[DeTomaso] Has anyone researched hood vent designs?

Ken Green kenn_green at yahoo.com
Fri Aug 5 00:05:17 EDT 2016


People who have gone seriously fast all seem to agree that proper hood vents make a big difference, especially over about 140.  As far as pressure on the hood building, the air flow through the grill may grow even more with speed, and the pressure difference is the real issue.  I looked at a lot of closed wheel, mid engine, race cars, and virtually all of them vent the radiators through the hood area.
Ken

      From: Mike Drew via DeTomaso <detomaso at server.detomasolist.com>
 To: julian_kift at hotmail.com; tecnosound at hotmail.com; rkunishige at hotmail.com; scottcouchman at yahoo.com; detomaso at server.detomasolist.com; kenn_green at yahoo.com 
 Sent: Thursday, August 4, 2016 8:55 PM
 Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
   
  In a message dated 8/2/16 7 55 50, julian_kift at hotmail.com writes:

    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.

  >>>I don't know about high triple-digit speeds, but the hood is a
  low-pressure area at speeds typically seen on the road (even low
  triple-digit speeds).  You can test this for yourself by simply
  unlatching the hood and going for a drive.  At freeway speeds, it will
  'float' an inch or two above the latch, as vacuum from above (probably
  aided by pressure from below) lifts it slightly.
  I don't know what, if any effect might be realized by introducing hood
  vents with all other things being equal.  Providing a path for air to
  exit through the hood rather than pushing up on the underside of it
  might be a thing?
  (Geoff Peters had a very thin carbon fiber hood, with vents, on his
  GT5, and he found that at high speeds, it would deform so much by
  lifting in the center, that the pin would move forward and pop out the
  front side of the latch and then the hood would fly open and hover a
  few inches above the latch!)
  An air dam, particular a proper Gr4/GT5 air dam, provides meaningful
  downforce and probably helps prevent air from underneath from pressing
  up on the underside of the hood, as others have mentioned....
  If you look at the GT40, the early cars came with two deep triangular
  hood vents, while the later ones came with a single very large vent,
  which was undoubtedly far more effective.
  Having said all of that, I've run my car at 130+ mph on the track with
  a simple, small GTS mini air dam and no hood vents, and the car ran at
  180 degrees with not a bit of front-end lift.  I wouldn't assert that
  the front end would be similarly planted at 200 mph, but then again, I
  have no intention of going anywhere near 200 mph so it's completely
  academic....
  Mike

_______________________________________________


Detomaso Email List is not managed by POCA
Posted emails must not exceed 1.5 Megabytes
DeTomaso mailing list
DeTomaso at server.detomasolist.com
http://server.detomasolist.com/mailman/listinfo/detomaso

To manage your subscription (change email address, unsubscribe, etc.) use the links above.

Members who post to this list grant license to the list to forward any message posted here to all past, current, or future members of the list. They also grant the list owner permission to maintain an archive or approve the archiving of list messages.

  
-------------- next part --------------
   People who have gone seriously fast all seem to agree that proper hood
   vents make a big difference, especially over about 140.  As far as
   pressure on the hood building, the air flow through the grill may grow
   even more with speed, and the pressure difference is the real issue.  I
   looked at a lot of closed wheel, mid engine, race cars, and virtually
   all of them vent the radiators through the hood area.
   Ken
     __________________________________________________________________

   From: Mike Drew via DeTomaso <detomaso at server.detomasolist.com>
   To: julian_kift at hotmail.com; tecnosound at hotmail.com;
   rkunishige at hotmail.com; scottcouchman at yahoo.com;
   detomaso at server.detomasolist.com; kenn_green at yahoo.com
   Sent: Thursday, August 4, 2016 8:55 PM
   Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
     In a message dated 8/2/16 7 55 50, [1]julian_kift at hotmail.com writes:
       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.
     >>>I don't know about high triple-digit speeds, but the hood is a
     low-pressure area at speeds typically seen on the road (even low
     triple-digit speeds).  You can test this for yourself by simply
     unlatching the hood and going for a drive.  At freeway speeds, it
   will
     'float' an inch or two above the latch, as vacuum from above
   (probably
     aided by pressure from below) lifts it slightly.
     I don't know what, if any effect might be realized by introducing
   hood
     vents with all other things being equal.  Providing a path for air to
     exit through the hood rather than pushing up on the underside of it
     might be a thing?
     (Geoff Peters had a very thin carbon fiber hood, with vents, on his
     GT5, and he found that at high speeds, it would deform so much by
     lifting in the center, that the pin would move forward and pop out
   the
     front side of the latch and then the hood would fly open and hover a
     few inches above the latch!)
     An air dam, particular a proper Gr4/GT5 air dam, provides meaningful
     downforce and probably helps prevent air from underneath from
   pressing
     up on the underside of the hood, as others have mentioned....
     If you look at the GT40, the early cars came with two deep triangular
     hood vents, while the later ones came with a single very large vent,
     which was undoubtedly far more effective.
     Having said all of that, I've run my car at 130+ mph on the track
   with
     a simple, small GTS mini air dam and no hood vents, and the car ran
   at
     180 degrees with not a bit of front-end lift.  I wouldn't assert that
     the front end would be similarly planted at 200 mph, but then again,
   I
     have no intention of going anywhere near 200 mph so it's completely
     academic....
     Mike
   _______________________________________________
   Detomaso Email List is not managed by POCA
   Posted emails must not exceed 1.5 Megabytes
   DeTomaso mailing list
   [2]DeTomaso at server.detomasolist.com
   [webicon_gray.png]
   [3]http://server.detomasolist.com/mailman/listinfo/detomaso
   To manage your subscription (change email address, unsubscribe, etc.)
   use the links above.
   Members who post to this list grant license to the list to forward any
   message posted here to all past, current, or future members of the
   list. They also grant the list owner permission to maintain an archive
   or approve the archiving of list messages.

References

   1. mailto:julian_kift at hotmail.com
   2. mailto:DeTomaso at server.detomasolist.com
   3. http://server.detomasolist.com/mailman/listinfo/detomaso


More information about the DeTomaso mailing list