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Problem with O.S. radial engine

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Problem with O.S. radial engine

Old 07-13-2015, 06:10 AM
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outacontrol41
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Default Problem with O.S. radial engine

I have a new in the box O.S. Sirius FR5 - 300 radial engine that I recently mounted on a Hangar 9 30cc Beaver. The engine starts very easily and idles flawlessly. The big problem is it only runs on the top 3 cylinders...the bottom 2 stay cold and do not ignite. It seriously lacks power. Once in a while, one or both of the bottom cylinder kicks in and it turns into a powerhouse and revs way up normally as it should...but this is rare. It is getting fire to all the glow plugs using a McDaniels onboard 5 cyl. glow driver and 4.8 volt 2400 mAh sub C 4pack. Ignition is definitely not the problem - seems to be a fuel problem. I broke the engine in (or in process of, 2 hrs. run in) using Cool Power 15%. Should I switch to 10% or some other type of hotter burning fuel? I'm using O.S. 'F' plugs as recommended in owner's manual.
Very disappointed in this engine so far and looking for answers. This does not seem to be a popular engine so problem solving conversations are hard to find. Thank you to anyone who can chime in with some much needed help.
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Old 07-13-2015, 07:07 AM
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jetmech05
 
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Could be a few things. It's my understanding that fuel is delivered to the cylinders by an impeller. So if getting fuel to the top cylinders you should get fuel to the bottoms. Are your intake valves stuck or sticky? Or is there some kind of obstruction keeping you from drawing fuel? Or in my opinion the most likely the timing is off, in other words the intake valve is not opening or closing when it should.
Good luck
Old 07-13-2015, 07:19 AM
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outacontrol41
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I was thinking more that the fuel is weak as it is always the bottom 2 cylinders, and when I take the plugs out they are filled with fresh unburned fuel after I shut the engine off...it seems they are drowning out the glow plug. Also as mentioned, once in a while after a few minutes of steady idle, when I punch it to full throttle...ALL cylinders fire properly and the engine sounds fine, if only for a few seconds before the bottom 2 cylinders kick out again. This seems to suggest the timing and intake valves are fine...the fuel is not igniting as it should at the bottom 2.
Old 07-13-2015, 11:16 AM
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RBACONS
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If the cylinder is getting fuel but not igniting, I would look at the McDaniel on-board glow. Fuel but no fire sounds like a weak voltage to the glow plugs in question. Have you put a volt meter on the plug caps in question to see what voltage is really getting to those plugs (this may be difficult due to the pulsed nature of the McDaniel system). A slight voltage drop may be all it takes for those cylinders to not fire given that the lower cylinders usually run colder due to the fuel pooling on the plug.

I assume you have the MCD475. I see a couple of potential issues to look at. 1. For a 5-cylinder system, they call for a 4000 mah battery, not the 2400 that you say you are using. However, I think that should only affect your run time unless all plugs are pulsed in unison in which case I don't think the 2400 mah pack has enough poop to drive 5 plugs at the same time. 2. It looks like a "some assembly required" system. Are you confident your solder joints are 100%? 3. Are you sure you used the recommended gauge of wire for your battery pack to minimize losses.


For my 9 cylinder radial (Seidel), I gave up on the commercial drivers and made a simple, never fail, one using a 7000 mah 1.2V "F" cell controlled by a servo. You can get one for about $16 (Batteries America). With the McDaniel, it looks like there is a connector between the controller and the plug wires, in which case you could run a simple test disconnecting the controller and driving the plugs with the F cell. That would at least eliminate or confirm the McDaniel system as a possible cause
Old 07-13-2015, 01:43 PM
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You can also go directly into the OS support forum and ask Bill Baxter or even phone him at Towers service and support. I love the looks and sound of the round engines but like most of us can't afford one. The price holds most of us back or they would be a lot more popular.
Old 07-13-2015, 02:16 PM
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outacontrol41
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Originally Posted by Gray Beard View Post
The price holds most of us back or they would be a lot more popular.
I never realized it but that is probably true...
Old 07-13-2015, 03:00 PM
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I worked on and flew recips C-131, C-119, C-118, and T-28's. Always loved to start em and listen to them
Old 07-13-2015, 06:07 PM
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Jim Branaum
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Originally Posted by Gray Beard View Post
You can also go directly into the OS support forum and ask Bill Baxter or even phone him at Towers service and support. I love the looks and sound of the round engines but like most of us can't afford one. The price holds most of us back or they would be a lot more popular.

Yeah, I want one...
Old 07-14-2015, 05:43 AM
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do335a
 
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Speaking of fuel, is it fresh? You should also be aware that a lower nitro content fuel runs cooler than a higher nitro fuel. We learned that with a real live demo with .049 engines as kids. They would not start or run well on the regular 10%-15% fuels yet were real stompers and easy to start with Missile Mist, which was 25% nitro.

Just curious on this point. If you rotate the engine so that the bottom cylinders are not at the bottom but the top, with no other changes, what happens? Do they still fail to fire?

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