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Author
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Topic: Forward facing hood scoops don't work
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SundanceKid
Gearhead Posts: 1137
From: UT
Registered: Feb 2001
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posted 02-07-2004 01:35 AM
   
I have found forward facing scoops less then 4" high and further back then 4" from the leading edge of the hood are not functional. In some cases a low pressure area can form in front of a sealed scoop and cause less flow.Opinions?
Theories? This excludes naca ducts btw. Just curious what everyone's opinion of this statement is?
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V8 Thumper
Gearhead Posts: 4044
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 02-07-2004 02:06 AM
My machinist likes cold air induction via ducting. You know, like Thunderbolt Fairline style. He still likes hood scoops to 'vent' the motor compartment; tends to keep things cooler providing a forced air circulation past the collectors and out the bottom of the car. I dunno, the principle sounds good I guess. I do like the ducting deal though  ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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Mpcoluv
Gearhead Posts: 1144
From: Charlotte NC usa
Registered: Apr 2001
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posted 02-07-2004 09:04 AM
quote:
Originally posted by SundanceKid:
I have found forward facing scoops less then 4" high and further back then 4" from the leading edge of the hood are not functional. In some cases a low pressure area can form in front of a sealed scoop and cause less flow.Opinions?
Theories? This excludes naca ducts btw. Just curious what everyone's opinion of this statement is?
What you are referring to is that you need to get above the "boundry layer" of turbulance along the surface of the hood.
However I think it is going too far to say that the scoops "do nothing". There is plenty of evidence that my Boss 429 scoop supplys some air into the engine compartment.
Bugs seem to get squashed by my air filter....
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rustang@home
Journeyman Posts: 23
From: Clarion, PA
Registered: Jan 2004
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posted 02-07-2004 10:41 AM
The affectiveness of a forward facing hood scoop and it's best placement is going to vary from car model to car model. An early mustang pushes alot of air with that flat front end compared to late model stuff. So an old 'stang would probably require an opening higher on the hood to get to the clean air. A late model should have cleaner air closer to hoodline so you should be able to run a "shorter" scoop.My '67 stang with a 5" snorkel sealed to the carb was a minimum of .25 quicker on any day, so I know it worked. The Boss 429 scoop on my '68 was similarly affective. [This message has been edited by rustang@home (edited 02-07-2004).]
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MidLifCrisis
Gearhead Posts: 323
From: USA
Registered: Oct 2001
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posted 02-07-2004 07:50 PM
SundanceKid, you are correct to a point. As rustang stated aerodynamics vary from car to car. Carrol Shelby found that the scoop on the 65'-66' worked better with the opening facing the windshield, but approved it for production facing forward because it looked better.
The 68' Shelby's scoops at the leading edge of the hood pick up substantial more air than the 67' scoop placed mid hood.
These early cars did not use air dams or chin-spoilers until the Bosses or possibly the Trans-Am road racing series. Therefore air was present rushing underneath the car. This air moving below should be suffient enough to create a low pressure system in the engine compartment, thus aiding in pulling air through the hood scoop. If I was building another Go-Fast car, I would put the scoop on for the Ooohs and Ahhhs, and duct the snorkel to underneath the car, through the chin-spoiler, but that's just me. There are hundreds of different ways and opinions. Charlie
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Moneymaker
Administrator Posts: 21725
From: Lyons, IL, USA
Registered: May 99
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posted 02-07-2004 09:00 PM
We could debate this one all night.  ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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SundanceKid
Gearhead Posts: 1137
From: UT
Registered: Feb 2001
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posted 02-07-2004 09:59 PM
That was the point
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CHIPSBAD67
Gearhead Posts: 276
From: LOU,KY;USA
Registered: Sep 2003
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posted 02-07-2004 11:16 PM
i wonder if cowl hoods are as effective on some models. i can tell you there's a young guy that runs a silver 65 coupe in nmra, nick something, with the old teardrop hood for clearance. the point is he has air ducted from the cowl vents in front of the windshield and opening cut under the back of the hoodline ducted to intake. looks kinda nascar but as much air that blows in through my cow vents, i bet it works well and theres no need for a scoop or cowl hood. by the way, he runs a 408 and that car is wicked.------------------
306, 4speed, 4.11's....best 1/8 mile 7.58 at 92mph with 1.72 60ft. PUMP GAS/NO ADDERS/STREET TIRES
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CHIPSBAD67
Gearhead Posts: 276
From: LOU,KY;USA
Registered: Sep 2003
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posted 02-07-2004 11:18 PM
personally like a flat stock hood in any case. the factory one for the 66 427 fairlane looks good though.
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jsracingbbf
Gearhead Posts: 2160
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 02-08-2004 01:06 AM
The best Scoops have "butterflies" in them. 
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SteveLaRiviere
Administrator Posts: 37258
From: Saco, Maine
Registered: May 99
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posted 02-08-2004 06:03 PM
You can verify it yourself with a homemade manometer. I experimented with that a few eons ago and I sure found positive air pressure at my scoop inlet. ------------------
'70 Mustang Mach 1 351C 4V/FMX/3.25 Open
'70 Mustang Convertible 250 I6/3 speed/2.79 Open
'72 Mustang Sprint Hardtop 351C 4V/FMX/4.30 Trac Loc
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
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rustang@home
Journeyman Posts: 23
From: Clarion, PA
Registered: Jan 2004
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posted 02-08-2004 07:54 PM
quote:
Originally posted by SteveLaRiviere:
You can verify it yourself with a homemade manometer. I experimented with that a few eons ago and I sure found positive air pressure at my scoop inlet.
Another way is taping short pieces of yarn in the areas you want to observe how the air's flowing.
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Ryan Wilke
Gearhead Posts: 1700
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 02-09-2004 10:06 AM
quote:
Originally posted by SteveLaRiviere:
You can verify it yourself with a homemade manometer. I experimented with that a few eons ago and I sure found positive air pressure at my scoop inlet.
Positive air pressure is a good thing....and cooler air is also a good thing for max power. But as the evening comes on, the temps change and now we'd have to adjust our tune due to the difference in air delivery temps to keep our racers ET consistant. Maybe, for consistancy's sake, if a fella used an open filter element without a scoop, (we can figure the underhood air pressure would stay consistant) possibly the air temp (via underhood heat) wouldn't change as much than if we were using a fresh air scoop/duct and thus provide a more consistant air charge to the carb for a more consistant tune? Has anyone done any air temperature measurements AT THE CARB/AIR CLEANER and compare the affect on performance as air temps change? Does that make sense - what do ya think?
Ryan
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Kellxr7
Gearhead Posts: 315
From: Canada
Registered: Mar 2003
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posted 02-09-2004 10:18 AM
I was considering ram air for my car with a cobrajet scoop,(the type with the signal lights) it doesnt have alot of area where the air flows in. Would it be a waste of time to cut a hole in my hood then? (I mainly want the scoop for looks) but figured I may as well make it functional, but if it isnt going go do a whole lot for me I may as well use it for decoration?
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indyphil
Gearhead Posts: 1365
From: Lafayette, IN, USA
Registered: Jul 2002
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posted 02-09-2004 11:22 AM
Be careful with manometer measurements. You have one end in the engine compartment near the intake, the other may be in the car with you. When cars go fast the interior of the car often gets low pressure from the air rushing over it and past the windows. That might make it look like the engine is getting a positive pressure but it all depends on your point of reference. I like the ducted style as well but dont like the look of all the dryer hose under the hood. Maybe I can swap over to the cheesy chrome filter for car shows and switch back to the ducted system when I want to really drive the car. I do like the 68 GT500 hood style, im sure it must do something for extra pressure. ------------------
'68 coupe 289 C code
66 heads, edel 600cfm carb, performer intake, dual exhaust http://www.geocities.com/ottouk_77/68mustang.htm
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-09-2004 04:05 PM
quote:
Originally posted by Ryan Wilke:
Has anyone done any air temperature measurements AT THE CARB/AIR CLEANER and compare the affect on performance as air temps change? Does that make sense - what do ya think?
Ryan
I'd like to see to that too. I think even without any scoop at all, outside air temps will still afect times and tuning. So why not use that cool air ?
------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-09-2004 04:08 PM
quote:
Originally posted by Moneymaker:
We could debate this one all night.
Come on now, with all those years of playing with these you must have knowledge about this ? I was told on my 65 the scoop needed to be at least 3" tall to start getting ram air. Based on using the 429 boss scoop placed near the windshield end of the hood. ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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Moneymaker
Administrator Posts: 21725
From: Lyons, IL, USA
Registered: May 99
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posted 02-09-2004 04:12 PM
I know some Pro Stock racers that would argue about the positives of front facing hood scoops.
Ever seen a Pro Stock car with a cowl hood?  ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-09-2004 04:27 PM
quote:
Originally posted by Moneymaker:
I know some Pro Stock racers that would argue about the positives of front facing hood scoops.
Ever seen a Pro Stock car with a cowl hood?
Is that because of the added drag from a front facing scoop ?
I think they look cool, that has to be worth something.
------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics [This message has been edited by Fastymz (edited 02-09-2004).] [This message has been edited by Fastymz (edited 02-09-2004).]
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FiveOFastback
Journeyman Posts: 46
From: Bethlehem, PA, USA
Registered: Nov 2003
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posted 02-09-2004 04:37 PM
I do know that in some cases with certain cars there is a lot of pressure against the windshield. Cowl induction hoods would serve a better purpose in that case. Maybe that's why LS-5 and LS-6 chevelle's had them as an option. Be nice to have a windtunnel in your yard to test with.
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Moneymaker
Administrator Posts: 21725
From: Lyons, IL, USA
Registered: May 99
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posted 02-09-2004 04:42 PM
NO! 
They have front facing scoops.....SCOOP!They seek out the highest pressure area and that's where they strategicly place the hood SCOOP opening.
Manufacturers such as FoMoCo, Chrysler, and GM tried to do the same thing with their cold air packages. Chevrolet was the lone exception. They geared there cold air stuff towards the cowl or raised hood openings. ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-09-2004 05:12 PM
quote:
Originally posted by Moneymaker:
NO!
They have front facing scoops.....SCOOP!They seek out the highest pressure area and that's where they strategicly place the hood SCOOP opening.
Manufacturers such as FoMoCo, Chrysler, and GM tried to do the same thing with their cold air packages. Chevrolet was the lone exception. They geared there cold air stuff towards the cowl or raised hood openings.
I know they do,
I was asking about what the arguements would be from them ?
"I know some Pro Stock racers that would argue about the positives of front facing hood scoops." I just worded my question bad.
------------------
SCOOP
oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics [This message has been edited by Fastymz (edited 02-09-2004).]
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Mpcoluv
Gearhead Posts: 1144
From: Charlotte NC usa
Registered: Apr 2001
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posted 02-09-2004 05:40 PM
BTW a non sealed "cowl induction" hood will reall become a under hood vent at speed unless there is a good sealing airbox present.
Hey for you more knowledgable guys, what is the large Pro-stock style scoop for on Chuck Samuels Por 5.0 car? there is nothing under it that I can see that would warrant a scoop. The intercooler is where the passenger seat would normally go.
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Daniel Jones
Gearhead Posts: 575
From: St. Louis, MO
Registered: Aug 99
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posted 02-09-2004 07:28 PM
> NO! They have front facing scoops.....SCOOP!and for good reason. The pressure rise associated with a hood scoop
is from the conversion of dynamic pressure into static pressure. When
a moving gas like air is brought to a halt, there is an attendant rise
in pressure (the kinetic energy is converted to static pressure).
Bernoulli's equation illustrates this: P + (rho*V**2)/2 = constant
where: P = air pressure
rho = air density
V = air velocity When you decrease the air velocity, pressure or density (or both) must
increase to keep the quantity a constant. The velocity in the above
equation comes from the vehicle's velocity moving through the air mass.
If you are able to completely bring the incoming air to a stop, all
of the velocity will be converted to pressure. This is known as the
stagnation pressure and is the best you can possibly do. If you think
about it a bit, you'll see that a forward facing scoop with a flat face
can more closely bring the flow to a stop than a sloped windshield can. > I was told on my 65 the scoop needed to be at least 3" tall to start
> getting ram air. Based on using the 429 boss scoop placed near the
> windshield end of the hood. That's because of the boundary layer. Air near a surface, tends to
cling to the surface and slows down. The farther back on the body,
the thicker the boundary layer becomes. It's best to be at the leading
edge of the hood or bumper to stay out of the boundary layer.
Alternatively, you can raise the scoop out of the boundary layer.
A reasonably inexpensive way to test the boundary layer thickness is
with a hang glider air speed indicator mounted at different distances
from the body. If, for example, the boundary layer is 2" thick, then a
scoop less than 2" tall will be less effective than one 4" tall. There
will be no "ram-air" effect for a scoop within the boundary layer but
you will still get a benefit from cooler air. > What you are referring to is that you need to get above the "boundry
> layer" of turbulance along the surface of the hood Remember that turbulence and boundary layers are separate issues.
There are both laminar and turbulent boundary layers. For the topic
under discussion, turbulence is not the important characteristic. > I was considering ram air for my car with a cobrajet scoop,(the type
> with the signal lights) it doesnt have alot of area where the air
> flows in. Would it be a waste of time to cut a hole in my hood then? It's not a waste of time if you duct cooler air to the carb, which
the CJ scoop will do (assuming you are currently taking the air in
from under the hood now). The conversion of dynamic to static
pressure is a linear function of density (which is itself a function
of temperature) and a function of the velocity squared. It's quite
eaay to calculate the static pressure rise. Below 100 MPH, the ram
effect is pretty small and the cooler air is the stronger effect.
As the speed goes above 100 MPH, the ram air effect increases more
rapidly and becomes dominant since it is a function of the velocity
squared. > This excludes naca ducts btw. As well it should. A properly designed scoop will have better pressure
recovery than a NACA duct. NACA ducts are special purpose devices
that provide the best pressure recovery possible without having a
projecting scoop which disrupts the boundary layer. There's a also drag
penalty to be paid with the projected area of a scoop but, for the speeds
we're talking about, scoops are best. Dan Jones
Boeing Aerodynamics and Flight Controls
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-09-2004 08:00 PM
So if I understand you right, your saying SCOOPS rule ?I've always been told that cold air ram air doesn't come into effect below 80-100mph's. Where as Cold air starts making more power at any speeds even at rest,Then without it. ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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MidLifCrisis
Gearhead Posts: 323
From: USA
Registered: Oct 2001
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posted 02-09-2004 08:01 PM
WOW, Dan! You must be some kind of "rocket scientist"! Very impressive. You really put it all together. Could you elaborate more on the NACA ducts, please. Thanks, Charlie
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-09-2004 08:05 PM
quote:
Originally posted by MidLifCrisis:
WOW, Dan! You must be some kind of "rocket scientist"! Very impressive. You really put it all together. Could you elaborate more on the NACA ducts, please. Thanks, Charlie
Also are there any other set ups that work better then others, like the NACA, or cowls ect ???
Ram air set up with the inlets in the grill or front of car ?
------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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rustang@home
Journeyman Posts: 23
From: Clarion, PA
Registered: Jan 2004
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posted 02-09-2004 08:31 PM
It pays to watch the pros. I saw Billy Glidden show up at Maple Grove one time with a cowl induction hood on his Super Street Mustang. By the third round of qualifying it was replaced with his old forward facing scoop and I've never seen a photograph of any of his cars since with cowl induction
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Ryan Wilke
Gearhead Posts: 1700
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 02-10-2004 09:01 AM
quote:
Originally posted by rustang@home:
It pays to watch the pros. I saw Billy Glidden show up at Maple Grove one time with a cowl induction hood on his Super Street Mustang. By the third round of qualifying it was replaced with his old forward facing scoop and I've never seen a photograph of any of his cars since with cowl induction
....and as we all know, Billy Glidden runs in the neighborhood of 200-mph. So - as Dan explained,"...Below 100 MPH, the ram effect is pretty small and the cooler air is the stronger effect. As the speed goes above 100 MPH, the ram air effect increases more rapidly and becomes dominant...". So for Billy, the ram affect is more of a "HP builder" for his setup. However, I'd guess that the majority of us here at M&M run less than 130-mph, so the ram affect is less of a HP building factor than a the temperature of the incoming air. So for most of us, it seems that we'd benefit the most by first getting cooler air to the carb (anyway we can) and then, if we can add any pressure via the ram affect we would get a bit more benefit....... Lastly, as SCOOP said, "I think they look cool, that has to be worth something." So each of us need to determine what the value of the 'kool look' factor of a particular style of scoop is or the simple convenience of having the extra room a particular scoop provides for our bulging carbs and engine packages...... Ryan ------------------
'69 Mach I; 306"; 4-spd; drag racer.
'65 F100 Short box; 390"; 4-spd; Tow Truck.
'85 GT Convert.; last carb'd 5.0L; 5-spd; street cruiser.
'94 Ranger; commuter/parts hauler.
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jsracingbbf
Gearhead Posts: 2160
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 02-10-2004 09:24 AM
Here's something to think about. doesn't billy Glidden run forced induction? some type of large turbo I think right? Also take a look at Blower cars, doesn't the scoop face forward on these cars? If it was not needed then couldn't they turn it around and help the drag coefcient? conclusion, forward facing scoops work very well depending on where they are mounted, as indicated by Dan's post. ------------------
JS
Run what you brung and hope you brung enough!
69 Mustang Pro ET Drag
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Billy Mac
Gearhead Posts: 450
From: S.Ga
Registered: Aug 2003
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posted 02-10-2004 10:20 AM
Well.....YES......They were called Pro Stock TRUCKS!!!!......7.40's and .50's.....with SMALL BLOCKS!!!!!!!!!Too cool.....Unfortunately....as with their 500 inch counter parts....too many non-Blue Ovals...or is it....not enuff Blue Ovals??
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Greg Pettit
Journeyman Posts: 95
From: Dallas, TX
Registered: Nov 2001
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posted 02-10-2004 10:25 AM
Do not be too quick to discount the ram effect. Take a small trash bag with a similar size opening as a hood scoop and swing it around so it fills with air. There is a LOT of resistance, which means there is a positive pressure in the bag. And that is with swinging the bag at only a couple of MPH! Greg ------------------
'71 Torino GT 466, Edelbrock CJ RPM heads, 11.15:1, 250/262 solid flat tappet, .614/.640 lift, 850 DP, C6 w/3500 stall
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Rustang
Gearhead Posts: 576
From: Clarion PA
Registered: Nov 2000
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posted 02-10-2004 10:47 AM
quote:
Originally posted by jsracingbbf:
Here's something to think about. doesn't billy Glidden run forced induction? some type of large turbo I think right? Also take a look at Blower cars, doesn't the scoop face forward on these cars? If it was not needed then couldn't they turn it around and help the drag coefcient? conclusion, forward facing scoops work very well depending on where they are mounted, as indicated by Dan's post.
no...he was running nitrous. Come to think of it, he ran nitrous in Pro Stock too
------------------
'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=??
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indyphil
Gearhead Posts: 1365
From: Lafayette, IN, USA
Registered: Jul 2002
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posted 02-10-2004 01:07 PM
Dont forget to include visibility into the equation. Not important for going in a straight line, but I really like to be able to see where im going in my street car.I think for most cars under 100mph a big scoop is great but we wouldnt be able to see very well if its up in the hood. ------------------
'68 coupe 289 C code
66 heads, edel 600cfm carb, performer intake, dual exhaust http://www.geocities.com/ottouk_77/68mustang.htm
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SteveLaRiviere
Administrator Posts: 37258
From: Saco, Maine
Registered: May 99
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posted 02-10-2004 01:09 PM
That's for sure. I used to have a 7" snorkel scoop on my Sprint back in the old days. Never again, although it was cool at the time.------------------
'70 Mustang Mach 1 351C 4V/FMX/3.25 Open
'70 Mustang Convertible 250 I6/3 speed/2.79 Open
'72 Mustang Sprint Hardtop 351C 4V/FMX/4.30 Trac Loc
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
|
posted 02-10-2004 01:34 PM
I guess you two need some phone books to sit on.
Whats more cool then having to look around a blower or a large scoop. I don't think Dan's point is that there is no ram affect below 100 just thats where it really starts working best. The combo of ram air and cold air works the best. If you have to have just one, then go with the cold air . ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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SteveLaRiviere
Administrator Posts: 37258
From: Saco, Maine
Registered: May 99
|
posted 02-10-2004 01:37 PM
quote:
Originally posted by Fastymz:
Whats more cool then having to look around a blower or a large scoop.
Not running over a family of four. ------------------
'70 Mustang Mach 1 351C 4V/FMX/3.25 Open
'70 Mustang Convertible 250 I6/3 speed/2.79 Open
'72 Mustang Sprint Hardtop 351C 4V/FMX/4.30 Trac Loc
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
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Daniel Jones
Gearhead Posts: 575
From: St. Louis, MO
Registered: Aug 99
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posted 02-10-2004 02:00 PM
> WOW, Dan! You must be some kind of "rocket scientist"! Yup. My rocket science courses were taught by one of our Germans.
"Our Germans are better than their Germans." > Could you elaborate more on the NACA ducts, please. The NACA duct is the result of an attempt to get required inlet
or cooling air while minimizing the drag penalty. The proportions
of the duct are important and must be matched to the speed region.
See http://naca.larc.nasa.gov/reports/1948/naca-rm-a7i30/ for details. I help a friend out on a Formula 1 air racer of his design. Formula 1
air racers use a spec engine of fairly low power and get their speed
from minimum cross-sectional and streamlined design. For the engine
inlet air, a properly designed duct was faster than a NACA duct due
primarily to the ram effect at say 200 knots. > Also are there any other set ups that work better then others, like
> the NACA, or cowls ect ??? Ram air set up with the inlets in the
> grill or front of car ? Ram air scoops built into the grille, bumper, or headlights are usually
best because there's little drag penalty. NACA ducts are good for places
where you don't want to disturb the boundary layer (e.g. in front of an
jet engine inlet or wing) or in places where the boundary layer is thick
and building a tall scoop is prohibited. Dan Jones
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Red65
Gearhead Posts: 112
From: Northglenn, CO, USA
Registered: Jul 2002
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posted 02-10-2004 02:41 PM
At least we don't have the problem where we need to block the inlet to get more power (see SR-71)
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sixtyeight
Journeyman Posts: 9
From: lineville iowa usa
Registered: Dec 2002
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posted 02-10-2004 04:39 PM
If a guys lucky enought to get some positive pressure to the carb, from a well thought out ram air system. How does the added pressure affect jetting?
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kid vishus
Gearhead Posts: 5248
From: middle of NC
Registered: Oct 2000
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posted 02-10-2004 05:06 PM
quote:
Originally posted by Fastymz:
Whats more cool then having to look around a blower or a large scoop.
You also have to take into consideration local laws. Most places have a "visual impairement" law that prohibits objects from being more than "x" amount of inches above the cowl. I had a buddy in Iowa who got a ticket because he had velocity stacks on top of carbs on a tunnelram. They pulled him over and measured it and gave him a ticket for it because it was "too tall."
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Fastymz
Moderator Posts: 14201
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 02-10-2004 05:49 PM
Ok you guys are right sometimes large scoops get int he way,and can get you a fine. Around here you don't see many cars pulled over for little things like that. Just mostly speeding or racing then they nail you good. During Hot August Nights you can run about anything on the street and they do. One year there was a V-8 powered speed boat cruising around town. Open headers and slicks all over the place. Heck even during cruise nights once a week. You see all kinds of cars that should never be on the street.Even being a short guy at 5'10" I can see just fine over my scoop. I wouldn't have one any taller because I like to see whats on the right side of the car too. ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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steve'66
Gearhead Posts: 7226
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-10-2004 08:20 PM
quote:
Originally posted by sixtyeight:
If a guys lucky enought to get some positive pressure to the carb, from a well thought out ram air system. How does the added pressure affect jetting?
Just like a small shot of nitrous or a pound of boost. It will lean the engine out, so up the jet sizes depending of density altitude of the air. SteveW
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sixtyeight
Journeyman Posts: 9
From: lineville iowa usa
Registered: Dec 2002
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posted 02-11-2004 12:06 PM
How would you adjust the jetting if your ram air system(imaginary in a 1/4 mile pass) prouduced 1 pound of boost at 50 mph and 2 pounds at 100 mph etc. Would that require some sort of variable jetting system to keep up with the changing demands?
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Ryan Wilke
Gearhead Posts: 1700
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 02-11-2004 03:30 PM
quote:
Originally posted by sixtyeight:
How would you adjust the jetting if your ram air system(imaginary in a 1/4 mile pass) prouduced 1 pound of boost at 50 mph and 2 pounds at 100 mph etc. Would that require some sort of variable jetting system to keep up with the changing demands?
....I think you just have to shoot for something in the middle ground.... similar to the rest of the engine....none of them (intake flows, exhaust flows, etc.) are linear or constant they all operate under a bell-curve efficency.
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Dad Vishus
Gearhead Posts: 642
From: Moscow, Iowa, USA
Registered: Dec 2001
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posted 02-13-2004 10:48 PM
Guess I'll toss in my .02 on this. We had a little "incident" once with the Granada years ago that required removal of the snorkel that came on the car. It was unsealed with an 11 inch Dia. K & N airfilter inside the scoop. The car picked up quite a bit in the quarter without the scoop. I honestly can't rmember the exact numbers, but it was noticeable. We never figured out why, but we did put another scoop on it primarily for clearance. We did make an airpan to seal it. I do know that taking the airpan out of the new scoop slowed the car down 5 or 6 hundredths. I've got a scoop on my car, which I don't really like, but I need the clearance for the top of the toilet on a 2 inch spacer. I thought about a cowl induction, but I don't think it would look good on my Falcon so I guess I'm stuck. As to whether forward scoops work, I think there are several conditions that effect them, so there is no correct answer for all cases, maybe. Dan, You probably work close to where I did for a short time back in the late 60s. I was in McDonnells drafter training program in St. Louis. The coolest part of the job was getting a tour of the plant and seeing a Phantom drop tested. They lifted that plane about 30 feet off the floor and cut it loose. BANG! Guess if it wouldn't stand that, it wouldn't hold up to a carrier landing. ------------------
63 Falcon 377 Cleveland stroker Flying Toilet alchohol injection. 6.19 @ 110 MPH 1/8 mile
2002 Ranger FX4 daily driver
2000 F350 PSD Crew cab dually - Like commuting in a B52!!
98 US Cargo Phantom II 28'
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Daniel Jones
Gearhead Posts: 575
From: St. Louis, MO
Registered: Aug 99
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posted 02-15-2004 10:37 PM
> Dan, You probably work close to where I did for a short time back in the
> late 60s. I was in McDonnells drafter training program in St. Louis. The
> coolest part of the job was getting a tour of the plant and seeing a
> Phantom drop tested. They lifted that plane about 30 feet off the floor
> and cut it loose. BANG! Yes, not too far from there. > Guess if it wouldn't stand that, it wouldn't hold up to a carrier landing. Yup. Carrier landings are basically controlled crashes. In my job,
I've had the chance to fly the F/A-18 Hornet flight simulators (the
40 foot domes with real cockpits inside) and can tell you that night
carrier landings are tough. At first, the carrier is just this little
dot in the vast ocean. It comes up quick but just never gets very big. Dan Jones
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cracing
Gearhead Posts: 159
From: Saltillo Miss. USA
Registered: Jan 2002
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posted 02-16-2004 09:07 AM
" It comes up quick, but doesn't get very big" Thats what SHE said
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Bob Hopkins
Gearhead Posts: 282
From: BRIDGEPORT NJ USA
Registered: Jan 2001
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posted 02-16-2004 11:36 AM
McDonald Douglas I remember that place I worked there 67-68 in final-assembly hanger,My first wife worked up in drafting,and my older brother worked there from 61-62 up till he died 2 years ago. When I worked there it was boom time 5 F-4's went out every night 6 nights a week{we has that little trouble in NAMusing them up}musta been 5000 people tring to find a place to park every night!!!!
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bushman
Journeyman Posts: 19
From: newberg, OR, USA
Registered: Feb 2004
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posted 02-20-2004 02:25 AM
If there are issues with low pressure or slow air when using a low scoop (2" or so), why not install some small turbulators (spoilers, stall strips) before the scoop to break up the boundary layer and get high speed air to rush down at the inlet?
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Daniel Jones
Gearhead Posts: 575
From: St. Louis, MO
Registered: Aug 99
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posted 02-20-2004 01:01 PM
> If there are issues with low pressure or slow air when using a low scoop
> (2" or so), why not install some small turbulators (spoilers, stall strips)
> before the scoop to break up the boundary layer and get high speed air to
> rush down at the inlet? It doesn't work that way. Vortex generators and trip strips are used
to cause the boundary layer to change from laminar to turbulent. This
is done to forestall pressure separation, since laminar boundary layers
separate (detach from the body) much more easily than turbulent ones.
A separated boundary layer is bad because there's little flow in the
spearated region. A turbulent boundary layer is bad because the flow
is chaotic, with less of it moving in the desired direction (into the
scoop) and it's still aboundary layer so the net velocity is low. You
either want to move the scoop out of the boundary layer and into clean
air or strip off the boundary layer (using suction or a splitter that
trims off the boundary layer right before the scoop). Dan Jones
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bushman
Journeyman Posts: 19
From: newberg, OR, USA
Registered: Feb 2004
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posted 02-21-2004 02:24 AM
So how would this splitter work? Is it like to a vent that diverts the boundary layer down through the hood? An open slot or a louver maybe?
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Daniel Jones
Gearhead Posts: 575
From: St. Louis, MO
Registered: Aug 99
|
posted 02-23-2004 05:21 PM
> So how would this splitter work? Is it like to a vent that diverts the
> boundary layer down through the hood? An open slot or a louver maybe? Place bottom of scoop above the top of the boundary layer, then divert
boundary layer to low pressure region. Strips off boundary layer and
provides clean air to the scoop. Dan Jones
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