REFLECTOR: ram air

[Johnny Thompson]

Jack

Do you have the kit or part number?  Lots to chose from at airflow
performance.  I have a 540K 300 HP which will be different from the 540C/D
but should get me into the right area of the catalog.  Also plan on pulling
cold air through the filter because of the DA in Arizona. I like the scoop
attached to the fuselage.   Thanks.
                                            Johnny Thompson
                                            Sahuaria Az -5 RG

----- Original Message ----- 
From: <J.F.Sheehan at larc.nasa.gov>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Wednesday, July 05, 2006 8:21 AM
Subject: Re: REFLECTOR: ram air


The theoretical is possible with a very good designed intake. The practical
gain in manifold pressure is somewhere between 1/2inch and 1 inch MP. The
opening of the ram air scoop should be sized for the volume. The passage to
the servo should be a little larger to allow the volume to expand thus
maintaining the same pressure at the servo. I used a air scoop from Velocity
I don't know if it is on the store web site but you can call. The scoop is
mounted under the airplane just forward of the firewall with the end of the
scoop coming up right behind the firewall. I have the scoop attached as part
of the lower cowl. If I had it to do over I would make it attached to the
fuselage so that i did not have to remove the scat hose connecting the scoop
to the servo each time I removed the cowl. (Hind sight) Thw scat tube (4
inch dia) is connected to a  airflow performance adapter (made for IO-540).
(www.airflowperformance.com) It has a butterfly valve which allows me to
select ram air or filtered air. The filtered air is taken from inside the
engine compartment through a K&N air filter attached to the adapter. ( race
car style).
In flight I see a difference of 3/4 inch MP at 10K feet between the filtered
air and the ram air. Photo of adapter shows the air filter the open end of
the adapter goes to the scoop. it is important to get the scoop opening at
lest 3/4 inch away from the fuselage in order to be out of the boundary
layer to keep the drag a low as possible. scoop needs a nice rounded edge
not a sharp edge.
I think it was worth the effort and expense

Jack Sheehan
N55XL
Race 55