This is a photo of someone else's vette tricked out to race and it has a rather large front air dam under the nose. I know that at higher speeds without it air gets under the hood and lifts with positive pressure the front end and makes steering an adventure (above 130 or so mph?).

How exactly does this function? Does it being lower literally force air away from getting under the hood in the first place, blocking it from that path? If so, that adds wind resistance to the front of the car which takes power to overcome wouldn't it?

How does this actually function and is it to keep the front end from getting too much positive air pressure?

Thanks...trying to learn and this looked like a good example.

Lance P.

 

If you keep air from going under the car, it creates an area under the car with less air pressure. This "sucks" the car down, adding downforce. The reason I use quotation marks around "sucks" is because it doesn't really suck. Atmosphereic pressure pushes down on it. There is really no such thing as suction. Your piston doesn't suck air/fuel into the cylinder, atmosphereic pressure pushes it in.

But I digress. An added bonus to keeping air from going under the car, is that air going thru the radiator is drawn by the low pressure area under the car, improving the engine cooling.


Scott

 

I usually just refer mentally to what you describe clear enough for me to follow as positive and negative pressure between the car and the road interface. I always thought it was kinda strange that the radiator cools the hot fluid from the engine's combustion in front of the engine then blows the just extracted, heated air right back on the engine! In a car with tight engine space that probably isn't as helpful as it might be.

If they ever build a mid engine car I'd hope any cooling heat exchangers would be behind or outside the engine enough to not "reheat" the engine even as modest as that is.

 

That spoiler cleans up airflow underneath for less drag. A high speed race car may have panels added to make the underneath smooth.

The Indy ft. spoiler designed for our Vettes w/ wind tunnel cleans up airflow underneath & sweeps the airflow around the front tires for less drag & scoops up air for cooling.


I have been rec. Indy ft. spoiler for all 68-79 ! I put mine on as soon as possible, so early that the paint matches & it appears original.

 

The hot air being blown back on the engine still has a cooling effect because it is cooler than the hot running engine and the exhaust manifolds. Check the engine surfaces with a temp gun.

 

I just got the one from Ecklers. I had a small thread on it. Take a look. BTW, was in stock and shipped within 4 days.



http://forums.corvetteforum.com/c3-t...-of-these.html

 

First, before anyone goes off on a tangent about how wings work, it's worth keeping in mind that we are dealing with a body in ground effect here. In this case, however the pressure differential (∆) is accomplished, lower pressure beneath the body than that above it always means downforce. Since any ∆ is multiplied by the footprint area of the body, it doesn't take a whole lot to start adding up.

A well designed front air dam on a low riding car is very good at reducing the amount of air traveling beneath the body. Add a proper splitter and its affect can be significanlty improved. The PC dam happens to have somewhat of a semi-splitter designed in, tho the OEM one requires additional bracing for sustained speeds. Yes, all of this usually helps us draw air thru the rad and pull hot underhood air out too. For more specific discussion of underhood aero... http://forums.corvetteforum.com/c3-t...ics-et-al.html

Cleaning up underbody impingements would help that air evacuate more efficiently, but until you start going to extremes would be of secondary importance to reducing the volume of air under the car to begin with. That said, a proper diffuser appears the logical place to begin underneath, especially given that the rear bumper of the C3 looks much like a parachute with the spare carrier removed.

Since pressures vary from one area to the next, both above and below the body, IMCO a front dam should not be discussed without consideration of the opposite end of the car. The PC rear spoiler functions to slow airflow above the rear of the car, thus creating higher pressure there. This also creates a lower pressure area behind the spoiler, which in turn helps evacuate air more efficiently from beneath the rear of the body. While it may not be critical at lower speeds, you don't have to be traveling as fast as you might think for aero imbalance towards oversteer to put you into a 1st order predicament. (BTDT)

FWIW, the PC aero package as a whole reportedly reduced late C3 drag coefficient by ~15%, so it's not merely cosmetic.

Hope that's worth $.02


TSW

 

So, if I understand this correctly, if using this air dam from Eckler's, I need to have some type of rear spoiler, or wing? Thanks for the info link. Very helpful.

 

Depends a bit upon how you drive. To my jaundiced eye most cars with one piece but without the other look incomplete, but the faster you go the less of a styling preference and more of a safety issue it becomes.

BTW, most aftermarket air dams do not inlcude an integral lower rad extension as does the PC dam, whick without retention of the stock one allows air to escape back underneath.

 

One would also take into consideration the rest of the design like 68-77, conv. or 78-82.

The C3 design was lifting at the front. The original 68 rear spoiler design was cut way down after aerodynamic studies & actual high speed tests for production. Front fenders were cut down. An aerodynamic dam was added to the front.

 

Lower rad extension = lwr radiator ext.? Also, what is a PC dam?


Found this article I had saved.

http://www.racecar-engineering.com/t...-aerodynamics/


Thanks Skunkworks for the info. BTW, saw the old thread where we were talking about Holloman. I was 8th FS. My grandfather taught George Preddy to fly before WW2 - Preddy was 7th FS, "Screamin Demons", like the t-shirt you have.

 

PC = Pace Car

 

 

Sorry, "lower radiator extension" may not be the industry accepted term for the baffle area which extends up from the center section of the PC (Pace Car) dam to seal it to the rad.

Haven't had all that many visitors to that thread lately, probably because I rarely post my signature... Cripes A'Mighty! Glad your grandfather instructed for our side.

 

Also another advantage for that air dam in the first post is that it has those two holes in it. Connect hoses up to that and route them to the center of the brake rotors for cooling. Helps keep brake fade from occurring.

 

The one from Eckler's has the 2 holes also. Brake cooling, great idea!

 

Wait a minute, Scotty!! I thought you just said "there is no 'low' pressure" or "suction".... only 'higher' pressure". [Well, OK.... 'higher' than what??? ]

 

Why is so hard in your little pea brains to make a C-3 go 200+ mph when a NASCAR restrictor plate motors can???????????????

I did Little bit of thought before heading to Bonneville Salt Flats

 

George, I thought you knew by now I'm not in the camp who believes a C3 can't do 200+. Heck, Sundowner has broken 240!

 

while cruising in 100* heat yesterday i was running around 212*.i have done everything to seal the areas around the cowling and flushed the radiator twice with lime away.new t stat hoses etc.interesting what theskunkworks says about the rear hood gasket.of course i have none and did not know there was supposed to be one.i noticed extreme turbulance in this area in the form of rapidly changing temps and air flow to the passenger compartment,while the t tops were off of course.i don't usually run with the tops off so i had not noticed this before.does anyone have a diagram and or instructions on how to best install the rear hood gasket?what happened to me yesterday bears out what he says.