Removing ram air duct - Legacy

Forums: 

From: Adam Molny <Adam [at] ValidationPartners.com>
Sender: <marv [at] lancaironline.net>
Subject: RE: [LML] Removing ram air duct - Legacy
Date: Sun, 02 Dec 2007 11:20:49 -0500
To: <lml [at] lancaironline.net>

>With ram air open I would see a 1.5 inch increase in MP but

>with it cut it still gets 1.3 inches.  

> - Art Jensen



What would MP be with nothing at all connected to the throttle body? The

IO-550N engine air intake is located in the high-pressure side of the intake

plenum. Common wisdom says that a ram air duct facing into the slipstream

boosts MP, but we already have two big scoops, namely the cooling inlets!

Pressure rise from a ram air duct should be nearly identical to the air

pressure inside the cowl. Anyone have any thoughts?



I'm seriously considering leaving off the ram air tube altogether. Now I

just need a way to keep birds and big rocks out of the engine.



-Adam Molny, unfiltered

(me, not the plane)





Removing ram air duct - Legacy

From: <Sky2high [at] aol.com>
Sender: <marv [at] lancaironline.net>
Subject: Re: [LML] Re: Removing ram air duct - Legacy
Date: Mon, 03 Dec 2007 00:17:48 -0500
To: <lml [at] lancaironline.net>

In a message dated 12/2/2007 10:21:35 A.M. Central Standard Time,
Adam [at] ValidationPartners.com writes:

What
would MP be with nothing at all connected to the throttle body? The
IO-550N
engine air intake is located in the high-pressure side of the
intake
plenum. Common wisdom says that a ram air duct facing into the
slipstream
boosts MP, but we already have two big scoops, namely the
cooling inlets!
Pressure rise from a ram air duct should be nearly
identical to the air
pressure inside the cowl. Anyone have any
thoughts?

Adam,
 
Of course.  In my wee Lancair at about 183 KIAS (typical
cruise) I see about 12" H2O above ambient static pressure in the upper
cowl.  That is approximately  .85" Hg (MAP).  However, that does
not take into account any more than engine cooling air being bled off for
the induction system or oil cooler since they have separate intakes.  You
are talking about the superior intake setup for Continental engines - cold air
in to cold runners - rather than those of us that suffer with induction air
being run thru the oil sump.
 
At 183 KIAS I should be seeing about +1.5" Hg added to the MAP because of a
dedicated ram induction port.
 
Scott Krueger
AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL
(KARR)

Darwinian culling phrase: Watch
This!






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Removing ram air duct - Legacy

From: <MikeEasley [at] aol.com>
Sender: <marv [at] lancaironline.net>
Subject: Re: [LML] Re: Removing ram air duct - Legacy
Date: Mon, 03 Dec 2007 14:27:41 -0500
To: <lml [at] lancaironline.net>

Adam,
 
I have removed my ram air and installed a second air filter on my ES. 
My measurements show an insignificant loss of MP without the ram air and some
improved cooling.  The butterfly valve isn't very air tight and I feel
better feeding my engine 100% filtered air.
 
Mike Easley
Colorado Springs






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Removing ram air duct - Legacy

From: Fred Moreno <fredmoreno [at] optusnet.com.au>
Sender: <marv [at] lancaironline.net>
Subject: Removing ram air duct - Legacy
Date: Mon, 03 Dec 2007 14:27:41 -0500
To: <lml [at] lancaironline.net>

Adam
wrote: 

"Common
wisdom says that a ram air duct facing into the slipstream

boosts
MP, but we already have two big scoops, namely the cooling inlets!

Pressure
rise from a ram air duct should be nearly identical to the air

pressure
inside the cowl. Anyone have any thoughts?"

 

Indeed
I do.  You are correct.  A bit of care is needed, however.

 

My
Lancair IV mounts an IO-550 and so has the same induction air problems/opportunities
as the Legacy.  I did not much care for the factory Legacy/ES induction
"ram air" system because of the flow blockage, small tube size, and poor
inlet flow coefficient arising from the sharp-edged angle-cut aluminium tube. 
And it costs a lot. 

 

But
the concept of collecting air from inside the plenum is sound - if one makes
sure the air inducted is cool and the pressure recovery into the cowl is
acceptably high, giving a bit of free horsepower from the recovery of ram
pressure.

 

Many
measurements show about 20F rise in air temperature in the upper cowl which can
cut HP is inducted into the engine.  It is incorrect to attribute this to
ram air heating.  The same ram air and friction effects create a similar
temperature rise on the OAT sensor.  The temperature rise inside the top
of the cowl is in addition to the ram air compression effect. 

 

So
what is heating the air?

 

It
is the air whipping through the inlets, then passing across the tops of the
fins of the front cylinder heads without going downward past the rest of the
head.  A portion of the cooling air passes over the top of the front
heads, is heated modestly, and then flows back and mixes with the balance of
airflow.  This then finds it way down through fins (and leaks) into the
lower cowl driven by the pressure difference between the top and bottom of the
engine.  One has to be careful to avoid prematurely heating the air, and
then sucking it into the engine.  Twenty degrees temperature rise causes about
3.5-4% loss in horsepower, about the same losing an inch of manifold pressure.

 

I
built my own induction system out of fibreglass patterned on the factory
layout, but including some improvements.  Features include:

 

1)
Air filter for ground and low level operation.

2)
A large flapper valve that directs air either from the air filter or the
unfiltered inlet.  No screws are used to hold the flapper onto the
shaft.  Rather it is bonded in place and wrapped with 3 BID.  A micro
switch indicates if the valve is cracked open bypassing the air filter.

3)
A larger, shorter unfiltered air inlet.  The cross sectional area is about
1.5 times that of the throttle body so velocity is lower and friction losses
cut by more than half. The inlet tapers and includes a small bell mouth opening
(not much room in there) to improve the inlet flow coefficient.  I set the
inlet off to the side of the cowl inlet stream so as to not block the flow from
the cowl inlet and to minimize water, bug, and bird entry to the engine.

 

Referring
to Chris Z's excellent article in Sport Aviation referenced by Scott, I
subscribe to the external deceleration theory of cowl inlet design with most of
the flow slowing occurring in front of the inlet where the deceleration process
is frictionless.  I have sized the inlets (6 inch diameter) so that at
high cruise the inlet velocity through the cowl opening is 40% of the free stream
velocity.  This means that 86% of the free stream ram pressure is present
at the inlet plane, and it is up to me to get as much of the remaining 14% as I
can after the flow enters the plenum.

 

 Photos
are shown below.  The part was made from a foam master which was then
covered with fibreglass, slit in half horizontally, foam chewed out, cleaned
up, and then bonded together with the flapper valve captured inside.  The
flapper valve shaft is made from 1/4 inch hydraulic tubing.  It took a lot
of fussing to get the flapper valve to seal without leakage (no obvious
daylight when the flapper is seated).

 

Fred
Moreno

 

 

 

 

 


Image


image001.jpg


Image


image002.jpg


Image


image003.jpg

Removing ram air duct - Legacy

From: Craig Berland <cberland [at] systems3.net>
Sender: <marv [at] lancaironline.net>
Subject: [LML] Removing ram air duct - Legacy
Date: Tue, 04 Dec 2007 07:23:38 -0500
To: <lml [at] lancaironline.net>
I
built my own induction system out of fibreglass patterned on the factory layout,
but including some improvements.  

 Photos are shown below.  The part was made
from a foam master which was then covered with fibreglass, slit in half
horizontally, foam chewed out, cleaned up, and then bonded together with the
flapper valve captured inside.  The flapper valve shaft is made from 1/4
inch hydraulic tubing.  It took a lot of fussing to get the flapper valve
to seal without leakage (no obvious daylight when the flapper is
seated).

Fred
Moreno

 

 

Fred, you dog you....very
nice.

Craig Berland

 

 

Removing ram air duct - Legacy

From: Gary Casey <glcasey [at] adelphia.net>
Sender: <marv [at] lancaironline.net>
Subject: Re: Removing ram air duct - Legacy
Date: Tue, 04 Dec 2007 09:20:22 -0500
To: <lml [at] lancaironline.net>

Most excellent work, Fred!  It's a work of art and should be effective as well.

Gary
....

 Photos are shown below.  The part was made from a foam master which was then covered with fibreglass, slit in half horizontally, foam chewed out, cleaned up, and then bonded together with the flapper valve captured inside.  The flapper valve shaft is made from 1/4 inch hydraulic tubing.  It took a lot of fussing to get the flapper valve to seal without leakage (no obvious daylight when the flapper is seated).

 

Fred Moreno

Removing ram air duct - Legacy

From: Chuck Jensen <cjensen [at] dts9000.com>
Sender: <marv [at] lancaironline.net>
Subject: Re: Removing ram air duct - Legacy
Date: Tue, 04 Dec 2007 18:24:14 -0500
To: <lml [at] lancaironline.net>
Fred,
 
I
inadvertantly deleted your posting related to the flapper valve/control. 
Would you be so kind as to email me the posting and/or
pictures.
 
Thanks,
Chuck
Jensen

Diversified Technologies

2680 Westcott Blvd
Knoxville, TN  37931
Phn:    865-539-9000 x100

Cell:   
865-406-9001

Fax:     865-539-9001
cjensen [at] dts9000.com

Removing ram air duct - Legacy

From: Adam Molny <Adam [at] ValidationPartners.com>
Sender: <marv [at] lancaironline.net>
Subject: RE: Removing ram air duct - Legacy
Date: Thu, 06 Dec 2007 14:40:30 -0500
To: <lml [at] lancaironline.net>

>Indeed I do.  You are correct.  A bit of
care is needed, however.

 

Excellent write up Fred. Thanks!

 

-Adam Molny

Removing ram air duct - Legacy

From: <MikeEasley [at] aol.com>
Sender: <marv [at] lancaironline.net>
Subject: Re: [LML] Re: Removing ram air duct - Legacy
Date: Fri, 07 Dec 2007 19:13:53 -0500
To: <lml [at] lancaironline.net>

On the subject of ram air ducts, Lancair has an SB on the duct, loose
screws being eaten by the engine.
 
 
Mike Easley
Colorado Springs






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Removing ram air duct - Legacy

From: Steve Colwell <mcmess1919 [at] yahoo.com>
Sender: <marv [at] lancaironline.net>
Subject: Removing ram air duct - Legacy
Date: Sun, 16 Dec 2007 16:19:06 -0500
To: <lml [at] lancaironline.net>

Here is my take on the induction for our Legacy.  This is
the largest K&N Filter I could fit without blocking the inlet.  If
K&N is to be believed, and according to Vangrunsen’s RV tests they
can, the reduced turbulence increases flow by an inch plus of MP.  I do not
have comparison figures yet but my reasoning is the Lancair Ram Tube is vented
to the cowl upper plenum when the butterfly valve is open to Ram so any
additional ram pressure would be lost, right? 

 

The downside is I don’t have alternate air with the current
configuration but the radiant heat from the cylinder (and the 20 degree temp
rise I did not know about, thanks Fred) may keep enough of the filter ice free
until I can execute the instant U turn and or decent when icing occurs.   Or
maybe these factors will offset any anticipated gains.  I will test with
temp probes and without the Filter and Tube to get some numbers.

 

 

Steve Colwell  15SC FLYING!

Removing ram air duct - Legacy

From: Bill & Sue <5zq [at] cox.net>
Sender: <marv [at] lancaironline.net>
Subject: Re: [LML] Removing ram air duct - Legacy
Date: Mon, 17 Dec 2007 07:25:14 -0500
To: <lml [at] lancaironline.net>
Nice job on the induction, Steve. Can you tell us
which K&N filter this is. Also, where did you get the bent rubber connector
between the intake pipe and the filter? Thanks.
 
Bill Harrelson
N5ZQ 320 1,450 hrs
N6ZQ  IV under construction

 

Removing ram air duct - Legacy

From: Steve Colwell <mcmess1919 [at] yahoo.com>
Sender: <marv [at] lancaironline.net>
Subject: Removing ram air duct - Legacy
Date: Tue, 18 Dec 2007 17:10:11 -0500
To: <lml [at] lancaironline.net>

Bill,

 

This
is the Filter link with specs  
http://www.knfilters.com/search/product.aspx?Prod=RX-3900-1  
I bought the Silicone Rubber Connector in a Baxter Auto Parts store in
Oregon.  It was in a Canadian Race Car Parts catalog and I can’t locate
the invoice or remember the brand.  If you can’t find it, I will be
back in Oregon in January.

 

Steve



Subject: [LML] Re: Removing ram air duct - Legacy

 

Nice
job on the induction, Steve. Can you tell us which K&N filter this is.
Also, where did you get the bent rubber connector between the intake pipe and
the filter? Thanks.

 

Bill
Harrelson

N5ZQ
320 1,450 hrs

N6ZQ 
IV under construction