Side Gill Aero Q's

[JPhil]

Well this brings up something I noticed when I pulled the hood to pull the motor. On my radiator, all the fuzz & leaves were in a shallow V on the top third of the radiator. Indicating to me that that is where the airflow is. Looking at the big-ass vacuum tank across the frame horns ('73 model) & the lower splashguard & the headlight vacuum buckets, I could see how the airflow would be directed this way. I long ago removed the front license plate & mount and put a grill there for straight-in airflow, but those items still interrupt the airflow.
Made me wonder about a curved sheetmetal vane over the vac tank to direct more air to the lower portion of the radiator. (And a 1/8" mesh screen in front of the rad to catch leaves & etc.)

 

[vette427sbc]

I guess Ill have to find a video editor and shorten it before I try to upload it to youtube again...

 

[69427]

Take a look at the pictures I have in my 'album'. I did a yarn run a few years ago and the gills do vent out.

Do you remember the speed in this picture?

This reminds me of something I've been thinking about for a long time. We all can agree that the bottom of our antiques is not a low drag/pressure area. My question is where is the majority of undercar air coming from? Is it all from the engine compartment, or is a lot of it flowing from the sides of the car and making its way under the car? I'm planning on trying to divert a portion of the underhood air out to the side louvers, but if the air is still going to come in from the sides that defeats much of the purpose of blocking air from flowing from the engine compartment to under the floor. It looks like the "under door trim piece" (I'm having a mental block of what that's called at the moment) could be sectioned lengthwise and made a couple inches deeper/lower to block off some of the air that might try to enter from the sides. But, if the air is trying to exit from the underbody area I certainly don't want to trap it there. My car is still disassembled (and with expired plates) so it will be a bit until I could make some measurements. Anyone have any data on this issue?

Thanks,
Mike

 

[JPhil]

As I see it, much of the air comes in under the car---it's a wedge, some going over the top, some forced down under, some into the engine bay. That creates low pressure above the car, high pressure under the car, and turbulence inside the engine bay which is open to the underneath. There is also lots of resistance & turbulance under the car due to the mechanical equipment.
An air dam in front to divert air from going under the car will help lower the the undercar pressure and thus reduce uplift. But of course, air 'dam' also creates resistance in it's own right, but the benefits are worth it. The only way to reduce engine bay turbulence and resulting undercar turbulence is to vent the the grill airflow (radiator cooling flow) out the top of the hood or out the sides, into lower pressure airstream. Panning of the undercarriage is the only way to smooth undercar airflow.
You are also packing air into & behind the wheel wells from the spinning tires. It creates turbulence which adds to drag & ill handling.That's the reason for top fender vents & wheel skirts on Bonneville cars.

 

[mrvette]

As I see it, much of the air comes in under the car---it's a wedge, some going over the top, some forced down under, some into the engine bay. That creates low pressure above the car, high pressure under the car, and turbulence inside the engine bay which is open to the underneath. There is also lots of resistance & turbulance under the car due to the mechanical equipment.
An air dam in front to divert air from going under the car will help lower the the undercar pressure and thus reduce uplift. But of course, air 'dam' also creates resistance in it's own right, but the benefits are worth it. The only way to reduce engine bay turbulence and resulting undercar turbulence is to vent the the grill airflow (radiator cooling flow) out the top of the hood or out the sides, into lower pressure airstream. Panning of the undercarriage is the only way to smooth undercar airflow.
You are also packing air into & behind the wheel wells from the spinning tires. It creates turbulence which adds to drag & ill handling.That's the reason for top fender vents & wheel skirts on Bonneville cars.

AYou really don't wanna know how this got demonstrated to my dumb ass, but....:hissyfit::crylol: on a shark, the air pressure exerted on a hood is all from in front of the radiator, on my car with Spals in parallel to the radiator ...so blowing down on the airflow, toward the balancer....but being as I had to add a air dam above top of the rad support to block up and over airflow, it makes sense air pressure is in front of the rad, and on that portion of the hood,

I proved there is no air pressure under the major part of the hood with yarn some years ago....at least on MY car, witch is not really all THAT far from stock, in general airflow/body design....if it is, I sure as hell can't see it...

my curiosity is about that 'bucket effect' in the rear, so I need find some easy do inserts I can drill the body for to fit clean, just for cool looks and not to bother if they are bullshit...

:nuts: