Vented hood question...................
Instructor
Joined: Sep 2006
Posts: 134
Likes: 2
From: Bloomington Illinois
There's something I'm surprised no troll has jumped on - the rear fender vents. Something like: how will they be designed to keep water out of the rear speakers?
Sorry - should not have said that - bound to start something we don't want to read.
Sorry - should not have said that - bound to start something we don't want to read.
Race Director
Joined: May 2008
Posts: 10,742
Likes: 629
From: Manheim Pennsylvania
I forgot myself and got ahead of the intro date. We have not seen the final product, maybe the vent/vents will look great. Depending on the function, might offset design intervention. This morning I superimposed the vents on my C6, I don't think it will look to bad, just not what we were expecting.
Last edited by Larry/car; Dec 14, 2012 at 09:42 AM.
Safety Car
Joined: Jun 2004
Posts: 4,430
Likes: 81
From: Whidbey Island WA
I can live with a functional vent but overall I don't like them. Even a functional vent that is designed to say, "look at me, look at me, look at me, I'm a vent, this must be a fast car" is a no no to me. They should integrate into the design, not stand out on top of it.
Race Director
Joined: May 2008
Posts: 10,742
Likes: 629
From: Manheim Pennsylvania
I wouldn't say your in a minority, I just don't like what the rendering is depicting. However I don't want to appear old and set in my ways, So will wait for the unveiling, it could be a real plus. It will be interesting to see what the engineers are accomplishing.
Race Director
Joined: Feb 2012
Posts: 10,776
Likes: 11
Race Director
Joined: May 2008
Posts: 10,742
Likes: 629
From: Manheim Pennsylvania
There is a lot of C7 there as we see in the renderings. I am getting use to the vent and imagined it on the hood of my C6. It will Look better in person. My guess the vent will be body colored.
Last edited by Larry/car; Dec 14, 2012 at 01:51 PM.
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Melting Slicks
Joined: Mar 2007
Posts: 2,838
Likes: 6
From: San Diego CA
I can live with a functional vent but overall I don't like them. Even a functional vent that is designed to say, "look at me, look at me, look at me, I'm a vent, this must be a fast car" is a no no to me. They should integrate into the design, not stand out on top of it.
Unless it's well-integrated into the overal design of the car, a hood vent will resemble a ricer add-on. Jeez, I hope the C7 hood vent(s), if it has any, are body-colored. The snap-in black plastic look is so . . . ??
Melting Slicks
Joined: Nov 2005
Posts: 2,074
Likes: 309
You are absolutely right! GM is a world leader in fake hood scoops and vents and I will not buy another Vette if they put a functional vent or scoop on anything.
PS: Those side coves on the C2 thru C6 weren't functional, were they? OMG! Was I duped into buying a car with a functional vent without knowing it?
PS: Those side coves on the C2 thru C6 weren't functional, were they? OMG! Was I duped into buying a car with a functional vent without knowing it?
Melting Slicks
Joined: Nov 2005
Posts: 2,074
Likes: 309
Now a response from my left brain: the hood vent is a good thing. If you actually drive a Corvette at maximum effort (or any reasonably high-powered car) heat can start doing a number of undersireable things. I've heard of a C4 entered in the Silver State Classic open road rally that actually melted its' power steering reservoir. Fuel can boil (vapor lock). Hydraulic fluid life is shortened. Rubber and plastic parts become brittle. Power is lost. Nothing good can come from really high underhood temperatures. I have been a proponent for vented hoods simply for the reduction in temperature alone.
In addition to this benefit, I believe GM's engineers are also using this feature for aerodynamic benefits, ie; reducing lift. When you're doing more than 180 mph, you're going faster than most jet airliners are when they rotate and take off. Mercedes used to run a team of FIA GT1 sports racing cars. They quit when front end lift caused several of their cars to literally take off and do multiple somersaults until they crashed off the track into the trees at le Mans. This reminded them too much of their 1950's accident that killed 80 some odd spectators, I guess.
I wouldn't really expect a corvette to start flying like the Mercedes, but if the front end is getting light, then your steering effectiveness will decrease, which can be scary at high triple digit speeds. So if they are thinking about these two things, it's good.
As for the engine getting wet, don't worry. It's not dry under your hood when it rains no matter what you drive. Rain gets kicked up by the tires, it goes through the grill, it's pretty wet with or without the vent.
I actually like the vent, because it means they are doing real engineering.
In addition to this benefit, I believe GM's engineers are also using this feature for aerodynamic benefits, ie; reducing lift. When you're doing more than 180 mph, you're going faster than most jet airliners are when they rotate and take off. Mercedes used to run a team of FIA GT1 sports racing cars. They quit when front end lift caused several of their cars to literally take off and do multiple somersaults until they crashed off the track into the trees at le Mans. This reminded them too much of their 1950's accident that killed 80 some odd spectators, I guess.
I wouldn't really expect a corvette to start flying like the Mercedes, but if the front end is getting light, then your steering effectiveness will decrease, which can be scary at high triple digit speeds. So if they are thinking about these two things, it's good.
As for the engine getting wet, don't worry. It's not dry under your hood when it rains no matter what you drive. Rain gets kicked up by the tires, it goes through the grill, it's pretty wet with or without the vent.
I actually like the vent, because it means they are doing real engineering.
Le Mans Master
Joined: Feb 2011
Posts: 5,783
Likes: 400
From: Paoli, IN
St. Jude Donor '17, '19
Can someone educate me on hood vents.
How do they provide downforce? Do they do both provide downforce and cooling, or are they designed for either as a specific purpose? What is the adv / disadv. of having the hood vent in the middle or on the sides (like on the new mustangs). And last, how is the water displaced to the ground without disrupting the airflow coming out?
Thanks.
How do they provide downforce? Do they do both provide downforce and cooling, or are they designed for either as a specific purpose? What is the adv / disadv. of having the hood vent in the middle or on the sides (like on the new mustangs). And last, how is the water displaced to the ground without disrupting the airflow coming out?
Thanks.
Race Director
Joined: Feb 2012
Posts: 10,776
Likes: 11
Can someone educate me on hood vents.
How do they provide downforce? Do they do both provide downforce and cooling, or are they designed for either as a specific purpose? What is the adv / disadv. of having the hood vent in the middle or on the sides (like on the new mustangs). And last, how is the water displaced to the ground without disrupting the airflow coming out?
Thanks.
How do they provide downforce? Do they do both provide downforce and cooling, or are they designed for either as a specific purpose? What is the adv / disadv. of having the hood vent in the middle or on the sides (like on the new mustangs). And last, how is the water displaced to the ground without disrupting the airflow coming out?
Thanks.
This is from a article in High Performance magazine:Inside The 580HP Camaro ZL1
Aerodynamics
The '12 ZL1 is one of the first GM cars designed to create downforce, or negative lift. To accomplish this impressive feat, the ZL1 team spent around 100 hours testing at the General Motors Aero Lab (GMAL) wind tunnel, using Computational Fluid Dynamics. The team leaned on GM's Lead Development Aerodynamics Engineer, Tom Froling, as this retired F-16 pilot and aero expert played a big role in helping to form the ZL1's body. However, the initial goal for ZL1 wasn't a full-on aero package; it was to eliminate the Camaro's tendency to lift at high speed.
"The SS was styled to be beautiful, but the car's shape came at the expense of lots of front lift," Roma reveals. "But, that's not much of a problem for a car limited to 155 mph. As you go faster than 150, forces and lift go up exponentially. We knew that with the ZL1's additional power, it would spend more time at high speed. So we decided early on to add a front splitter, as we wanted a more aggressive front anyway." The splitter not only took care of the lift problem, it also added an aggressive look to the front end. A unique rear spoiler was added, and then the team was faced with the most difficult component of the aero project: the hood extractor. True to its name, the extractor provided cooling airflow, and also assisted in reducing front lift. But just when Tony and his team designed the perfect extractor for aero-world, the real world called. "Once we designed a great extractor, we looked at it and thought, "Wait…this thing has to sit out in the rain! And we knew that if the driver wasn't careful, this extractor was going to get everything in the engine bay wet." It took some effort, but eventually a water trough was created to work with the extractor.
"It was then that we thought, 'If we keep going, we can make some downforce,'" Roma says. So several sizes and shapes of rocker moldings were tried before they found the right one. Front wheelwell extensions were put in as functional styling elements, as they gently move air around the tires at speed, and also assist with brake cooling. The team played with varying sizes and numbers of slats for the upper and lower grille. And a rear diffuser that utilized wraparound elements was chosen.
Roma is quick to note how beneficial Froling's airflow expertise was to the ZL1 project.
"Tom made a huge impact on [the] ZL1. As an example, he really pushed the idea of a belly pan. We weren't sure, as you have to be very careful to not choke off airflow paths from the engine, and if it's done wrong they can inadvertently bake things like starters. "But we made one, and it turned out to be a win-win. The pan funnels air over the driveline, and directs air up to the rear trans mount, which made it run cooler. We ended up in a better place because of guys like Tom." The end result is a ZL1 that produces 65 pounds of downforce at an equivalent 150 mph--compared to 200 pounds of lift in a Camaro SS. And that downforce translates into lower lap times, too. And while top-speed stability is great, these aero pieces also enhance handling and braking when the driver is actually obeying posted speed limits. "The closer you get to zero lift, the less the body moves--even at 70 or 80 mph on the highway, the ZL1 feels more stable," Tony says. "It is less sensitive to forces like crosswinds, too. In the end, it's all about being a driver's car, and giving you that confidence."
Aerodynamics
The '12 ZL1 is one of the first GM cars designed to create downforce, or negative lift. To accomplish this impressive feat, the ZL1 team spent around 100 hours testing at the General Motors Aero Lab (GMAL) wind tunnel, using Computational Fluid Dynamics. The team leaned on GM's Lead Development Aerodynamics Engineer, Tom Froling, as this retired F-16 pilot and aero expert played a big role in helping to form the ZL1's body. However, the initial goal for ZL1 wasn't a full-on aero package; it was to eliminate the Camaro's tendency to lift at high speed.
"The SS was styled to be beautiful, but the car's shape came at the expense of lots of front lift," Roma reveals. "But, that's not much of a problem for a car limited to 155 mph. As you go faster than 150, forces and lift go up exponentially. We knew that with the ZL1's additional power, it would spend more time at high speed. So we decided early on to add a front splitter, as we wanted a more aggressive front anyway." The splitter not only took care of the lift problem, it also added an aggressive look to the front end. A unique rear spoiler was added, and then the team was faced with the most difficult component of the aero project: the hood extractor. True to its name, the extractor provided cooling airflow, and also assisted in reducing front lift. But just when Tony and his team designed the perfect extractor for aero-world, the real world called. "Once we designed a great extractor, we looked at it and thought, "Wait…this thing has to sit out in the rain! And we knew that if the driver wasn't careful, this extractor was going to get everything in the engine bay wet." It took some effort, but eventually a water trough was created to work with the extractor.
"It was then that we thought, 'If we keep going, we can make some downforce,'" Roma says. So several sizes and shapes of rocker moldings were tried before they found the right one. Front wheelwell extensions were put in as functional styling elements, as they gently move air around the tires at speed, and also assist with brake cooling. The team played with varying sizes and numbers of slats for the upper and lower grille. And a rear diffuser that utilized wraparound elements was chosen.
Roma is quick to note how beneficial Froling's airflow expertise was to the ZL1 project.
"Tom made a huge impact on [the] ZL1. As an example, he really pushed the idea of a belly pan. We weren't sure, as you have to be very careful to not choke off airflow paths from the engine, and if it's done wrong they can inadvertently bake things like starters. "But we made one, and it turned out to be a win-win. The pan funnels air over the driveline, and directs air up to the rear trans mount, which made it run cooler. We ended up in a better place because of guys like Tom." The end result is a ZL1 that produces 65 pounds of downforce at an equivalent 150 mph--compared to 200 pounds of lift in a Camaro SS. And that downforce translates into lower lap times, too. And while top-speed stability is great, these aero pieces also enhance handling and braking when the driver is actually obeying posted speed limits. "The closer you get to zero lift, the less the body moves--even at 70 or 80 mph on the highway, the ZL1 feels more stable," Tony says. "It is less sensitive to forces like crosswinds, too. In the end, it's all about being a driver's car, and giving you that confidence."
Last edited by BlueOx; Dec 16, 2012 at 02:36 PM.
Le Mans Master
Joined: Feb 2011
Posts: 5,783
Likes: 400
From: Paoli, IN
St. Jude Donor '17, '19
Race Director
Joined: Feb 2012
Posts: 10,776
Likes: 11
Well, just a guess but I suspect it acts to take air that would flow under the car (causing lift) and 'funnel' it up through some sort of trough that is shaped so that the air ends up pushing down the front of the car as it is funneled up through the vents.
Safety Car
Joined: Jun 2004
Posts: 4,430
Likes: 81
From: Whidbey Island WA
You reduce lift by directing air up, by channeling the flow so that it helps to accelerate the velocity of the air under the car, or both. There is some elegance her because it can reduce the cars functional frontal area taking what would have been drag in one way and converting into drag in another but beneficial way.
