low end on 4 stroke
12-04-2005 | 09:07 PM
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From: Formosa, ARGENTINA
low end on 4 stroke
I have about 1 1/2hours of runtime on a Magnum 91 4S. I followed break in procedures to a T and the engine is a gem.
However, the low end seems to me a little high. The engine is on a 40 sized 3D plane and on the landing approach I have to cut the engine or it wont land!
With a 14X6 MA on 10% the lowest reliable idle I can get is between 3000-3500. I have tweaked the low end needle valve. If I leave the glow starter on it I can get it a little lower.
With less than a gallon through the engine is the high low end just do to the engine needing to be broken in more or is 3000 RPM normal for idle?
However, the low end seems to me a little high. The engine is on a 40 sized 3D plane and on the landing approach I have to cut the engine or it wont land!
With a 14X6 MA on 10% the lowest reliable idle I can get is between 3000-3500. I have tweaked the low end needle valve. If I leave the glow starter on it I can get it a little lower.
With less than a gallon through the engine is the high low end just do to the engine needing to be broken in more or is 3000 RPM normal for idle?
12-04-2005 | 09:30 PM
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From: Tokoroa, , NEW ZEALAND
RE: low end on 4 stroke
If you're still using the glowplug you used to break the engine in with, or if it's not an OS-F type then change plugs now to a brand-new F-type. You'll find that you'll be able to knock 1,000 RPMs off that idle and the engine will handle much better all around.
12-04-2005 | 11:42 PM
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From: Springtown,
TX
RE: low end on 4 stroke
Well, a .91 spinning a 14 inch prop, pulling around what is likely a 4.5 to 5 lb 40 sized 3d plane will probably not be able to slow down enough to land under power! One of the issues of overpower a plane with such light wing loading a superior lift. Might just have to kill it to land everytime!
However, you should be able to idle down into the 2000's. I have two of these engines, and they all idle pretty low. But, they don't come with a good plug, so change it to a good one--OS F or H9 super plug and you'll notice an instant difference!
However, you should be able to idle down into the 2000's. I have two of these engines, and they all idle pretty low. But, they don't come with a good plug, so change it to a good one--OS F or H9 super plug and you'll notice an instant difference!
12-05-2005 | 06:05 AM
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RE: low end on 4 stroke
And the simple solution for most a/c that are too fast to land with the engine at idle is to put a prop on that engine with less pitch. That works great no matter what the power loading.
Most times, you'll never even notice a change in the top speed.
I've got a couple of .40 size models with powerful .46s on them. First thing I did was swap out the 6 inch pitch props that were the recommended ones, and bolt on 5 inch pitch. Granted, for one a/c, I had to cut down a 12x5 to keep enough blade to keep the engine warm enough, but the a/c lands at a fast walk now. Having more fan area is one of the best air brakes available, but only works if the pitch is low enough.
Most times, you'll never even notice a change in the top speed.
I've got a couple of .40 size models with powerful .46s on them. First thing I did was swap out the 6 inch pitch props that were the recommended ones, and bolt on 5 inch pitch. Granted, for one a/c, I had to cut down a 12x5 to keep enough blade to keep the engine warm enough, but the a/c lands at a fast walk now. Having more fan area is one of the best air brakes available, but only works if the pitch is low enough.
