I have been looking at the airflow diagram for our cars, and it has been troubling me. We use that diagram to say that air will not enter a hoodscoop, BUT that picture was drawn for a nonturbo Rex. So, if a scoop was added, there would be a place for the air to go, which requires a completely different picture. I was just messing around in photoshop, but this is what I think the flow diagram would look like with a turbo hood.

Kris

 

What is wrong with this thing? Why won't it let me upload a file?
Can someone host the pic?

Kris

 

i don't know but I would like to see that pic!!!!

 

Can someone host the pic?

 

I can.

email it to mchamp00@hotmail.com

 

AreExSeven-You should the pic now

Kris

 

Its giving me a bad file format error. try sending it again

 

try checking your email again.

 

Is this it?

 

that was the original, but I "edited" it in photoshop

Kris

 

Just checkin.

 

Can someone else host the photo?

 

 

That is the original, not the one I edited!!!!

 

When you saved the pic in Photoshop, what file extension did you use? You can select File > Export > Export to web to save it as a .gif.

 

Guys, this is a waste of time. It’s been proven that air does flow into the scoop, all that pressure vector diagram shows is that’s not the ideal place for the scoop for maximum airflow. It was however the most practical place for Mazda to place the IC on the engine when you weigh up many other factors. All designs are a compromise somehow, and those that relocate their IC’s to the front are simply happy to accept some of the downsides of that location (that Mazda weren’t) to get more performance.
It doesn’t matter if the diagram was for a Turbo or NA hood, it would make little difference at the end of the day. You can’t just Photoshop a diagram like that. It’s based on wind tunnel tests using proper measuring equipment. Anything you come up with is based on guesswork, and unless you pretty good with fluid dynamics, I doubt you’ll even be close.

 

you are missing the point of what I am saying.
Her is an example: The reason air flows through the front bumper (lines point in on the aero. pic) is because there is a hole for the air to go through. If there was no hole in the front bumper, then the arrows on the aero. pic would point out.
This is the same with the hood on that aerodynamics picture. The reason the arrows are pointing away from the hood is because there is no hole for the air to enter. With a hood scoop, the air would have a place to go; therefore, (following the example of the front bumper with and without a hole) the air will act much differently and flow into the scoop. Consequently, you cannot use the original picture to determine how a different setup would act.

In fact, I believe those arrows represent pressure zones, and the longer the arrow, then the greater the pressure. According to that, you want to place a scoop in the greatest pressure area, so the top of the hood was chosen, because the large pressure (long arrows) will create a forced induction.


Kris

 

Another attempt to post the picture:

 

The pic finally worked, but to get it under the alotted size, I had to shrink it down alot. It looks nowhere near as good as it did when it was larger.

oh well, at least it is up.

 

Does anyone have any feedback?

Does what I am saying sound plausible? (It makes perfect sense in my mind) I am I describing it properly?

Kris

 

I'm not trying to be nasty here, just correct your thinking. You are misreading the diagram. The area in front of the radiator is at higher pressure because it is the first part of the car to strike the air. It is slightly compressed before it's pushed out of the way. Simple, proven physics. Air is then pushed violently upwards and the airflow briefly detaches from the car causing a lower pressure above the bonnet line before reattaching just before the windscreen. The same thing then repeats over the windscreen and roof.
Fluid dynamics is incredibly complex. Unless you actually go out and measure the pressure at various points, you’re still just guessing, and based on your above assumption, guessing wrong. If you really want to prove this, get a low pressure gauge or make a water manometer and start testing. I’d be interested in the results.

 

AAHHHH! IT JUST DOES NOT MAKE SENSE!!!!!!! Physics and math are my strong points, but this just does not make sense. I have spoken with my physics teacher, and he agrees with what I said. Anyone really good with fluid dynamics and want to undertake a "little" project?

 

Which bit don't you understand?

 

It just seems like the lines pointing away from the car is where there is pressure on the car, correct? That seems like a great spot for a scoop, as it would have air forced into it. What am I missing?

 

Another detail is the low proximity of the scoop to the hood.
There is MUCH more air flow 3 inches away from the hood than there is right ON the hood, where the scoop is. This slower moving air is called the boundry layer- and those of you familiar with the dynamics of exhaust flow will recocnize that. The flow over the hood for the first few inches is not laminar by any means, This flow region is much more viscous than the above flowing air.


I looked at the diagram- there is WAY too much assumed compensation there. There is NO WAY that you will actually draw a VACUUM in front of where the scoop is!
There isn't enough air flow through the scoop to affect the pressure regions that much when the car is travelling at 60 miles per hour.

Also- the only place the pressure will be changed the most (compared with the n/a chart) is above the leading edge of the scoop- where there will be a higher pressure zone, and immediately and behind the scoop, where it will be lower pressure than the smoothly arcing NA hood.