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Qik Nip
Joined: 16 Jan 2015 Posts: 130 Location: Kentucky
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Posted: Fri Oct 05, 2018 12:07 am Post subject: NACA Duct measurement request |
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Can anyone here with a 924 Turbo sitting in their garage do me the favor of measuring the width, depth and length of the NACA vent in the hood? I'm considering "grafting" one on the driver's side hood of my land speed (naturally aspirated) 924. Thanks
Rick _________________ '79 NA 924 Land Speed Car
Bonneville G/CPRO record @ 149.825MPH
Arkansas Mile G/CPRO record @ 138.0 MPH
Great Lakes SCCA SM points champion '09,'10,'11 |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Fri Oct 05, 2018 3:23 am Post subject: |
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Can check mine when I get home, if no-one beats me to it... _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Qik Nip
Joined: 16 Jan 2015 Posts: 130 Location: Kentucky
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Posted: Fri Oct 05, 2018 5:10 am Post subject: |
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924RACR wrote: | Can check mine when I get home, if no-one beats me to it... |
Thanks. So far you're it!
Rick _________________ '79 NA 924 Land Speed Car
Bonneville G/CPRO record @ 149.825MPH
Arkansas Mile G/CPRO record @ 138.0 MPH
Great Lakes SCCA SM points champion '09,'10,'11 |
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Cedric
Joined: 27 Aug 2004 Posts: 2600 Location: Sweden
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Fri Oct 05, 2018 7:11 am Post subject: |
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length 15", width 7", depth 1.5"... add maybe 1/2" all around for the "outside" dimensions for grafting on the hood. Maybe not super-precise, but should give you some idea of the general size... _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Qik Nip
Joined: 16 Jan 2015 Posts: 130 Location: Kentucky
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Posted: Fri Oct 05, 2018 9:13 am Post subject: |
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Cédric wrote: | Im curious, why do you want it? |
Cedric:
I hope to get cooler air into the engine while avoiding the added air resistance created by a traditional hood scoop. The air under the hood of a fast moving car is subject to tremendous turbulence and I fear is resulting in each of the four carburetor throats receiving differing quality and quantities of air. I plan to plum the NACA vent into an air box enclosing all four of the Weber throats to both "quiet" it and deliver cooler (therefore more dense) air to the engine.
At least that's the plan!
Rick _________________ '79 NA 924 Land Speed Car
Bonneville G/CPRO record @ 149.825MPH
Arkansas Mile G/CPRO record @ 138.0 MPH
Great Lakes SCCA SM points champion '09,'10,'11 |
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Qik Nip
Joined: 16 Jan 2015 Posts: 130 Location: Kentucky
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Posted: Fri Oct 05, 2018 9:14 am Post subject: |
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924RACR wrote: | length 15", width 7", depth 1.5"... add maybe 1/2" all around for the "outside" dimensions for grafting on the hood. Maybe not super-precise, but should give you some idea of the general size... |
Thanks Vaughn! _________________ '79 NA 924 Land Speed Car
Bonneville G/CPRO record @ 149.825MPH
Arkansas Mile G/CPRO record @ 138.0 MPH
Great Lakes SCCA SM points champion '09,'10,'11 |
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gegge
Joined: 27 Jul 2007 Posts: 1124 Location: Sweden
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Posted: Sat Oct 06, 2018 5:22 am Post subject: |
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Remember that the hood is a low-pressure zone. Why not try connecting the carburator plenum directly to the batterybox? That is high pressure! Poor man´s turbo _________________ Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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MikeJinCO
Joined: 08 Jun 2010 Posts: 1227 Location: Maysville, Colorado
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Posted: Sun Oct 07, 2018 5:35 am Post subject: |
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Pegasus Racing has some NACA ducts that are meant to be fit into side windows, not sure about the size as far as airflow. I made a bucket to fit in the driver side headlight bucket somewhat similar to the fixed headlight conversion. Then I found an 3" tapered inlet inlet at summit racing. I haven't quit figured out how to install it neatly , yet, as it is not a refined part and I have the stock steel front panel. It probably would increase the drag. I still have the mold if interested.
I recall seeing your photo's and if you have the Dprod front end from CCP in Florida you might look at using the lower brake air duct if you haven't sealed it off. _________________ Mike
'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild) |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Qik Nip
Joined: 16 Jan 2015 Posts: 130 Location: Kentucky
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Posted: Mon Oct 08, 2018 5:51 am Post subject: |
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gegge wrote: | Remember that the hood is a low-pressure zone. Why not try connecting the carburator plenum directly to the batterybox? That is high pressure! Poor man´s turbo |
Now that's interesting. To those wondering about his low pressure comment, NACA vents don't work well unless they are positioned in a high pressure area. That does however bring into question the use of the NACA on the turbo 931... Although a blower pulls air and perhaps therefore doesn't need a forced feed...
Anybody got the lowdown on that issue?
Rick _________________ '79 NA 924 Land Speed Car
Bonneville G/CPRO record @ 149.825MPH
Arkansas Mile G/CPRO record @ 138.0 MPH
Great Lakes SCCA SM points champion '09,'10,'11 |
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poor-sche
Joined: 06 Jan 2017 Posts: 80 Location: Los Angeles, CA
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Posted: Mon Oct 08, 2018 12:59 pm Post subject: |
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The naca duct dumps air directly in front of the battery box and down onto the exhaust manifold. Its purpose is for cooling and looking cool.
The factory air box pulls air from the opposite corner of the engine bay (next to the drivers side head light). _________________ 1980 - 931 |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Mon Oct 08, 2018 6:28 pm Post subject: |
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Not sure the that the NACA 'dumps' air.........remember air also flows under the car. My understanding is air is being drawn out of the back of the engine tray and under the car. This draws air into the engine bay via the NACA (and nose vents in the turbo). This keeps the engine bay and more specially with the NACA, the exhaust side flowing with cooler air. The NACA adds to the engine bay air flow and does not 'scoop' air into the bay. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
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gegge
Joined: 27 Jul 2007 Posts: 1124 Location: Sweden
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Posted: Tue Oct 09, 2018 4:41 am Post subject: |
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Since the NACA is situated right above the exhaust/turbo and hot air is rising, in addition to a low pressure zone...
A NACA duct is only working properly in high speed, that is MACH speed. The ram pressure or air flow volumes is poor compared to protruding scoops. The trade-off to drag I guess.
I belive NACA was a cool design feature in 70´car design. The Countach, Espada, Montreal, Mustang and 931 to mention a few. And F40 of course, ten tears later. _________________ Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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Fifty50Plus
Joined: 28 Feb 2008 Posts: 1353 Location: Washington DC area
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Posted: Tue Oct 09, 2018 9:33 am Post subject: |
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NACA ducts work very well on race cars to put air in the cockpit for driver cooling. Adding flexible tubing allows us to aim the air wherever we want. _________________ 1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car |
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