Ducted hood vents...

I was wondering the other day, why don't more cars have ducted hood vents for the radiator?

Not needed on street cars, causes huge packaging problems.

It's true that there are no meaningful aerodynamic advantages at street-legal speeds, but I don't think the packaging problems are anywhere near as big as the cleanliness problems. Most cars have empty space where the vents could go.

However, lots of dirt and road debris gets kicked up through these vents. It's uisually not a huge problem on track because tracks are kept clean. Also your average Joe will not appreciate being showered in brake dust through the front windows.

Edit: Whoops, thought you meant fender vents.

NVH?

What advantage would they have in a street vehicle? It exposes the radiator to damage more easily. It takes up more space. It might cause the engine to be moved back into the firewall.

Manufacturing a hood like that isn't cheap or easy either. You can't easily stamp out that shape. You could probably do it with multiple pieces, but that adds cost for benefits that won't be needed or even felt in street driving.

I think the C7s have a ducted hood, but they're the only ones I can think of.

GameboyRMH wrote: It's true that there are no meaningful aerodynamic advantages at street-legal speeds, but I don't think the packaging problems are anywhere near as big as the cleanliness problems. Most cars have empty space where the vents could go.

You'd be surprised... Even with the small stock hood vents, cooling gets worse as you go faster in the Jeep, starting around 55 - 60 mph due to pressure buildup in the engine bay. Drag a trailer up a hill at 50, it stays nice and cool. Drag the same trailer on flat ground at 65 and you'll see the temps climb a little...

rslifkin wrote:

GameboyRMH wrote: It's true that there are no meaningful aerodynamic advantages at street-legal speeds, but I don't think the packaging problems are anywhere near as big as the cleanliness problems. Most cars have empty space where the vents could go.

You'd be surprised... Even with the small stock hood vents, cooling gets worse as you go faster in the Jeep, starting around 55 - 60 mph due to pressure buildup in the engine bay. Drag a trailer up a hill at 50, it stays nice and cool. Drag the same trailer on flat ground at 65 and you'll see the temps climb a little...

Oh sorry I thought we were talking about the fender vents. Yes there are big cooling advantages to a ducted radiator, even at street speeds, and yes there would be packaging problems in putting them on most street cars. Also a bit of a cleanliness problem since road spray will get pushed through it in the rain.

In reply to GameboyRMH:

Yeah, fully ducted would be a pain on a street car. But a well designed vent setup can still pull a good bit of extra air through the rad even without being fully ducted and causing packaging problems.

don't neglect the cooling required for an engine bay. Even though the air coming of a rad is 200+ degrees, there is some effect of the flow through the engine bay at keeping the exhaust from cooking the rest of the components.

I've had vehicles where the amount of air allowed through the grill was reduced significantly without overheating.

mid engine cars would be easiest to do that type of venting on as it solves the packaging issue, but still a little too race car-ish set up to really worry about for a street car

scardeal wrote: I was wondering the other day, why don't more cars have ducted hood vents for the radiator?

Why do I envision that packed with snow?

STM317 wrote: I think the C7s have a ducted hood, but they're the only ones I can think of.

trucke wrote: Why do I envision that packed with snow?

Judging by the vents on my Jeep, the snow would be gone before the engine was finished warming up.

Dr. Hess wrote:

STM317 wrote: I think the C7s have a ducted hood, but they're the only ones I can think of.

They're fairly common on supercars, although that's bordering onto a race car.

The Elise owner's manual specifically says to remove the snow from the vents.

rslifkin wrote: In reply to GameboyRMH: Yeah, fully ducted would be a pain on a street car. But a well designed vent setup can still pull a good bit of extra air through the rad even without being fully ducted and causing packaging problems.

Yeah, my '13 GT Mustang had a vented hood from the factory.

stafford1500 wrote: don't neglect the cooling required for an engine bay. Even though the air coming of a rad is 200+ degrees, there is some effect of the flow through the engine bay at keeping the exhaust from cooking the rest of the components.

Radiator air doesn't pick up 100% of the heat so it's nowhere that hot, but your point is still valid.