Recomended Open
02-13-2010, 02:48 PM
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Recomended Open
I am a new commer to combat. I have experiance with OS .25 fx engines and own several. I also own one near new Webra Speed .25. I have barely run the Webra but so far I find the OS to be much more user friendly. What engine is considered " THE ENGINE to USE " for open B and why?
Same question for 2548. Best engine choice and why ?
Same question for 2548. Best engine choice and why ?
02-13-2010, 03:15 PM
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RE: Recomended Open
Get some time on the Webra. You will soon prefer it over the OS, which basically is a beginner's engine. A jack of all trades, but master of none.
02-13-2010, 06:17 PM
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RE: Recomended Open
The 25fx is a very popular Open B and 2548 engine and no mystery why. They run great, needle good, and take lots of abuse.
With a moose can, it is in my opinion the most user friendly open B engine ............too bad they discontinued it. Same thing applies to 2548.
I haven't tried one yet, but I hear that the 25AX is a dog turd..........looks like the OS folks may have fouled up.
I have Webras and they run great too.
You gonna be at Lone Star Combat Nats?
With a moose can, it is in my opinion the most user friendly open B engine ............too bad they discontinued it. Same thing applies to 2548.
I haven't tried one yet, but I hear that the 25AX is a dog turd..........looks like the OS folks may have fouled up.
I have Webras and they run great too.
You gonna be at Lone Star Combat Nats?
02-14-2010, 12:19 PM
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RE: Recomended Open
I have 4 or 5 Webras and a gaggle of FX's.
On a mousse can, the Webra blows away the FX. One of mine turned a MAS 9x4 at over 22k, which is stupid-fast for that prop, it starts flexing and such. so I use an APC 9x3 combat on the Webras (except for one, which ate serious dirt and needs the smaller MAS 9x4 just to get up to a solid 19.5k).
Most stock OS FXes on the MAS 9x4 can hit a bit over 19k on 15% nitro.
The problem with the Webra is that spare parts are unobtainable as far as I can tell. And that's bad because the needle and fuel nipple assembly that is pressed into the side of the carb breaks really easily. sometimes a hit will cause the spray bar to crack internally, and you can't see the damage, but suddenly the engine won't run right.
The Webra also has a massive carb intake, which means it doesn't draw fuel well, so it's critical you get the tank position right (or use a bladder, which I don't, I just get my tank right). You also need to launch a mousse can equiped webra really rich, because set up right, it will unload like crazy in the air, come on the pipe and start sucking fuel like mad. If you lean it like an OS, it WILL be too lean in the air, and RPM will drop.
When my Webras in my old 2610 planes were set and running, when I pulled a high-G turn, the engine would lean a tad, pick up RPM, and the plane would actually accelerate through the turn and was faster turning than flying straight, which was amazing, and a great advantage in the air. But you can only get that if you set the engine a little rich on the ground. Use the pinch test to get that right.
Oh, and a Webra will empty a 6oz tank in less than 6min. So in many combat contests, I'd wait 30-45 seconds after start engines to fire up, launch at part throttle (or full, then pull back right after I released the plane if it was windy), and not go full power until "start combat". Sometimes I'd still run out of fuel before the end. That's using a hayes 6oz.
Also, the Webra use a press fit prop hub over the front bearing, which is hard to clear if you eat string. I find that annoying on a lot of engines (Magnums are the same way, only OS has a prop hub that just comes off in your hand)
Anyway, the OS is MUCH easier to get working and keep working, parts are more available, power is solid, and so many guys have them that help or parts is usually for the asking at a contest. I don't run my Webras much anymore because if one is damaged, it's done.
now, for 2548, the Webra is junk, don't bother with it, you want the OS FX, it's really hands-down the best engine for 2548 and Limited B right now. The Webra is designed to run at high RPM, and wants a small prop and high RPM to make power. When I put a standard non-tuned expansion chamber muffler on my Webras, and bolted on the mandated 10x3 APC or 10x4MAS, the Webra just couldn't make any power and was a sitting duck, the OS FXes clearly have more low-end torque to turn the bigger props.
My impression of the AX is that it's designed for low end torque with bigger props, but I don't know how that translates to the 2548/LimB props at this point, those props might still be too small for the AX to really produce the power. I don't have an AX, so beyond theory, I can't commend.
On a mousse can, the Webra blows away the FX. One of mine turned a MAS 9x4 at over 22k, which is stupid-fast for that prop, it starts flexing and such. so I use an APC 9x3 combat on the Webras (except for one, which ate serious dirt and needs the smaller MAS 9x4 just to get up to a solid 19.5k).
Most stock OS FXes on the MAS 9x4 can hit a bit over 19k on 15% nitro.
The problem with the Webra is that spare parts are unobtainable as far as I can tell. And that's bad because the needle and fuel nipple assembly that is pressed into the side of the carb breaks really easily. sometimes a hit will cause the spray bar to crack internally, and you can't see the damage, but suddenly the engine won't run right.
The Webra also has a massive carb intake, which means it doesn't draw fuel well, so it's critical you get the tank position right (or use a bladder, which I don't, I just get my tank right). You also need to launch a mousse can equiped webra really rich, because set up right, it will unload like crazy in the air, come on the pipe and start sucking fuel like mad. If you lean it like an OS, it WILL be too lean in the air, and RPM will drop.
When my Webras in my old 2610 planes were set and running, when I pulled a high-G turn, the engine would lean a tad, pick up RPM, and the plane would actually accelerate through the turn and was faster turning than flying straight, which was amazing, and a great advantage in the air. But you can only get that if you set the engine a little rich on the ground. Use the pinch test to get that right.
Oh, and a Webra will empty a 6oz tank in less than 6min. So in many combat contests, I'd wait 30-45 seconds after start engines to fire up, launch at part throttle (or full, then pull back right after I released the plane if it was windy), and not go full power until "start combat". Sometimes I'd still run out of fuel before the end. That's using a hayes 6oz.
Also, the Webra use a press fit prop hub over the front bearing, which is hard to clear if you eat string. I find that annoying on a lot of engines (Magnums are the same way, only OS has a prop hub that just comes off in your hand)
Anyway, the OS is MUCH easier to get working and keep working, parts are more available, power is solid, and so many guys have them that help or parts is usually for the asking at a contest. I don't run my Webras much anymore because if one is damaged, it's done.
now, for 2548, the Webra is junk, don't bother with it, you want the OS FX, it's really hands-down the best engine for 2548 and Limited B right now. The Webra is designed to run at high RPM, and wants a small prop and high RPM to make power. When I put a standard non-tuned expansion chamber muffler on my Webras, and bolted on the mandated 10x3 APC or 10x4MAS, the Webra just couldn't make any power and was a sitting duck, the OS FXes clearly have more low-end torque to turn the bigger props.
My impression of the AX is that it's designed for low end torque with bigger props, but I don't know how that translates to the 2548/LimB props at this point, those props might still be too small for the AX to really produce the power. I don't have an AX, so beyond theory, I can't commend.
02-14-2010, 12:28 PM
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RE: Recomended Open
Your post confirms my suspicions and findings. I have only made one flight so far with the Webra (9x4) APC prop and 12% nitro, glow plug ??? I have no clue what it is, something I pulled out of my used plug box. I took off slightly rich and it ran good for about 2 minutes or so and then started sagging. I wouldnt say that it was ever truly "on" the pipe but it might have been. My needle only needs to turn a small amount to go from too rich to run to too lean, ( maybe 1/2 to 3/4 turn).
What is the best plug and fuel for this engine ?
What is the best plug and fuel for this engine ?
02-14-2010, 10:28 PM
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RE: Recomended Open
Best fuel and plug, not sure. I use K&B 7300 (HP) plugs, and 15% to 20% nitro on the fuel, depending.
If it's running good for 2min, then sagging, what happens if you launch with half a tank of fuel? If you run for another 2min and then sag, you probably have a tank setup issue, or you're too lean. also check you're muffler pressure if using a conventional tank. If it just won't run right at half a tank or so, then I'd suspect a problem with the tank pickup. If you find you have to richen at half a tank vs a full tank to run right (or get the same RPM on a tach), then your tank is probably too low, or you have something else with the fuel draw.
Fwiw, I never thought of the Webra as hard to needle or touchy engines at all, mine were always easy and smooth running, and had surprisingly good idles for having such a huge carb opening. But then I always made sure my tanks were mounted rather high with these engines, fuel draw with high performance engines is just so critical.
If it's running good for 2min, then sagging, what happens if you launch with half a tank of fuel? If you run for another 2min and then sag, you probably have a tank setup issue, or you're too lean. also check you're muffler pressure if using a conventional tank. If it just won't run right at half a tank or so, then I'd suspect a problem with the tank pickup. If you find you have to richen at half a tank vs a full tank to run right (or get the same RPM on a tach), then your tank is probably too low, or you have something else with the fuel draw.
Fwiw, I never thought of the Webra as hard to needle or touchy engines at all, mine were always easy and smooth running, and had surprisingly good idles for having such a huge carb opening. But then I always made sure my tanks were mounted rather high with these engines, fuel draw with high performance engines is just so critical.
02-14-2010, 11:29 PM
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RE: Recomended Open
My engine certainly isnt broken in yet. It only has about 3 or four tanks of fuel through it. I also wondered if my muffler was the right length for the prop/rpm I am running. First things first I suppose and that would be to get the engine broken in. The center of my tank is just slightly below the center of the carb.
02-15-2010, 09:40 AM
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RE: Recomended Open
everything Montague said is exactly correct. the Webra on a muffler with a 2548/LimB prop is a stone. On a mcp with a smaller prop it is a powerhouse. I have had some webras that would not get on the pipe with a 9x4MA and had to clip the tips 1/8" to get the engine on the pipe, it really likes to rev and if it's bogged down it will be doggy. the fuel consumption is very high. even though I love the power i generally prefer the user friendliness and reliability of the FX. I save my webras for Nats when i figure you want all the power you can get. but i'm nervous every time i start them.
