Radiator Drag

[SVOboy]

That's true, I'd never really thought of that!

Anyone know a semi driver?

Ninja Edit: Neat read, only casually mentions radiator size though: http://gcep.stanford.edu/pdfs/ChEHeX...0_11_trans.pdf

Edit II: Also, this: http://ffden-2.phys.uaf.edu/645fall2.../solutions.htm

[WisJim]

Originally Posted by Sludgy

Ever look at the radiators of large semitrailers? They all have what appears to be a canvas with a V shaped notch covering the radiator. At least in winter. Is reducing radiator drag that simple?

I have only seen this on semi tractors in cold weather, and assume it is to keep from cooling too much. Some have active louvres on the front of the radiator, but not as common.

[GasSavers_Ryland]

my thought on it is that any air that enters thru the grill has to exit the engine compartment, and the engine compartment is not aerodinamic, so it's not so much the smoothness of the grill, but the rout the air takes.
I have a half radiator, with all but about 5"x5" hole left open, and when it was 105F out, the temp gauge never budged above half way.

[MetroMPG]

banana's right, SVOman. You still need to block the "excess" holeness in the front of the car.

Though one advantage of using a smaller radiator may be quicker warm-up times since there'll be a smaller coolant volume.

[omgwtfbyobbq]

While not totally related to the discussion, I found this. Pretty good read.

The area between the hood on top, the valence on the bottom, and the headlight cans on each side can be thought of as forming a cooling air plenum which should guide air through the radiator. However, because Datsun designed the hood and valence for looks and not function, quite a bit of the air in this plenum "leaks" out into the front fender wells, through holes in the radiator bulkhead, and under the radiator. All the air that avoids transiting the radiator produces some lift (about 75 pounds at 60 mph) and raises the front of the car slightly, producing a slight reduction in traction, an increase in toe-in, and slightly more positive camber.

I was also thinking about fabbing diy louvres when I start doing aero stuff. I have a couple house vents I picked up for free, and if I can rig a spring on each to keep them closed, I can easily run a cable to the cab to pull them open. I could even block off behind the rad and try to have the air flow down under the car after it goes through the rad, but then I was thinking...
What if the engine block needs some air flow for cooling, so I may need to do some testing too... All in all, too much talk, not enough action!

[SVOboy]

Darin, of course it still needs to be blocked, but if I had a half radiator and left the hole on the other side,

[Gary Palmer]

Why don't you just block off 1/2 of the radiator, that way it ccostt's a lot less and you cann unblock it if you need it?

[vegasjetskier]

According to Road Vehicle Aerodynamics, the drag of the entire cooling system is somewhere between Cd = 0.02 and 0.06, depending on the vehicle.

Originally Posted by SVOboy

We all know the radiator causes hella drag, right? And we also know that a block is kewl for reducing that drag. However, what I'm wondering is does anyone have any information on how much drag it really is? I'm sure I've seen it somewhere, but I can't recall at all.

Reason I ask is I might be getting a half radiator and I'm wondering if it's worth having my friend fab up some mounts for it.

[SVOboy]

Ah, good info, got any links? I really need to start working on the link archive! *boo* myself

Gary, having a half-radiator will also reduce weight in the crucial up front portion of the car, look more bling, give more room to work, and lemme run a turbo if I decide to go the LPT route somewhere in the future.

[vegasjetskier]

Nope, no links, just the book itself. I can post more if you're interested (I need to work on my typing speed). What specifically do you need?

Originally Posted by SVOboy

Ah, good info, got any links? I really need to start working on the link archive! *boo* myself