DonFromTX

DonFromTX

Well Known Member
I am way over my head, trying to design a Ram air type alternate air for my plane. The air filter/intake is on top of the engine, passenger side. I want to make a top of the cowl (I think) ram air intake with of course a cockpit push/pull cable control. Any ideas or experience appreciated.
 
keep simple

Don

I think you might consider keeping things simple. If you make a good inlet that incorporates or feeds a filter with large enough area to reduce pressure drop to near zero, then there is nothing to be gained by adding the complexity for a filtered and unfiltered arrangement.

What are you trying to accomplish with this mod? Better breathing, More speed?, ect.

If you post some photos/drawings of your engine arrangement and what you have in mind I am sure you will get a bucket load of ideas.
 
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Let's separate two different aspects, converting dynamic pressure to increased static, and running unfiltered.

Dynamic: at 3000 feet and 135 mph, standard day, the max available Q is only 0.6"Hg, and it is impossible to get all of it. Low airspeed means there is not a lot to be gained.

Unfiltered air: many "ram air" users brag about MP gains, but it's only because they bypass a restrictive filter. As Wade says, it is entirely possible to develop a filtered system with very little restriction....so why eat dirt?

For an RV-12 application I'd work out a simple nosebowl opening feeding a large area filter. You'll convert some Q to static without worry or management, even when you're down in the dust and bugs.
 
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I appreciate the comments, thanks guys. Here is the currently accepted intake system (view from passenger side of engine compartment). I know not how restrictive the filter is (or isn't), but just seems to me to be screaming for improvements. I don't mind being wrong, so keep the comments coming.
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The loss from ingesting hot air is what I'd worry about.

Here's a starting point for ideas; you might even be able to use the actual part with a few mods:
http://www.vansaircraft.com/cgi-bin...83-34-576&browse=engines&product=fab-vertical

As others have said, you could just make a direct line to feed the inlet of this air box, & forget about bypassing the filter. Remember that the inlet area of this box is much bigger than what you need (your actual cowl inlet doesn't need to be any bigger than the throttle body inlet, if you do the 'plumbing' right). The box should be fed by a tube from outside the cowl, obviously. A long run of SCAT tubing would be a relatively poor choice, because the wall corrugations are pretty draggy. You can make a rigid duct with fiberglass & epoxy, or a flexible one with fiberglass & silicone, or just use aluminum tube or silicone hose, if you can set up a more or less straight path to your cowl inlet. (Don't try to use silicone where it's directly exposed to gasoline.)

Does that help?

Charlie
 
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DonFromTX said:
Here is the currently accepted intake system (view from passenger side of engine compartment). I know not how restrictive the filter is (or isn't), but just seems to me to be screaming for improvements.
Click to expand...

That it does. Got a part number for that filter? Looks very restrictive. And is that a temperature sensor screwed into the end of it?
 
From your picture, yes it does look restrictive.

I would agree with Dan and use a lower nose (lower cowl) mounted inlet to feed a filtered box that you attach to the intake. Don't know how much room you have, but maybe attached to the right lower cowl side.
 
Yes, that is a temp sensor that tells the ECU what the inlet temp is. Not necessary to be in that exact location.
 
3" x 2" cone just a little over 2" high....tiny little thing with short pleats.

The standard OEM replacement flat K&N is a 33-2422. No way to judge media area from the website info.

The performance replacement is a RC-9630, a 4.5 x 3.5 cone with a 5" height.....much larger than the RC2340.

If you have the cowl space just build in a large volume airbox with a big flat filter, fed with cool air from the cowl nose.
 
Yes that does seem to be the direction I am heading. I got lots of room over there to play with different designs.
 
If it an't broke why fix it!

This is on a 100hp engine in an EAB that will conform to LSA flight chracteristics. Why complicate the install? If its being flown in its current form why change it?:confused:
 
You have an excellent point there, but unfortunately I am one of those always trying to reinvent the wheel. The current system works, but was of course a compromise of costs and complexity, and if I can tweak a little more efficiency out of the installation - that is where I want to be. (Oh yeah, 110 hp engine)
Jetguy said:
This is on a 100hp engine in an EAB that will conform to LSA flight chracteristics. Why complicate the install? If its being flown in its current form why change it?:confused:
Click to expand...
 
Get that baby in the air.

I say get it done and flying. The wheel may spin fine without reinventing anything. ;)
 
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