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Discussion Starter #1
I suspect not, but does anyone know for sure?

Reading Phillip's post on the positive effects of cold air on engine performance has given me an idea, but I don't want to waste my time on something that won't make a difference.

Thanks!
 

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It will to some degree that is evident by all the bugs that hit the firewall that must be cleaned from time to time. If the scoop were turned around with the opening at the base of the windshield like a 69 Z-28 it would work great but it sure would look odd on a cobra.
Don

[ January 01, 2005, 07:29 PM: Message edited by: Don DePontee ]
 

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FFCobra Master Craftsman
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I saw this issue covered on a TV program. I understand that the location of this scoop or the scoops on most cars are more decorative than functional. For max air flow, the scoop opening should be much closer to the front of the car because the center of the hood is a relatively low presure zone as compared to the leading edges.
 

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Guys,
At the very least it will let OUT hot air. I'm not sure that bug splatter count as an indication as air entering. More like hit-n-run trapped. Air does come up from under the car and probably helps from lifting at speed (120mph plus).
Thanks,
Ron
 

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Quite a few years ago I had a '75 Trans Am with a shaker (facing rearward). I took out the factory installed plate that covered the opening to make it functional. At speed during rain, the beads of water on the hood would travel back toward the windshield and then curve around toward the midline and go forward toward the shaker, due to the high pressure area in front of the windshield (and of course, the big suck from the Rochester carb, especially the secondaries when I had my foot in it!). This seems to support the other posts suggesing that there's not much static pressure at the center of the hood. There may be some ram effect from dynamic pressure, but the scoop has a pretty low profile, so most/all of it may be in the boundary layer that has little air movement. I'll ask one of my aeronautical engineer colleagues how thick the boundary layer may be at car speeds (although they usually deal with airplane speeds).

- Steve
 

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I suspect that you need a turkey pan and a foam seal to get cold air into the carb.

If you're EFI, Cobra Earl has a really nice 5" duct for the oil cooler (or brake duct, if you prefer) opening, that you can run to the EFI system.

cold air induction is almost like free horsepower.

Forrest
 

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Paddles,
Why not tape some strands of knitting wool on the hood in front of the scoop and around it. Then you can see the air flow as you drive.

Bill G
 

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Bill,
In continuation - if one did tape the tel-tails (a la wind tunnel) on the hood you could monitor with the scoop open and with it blocked off. Heck you could mount a video camera on a quickjack and record it to share.


Might be fun when I have nothing ensle to do on my car, but it would be neat to really see it. I guess one indication of functionality of our scoop is the hood on the daytona coupe.


 

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Discussion Starter #9
Thanks for all of the replies, gents.

I decided to call Craig H., aka Rocket Scientist, yesterday and pose this question to him. As usual, he had the answer.

Craig has determined that, due to the radius of the hood (gently curves from the nose all the way to the scoop entrance - no flat areas), that laminar air flow still exists at that point. Boundary layer separation will eventually occur forward of the scoop opening as the car's speed reaches a certain point, but that speed is likely beyond any number found on my speedometer. He also recommended the turkey pan and foam seal.
 

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Paddles,
Did Craig H take into account the HUGE grill opening on these cars? Just taking into acount the shape of the hood and the location of the scoop I would expect some ram effect.
On the other hand, I expect there's so much ram effect getting into the engine compartment thru the grill opening that the compartment is actually a high pressure area itself.
Now if you were to seal the scoop to the intake and isolate it from the engine compartment, I would think it would draw quite well.

d



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This car was parked beside me at the '04 Mitty at Atlanta. I felt pretty "inadequate"....as you can see by the number on the side.

But this is his Cold Air Induction System. Catching the air coming over the radiator and directing it into the filter/carb. I think there was a matching face attached to the underside of the hood that boxed the air in.

The "vintage" look was lost but with 572 on your car...who cares. I was impressed with the workmanship. I think this car was from down on the Carolina coast.

Lets all go to the 05 Mitty in April. Maybe he'll return.
 

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This scoop will most likely draw a bit more air than the stock scoop. :D

 

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I cannot contribute from an airflow dynamics point of view . But, I can tell you my motor is VERY noticeably faster with snappier throttle response at speed with my Moroso Air Pan, sealed to the scoop by 2" wide foam, with the Edelbrock Pro Flo foam element air cleaner. I want to get away from the foam element and hope this winter will result in a low profile K&N set up. I have added power to my motor at stages and my estimate is I feel a solid 20HP bump and the response is much crisper. Once the temps reach around 35 degrees the Air Pan had to be swapped for a 14" drop base. In those temps, when doing short winter rides, some highway with with frequent local stops, I found the motor stumbled a bit then stalled at a red light. I lifted the Air Pan and found icicles on the venturis ! On cool spring /fall days after a highway run venturis on my Holley are COLD despite noticeable heat rising from under hood temps . On the dyno in front of a 6' fan, temps around 80 degrees, the motor after tuning made additional 8 rwhp by closing the hood with the Air Pan over open hood with open carb. Whether it is cold air or cold ram air sealing the scoop works IMHO. I tried and measured all suggested applications from www.ramairbox.com . I found their system is way too big for my MKI FFR, with 351W and solid motor mounts. Here are some more websites which I hoped would allow an improvised air box downline from a carb bonnet.
www.vs57.com/bonnets.htm
www.csucarbs.com
www.performancecarburetors.com/bonnets.htm
www.superiorairflow.com ( I measured 4Hx4Wx7"L this as too big for my FFR hood clearance) Aaagh !!

[ January 03, 2005, 10:53 AM: Message edited by: JAM1775 ]
 

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JAM, do you have any pics of your Moroso pan setup?
 

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Update on the scoop airflow issue... I posed the boundary layer question to two of the professional aeronautical engineers in my group - they actually do this kind of analysis for airplanes. They agree that there is probably laminar flow over the hood as far back as the scoop. However, the depth of the boundary layer would start out thin and then increase in thickness as it progresses farther downstream (i.e. more and more of the surrounding air is dragged along). On a large airplane (e.g. 747), it may be 1-2 ft thick towards the aft end of the fuselage. However, this close to the leading edge of the hood of a cobra, it is probably 0.5 inches or less in depth. So, that would lead one to guess that most of the scoop should be in the high speed airflow. On the other hand, some folks have pointed out that the engine compartment may actually be at a higher pressure due to the ram air effect of the cowl opening. If that is so, the airflow could stagnate right in front of the scoop. These two counteracting forces may explain why a turkey pan seems to improve performance: it isolates the ram effect of the scoop from the elevated air pressure in the engine compartment, allowing the scoop to me more effective.

If no one does it before I get #4980 on the road, I'll try attaching some yarn as was suggested in the earlier messsages and let you know what I discover.

For JAM1775: That's why light aircraft have carburetor heat - without it, the carb will ice up, followed by a lot of silence and then a big crunch. You have to be very careful moving a lot of cold, moist air through the venturi of a carb. Here's a website that explains the problem: http://www.misterfixit.com/carbice.htm. As is noted on the site, you could also have a problem with the diverter valve (assuming you have one).

SS
 

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I've thought about this problem a lot in a number of my cars. I'm not one to crank numbers and just rely on them....I go and experiment. On a Subaru 2.5RS, which has a big hood scoop and 2 forward hood vents, all are blocked on this car, but could be used. My experiment was easy enough to do. I unblocked all of these and ran the car after the car sat outside and got snowed/iced all over. After driving about 60 miles, the exiting heat from the front 2 vents showed that heat from the engine compartment was indeed coming out and melting the ice on the hood coming back from the vents. The intake scoop (similar to a WRX for intercooler intake) had absolutely no melting of the snow/ice.

I've also seen a number of Subaru and Neon projects using the cowl as an intake source for high pressure air that is then fed into an air cleaner.

For a Cobra, it would seem a bit difficult to release the air pressure underhood as I would expect to have to find an exit near the front, like the Daytona. Not cosmetically a good option. I'd think that a combination of running a hose into the oil cooler area and blocking off the rest of that area and running that into an airbox for the intake is a first step. Next is to either block or use the brake duct holes. Next is to block the hole above the radiator. Now with most of the "extra" air intakes into the engine compartment a low pressure exit is needed. I'm thinking now, perhaps the front surface of the wheel wells?
 

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Steve...your post makes sense to me as I do remove the air pan each season once it gets to the low/mid 40's. As far as sealing it does seal to the scoop therefore is not really effected by the upward air from the surrounding engine compartment only what is either forced or scavenged from the hood area. As far as "silence and then a big crunch" Good thing we're only 5 inches from the ground !
 
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