OS 25 FX how to get more power  
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OS 25 FX how to get more power - 3/27/2007 6:46:42 AM   
Flyboywbl


 

Posts: 199
Joined: 7/12/2002
From: Bozeman, MT, USA
Status: offline 		Hey yall i was wondering if there are any mods i can do to my three OS 25 fx's (they are all on lanier slashers). I turn about 15,000+ with a MAS 9x4 and i'm at 4500 ft. I'm running byron fuel with 15% nitro and 20%oil. I've seen guys with these engines running 22,000+ RPM's. I don't know what there secret is but i wish i could turn that many! The only tools i have are your basic rc tools and a dremel. I'm willing to go out and buy any dremel attachment but i don't really want to buy any new tools. Can i acheave this awsome power? Please let me know If there is a website or forum that goes into detail with some mods i could do and pics would be nice to
thanks for all your help!
-Matt

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RE: OS 25 FX how to get more power - 3/27/2007 12:52:57 PM   
RC MANIAC119


 

Posts: 571
Joined: 11/3/2003
From: muskegon, MI, USA
Status: offline 		Matt............The first thing you need to do is take out the baffle inside the muffler! This is a simple fix that can add and extra 1000 RPM.

Loosen the nut on the backside first....before you attempt to remove the long retaining screw. When you have the muffler split apart you will see the baffle.........take it out, put the muffler back together, and don't forget to use some Locktite!!

Enjoy your new speed!!

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RE: OS 25 FX how to get more power - 3/27/2007 1:50:57 PM   
Montague



Posts: 4632
Joined: 4/19/2002
From: Laurel, MD,
Status: offline 		What you want to do is remove the muffler and install a mousse can. The mousse can is a short tuned pipe and is good for 1,000-2,000 rpm, depending.

What prop are you using? The fastest turning props are the old Master Airscrew GF/2 props. APC and the new MAS GF/3s don't turn the same RPM for a number of reasons. For most flying the APC and newer MAS props are more efficient, but for hard turns, the "lower gear" of the old props work better. MAS still makes the GF/2 in the 9x4 size if you ask them directly and order a dozen or so at a time. That's where I get mine.

The fastest I've gotten an unmodified OS was around 19.5, on a mousse can with the above prop on 15% fuel. To go faster, get some powermaster fuel with higher nitro. I was using a mix of 30% and 15% to get 22.5% for a while, and that's good for at least 500rpm, maybe more. Some guys run straight 30%.

Play with glowplugs. When you start going to higher RPM, you usually want a colder plug. Also, the OS plugs are slightly short, which lowers the compression a little. I use the K&B 7300 plug, but there are plenty of other good ones out there.

Break-in really matters as well when you want top power. You really need to use a small prop and do a careful temp cycle break-in. And never, ever, run the engine "4cycle" rich, or at low throttle more than you have to. Cold running wears down the piston/liner fit and causes the engine to loose power at the top end. Not enough for a sport flyer to notice, but when you're going for peak power, it shows up.


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RE: OS 25 FX how to get more power - 3/27/2007 9:19:04 PM   
Flyboywbl


 

Posts: 199
Joined: 7/12/2002
From: Bozeman, MT, USA
Status: offline 		baffle was already gone, thanks for the tip though. That was actually one of the first tips I got when i first started flying 7 years ago. Now i do it to all my two strokes. I've heard i can take the shim out of the head to up the compretion. I'm not alowed to fly a mosse can muffler at my club due to noise complaints. We all just fly the stock FX muffler.
thanks
-Matt

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RE: OS 25 FX how to get more power - 3/27/2007 9:40:17 PM   
daven



Posts: 6909
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		Can you use an ultrathrust or jettstream style muffler?

That would help a lot!

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RE: OS 25 FX how to get more power - 3/27/2007 10:18:40 PM   
rcfury



Posts: 968
Joined: 10/19/2003
From: Manassas, VA, USA
Status: offline 		You can use the jett muffler if you want. Ive got a few members of my club who use them with great results. Its just expensive. Plus, when you are dealing with rc combat you really dont want to loose the pretty ultratrust muffler due to a midair. I have a moose can pipe that i made on my OS 15 with awesome results, and it lighter than the jett pipe.

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RE: OS 25 FX how to get more power - 3/28/2007 3:45:36 AM   
RC MANIAC119


 

Posts: 571
Joined: 11/3/2003
From: muskegon, MI, USA
Status: offline 		Get a MACS Muffler/tuned pipe for that beast....

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RE: OS 25 FX how to get more power - 3/28/2007 4:55:37 AM   
yankee samurai


 

Posts: 125
Joined: 5/14/2003
From: Blackfoot, ID, USA
Status: offline 		If you're concerned about noise the mousse can set up is actually quieter than a stock muffler. The Mac's black muffler offers little performance gain if any. I see you're from Bozeman do you know Phil Battle or Charlie Pfliger? They both attend my contests twice a year.

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Randy Shiosaki

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RE: OS 25 FX how to get more power - 3/28/2007 6:00:17 AM   
Flyboywbl


 

Posts: 199
Joined: 7/12/2002
From: Bozeman, MT, USA
Status: offline 		Yah i know them. Charlie taught me every thing i know pritty much. I just started combat last summer and know i have three lanier slashers. I think once i start crashing them beyond repair i'm going to start working on my own design. Anyway i think i will make it out to ID this year and get torn up. i'll probibly see you there.
-Matt

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RE: OS 25 FX how to get more power - 3/29/2007 3:39:49 AM   
yankee samurai


 

Posts: 125
Joined: 5/14/2003
From: Blackfoot, ID, USA
Status: offline 		Matt,
Come on down. Charlie can tell you how much fun it is. There are usually eleven Open B pilots that show up. I don't know if you know Ron Horton, he is from Billings and is getting back into combat. He told me he would be there. Plus pilots from Ogden Utah, Boise and Ontario Oregon, it's a hoot hope to see ya there.

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Randy Shiosaki

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RE: OS 25 FX how to get more power - 3/30/2007 1:30:22 PM   
Capn America


 

Posts: 238
Joined: 9/22/2003
From: Holiday City, OH, USA
Status: offline 		If you are limiting yourselves to stock mufflers, you are not going to see a lot of rpm. You can up the rpm by drilling the outlet on the muffler to a larger size. It will pick you up some more rpm, only good for wide open runs though as it also decreases backpressure that creates your fuel pressure.

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RE: OS 25 FX how to get more power - 3/30/2007 1:40:19 PM   
flyinrog



Posts: 5747
Joined: 9/3/2002
From: Burlington, NC, USA
Status: offline 		Not big in combat, but you guys keep talking 1 to 2k increase with muffler stuff,,this guys talking about a 7k improvement 15 to 22k ..there has to be more than exhaust to this!!..porting,props,nitro?....Rog

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RE: OS 25 FX how to get more power - 3/30/2007 3:28:20 PM   
Montague



Posts: 4632
Joined: 4/19/2002
From: Laurel, MD,
Status: offline 		Rog,

I think part of it is the prop, as in my earlier post.

And part of it is break-in. proper temperature cycling break in with a small prop can make a big difference in top end RPM.

And frankly, I've never seen an OS FX hit 22k. I have seen 19.5k on a stock OS.

One way to get more power is to replace the carb or drill it out. An OS .28 or .32 carb along with the tuned exhaust is a big improvement.

You need to get more fuel and air in, and more exhaust out. It's really as simple as that. So, larger carb throat and tuned exhaust or less backpressure on the exhaust.

However, opening the carb throat and messing with the muffler will make the mixture settings a lot more sensitive and make the engine "peaky". OS engines are known for having a very easy to set needle and strong fuel draw. All these mods will make the needle more critical, and will make it harder for the engine to draw fuel, so your tank setup will have to be more critical. The tank issue is why some guys use bladder fuel systems which provide fuel under pressure. Personally, I don't think they are necessary since you can get plenty of power using a stock tank, stock engine, and mousse can. That's all I do.



< Message edited by Montague -- 3/30/2007 4:12:57 PM >


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Kirk Montague Adams
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RE: OS 25 FX how to get more power - 3/31/2007 1:45:32 AM   
The Internet Killer


 

Posts: 222
Joined: 8/21/2005
From: Ferndale, WA, USA
Status: offline 		Drill out the carb ????

Any recomendations on how much to try ??

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RE: OS 25 FX how to get more power - 4/1/2007 10:41:59 PM