[Healeys] 100M cold air boxes and flow

[Alan Seigrist]

Adam -

Any flow inefficiencies in the cold air box design are overcome by the
positive air differential created by having the front end of the CAB
paper tube face directly forward into the oncoming air stream when
driving at high speed.  In fact, the speed ram effect will provide
more HP improvement than having cold dense air going into the carbs.

If you look at pictures of some 100S/4 racers in the day, many of the
cars have run the paper air tube past the grill or even through the
shroud into the oncoming air stream to maximize positive pressure in
the CAB.

It's about the air pressure, not the air temperature.  Basically it's
a cheap supercharger when you are driving fast.

Alan

On 1/14/12, Adam Nolde <adamnolde at yahoo.com> wrote:
> All,
>
> Has anyone conducted or read the results of anyone else's research
> regarding the fluid dynamics of the 100M cold air box?
>
> I'm no engineer, but a
> keen mind looking at the 1956 cold air box design can quickly work out the
> fact that it may have some ill effects on air delivery at higher RPM's.  I'm
> specifically concerned about the size and depth of the box causing delivery
> issues for both, but more likely the rear carb.
>
>
> I've done some very crude
> calculations and crude bench testing just as a base to understand the flow
> involved and the possible scale.  I've learned my engine can suck as much as
> 263CFM at 100% VE, but obviously it should be less, so I use this as a max.
> That puts the velocity at each carb above 85mph static, but much faster
> during
> intake stroke.  The velocity at the air box inlet is above 65mph static.
> The
> box depth in front of each carb opening is only 1.75".  I can see potential
> for not only vacuum creation and inefficient atmospheric replacement, but
> add
> to that the inefficient dynamics of the flat and non radiused orifices.
> I've also discovered a fair amount of scavenging occurs between carb
> orifices
> in-spite of the wide and presumably ample open ended box.
>
> Anyway, I've
> theorized that the probable advantage of thermodynamic control supplied by
> the
> air box, may be negated by its inefficient design and inability to supply
> sufficient volume.
>
> If anyone has done or knows of some CFD (computational
> flow dymanic) modeling and, better yet, 3d image modeling.  Please let me
> know
> where to access the information.
>
> Thank you and kind regards,
>
> adam nolde
> 203-606-4675
>
> [demime 1.01d removed an attachment of type image/jpeg which had a name of
> 100M.jpg]
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