OEM Hood Venting, Ideas/results?
06-21-2011, 03:47 PM
#11
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I am definitely not disputing the hood vents, they work for sure, especially sitting on hot days, but i feel sure it could be improved while in motion because it doesn't have any directionality, which is what all other performance hoods have. I just like to tinker a bit, so i am trying to improve its venting while in motion, like a j's etc, but much much cheaper
But considering most people do things like upgraded radiator etc, aswell, the radiator and fans would push alot out, but this is where the issue lays, air in or air out! lol. For air out, a simple design, like angle slats would help the heat flush out into the oncoming wind better than the turbulence the basic cuts have. Where as a naca duct style would push more air in, and in theory, more cool air going in, pushes the hot air down and out of the bay, i dont see how it would stop the air circulation since naca ducts give air a directionality as it comes it, and its going it a similar direction to oem. Input?
But considering most people do things like upgraded radiator etc, aswell, the radiator and fans would push alot out, but this is where the issue lays, air in or air out! lol. For air out, a simple design, like angle slats would help the heat flush out into the oncoming wind better than the turbulence the basic cuts have. Where as a naca duct style would push more air in, and in theory, more cool air going in, pushes the hot air down and out of the bay, i dont see how it would stop the air circulation since naca ducts give air a directionality as it comes it, and its going it a similar direction to oem. Input?
06-21-2011, 11:24 PM
#12
man, i jumped in the middle of things and hard to know where to start. so you are trying to keep the intake temps down?
i guess i'll start off by saying the obvious to an engineer. the radiator works by a high and low pressure system. the in coming air causes a high pressure in the front. the engine bay has many places for the air to escape, mainly the bottom to form a low pressure system. the higher the high pressure zone and the lower the low pressure zones the better cooling you get for the radiator. one way to get higher pressure is to drive faster (my excuse to the officer) or seal the front better like cooling plate or what honda has already done. a way to get a lower pressure is to some how let more air out. how you lets more air out is but making more holes to let it out or making a vacuum.
so, what you proposed is to let more air in behind the radiator. the down force that you thought of will be negated by the upward lift the air pushes down for the bottom of the bay. if you let air in behind the radiator, this will was the "low" pressure zone to increase pressure. this will lower the cooling of the radiator. this will lead to a hotter coolant temperature and a hotter engine. if you think about it, if you have cooler iat but a hotter engine. wont the powers negate? or decrease? i definitely see how this can lower iat but not overall cooling. it is true that blowing air into the bay would help remove the heat from the engine or the header. even if you said that the in coming air would help cool the engine, you would be kinda right. but, water/coolant has a high specific heat that allows it keep the engine bay cooler than just blowing air. this is why a wrapped my CAI in header heat wrap. so i can pour water on it to keep it cool.
most hoods designed by a company like asm have their own testing wind tunnel ( that or they just have their car in some random wind tunnel taking pics). if you look at their designs, they have vents but the hood is designed for air to flow over the vents. this causes a vacuum to suck air out of the engine bay. this will help with cooling the radiator and removing the heated air that had rise to the top.
on your last post, importedpower, you are right that would not stop circulation. but it would decrease the difference between the pressure zones.
but i could be completely wrong and crazy.
i guess i'll start off by saying the obvious to an engineer. the radiator works by a high and low pressure system. the in coming air causes a high pressure in the front. the engine bay has many places for the air to escape, mainly the bottom to form a low pressure system. the higher the high pressure zone and the lower the low pressure zones the better cooling you get for the radiator. one way to get higher pressure is to drive faster (my excuse to the officer) or seal the front better like cooling plate or what honda has already done. a way to get a lower pressure is to some how let more air out. how you lets more air out is but making more holes to let it out or making a vacuum.
so, what you proposed is to let more air in behind the radiator. the down force that you thought of will be negated by the upward lift the air pushes down for the bottom of the bay. if you let air in behind the radiator, this will was the "low" pressure zone to increase pressure. this will lower the cooling of the radiator. this will lead to a hotter coolant temperature and a hotter engine. if you think about it, if you have cooler iat but a hotter engine. wont the powers negate? or decrease? i definitely see how this can lower iat but not overall cooling. it is true that blowing air into the bay would help remove the heat from the engine or the header. even if you said that the in coming air would help cool the engine, you would be kinda right. but, water/coolant has a high specific heat that allows it keep the engine bay cooler than just blowing air. this is why a wrapped my CAI in header heat wrap. so i can pour water on it to keep it cool.
most hoods designed by a company like asm have their own testing wind tunnel ( that or they just have their car in some random wind tunnel taking pics). if you look at their designs, they have vents but the hood is designed for air to flow over the vents. this causes a vacuum to suck air out of the engine bay. this will help with cooling the radiator and removing the heated air that had rise to the top.
on your last post, importedpower, you are right that would not stop circulation. but it would decrease the difference between the pressure zones.
but i could be completely wrong and crazy.
06-22-2011, 03:14 AM
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Makes complete sense, my primary idea on the naca design was for an undertray, like the one GP Fab is designing, because it blocks off alot of the engine bay's underside, and the underflow you were mentioning would be dwindled down greatly, in which case, the only openings would be the exhaust tunnel (which is where i was trying to direct air) and the few vents here and there he designs on it.
My second design (still working on it) uses vents similar to:
http://www.appleare.com/wp-content/u.../car_vents.jpg
and would allow the heat to push out the top of the bay, like you mentioned, but wouldnt allow much air to be pulled back in, like the other hood designs. Ill post more pics tonight
My second design (still working on it) uses vents similar to:
http://www.appleare.com/wp-content/u.../car_vents.jpg
and would allow the heat to push out the top of the bay, like you mentioned, but wouldnt allow much air to be pulled back in, like the other hood designs. Ill post more pics tonight
06-22-2011, 07:56 AM
#14
If you want cold air into the engine, do a cold air intake.
If you want hot air out of the engine bay, then do some reading and careful planning beforehand so you don't put the vents in the wrong place. If you put them too far back toward the base of the windshield, the high pressure zone there could force lots of air into the engine bay at highway speeds, reducing the pressure differential across the radiator. That reduces the radiator's effectiveness and could cause your car to run hotter.
This thread has a link to an attempt to measure the results of venting instead of guessing at them. It's a very interesting read.
https://www.s2ki.com/...under-the-hood/
If you want hot air out of the engine bay, then do some reading and careful planning beforehand so you don't put the vents in the wrong place. If you put them too far back toward the base of the windshield, the high pressure zone there could force lots of air into the engine bay at highway speeds, reducing the pressure differential across the radiator. That reduces the radiator's effectiveness and could cause your car to run hotter.
This thread has a link to an attempt to measure the results of venting instead of guessing at them. It's a very interesting read.
https://www.s2ki.com/...under-the-hood/
06-22-2011, 08:12 AM
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The link doesnt work. Ive been reading for days, and the hood vents are only useful at idle, while the car is in motion its doing very little. I origionaly came at this while trying to design a rain guard, which i pretty much have, but while im at it im looking at a design for improving the flow.
06-22-2011, 04:55 PM
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almost done with this design... my idea on how to mount is pretty simple as well.
Basicaly, you have the wire in your hood just like the basic venting. The louver style would simply bolt on top of that with some low profile allen bolts and washers on the bottom, ill try and draw it up.
Also, sending some feeler messages out to the fabricators i've bought things from before. The only issue i can for see is the fact that the holes are not all uniform, no one used an exact template.
Basicaly, you have the wire in your hood just like the basic venting. The louver style would simply bolt on top of that with some low profile allen bolts and washers on the bottom, ill try and draw it up.
Also, sending some feeler messages out to the fabricators i've bought things from before. The only issue i can for see is the fact that the holes are not all uniform, no one used an exact template.
06-22-2011, 11:14 PM
#18
Makes complete sense, my primary idea on the naca design was for an undertray, like the one GP Fab is designing, because it blocks off alot of the engine bay's underside, and the underflow you were mentioning would be dwindled down greatly, in which case, the only openings would be the exhaust tunnel (which is where i was trying to direct air) and the few vents here and there he designs on it.
My second design (still working on it) uses vents similar to:
http://www.appleare.com/wp-content/u.../car_vents.jpg
and would allow the heat to push out the top of the bay, like you mentioned, but wouldnt allow much air to be pulled back in, like the other hood designs. Ill post more pics tonight
My second design (still working on it) uses vents similar to:
http://www.appleare.com/wp-content/u.../car_vents.jpg
and would allow the heat to push out the top of the bay, like you mentioned, but wouldnt allow much air to be pulled back in, like the other hood designs. Ill post more pics tonight
on your second design, air is air pushed into the radiator to the engine bay. so you dont really have to worry about not having air pulled in to remove heat. although this works fine at cruising speeds. sitting at red lights, the fans do draw air into the bay, but its heated air.
06-23-2011, 06:30 AM
#20
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So, the way air moves through the engine bay...
To start, think about the car moving at speed, so you have constant positive pressure across the nose of the car, slightly less across the bridge of the hood, and then a spike where the hood meets the windshield. The way the S2000 is designed, air flows into the car through the front opening in the nose and gets split ahead of the radiator where the air is effectively blocked for high positive pressure, and can't get around the rad.
Cold air either travels through the radiator, which the car itself uses to stabilize engine temps to proper levels, or is shunted up, over the radiator to the top of the engine bay. Some of this cold air is directed to the intake horn, the rest flows over the top of the engine creating a relative high pressure zone.
Air that flows through the rad is pushed down by the top-level cool air, and it leaves under the car, so cold-air flow through the engine bay is already pretty well executed. When you cut the hood, you destroy the OEM capability to build high pressure at the top of the engine bay and thus most effectively evacuate hot air from it.
If anything was done to the hood, I'd think you'd want a duct directly behind the stock intake position to draw air into the engine bay, over the header, and then back out in an efficient manner, either back out through the hood or under the car. Since you have high pressure at the hood/windshield, under the car would probably be the best bet considering how the S2000 is set up.
For all the things you can do to help reduce engine bay temps, I've never seen vented hoods as the best solution. You could take the whole hood off, the ECU will still work to get the engine to a certain optimal temp, and I rarely see people consider this.
To start, think about the car moving at speed, so you have constant positive pressure across the nose of the car, slightly less across the bridge of the hood, and then a spike where the hood meets the windshield. The way the S2000 is designed, air flows into the car through the front opening in the nose and gets split ahead of the radiator where the air is effectively blocked for high positive pressure, and can't get around the rad.
Cold air either travels through the radiator, which the car itself uses to stabilize engine temps to proper levels, or is shunted up, over the radiator to the top of the engine bay. Some of this cold air is directed to the intake horn, the rest flows over the top of the engine creating a relative high pressure zone.
Air that flows through the rad is pushed down by the top-level cool air, and it leaves under the car, so cold-air flow through the engine bay is already pretty well executed. When you cut the hood, you destroy the OEM capability to build high pressure at the top of the engine bay and thus most effectively evacuate hot air from it.
If anything was done to the hood, I'd think you'd want a duct directly behind the stock intake position to draw air into the engine bay, over the header, and then back out in an efficient manner, either back out through the hood or under the car. Since you have high pressure at the hood/windshield, under the car would probably be the best bet considering how the S2000 is set up.
For all the things you can do to help reduce engine bay temps, I've never seen vented hoods as the best solution. You could take the whole hood off, the ECU will still work to get the engine to a certain optimal temp, and I rarely see people consider this.