Sealing the hood vent?

[Richbot]

Never underestimate the power of marketing over the laws of physics

[Scharbag]

Originally Posted by burtonsbs5114

I'm sure the engineers at BMW M GmbH, who spent years designing the engine/car, know nothing about physics and aerodynamics so when they placed a hood vent to act as an air inlet it actually works as an outlet. Makes perfect sense.

As others have pointed out, these are the same engineers that specified unreasonably tight rod bearing tolerances in the S65B40.

[Scharbag]

Originally Posted by Richbot

Never underestimate the power of marketing over the laws of physics

Just like Sony tried to convince the world that square drivers were better than round ones in the 80s...

(my dad bought a set of these piles of tripe - I destroyed them with GNR )

[Law]

Originally Posted by Scharbag

As others have pointed out, these are the same engineers that specified unreasonably tight rod bearing tolerances in the S65B40.

Like I mentioned on the first page, normally, with press releases that are meant to be ingested by the general public, I'd agree that some of the marketing speak should be taken with a grain of salt.

But the information/diagram is sourced from an internal BMW technical document, for BMW employees.
You're making the comparison to rod bearings; are you implying that BMW designed the opening as an outlet and are lying about it being an inlet?
Whether it is an outlet or inlet, the opening is functional, so logically, BMW really have nothing to gain from perpetrating a lie about its function because it's functional either way you look at it.

Design flaws & defects inevitably occur (and no manufacturer is immune to this), but to dismiss a manufacturer's entire R&D process because of it is quite unreasonable.

[Scharbag]

Originally Posted by Law

Like I mentioned on the first page, normally, with press releases that are meant to be ingested by the general public, I'd agree that some marketing speak should be taken with a grain of salt.

But the information/diagram is sourced from an internal BMW technical document, for BMW employees.
You're making the comparison to rod bearings; are you implying that BMW designed the opening as an outlet and are lying about it being an inlet?
Whether it is an outlet or inlet, the opening is functional, so logically, BMW really have nothing to gain from perpetrating a lie about its function because it's functional either way you look at it.

Design flaws & defects inevitably occur (and no manufacturer is immune to this), but to discount a manufacturer's entire R&D process because of it is quite unreasonable.

I am skeptical of everything. Therefore, yes, I am questioning the validity of their documentation. The laws of physics are not easily stretched and never broken. Admittedly, I am not an expert in this field as all fluid dynamics is a form of black magic or voodoo. I am, however, an engineer that works with fluids in pumping applications. The reason for my skepticism is the fundamental law of physics that states that any time any fluid flow (gas or liquid) is required to change directions, it takes force. Newton might have been a strange duck, but he was a bright duck.

This, in my mind, raises the the question that if an air stream is moving at a relative velocity of 100KPH across a ~flat opening parallel to the flow vector, what force is being applied to the air to cause it to change direction by more than 90° in order to flow into the engine? I would like to see the free body diagram that explains the validity of BMW's literature.

Here is an example of venting located on the hood surface that is used for exactly the opposite reason that BMW is stating on the M3.



At the end of the day, it really does not matter much as the M3 is fun as hell, regardless how the air flows!

Cheers,

[CSBM5]

It's very simple actually and no "laws of physics" are being undone. To the contrary in fact of course. If you don't have experience analyzing potential flow and boundary layer flow and understand pressure distributions, rising adverse pressure gradient, and the pressure recovery zone starting mid-hood to the windshield base, then randomly guessing what is going on is likely not going to work.

[Law]

Originally Posted by Scharbag

I am skeptical of everything. Therefore, yes, I am questioning the validity of their documentation. The laws of physics are not easily stretched and never broken. Admittedly, I am not an expert in this field as all fluid dynamics is a form of black magic or voodoo. I am, however, an engineer that works with fluids in pumping applications. The reason for my skepticism is the fundamental law of physics that states that any time any fluid flow (gas or liquid) is required to change directions, it takes force. Newton might have been a strange duck, but he was a bright duck.

This, in my mind, raises the the question that if an air stream is moving at a relative velocity of 100KPH across a ~flat opening parallel to the flow vector, what force is being applied to the air to cause it to change direction by more than 90° in order to flow into the engine? I would like to see the free body diagram that explains the validity of BMW's literature.

Here is an example of venting located on the hood surface that is used for exactly the opposite reason that BMW is stating on the M3.

Thanks for your response.

I can see where your argument makes sense and is related to what some others have said in the other pages.
But it's still entirely possible when you take account the pressure zones and vacuum of the engine intake, that the air can flow into the vent.
Now, whether or not BMW engineers were able to do that to perfect harmony is something we've yet to confirm.

But that's what BMW claims to have done.

All I am saying is, I understand the skepticism and a lot of good arguments can be made for both inlet & outlet hypotheses, but until someone really tests this out, the most reliable information we have is from the people that designed it themselves.
Yes...quite possibly the same people that also designed our bearings.
But still, they tend to know what they're doing most of the time

Originally Posted by Scharbag

At the end of the day, it really does not matter much as the M3 is fun as hell, regardless how the air flows!

Cheers,

Cheers to that.

[SkiFly01]

For those that have closed off the vent, have you noticed any difference in the intake sound?

[Redd]

Another situation where the hood vent becomes an intake is if both the front intakes are submerged in water, ie during a flood.

[Teufel_Hunden]

We've got 4 pages on this topic???

[G80indy]

Originally Posted by Scharbag

Just like Sony tried to convince the world that square drivers were better than round ones in the 80s...

(my dad bought a set of these piles of tripe - I destroyed them with GNR )

These are essentially round drivers- posts/rods that push on the flat surface driven by a round voice coil/magnet structure. A bit of hype.
;-) They weren't exactly built for dynamics.
But cool post nonetheless!

Been in the audio industry for over 30 years

[UPSROD]

Originally Posted by Teufel_Hunden

We've got 4 pages on this topic???

Yep, getting a little old! Why doesn't somebody tie some yarn to the vent and go for a ride at all speeds....see when it streams out and/or sucks in to the vent.