Ram Air Induction?  
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Ram Air Induction? - 8/25/2008 11:47:07 PM   
Pete55199


 

Posts: 10
Joined: 6/16/2008
From: Auburn, AL, USA
Status: offline 		I copied this post over from the ARF forum, thought it might fit here better.


Hi everyone, this is my first post here on RC Universe.

It's been a rainy day here in Alabama, thanks to Tropical Storm Fay, and classes at Auburn have been canceled for the day, so I had some spare time on my hands. First off, I have a Hangar 9 P-51 Mustang PTS, which I fly as often as I can. It's powered by an O.S. .46FX with an 11x6 prop mounted. I started looking at the motor this morning, and wondered, "What would happen if that thing had a ram air scoop on it?" That question immediately led to a resounding "Well let's find out!" I got out a spare sheet of balsa, some epoxy, and a spare piece of MonoKote and went to work. Here's what I ended up with:

http://s138.photobucket.com/albums/q264/Pete55199/Ram%20Air%20Induction/

Looks like it turned out ok, but I've never seen this done before, and have no idea if it'll make any difference or not. I'm certain that I'll have to richen up the mixture to avoid burning up the engine. But I was wondering, has anyone ever tried this before? If so, what kind of results did you get? It's raining outside right now, so I won't get a chance to test it out today. When I get that chance though, I'll be sure to write in with some results.

Thanks for reading!

~Pete
       Post #: 1

RE: Ram Air Induction? - 8/26/2008 4:59:51 AM   
jeffie8696



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RE: Ram Air Induction? - 8/26/2008 5:02:06 AM   
jeffie8696



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RE: Ram Air Induction? - 8/26/2008 1:29:03 PM   
da Rock



Posts: 6982
Joined: 10/11/2005
From: western, NC, USA
Status: offline 		You know, you can post photos right in each post. Don't need photobucket, and your readers see the picture with the text. It's much more convenient for everyone.

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RE: Ram Air Induction? - 8/30/2008 4:52:45 PM   
JustErik


 

Posts: 588
Joined: 7/19/2006
From: Charlottesville, VA, USA
Status: offline 		Or he could just post the image code.



Some folks, myself included, like to store photos (or other data) at a central on-line location like photobucket or whatever. It makes it easier to access them from various locations. Also, it frees up resources here at good old RCU.

To keep this on topic, I too would be interested in seeing the results from this experiment.

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RE: Ram Air Induction? - 9/2/2008 9:53:16 PM   
Stew99


 

Posts: 212
Joined: 3/6/2003
From: Huntsville, AL, USA
Status: offline 		Unfortunately, when you post photos offline I can't see them because our network blocks access to personal storage sites. I'm sure there are others with the same problem.

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RE: Ram Air Induction? - 9/3/2008 2:32:23 AM   
GRANT ED



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Joined: 4/13/2003
From: Adelaide, AUSTRALIA
Status: offline 		I seam to remember someone else trying this a while back. I think it didn't make any difference but let us know how you go. You might get a better result.

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RE: Ram Air Induction? - 9/3/2008 2:38:02 AM   
jeffie8696



Posts: 1283
Joined: 5/10/2007
From: coralville, IA, USA
Status: offline 		Is There any reason it wouldn't work? I did a web search and found that supercharging a 2 stroke doesn't work but I don't see why a slight increase in intake charge density would not result from this. It may only be slight but I hope it is enough to verify.

< Message edited by jeffie8696 -- 9/3/2008 2:46:27 AM >

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RE: Ram Air Induction? - 9/3/2008 11:19:40 AM   
da Rock



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From: western, NC, USA
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quote:

ORIGINAL: jeffie8696

Is There any reason it wouldn't work? I did a web search and found that supercharging a 2 stroke doesn't work but I don't see why a slight increase in intake charge density would not result from this. It may only be slight but I hope it is enough to verify.



You read that supercharging a 2 stroke doesn't work, and the same reasons apply to increasing the available air at the venturi.

Supercharging is really just getting more gas (fuel and air mixed in the proper ratio) into the combustion. And it actually does work in 2 strokes but only in a limited way. Tuned pipes do exactly that, increase the amount of gas in the combustion chamber. But they work with the gas after it's become gas (been mixed).

Your increased air isn't needed. What's needed is to get more gas through the front of the engine.

< Message edited by da Rock -- 9/3/2008 11:25:23 AM >

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RE: Ram Air Induction? - 9/3/2008 11:30:48 AM   
da Rock



Posts: 6982
Joined: 10/11/2005
From: western, NC, USA
Status: offline 		Supercharging in full scale works because the engine encounters less and less air as the airplane's altitude increases. We don't need to find more air for the carb with our models.

And atmospheric pressure is what makes our intakes work. That pressure is a much greater force than a bit of airflow prepping can provide.

Keep in mind that our intakes are closed for a great amount of each rotation. Flow stops but your ram air won't.

< Message edited by da Rock -- 9/3/2008 11:32:59 AM >

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RE: Ram Air Induction? - 9/3/2008 9:47:34 PM   
Jezmo



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From: Spring, TX, USA
Status: online 		There is a darn good reason why some of the free storage sites get blocked at the gateway. They sometimes offer up more than just the photo you are trying to view. (Read drive-by downloads of crapware.) I have them blocked on the networks which I administrate for just that reason.

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RE: Ram Air Induction? - 9/3/2008 9:59:03 PM   
Bob Mitchell


 

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Joined: 3/23/2008
From: Lexington, KY, USA
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quote:

ORIGINAL: da Rock
Your increased air isn't needed. What's needed is to get more gas through the front of the engine.


Speaking in general here about IC. IC engines are effectively air pumps, and the amount of power generated is proportional to the amount of air one can move through the combustion chambers. It's easier to move fuel through IC engines than it is air, so they are air limited, rather than fuel limited (in general). That's why power adders are designed to push more air (oxygen) through the engine, ie. superchargers, turbochargers, Nitrous, etc.


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RE: Ram Air Induction? - 9/4/2008 1:51:40 AM   
da Rock



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From: western, NC, USA
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quote:

ORIGINAL: Bob Mitchell


quote:

ORIGINAL: da Rock
Your increased air isn't needed. What's needed is to get more gas through the front of the engine.


Speaking in general here about IC. IC engines are effectively air pumps, and the amount of power generated is proportional to the amount of air one can move through the combustion chambers. It's easier to move fuel through IC engines than it is air, so they are air limited, rather than fuel limited (in general). That's why power adders are designed to push more air (oxygen) through the engine, ie. superchargers, turbochargers, Nitrous, etc.




The gas mentioned is the combination of the air and atomized fuel from the spray bar. And that gas has to be moved from the venturi where it's created, into the crankshaft opening that only opens intermittently. Our simple 2cycles don't move air by itself anywhere in our engines. They move gas. They have to move a fuel/air combination from the point of combination, and that move starts right where atmospheric pressure is acting to both combine the two components and to provide the muscle to move the combination into the intermittently opening shaft induction port.

Our engines aren't general IC engines. They're very specifically configured ones that have a very, very simple carb slap up against the "internal" part of our IC engine. Bigger IC engines really do have places where air can be pushed around before it gets into the engine. With out little engines, the area needed for carburation is more than adequate to move more air than is usually needed. The design of our engines actually limits what can be "rammed down the engine's throat". Our engines usually benefit most from the other end of the cycle. Tuned pipes have worked with model engines almost from the start. Why? Because the front of the engine can quite easily provide more than it's being asked to provide, and simply does so when the tuned pipe creates the demand. But try to force feed our engines and from the carb on back, there isn't the same easily provided increase in capability.


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RE: Ram Air Induction? - 9/4/2008 10:25:14 AM   
da Rock



Posts: 6982
Joined: 10/11/2005
From: western, NC, USA
Status: offline 		BTW, if it was simply a case of getting more air into the carb, a larger opening in the carb would work too.

That actually does work, but only to a very limited extent. Very limited. And the limitation isn't on providing additional fuel flow, because that is even easier to do. Our needle valves aren't anywhere near their maximum opening. And we can easily provide appreciably more pressure to the fuel to provide that a much greater rates.

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RE: Ram Air Induction? - 9/4/2008 4:05:30 PM