just the remnants of fuel from the last run in the pump and reg. To my surprise, opening the throttle fully and choking it with a thumb over the carb had the lines full with just a few flicks.
I am not the best at hand starting engines but I was able to hand start it from cold after half a dozen flicks and the same was true for every start that day.

With the APC 14x6 i saw 9,870rpm.
Old 03-24-2014, 01:01 AM
  #79  
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Originally Posted by CustomPC View Post
I tried hand starting mine on the weekend after it had been sitting for a week with no fuel in the tank and just the remnants of fuel from the last run in the pump and reg. To my surprise, opening the throttle fully and choking it with a thumb over the carb had the lines full with just a few flicks.
I am not the best at hand starting engines but I was able to hand start it from cold after half a dozen flicks and the same was true for every start that day.

With the APC 14x6 i saw 9,870rpm.
Like I said it's one of the best engines I've ever owned.
Old 03-24-2014, 01:06 PM
  #80  
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Any testing with 3 blade props, either 13x6, 13x8 or 14x7 ?
Old 03-24-2014, 02:47 PM
  #81  
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Let me look and see what I have it might be a while till I get it back on the stand again I'm tuning a bme 90 first.
Old 03-24-2014, 03:55 PM
  #82  
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ERIEQC, There are a couple of BME ST G90's listed rite now . . . . can you give any comparison, . . . or an opinion? Very interested ! !

T-man49 in Al
Old 03-24-2014, 05:02 PM
  #83  
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The 90 are the same size as the os 15 but I have a 16x6 prop for the 90 and a 14x6 for the 15 if you look at my videos above you will see what rpm I had with both props on the 15 now this is new out of the box so it will only get better. As far as the bme I bought it used about 2 years ago and I replaced the falcon ignition with a rxcel and it sat in the box till now I played very little with it because of my own fault I didn't really like it that well with some of the problems I had like I said my own fault so I got it straightend out and now this is the reason I want to get it tuned and on a plane and fly it. I had a very well known engine guru tell me I might want to have a few extra plugs around for it but again I change the ignition out, will have to wait and see on that. The 90 has the 1/4 32 plug the 15 has the cm6 plug which I think is a lot better plug. As far as what to tell you the 15 is a lot easier to tune or should say it's more forgiving to tune than the 90. The 90 has the big walbro carb hanging off the front if you put it in a yak it might be ok but extra or edge your going to cut the hell out of your cowl. Consider old tech verses new tech I would probable go with the 15. It's your money though do what you want.
Old 03-26-2014, 12:41 PM
  #84  
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Hey guys,
I would like to have your opinion. I have an Aeroworks Extra 260 .60-.90 size with a OS FS95. It's a great combination, but the fuel cost is too high, so I was thinking of replacing the 4 stroke by this os GT15. The final weight with it would be very close to 7.5 lbs. Do you think it will be good enough? I'm not looking for a crazy 3D plane.
Thanks
Old 03-26-2014, 03:48 PM
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I would'nt know why not I was going to mount mine in the Aeroworks 60-90 Extra 300 but I'm going to keep the BME 90 in that for now. So the one 15 I'm putting in a Funtana 50 and the other one I'm looking at the GP Revolver 60. I want to move away from all the Horizon products that I can the only reason I'm using the Funtana is because I have 2 of them 1 new in the box.

Last edited by erieqc; 03-26-2014 at 03:53 PM.
Old 03-26-2014, 04:12 PM
  #86  
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The GT15 turns the same props and same rpms as a .91 4-stroke.
My prop calculator says it's putting out 10lb static thrust with a 14x6 so it would definatly fly the plane.

The extra weight will effect the flying characteristics somewhat. It would probably fly IMAC and normal style aerobatics just fine but not full on 3D hovering manoeuvres.
Old 03-27-2014, 03:21 PM
  #87  
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Actually the main problem is not the power of the engine itself but getting the plane balanced, since Im adding a lot of weight to the nose. I have an excel spreadsheet with every contributor to the balance and I need to move the battery to the turtle deck. I was thinking of a fromeco relion 2600mah with regulator, but I will have to use a heavier battery for balance purposes. Any ideas about balancing the plane?
Old 04-15-2014, 12:17 AM
  #88  
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My GT15 just keeps getting better.

9,080rpm with an APC 14x8.
Old 04-15-2014, 12:28 AM
  #89  
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Originally Posted by CustomPC View Post
My GT15 just keeps getting better.

9,080rpm with an APC 14x8.
I think Custom PC is in luv .Hopefully i will be too as mine arrived yesterday . Cheers the pope
Old 04-15-2014, 12:41 AM
  #90  
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Originally Posted by the pope View Post
I think Custom PC is in luv .Hopefully i will be too as mine arrived yesterday . Cheers the pope
You might be right. The GT15 has so many endearing qualities it's impossible not to fall for it.

I've taken mine to the field the last 2 weekends. At least a half dozen club members asked me what it was and then muttered those fateful words "I think i'm gonna have to get me one of those" after seeing it run.
Old 04-15-2014, 07:05 AM
  #91  
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Originally Posted by the pope View Post
I think Custom PC is in luv .Hopefully i will be too as mine arrived yesterday . Cheers the pope
you'll it and won't look back
Old 04-15-2014, 09:14 AM
  #92  
Jim Schwagle
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With about 20 minutes of run time, on Regular gas, 28x1 gas/oil, mine was at 8800 RPM at full throttle and 1800 at idle, on an APC 14x8. The 1800 is a little low and I had to bump it up to about 2000 for a more reliable idle. It's still rich, especially at low throttle, but it just sips fuel. I've got an 8oz tank in the Sig 4-Star 64 and I could easily replace it with a 6oz. It uses about 2oz per 7 minute flight. I did replace the supplied spark plug with an NGK. Even as it is now, the engine has plenty of power for the plane. As it breaks in and I reduce the oil somewhat, it should be more than enough.
Old 04-17-2014, 07:31 AM
  #93  
eleft36
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Has anyone had success downloading the operators manual .pdf, not the HZ version??


tia, Al
Old 04-17-2014, 02:54 PM
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Jim Schwagle
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No problems, from the Tower web page for the motor.
Old 04-17-2014, 05:11 PM
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Originally Posted by eleft36 View Post
Has anyone had success downloading the operators manual .pdf, not the HZ version??
I scanned it for safe keeping. Here ya go.


This is the one that come with Engines purchased in Australia. I don't know if it's the same manual as Tower provide with US supplied engines.
Attached Files
File Type: pdf
OS GT15 Instruction Leaflet.pdf (1.11 MB, 155 views)
Old 04-17-2014, 05:22 PM
  #96  
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Originally Posted by Jim Schwagle View Post
........but it just sips fuel. I've got an 8oz tank in the Sig 4-Star 64 and I could easily replace it with a 6oz. It uses about 2oz per 7 minute flight.
Sips fuel is right. I did a 15 minute flight last weekend and used about 100mls of fuel. It feels kind of strange when you top off the tank for the next flight and you only have to do 2 cranks of the pump handle before fuel flows out the breather.
Old 04-17-2014, 06:33 PM
  #97  
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Thank you CustomPC,
I could not get the Tower(hobbico) pdf to download without it locking up explorer.
Al
Old 04-21-2014, 03:58 PM
  #98  
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I have run mine today for the second time. High speed needle valve is almost three turns open from the fully closed position and I read today 9800 rpm at full throttle! I know two engines wont be exactly the same, but how many turns is yours open?
Thanks,
Old 04-21-2014, 04:30 PM
  #99  
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Originally Posted by jmvt View Post
I have run mine today for the second time. High speed needle valve is almost three turns open from the fully closed position and I read today 9800 rpm at full throttle! I know two engines wont be exactly the same, but how many turns is yours open?
Thanks,

9,800rpm with what size prop?

I have no idea where my needles are at. They were perfect out of the box and i haven't moved them.
Old 04-21-2014, 04:48 PM
  #100  
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You are right, it is a Xoar 14x6. I followed the instructions to set the needle valve for the first run and it seems that with almost 3 turns it is pretty close to the max setting.

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