Airflow Question

[Genuine GM]

I have an idea that might not be legal at B-ville, but that is not what I am curious about.  I know many on here know more about airflow than I do, and I need that experience to see if this might work.

If a person was to "collect" under hood pressurized air, directed it through two 4 or 5 inch ducts (one down each frame rail), run the ducts up into the trunk (or enclosed pickup bed) and then duct them out the rear of the vehicle towards the upper 75% of the rear vehicle height. 
My thinking is that this would serve three purposes:
1.) help increase under hood airflow (air through radiator);
2.) reduce the under pressure from exiting under the vehicle (lift);
3.) and the air flowing out the rear would alter and lengthen the slip stream over the vehicle reducing drag at speed.

Any thoughts? Would this even be worth the effort.  I am thinking drag reduction for both increased speed and better mileage.

C. J. Daniel

[SPARKY]

MY unprofessional--east tex aggie NON engineer guess is that airdrag is airdrag no matter where its inside or outside

[Jonny Hotnuts]

Great thinking.....

not legal for most classes.
4.A

~JH

[holdfastgreg]

Just for future reference, its called by-pass air. (not sure if its legal in racing or not.)  The P-51 mustang had an opening under its nose nacelle that allowed fluid to bypass the airframe.  This added to the trust of the aircraft and thus was a contributing factor to its speed.  Later down the road, turbo fan's came equipped with a similar nacelle around the turbine to allow this bypass air to mix with the exhaust fumes creating high thrust levels.  Theres a lot that goes into this concept, hence why people get paid big bucks to come up with this stuff.

Not sure if it helps (probably doesn't) but your on the right track about fluid flow.

[SPARKY]

I think there was a eng cooling radiator in your P 51 "bypass" that added tremendously to the volume hence the pressure increase which created thrust

[Blue]

Regretably the P-51 "thrust from cooling scoop" is a myth.  It was nicknamed "Merideth thrust" after one of the North American Aviation engineers.  It turns out that a different engineer designed the cooling scoop, Merideth was the first to point out that their was a marginal amount of thrust recovery from the outlet partially offsetting the cooling drag at high altitude.

As to the ducting question, without adding power to the internal flow with a fan or exhaust ejecta, the drag from the internal flow will be more than just having everything go around the car.  It may be remotely possible to take some of the internal air and reduce some aft separation with it, but the only classes that would allow this are streamliners and lakesters and their are far better aero solutions for those.

[interested bystander]

Correct me if I'm wrong, but did not the underbelly scoop add additional LIFT to the Mustang?

Was under the impression that the airplane's configuration, turned upside down, of course,  influenced Colin Chapman to design the nearly all-conquering Lotus 75's side pods.

 Downforce, not thrust, the result.

[Cajun Kid]

Blue, or others ??


I am not sure if you have seen the air outlet holes behind the back glass on many LSR  Studebakers ?

I was told that 3 or 4   air duct tubes 2.5 " to 3"  diameter from under the car in the third member area,, ducting air to exit the tubes on the deck between the back glass and the trunk would let under car air exit and reduce Lift,, thereby helping keep more downforce on the rear and the wheels on the ground ?
 
Any Ideas  ?  I have yet to do this to my Stude and I am only a few weeks from painting,, so it would be nice to know if it helps and is legal for Classic Gas  Altered ?

Charles

[dw230]

Yes, it is legal in your class and proably a good idea in a sStude coupe if you want to keep the front windshield in place.

DW

[jimmy six]

Kid. At one time they were mandatory on Studebakers. If you didn't have them you spun at 185 almost a guarentee. With the ability to place all the "areodynamic drag junk" on the trunks guys have quit using them. Fast roadsters of the 50-60's all had them too.

Neil Thompson's Studie Comp Coupe went 300 with the tail lights removed, air ducts and no junk on the trunk.

I like the stock look and you can go plenty fast with air ducts...........Good Luck

[Cajun Kid]

Thanks Guys,,,

I have Junk on the Trunk,, kinda sorta like Hooley's Orange Stude,,,  but I guess I shall fab in those ducts to let the air out that gathers above the third member...  I thought with the side spill plates and rear spolier , I would be Ok,,, but the ducts sound like they can only help more and not hurt..

Charles

[Genuine GM]

Blue,

I agree about having all the air go around if possible, but in my scenerio, I am not concerned with B-Ville rules and the vehicle will have a grill, and radiator opening and a radiator.   No LSR car with a water tank and sealed nose.

I am talking about a vehicle (street driven, not just legal) that will be ran at the Texas Mile and the USFRA 130 or 150 MPH club, after being driven there.  

I am talking about a truck, not an aerodynamic sports car.  I know that air gets pressurized under the hood IF there is no place for it to go.  Unfortunately, most of the time the best place for it to escape it around the engine and out the bottom.  

I do know that Smokey Yunick did extensive testing with airflow ducting 50's, 60's and 70's with slab nosed Chevys.  He proved mph would go up by releasing the underhood air, but the actual methodology he used is rather vague and from what I can tell, something he took to the grave.  I have most of his books and while he talks alot about it, he elaborates on his methods little.  I am sure that was to keep a competitive edge.   In one example he gives, in many different books, he was sitting on the floor of a 55-57 Chevy and they where doing 120 mph, he unscrewed the heater block off plate from the firewall and the air flow blew him back, while the car gained 20 mph.  

I posted it here, because frankly, when it comes to airflow, the members on most automotive bulletin boards are lost in the woods.  I know more than most of them just from my helicopter maintenance background.

Perhaps the best thing for me to do is rig up a manifold with various ports on the firewall, tie it all to a psi gauge and drive at various speeds.  Then I can extrapolate some sort of data.

If you check my site listed in my sig, you will see the truck I am modifying to be a rolling test bed of ideas, while we gather parts for the V4F/MGR

C. J. Daniel

[will6er]

dw-

Would the air vents be legal on a Stude Gas Coupe?

Will6er

[panic]

Does someone have the exact wording and underlying argument behind "this isn't legal"?

[WZ JUNK]

Blue, or others ??


I am not sure if you have seen the air outlet holes behind the back glass on many LSR  Studebakers ?

I was told that 3 or 4   air duct tubes 2.5 " to 3"  diameter from under the car in the third member area,, ducting air to exit the tubes on the deck between the back glass and the trunk would let under car air exit and reduce Lift,, thereby helping keep more downforce on the rear and the wheels on the ground ?
 
Any Ideas  ?  I have yet to do this to my Stude and I am only a few weeks from painting,, so it would be nice to know if it helps and is legal for Classic Gas  Altered ?

Charles

We have the holes underneath the rear window on Hooley's Studebaker but they are not connected to anything.  We made them as we were told they needed to be there.  Some said that they needed to be connected to the bellypan and others said to the drivers compartment.  Later we were told that we did not have enough holes, that we had to many holes, or that we should cover them as they did not do anything.  We finally decided that they must not be needed as no one actually knew what they were for and Hooley has went 250 mph without them connected.  Seemed like a good idea at the time.

You get lots of good advise at Bonneville.  Some advise is better than others.  The most valuable advise comes from people who have had good experiences in your class, and with your body style.

John