Modified / Vented Rear Bumpers
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From: SFV
Originally Posted by tinkfist,Nov 17 2007, 02:47 AM
To promote downforce without drag on a car, you want air to move smoothly (laminar flow) and quickly under and over the car. Essentially, you want to turn your whole car into a wing as much as possible with its bias towards providing downforce rather than lift, i.e. creating high pressure over the car and low pressure under the car. A low pressure region, resulting in downforce, is the result of fast and smooth moving air within a region under the car only a few inches high. Front splitters, undertrays, and rear diffusers help the air move faster and smoother. What the vented/meshed bumper does is it encourages air to move from a small space to a larger space while still under the car. This greatly reduces the speed of the air (think of air passing through a nozzle). In addition, air that goes through a some sort of mesh or screen is only going to result in turbulent flow upon exit. That turbulent flow will create a low pressure region right were you do not want it, immediately behind your car!
Vented bumpers and hoods placed by manufacturers generally serve as a means to promote flow-through of air in order to cool something, usually the engine.
The aero gurus are free to correct the above, but I believe the jist is there. Vented bumpers just ain't aerodynamically functional.
Vented bumpers and hoods placed by manufacturers generally serve as a means to promote flow-through of air in order to cool something, usually the engine.
The aero gurus are free to correct the above, but I believe the jist is there. Vented bumpers just ain't aerodynamically functional.
Thanks in advance. 
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From: Bergen County, NJ
Originally Posted by unidextrous,Nov 16 2007, 06:39 PM
EternalLx made the statement that most Civics he sees around dont have the mods to back up the reasoning for having air reliefs in their bumpers. The CRX was an example to disprove that heavy mods are needed for aero mods. The car is in stock form, but fast enough..and aero mods can complement that.
Thats why I say weight doesnt play into the discussion.
Do you see where Im getting at?
Thats why I say weight doesnt play into the discussion.
Do you see where Im getting at?
I was always focusing on everyday civics I see on the streets, not drag civics or track civics with interiors stripped,race tires, etc as you keep bring up.
Also, what i stated last was plainly a view on styling... yet you bring up function.
It is functional let it be a S or a Civic but when its on a Civic with an stock engine and some bolt-ons; I can only assume that they did that for style and I for one cant see style in that.
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From: Bergen County, NJ
Originally Posted by ESCALVANTE,Nov 16 2007, 09:57 PM
Alright Alright!!! This sounds logical BUT, can anyone back this up?? If so, I will refrain from cutting up my rear bumper. Thanks in advance.
Thanks in advance. 
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From: Farmingdale, NJ
Originally Posted by EternalLx,Nov 16 2007, 10:43 PM
X2 on that... maybe we should ask people in the track forums?
Joined: May 2007
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From: OC
Interesting topic. Decided to search on it.
https://www.s2ki.com/forums/index.php?showt...dpost&p=7578500
https://www.s2ki.com/forums/index.php?showt...dpost&p=7578500
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From: Virgnia
Originally Posted by Sinji,Nov 16 2007, 01:06 PM
my favorite is still the one from asm. hopefully they realease it soon:
I like this one a lot!
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From: in my garage
Seriously Tom, stop stepping on my nuts here. 
My vented hood has reduced my lap times considerably, I can only imagine what venting my rear bumper will produce time wise.
My vented hood has reduced my lap times considerably, I can only imagine what venting my rear bumper will produce time wise.
(ymx777 @ May 5 2006, 04:19 PM)
Hi All,
I have run many CFD cases on rear wings and underbody interactions of a vehicle. I've actually design many aero devices for the s2000 (just for fun). Here's a couple of suggestions from my analytical experience:
2. If you look at a JGTC car, they have the lower portion of the bumper removed. This will reduce drag. Someone above stated that there is a pressure difference between trapped air and the wake region. This is infact true! Stagnant air has very high pressure compared to the wake region. The key is to minimize the surface area in which the pressure can act upon, therefore reducing drag. In aerodynamics, every little square inch counts.
Hope someone will find this helpful.
Hi All,
I have run many CFD cases on rear wings and underbody interactions of a vehicle. I've actually design many aero devices for the s2000 (just for fun). Here's a couple of suggestions from my analytical experience:
2. If you look at a JGTC car, they have the lower portion of the bumper removed. This will reduce drag. Someone above stated that there is a pressure difference between trapped air and the wake region. This is infact true! Stagnant air has very high pressure compared to the wake region. The key is to minimize the surface area in which the pressure can act upon, therefore reducing drag. In aerodynamics, every little square inch counts.
Hope someone will find this helpful.
