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From: "rijakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-882814@logan.com>
Subject: ramair-airfilters-etc.
Date: Mon, 18 Apr 2005 21:08:57 -0500
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----- Original Message ----- 
From: "Jerry Hey" <jerryhey@earthlink.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, April 18, 2005 6:48 PM
Subject: [FlyRotary] Re: Apex Seal Groove Wear and Air Filters was Re:
[FlyRotary]...


>
> On Monday, April 18, 2005, at 05:24 PM, George Lendich wrote:
>
> >
> >> Hi Ernest,  one assumption you make that I will throttle back for
> >> cruise, is probably not true.  At least I have seldom done so with my
> >> Continental powered Tailwind. I plan to take off full throttle and
> >> cruise right around 6000 rpm which is the sweet spot (lowest bearing
> >> load) for the 13B.  But your point about the complexity of the
> >> switchable intake is well taken.   I prefer the idea of filtered ram
> >> air and am going to see I can fit it under the cowl. It is amazing
> >> that
> >> we have been  able to talk ourselves into supplying unfiltered air at
> >> all.  Lot of rationalizing on that one. I am as guilty as anyone else.
> >>    BTW,  a few months ago I proposed the filtering ram air  on the
> >> other
> >> list and was told that filters and ram air did not go together.  I
> >> gave
> >> it up at that time but here we are again.   Jerry
> >
> > Jerry,
> > Am I wrong in thinking that a ram intake will force air through a
> > filter?
> > George ( down under)
>
> I am betting on it George.  Seems logical,  but pressure loss across
> the filter was the concern.  PL said the pressure loss would negate the
> ram air effect. I think that is a little strong.   I imagine there will
> be some performance degradation but not too much.  On the positive side
> there is Bill Jepson's report that filtered ram air is being utilized
> on motorcycles with good results. As someone else has noted, protecting
> the engine is worth a few  hp.       Jerry
> >
> >

Typical PL logic.......

If your filterbox is sealed, it will load with ramair pressure ( dynamic
pressure converted to static pressure, if I am not all wrong), whatever
value you get. Of course you will loose some pressure across the filter or
there would be no airflow through it (pressure drop/differential needed or
no flow....)
I doubt the ramair will be good enough to actually blow the air through the
filter - at our speeds (...else everyone would use "ram air supercharging"
:)),
IF you define "blowing" air into the manifold as "positive pressure" like
with a supercharger or a turbo.
However the higher the pressure BEFORE the filter, the less the engine will
have to suck ( to keep up with Rusty... :)) to get the air through the
filter.
How you increase the pressure in front of the filter doesn't matter -
charger/turbo/ram air/ holy spirit, whatever works.
If there is no ramair the engine still has to suck the air through the
filter, but at a higher total pressure differential, costing more power.

With ramair you can increase pressure direct into the manifold, a sealed
filterbox, the cockpit, where ever you want.
So why PL states you will loose the rameffect - I doin't know.
Maybe I miss something, but rameffect is rameffect, no matter what you
finally do with it....hell, you even can load a turbocharger with ramair if
you like - you will have that much more boost after the turbo!! :)

The perfect intake is pretty much unattainable:
-straight ramair via straight tuned intake tubes, with Direct injection, no
butterflies or anything in the way-
Whatever you put into the way of this perfect intake will increase the
pressure drop: curved intake tubes, butterflies, manifoldboxes, any turns
the air has to take, and eventually an airfilter if you use one.
Ramair will work to alliviate some or all of that - nothing specifically on
airfilters here.....

Correct me if I am wrong, please!

Thomas Jakits