[DeTomaso] Has anyone researched hood vent designs?

Tue Aug 2 22:26:27 EDT 2016

I might respectfully disagree (obviously not having tested this on my
own...)

The airflow over the car (like that over a wing) will be accelerated.  The
air going over the top of the car will create lift (as in the front of the
stock Pantera lifting up at speeds above 125 mph, such that handling gets
squirrely).  This lift is due to low pressure over the top of the car (again
like an airplane wing), which will tend to pull air out through the hood
vents.

I agree that ducting like GT-40s, Goran's picture, and Comp2 will be much
more efficient at exhausting air than the hibacci grates that most use.

I do agree this effect would be more pronounced with a flat bottom.  

Chuck 

-----Original Message-----
From: Julian Kift [mailto:julian_kift at hotmail.com] 
Sent: Tuesday, August 2, 2016 7:55 AM
To: James coyne; Rod Kunishige; scottcouchman at yahoo.com;
detomaso at server.detomasolist.com; Ken Green
Subject: Re: [DeTomaso] Has anyone researched hood vent designs?

Okay, let's put our engineering hats on and have some fun technical
discussion..... it sure beats the discussion over POCA of late!

I think (but readily admit my engineering degree is not in aerodynamics!)
hood vents and location play a minor part in overall aerodynamics.

Hood vents are a great way to provide additional cooling in traffic, but
perhaps  limited value at high speed when the front of the hood becomes a
high pressure area. Now you have opposing forces at play and at speed 'x'
the pressure is likely enough to overcome that produced by the radiator fans
(I imagine that 'x' would not be excessively high, perhaps even highway
cruising speed). So outside air now reverse enters the hood vents or at a
minimum restricts fan flow resulting in air that is forced under the car
i.e. back to the original Ford design concept. A Gurney lip on the frontal
edge of hood vents would help create a low pressure area, but I still
believe the air from the radiators will ultimately be forced under the car
at some speed now x+y.

As testament to the pressures on the hood Larry Stock told me that Mike
Cooke collapsed an aluminum hood at high speed.

As alternative thinking, most cars that employ an aerodynamic frontal hood
vent do so in combination with a full flat underside. I think this is a
critical element in the success of the design and one without the other is
likely non productive. Furthermore most running Pantera's in ORR have
reported that a front air dam is a key element in preventing front end lift
at +150mph, again attesting to restricting air flow under the car is the
most critical element.  I'd go for the front air  dam in combination with a
fully enclosed flat floor/tray as my first modifications and leave cutting
the front trunk aspect (and the ensuing frontal rigidity impact).

As an a side the popular radiator fan shrouds also become restrictive at
high speed and require opening up, some have achieved this with simple
hinged flaps that can freely open as the pressure through the radiator
increases.

Julian

________________________________
From: Ken Green <kenn_green at yahoo.com>
Sent: Monday, August 1, 2016 10:28 AM
To: James coyne; Julian Kift; Rod Kunishige; scottcouchman at yahoo.com;
detomaso at server.detomasolist.com
Subject: Re: [DeTomaso] Has anyone researched hood vent designs?

Probably more correct to say I intend the car to be able to run well over
150.  Not sure if I want to drive that fast on a country road.  I would be a
lot more comfortable having fun at lower speeds in an ORR, and trying the
flying mile type events to see how fast the car can actually go.

The older we get, the longer it takes to heal.

Ken

________________________________
From: James coyne <tecnosound at hotmail.com>
To: Julian Kift <julian_kift at hotmail.com>; Rod Kunishige
<rkunishige at hotmail.com>; "scottcouchman at yahoo.com"
<scottcouchman at yahoo.com>; Ken Green <kenn_green at yahoo.com>;
"detomaso at server.detomasolist.com" <detomaso at server.detomasolist.com>
Sent: Monday, August 1, 2016 9:00 AM
Subject: Re: [DeTomaso] Has anyone researched hood vent designs?

I believe it is indeed Ken's intension to run in the 150mph+ classes at open
road events .

________________________________
From: DeTomaso <detomaso-bounces at server.detomasolist.com> on behalf of
Julian Kift <julian_kift at hotmail.com>
Sent: Monday, August 1, 2016 7:49 AM
To: Rod Kunishige; scottcouchman at yahoo.com; Ken Green;
detomaso at server.detomasolist.com
Subject: Re: [DeTomaso] Has anyone researched hood vent designs?

This seems like an awful lot of work for little to no gain, is this a
dedicated race car that will be running the 150mph+ classes at an Open Road
Race?

Julian

________________________________
From: DeTomaso <detomaso-bounces at server.detomasolist.com> on behalf of Ken
Green via DeTomaso <detomaso at server.detomasolist.com>
Sent: Monday, August 1, 2016 7:00 AM
To: Rod Kunishige; scottcouchman at yahoo.com
Cc: detomaso at server.detomasolist.com
Subject: Re: [DeTomaso] Has anyone researched hood vent designs?

My gut feeing is the opening needs to be moved back to reduce air pressure
over the opening.  And that probably depends on speed.
Ken

      From: Rod Kunishige <rkunishige at hotmail.com>
 To: "scottcouchman at yahoo.com" <scottcouchman at yahoo.com>; Ken Green
<kenn_green at yahoo.com>
Cc: "detomaso at server.detomasolist.com" <detomaso at server.detomasolist.com>
 Sent: Sunday, July 31, 2016 10:13 PM
 Subject: Re: [DeTomaso] Has anyone researched hood vent designs?

  I really like the idea of boxing the trunk in your design.

  It means moving the support ribs for the hood.

  Can you enlarge the opening by starting closer to the radiator?
  From: Ken Green <kenn_green at yahoo.com>
  I think photos of that car were posted a year ago?  I want the car to
  look like a Pantera, not a GT40.
  en
  From: "scottcouchman at yahoo.com" <scottcouchman at yahoo.com>
  You should talk with Tony Ortiz in Arizona. He modified his Pantera to
  install front and rear GT40 clips.

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