does anyone know what kind of pressure affects which points on the bonnet and under the engine bay and which points have the best/fastest airflow.
I have another air intake idea and it just depends which areas suck and blow the best.
Hmmm, good question, going back to my days, many years ago as a student rocket scientist. (I dropped out of a Degree in Aeronautical Engineering, rocket science is hard work!) I think you\'ll find the very front of the car, where the air intake for the radiator is, is an area of high pressure because it\'s where the otherwise static air (for the sake of this description) is being met by the car trying to move through it. That\'s where you\'ll find the highest pressure. Across the bonnet itself you\'ll probably find the pressure is not hugely different from static as it\'s fairly flat and presents a low frontal area to the air you\'re trying to move the car through. In terms of airflow across the bonnet, without looking at wind then it\'s going to be dictated by the speed at which the car is moving through the air. There\'s not much in the way of aerodynamic addenda on the FC to create significant areas of low pressure under the car or high pressure in front of it.
In terms of generating some sort of ram effect for your intake, your best bet would be to position your air intake feed as far forward as you can, in front of the radiator so it\'s picking up the coolest possible air that is being forced into it by the car moving through the air. The largest area of suction will be directly behind the car in the low pressure left by the car forcing its way through the air. You might get some low pressure right at the point where the plane of the windscreen meets the bonnet at the air is forced over the bonnet but it would only be small.
Ahh Will... Eloquent as always. Great answer.
You\'ve seen my ghetto scoop havent you? Now say i was to get a cone filter and make a tunnel from scoop to behind and under the engine (think of the v-mount type setup or on kleers skyline), im guessing that could be a low pressure area there and create a ram effect.
Umm... Let me know what you think.
So you\'re trying to enhance the airflow passing the filter by taking advantage of a natural pressure difference between two points. Interesting and a good theory.
I think you might be chasing a negligible advantage here by routing a pipe from high to low pressure. You\'ll certainly get the best possible airflow by putting your air intake in an area of high pressure but until you\'re getting up to silly speeds (transonic type stuff at least) you\'re not going to get enough pressure difference using a ram-tube to get any additional suction. You\'d be best off looking at ensuring you\'re getting as much cool, fresh air to the air intake as you can than chasing some ram effect that is probably not going to make much difference until you\'re doing massive speed. Don\'t forget that the engine actively sucks air in so it\'s probably creating more low pressure than you could hope to just by running.
Here are the bits of testing autospeed have done:
http://autospeed.com/cms/title_Undertrays-Spoilers-Bonnet-Vents-Part-1/A_2159/article.html
http://autospeed.com/cms/title_Undertrays-Spoiler-Bonnet-Vents-Part-2/A_2160/article.html
http://autospeed.com/cms/title_Undertrays-Spoiler-Bonnet-Vents-Part-3/A_2162/article.html
I know that with an MX5 there is a good high pressure point next to the firewall, the best cold air intake is done by drilling through part of the firewall into the area where the wipers sit which has a high pressure due to the screen.
the only thing that really made me think about this is this...
(http://sphotos-e.ak.fbcdn.net/hphotos-ak-prn1/523271_469442923090326_1213437495_n.jpg)
notice the massive great hole in the bonnet for the air to come out after going through the radiator (which is at a 45 degree angle i think). obviously, the force of the air just going through the front is enough to push it through, but I was wondering if there would be any point in doing the same for an air filter, then the high/low pressure areas came into play. the thing is, even if it doesn\'t create too much difference with ram effect, I would\'ve thought the cold clean air being used only and directly for the air filter then being sucked out, creating one single continuous flow of air, and not going into the engine bay and swirling around, would be beneficial.
Personally, I\'d be using a side opening for an air intake which is open at the front into an airbox type arrangement. Similar to an OEM system which uses a dirty air duct from under the bonnet shut line through to an airbox, but without the DAD in this case. You\'ll probably get the most benefit of any ram effect using this method.
There is a lot of merit in using the scuttle panel and drawing in at the back of the bonnet - provided you have a good cross-sectional area for flow-in imo
It\'s proved the most popular/successful method on a few cars now for a cold air draw.
Remember that just behind the air filter is in negative pressure (gauge) anyway.
think of it as a basic air duct, such as standard, but more direct and rather than just ending in the airbox and swirling around until the intake sucks it in, its being pulled through and out underneath the car, so there is always direct air flow (at speeds, I\'ll get onto lower speed in a tick) through the "duct" and filter.
Now... I may be thinking too much... buuuuut... at low speeds, there won\'t be much clean cold, fresh air going through the duct, now, what if I made up some sort of retractable fan system, think radiator fans. So at low speeds (say 20mph or less) the fans are down and on, sucking air through the duct and air filter (one set of fans each end of the ducting), then, when the car goes over 20mph or maybe on a manual toggle switch, the fans are retracted up and out of the way to allow freer air flow through the duct.
Ok, just read those links m1tch stuck up... Third one was by far the most interestinh. From what i can tell, my ghetto bonnet vent (directly above the airbox) is in a low pressure area and is most likely throwing air out instead of pulling it in. Which sucks (or not as the cas3 may be).
So, two options... I extend my ghetto vent right down onto the front of the bumper, taking maximum advantage of the high air pressure area there, or i try the idea i previously outlined, combined with the vent extension.
Quote from: Skifledanabit;835930Now... I may be thinking too much... buuuuut... at low speeds, there won\'t be much clean cold, fresh air going through the duct, now, what if I made up some sort of retractable fan system, think radiator fans. So at low speeds (say 20mph or less) the fans are down and on, sucking air through the duct and air filter (one set of fans each end of the ducting), then, when the car goes over 20mph or maybe on a manual toggle switch, the fans are retracted up and out of the way to allow freer air flow through the duct.
Complex. Unnecessary imo.
Keep it simple, or you\'ll probably end up creating more problems for yourself later!
I\'d use the bumper.
What he said.
Waaaaay too much stuff to get maybe a tiny advantage at low speeds.
That massive hole in the bonnet of that car should be basically for a V mount setup, or they have moved the radiator to a slightly different position.
Remember that air flows from a high pressure to a low pressure, the bigger the difference in the pressures the faster the air will flow - have a read of the below article for the MX5 and you will see what I mean about a high pressure feed.
http://autospeed.com/cms/title_FreeFlowing-a-Miata-MX5/A_110680/article.html
Here is what I did on my Mazda 323F a while back, the intake (which is actually a landrover discovery foglight surround) was placed in a high pressure area on the bumper meaning that there was always high pressure air ready when the throttle butterfly was opened which helped with throttle response.
(http://i93.photobucket.com/albums/l49/m1tch_2006/DSC00006.jpg)
I would also suggest having a look at the brake ducts in the front bumper - my idea with them was that instead of the air flowing directly through to the brake ducts you could intercept the airflow into the front of the bumper, there is an air tank in the way on the drivers side but I think the passenger side is free to run something. Pop the headlights up and look down into the bumper you will see that there is already a cutout there for some air to come in and the rest flows to the brakes to cool them. Perhaps put a divider of plastic or something in 1 of the brake ducts and direct it into the engine bay though a duct - you may have to move those relays to get a hole or something.
Quote from: m1tch;835951Pop the headlights up and look down into the bumper you will see that there is already a cutout there for some air to come in and the rest flows to the brakes to cool them. Perhaps put a divider of plastic or something in 1 of the brake ducts and direct it into the engine bay though a duct - you may have to move those relays to get a hole or something.
That\'s what I intend to do once I get the courage to start cutting into stuff and the cash to buy a K&N Airbox setup :)