Mayf:
It's always a treat to visit your site! I checked into the table of
coeffecient of drag comparisons. Well, at least the Tiger has a better
cd than a Hummer, Caterham or a Hennessy Viper. It may have the
aerodynamic efficiency of a brick :-) but I do love my Sunbeam!
Regards
David Sosna
DrMayf wrote:
> 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
>>>>
>>>
>>
>>
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