This bit about scoops and size is of some interest to me. We have had this
discussion many times on the land-speed racing list. Here is the deal. The
scoop never needs to be larger than what the motor needs at any particular
speed. Now this is an interesting concept because at the higher speeds, the
scoop can be small, but at lower speeds, it needs to be large. The reason
thst this is so, is that when the motor is at full song but the car is at
low speeds, the cfm of the engine needs to be matched by a scoop that can
supply the amount of air needed. The air going into the engine is at a
pretty high velocity while that going into the scoop is slow. Have to do a
flow balance to make it work. At high speeds, the motor is still turning the
same rpm and the cfm requirements are the same but the car is going fast and
in the flow balance the scoop opening gets smaller. We have decided that the
best scoop is one that is sized correctly for top speed and full engine rpm,
with small doors in the side and /or top that open to effectively increase
the scoop opening size. As to having a large scoop, remember that large adds
drag and drag EATS horspower. So if you want to go fast, then get a smaller
scoop, one that is sized for engine requirement at speed and has the least
frontal area. There are some interesting internal air ballistics involved
also. The air must be taught to flow in the correct direction but in such a
manner not to cause one or more of the throttle bores to become lean becaue
too much air is flowing through it and vice versa. As to the supercharging
effect due to bringing the air to a halt in the scoop, ie pressurizing the
scoop, it is really pretty minimal. the dynamic pressure is easy to
calculate: 1/2 * rho * V * V where rho is in slugs/ft^3, V is in ft per
second. For standard conditions, rho is 0.002377 slugs/ft^3 and say speed is
120 mph which is 176 ft/second. Then dynamic pressure in lb/ft^2 is 0.002377
* 176 * 176 /2 = 36.8 lbs /ft^. Divide this by 144 in^2/ft^2 to get psi =
0.256 psi. Pretty minimal supercharging effect and truly not worth the
effort. Certainly wouldn't have to worry about an intercooler, LOL... Should
you be interested further, please see my web site in the analyses section
for more information on how to size a scoop ...
http://www.teknett.com/pwp/drmayf/analyses.htm
I hope this doesn't add confusion to the thread...
mayf, the red necked ignorant desert rat in Pahrump, just in from planting a
dozen trees....
----- Original Message -----
From: "Larry Paulick" <larry.p@erols.com>
To: "Ronak, TP (Timothy)" <Timothy.Ronak@AkzoNobel.com>
Cc: "'Scott Hutchinson'" <shutchin@netjets.com>; <tigers@autox.team.net>;
<drmayf@teknett.com>
Sent: Wednesday, April 30, 2003 9:12 AM
Subject: Re: Fresh Air Induction
> Scott, the smaller intake with longer runners is valid for intake
> manifolds to make torque. I have never heard of this design for an air
> intake.
>
> If you look at any of the functional scoops on the drag cars, they are
> all large to pack as much air as possible in a ram effect into the
> intake system.
>
> The pitot tube for air planes is as Tim describes.
>
> Larry
>
> Ronak, TP (Timothy) wrote:
> > Scott,
> > I still ascribe to the big surface area higher pressure per square inch
at
> > the carb theory. The other limitation is the laminar flow right against
the
> > hood working to diminish the actual working surface area of the opening.
The
> > old Ram air under bumper kits the Detroit guys put on the 60-70 muscle
cars
> > had 2-3 times the opening surface area of what was at the carburetor
throat.
> > The pitot tube point is valid but I thought the pitot tube was used to
> > create a measured vacuum. I am certainly not a pilot nor an airplane
expert.
> > Probably the most significant opportunity is to obtain cool air from
outside
> > the engine bay.
> >
> > Best Regards,
> >
> > Tim Ronak
> > Business Development Manager
> > Akzo Nobel Coatings
> > Off: (949) 305-5393
> > Fx: (425) 955-6268
> > Cell: (949) 289-3357
> > email: timothy.ronak@akzonobel.com
> > VM: (800) 234-6747 ext. 2257#
> >
> > This message, including attachments, is confidential and may be
privileged.
> > If you are not an intended recipient, please notify the sender then
delete
> > and destroy the original message and all copies. You should not copy,
> > forward and/or disclose this message, in whole or in part, without
> > permission of the sender.
> >
> > -----Original Message-----
> > From: Scott Hutchinson [mailto:shutchin@netjets.com]
> > Sent: April 29, 2003 8:28 PM
> > To: 'Ronak, TP (Timothy)'; tigers@autox.team.net; drmayf@teknett.com
> > Subject: RE: Fresh Air Induction
> >
> > Tim,
> >
> > Not sure that a larger scoop would help you out. In many ways having a
> > smaller scoop with a long runner to the intake gives the best effect.
> > Much like a pitot tube on an airplane.
> >
> > Scott
> >
> > -----Original Message-----
> > From: Ronak, TP (Timothy) [mailto:Timothy.Ronak@AkzoNobel.com]
> > Sent: Tuesday, April 29, 2003 8:17 PM
> > To: Timothy.Ronak@AkzoNobel.com; tigers@autox.team.net;
> > shutchin@netjets.com; drmayf@teknett.com
> > Subject: RE: Fresh Air Induction
> >
> > Well DrMayf,
> > The air box will probably not make a huge difference on the chassis dyno
> > as
> > that is a static test without the car speeding down the road. I still
> > will
> > try the stock base and filter and then the flat base and taller filter
> > to
> > see if there is a gain due to filter size. Larry P. and I shared some
> > discussion over this a few weeks ago. But I do plan on going to the Drag
> > strip and see if the same 2 tenths of a second ET drop occurs that I
> > have
> > experienced on other cars where I installed a fresh air system (20 HP at
> > speed due to a cooler denser charge of air). I suspect a 2 fold gain due
> > to
> > cooler air as well as a marginal 'Ram Air' effect although the scoop
> > opening
> > is not as large as I would like. Trying to keep it looking relatively
> > stock.
> >
> > Best Regards,
> >
> > Tim Ronak
> > Business Development Manager
> > Akzo Nobel Coatings
> > Off: (949) 305-5393
> > Fx: (425) 955-6268
> > Cell: (949) 289-3357
> > email: timothy.ronak@akzonobel.com
> > VM: (800) 234-6747 ext. 2257#
> >
> > This message, including attachments, is confidential and may be
> > privileged.
> > If you are not an intended recipient, please notify the sender then
> > delete
> > and destroy the original message and all copies. You should not copy,
> > forward and/or disclose this message, in whole or in part, without
> > permission of the sender.
> >
> > -----Original Message-----
> > From: DrMayf [mailto:drmayf@teknett.com]
> > Sent: April 30, 2003 7:34 AM
> > To: Ronak, TP (Timothy); Tiger News Group List (E-mail)
> > Subject: Re: Fresh Air Induction
> >
> > Tim, now that you have it finished, are you going to dyno check the
> > performance before and after? WOuld be interested in the numbers..
> >
> > mayf
> > ----- Original Message -----
> > From: "Ronak, TP (Timothy)" <Timothy.Ronak@AkzoNobel.com>
> > To: "Tiger News Group List (E-mail)" <tigers@autox.team.net>
> > Sent: Tuesday, April 29, 2003 1:27 PM
> > Subject: Fresh Air Induction
> >
> >
> >
> >>Listers,
> >>I finally got the project done and had several requests for plans,
> >
> > etc. I
> >
> >>have copied templates for the Fresh Air Box including measurements and
> >
> > a
> >
> >>"how to" article. Because the templates were 'life sized' they needed
> >
> > to
> > be
> >
> >>copied on an Oversized copier. Kinko's really sticks it to you when
> >
> > you do
> >
> >>big snip
> >
> >
>
>
>
> #################################################################
> #################################################################
> #################################################################
> #####
> #####
> #####
> #################################################################
> #################################################################
> #################################################################
>
> #################################################################
> #################################################################
> #################################################################
> #####
> #####
> #####
> #################################################################
> #################################################################
> #################################################################
|