Can The Radiator Duct Reduce Drag

[buterworth]

Some sport car have a radiator venting Duct.With the duct,the air will pass through the radiator and then run to the top of the hood.

Can this radiator duct reduce drag and increase downforce?

My car is FWD,but I've still got enough room to install a duct behind the radiator.I want to cut a hole on the hood to try this thing,but I've no idea whether it works.

[tristancliffe]

The can and do reduce drag. The downforce/lift is probably pretty negligable though.

[Chris Y]

I think they're also intended to scavenge airflow through the rad, are they not?

[buterworth]

BTW,will it cause engine Overheating ?

[Rubinho]

Originally Posted by buterworth

BTW,will it cause engine Overheating ?

If anything a correctly designed duct will increase flow through the radiator.

[buterworth]

Originally Posted by Rubinho

If anything a correctly designed duct will increase flow through the radiator.

But most Leman prototype have no radiator ducts at all.

[Adam43]

Modern prototypes don't have the radiator at the front like that. (Off topic: I would introduce a rule that the radiator has to be at the front). I remember a few older generation prototypes that did.

Getting the air out is as important as getting it in. Doing this nearer the front of the car (away from the windscreen where there is a high pressure region) sounds like a good idea to me.

[grantp]

I recall someone experimenting on an F1 car several decades ago and discovering that mounting a radiator end on to airflow rather than forcing ais through it made no difference at all to the temperatures of the fluids it was cooling. Which they assumed meant that all heat loss is limited (mostly) by surface losses rather than air through put.

You may need to consider what other effects installing the ducting might have both for the temperature of components that are not cooled (or are warmed in cold environments) by the engine compartment design AND what effect it might have on aerodynamics, stability, etc. All related to your local environment (for tempratures) and what sort of driving you undertake. Presumably if you are considering this the primary benefit you seek will be for top speed and related temperature management so you need to be sure you are not likely to introduce handling problems related to aero effects.

[JohnD]

Yes, the cooling drag (NOT the whole car drag) can be reduced by a half or more.
See Prof.Zatz's book "Race Car Aerodynamics", p.216, and the source of his opinion SAE paper 810185, cost you $15 from: http://www.sae.org/technical/papers/810185
John

[Rubinho]

Originally Posted by buterworth

But most Leman prototype have no radiator ducts at all.

But most Formula cars do. Your point being?

[Cameron Winton]

Be careful where you put the exhaust ducts. I have heard of circumstances where the radiator exhausted into a high pressure area and the airflow was reversed through the radiator. I believe one example is why they put the aerofoil on the front of a Metro 6R4.
Be careful where on the hood you put the exhaust ducts. It can be a high pressure area, especially closer to the windscreen.
On a saloon car, a lot of the radiator air can exhaust underneath the car and induce lift. If you look at the front of a supertourer or GT car, you will see a lot of effort has gone into designing radiator ducting. Quite often thay are mounted very low and exhaust through side ducts immediately in front of the front wheels.
Quite a complex area of aero. Involves heat transfer as well as aerodynamics. Best to look at what others with access to expertise and wind tunnels have done and copy. Having said that, they still get it wrong!

[buterworth]

Originally Posted by Cameron Winton

Be careful where you put the exhaust ducts. I have heard of circumstances where the radiator exhausted into a high pressure area and the airflow was reversed through the radiator. I believe one example is why they put the aerofoil on the front of a Metro 6R4.
Be careful where on the hood you put the exhaust ducts. It can be a high pressure area, especially closer to the windscreen.
On a saloon car, a lot of the radiator air can exhaust underneath the car and induce lift. If you look at the front of a supertourer or GT car, you will see a lot of effort has gone into designing radiator ducting. Quite often thay are mounted very low and exhaust through side ducts immediately in front of the front wheels.
Quite a complex area of aero. Involves heat transfer as well as aerodynamics. Best to look at what others with access to expertise and wind tunnels have done and copy. Having said that, they still get it wrong!

Thank for your reply.
Yes,it's dangerous to put the duct close to the windscreen.My can is a traditional FWD car and the dust can't be installed close to the windscreen by and means.I think it will be safe.

[JohnD]

Find where the high pressure bubble in front of the widcsreen is by the tuft method. Tape wool tufts 4-6" long to the bonnet, drive the car and look, or have someone else drive by and take pics.
If the tufts lie close to the bonnet, its laminar flow. If they wave about or even lift, it's not and probably high pressure.

John

[AlexH]

It will help reduce drag, but the exit is important, also a small gain in down force can be achieved if the radiator is tilted forwards slightly.