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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
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