g00kb0i Posted July 30, 2008 Share Posted July 30, 2008 hello, im not sure if this is the right section to post this but i had a question and wanted your opinion's. i was wondering which way i should angle the radiator for better down-force from the front end? it will be fully sealed off and vented either way. the green is the radiator and the yellow is for the ducting. i keep thinking it's one way, but because it actually flows through, is it the other? im lost... thanks for your time guys. pic 1 pic 2 Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 30, 2008 Administrators Share Posted July 30, 2008 ***Moved to appropriate forum... *** Quote Link to comment Share on other sites More sharing options...
Challenger Posted July 30, 2008 Share Posted July 30, 2008 Not 2. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted July 30, 2008 Share Posted July 30, 2008 Mine is like pic #1 but not as radical of an angle. This should give you an idea of how I did mine. This shot is from my mock-up Dragonfly Quote Link to comment Share on other sites More sharing options...
g00kb0i Posted July 30, 2008 Author Share Posted July 30, 2008 i know #2 makes no sense, but from searching johnc states " It looks like your oil cooler is in front of the lower radiator core support. Bore a couple holes on the back side of the core support and add some reinforcement to the support itself. Run a belly pan to behind front corssmember and be sure to seal the front, top, bottom, and sides of the heat exhanger area so that all the air goes through into the engine compartment." so does this mean that it should not be vented through after the radiator? only pre-radiator? which makes me believe #2 without the ducting behind the radiator because the air will "catch" in front of the radiator with the ducting. my dilemma is that all the venting done to race cars seem to have it vented through the hood in which i plan on mimicking to try and reduce the front "lift" effect. such images of the vented radiator to the hood are as follow. i always thought that it was due to engine compartment space that didnt allow for these types of ducts to be utilized. where as in the s30z, the space is more adequate. Quote Link to comment Share on other sites More sharing options...
Challenger Posted July 30, 2008 Share Posted July 30, 2008 Thats some sweet pictures. What kind of cars? Quote Link to comment Share on other sites More sharing options...
g00kb0i Posted July 30, 2008 Author Share Posted July 30, 2008 sorry for misleading you guys, but the pics above are not my cars. just some pics of cars and interesting stuff that i save. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 30, 2008 Share Posted July 30, 2008 I'd like to see more pics of the second car if you have them. I think johnc was trying to say that if you have an oil cooler in front of the radiator and no seal between the air dam and the radiator, then the air doesn't have to flow through the radiator. By sealing everything up to the core support you ensure that the air going in has to go through the radiator. Once that is done, the idea is to get the air out of the engine compartment. Best way to do that is through the top or the sides. Out the bottom is worst in terms of downforce. Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted July 30, 2008 Share Posted July 30, 2008 My radiator is installed as in example 1. It has been tilted forward 48 degrees, and the bottom has been moved back to just forward of the sway bar. The radiator is completely sealed to the opening in the air dam wit ha rubber gasket. All air that enters the radiator exits through the hood. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 30, 2008 Share Posted July 30, 2008 What Jon said about my quote above - it was about cooling efficiency. I've actually never heard of anyone using the radiator as a downforce generating device. IMHO it wouldn't be very effective in that role because its supposed to have air lowing through it perpendicular to its orientation. Angling the radiator also requires angling the airflow to give it as straight a shot as possible. Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted July 30, 2008 Share Posted July 30, 2008 think of it this way: Air has inertia, whenever you deflect the air, its going to react with an equal and opposite force. So if you deflect air upwards (radiator air exiting out the hood) then the air is going to push down on your car, downforce. Its not really that simple... but for this sort of case, it is that simple. Quote Link to comment Share on other sites More sharing options...
g00kb0i Posted July 30, 2008 Author Share Posted July 30, 2008 thanks everyone for the help, greatly appreciated! but isnt the cause of the lift effect in the s30 due to all the trapped air in the engine compartment, therefore properly ducting 95% of the incoming air to pass the radiator as perpendicular as possible and then to continue to follow through the ducting to a vented hood? wouldnt that eliminate that effect and add down force in the process? here are the extra pics as requested. its from a mini and the website is as follows: http://www.kimini.com sorry but i didnt resize the pics on purpose so you can see the intricate fabrication work. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 30, 2008 Share Posted July 30, 2008 So if you deflect air upwards (radiator air exiting out the hood) then the air is going to push down on your car, downforce. I guess we're talking about two different things. I was referring to the radiator and you were referring to the ducting. Again, the radiator itself provides little, if any downforce - and it shouldn't if its going to operate efficiently as a heat exchanger. In my thinking, the ducting in front of the radiator should be designed to improve the efficiency of the radiator first, and then secondarily add some aero benefits. The primary aero benefit, IMHO, is to keep airflow through the radiator as limited as possible (per engine cooling requirements) to reduce drag and increase downforce. The ducting behind the radiator, in my thinking, should meet the same requirements as the ducting in front of the radiator, although the downforce benefits are very limited because the radiator reduces air velocity by an order of magnitude. Ducting at the front of the hood as pictured above has an indirect affect on overall vehicle downforce by exhausting high pressure under hood air into the low pressure area at the top of the hood. This reduces overall front lift by some amount. Quote Link to comment Share on other sites More sharing options...
g00kb0i Posted July 30, 2008 Author Share Posted July 30, 2008 which is why i have my two diagrams. at first thought, it was #1 because the the whole picture looked right, but as i thought about it, the impact of the initial high velocity air would work with #2. i remember reading somewhere that the air becomes turbulent and almost stagnant after the heat exchanger. this led me to believe that the air exiting after the radiator wouldnt matter as much. but at the end of the day, i still see #1 as being correct. so im lost... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 30, 2008 Share Posted July 30, 2008 Force air under the car = upforce. Force air over the car = downforce. As John says, the big benefit here is limiting the amount of air that comes through the the front end of the car. Stock the Z has a hole between the core support and the front valance, the core support and the hood, and holes on both sides of the core support. It's safe to say that more air gets into the engine compartment than goes through the radiator, and also that whatever gets in has to go out the bottom of the car, unless you have hood vents, and I don't think the 280 vents will evacuate all the air that comes in through all the holes either. When the air is forced under the car, you get lift. As a side benefit, the top of the hood is a low pressure area so air coming out of a vent or a radiator duct will get SUCKED out which should improve cooling. I don't know the specifics, but I've read of race cars with radiator fins removed to allow freer air flow. That might change the dynamics a bit and cause a ramped exhaust from the radiator like blueovalz and 74_5.0L_Z have to create more downforce than they otherwise would. Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted July 30, 2008 Share Posted July 30, 2008 While I was finalizing the design of my front end, I did a little bit of research. One of the best references that I found was a web site about cooling wankel powered aircraft. The author of the web page (Paul Lamar ) has since removed the content from the web and published a book with the content. The web page that links to the author is here: http://www.rotaryeng.net/how-to-cool12.html The web page and the book that sprang from it are a great compilation of data that sprang from research on cooling piston engine powered fighter aircraft at the end of World War Two. This book does a great job of summarizing the information from Kucheman and Weber's "Aerodynamics of Propulsion", and from London and Kay's "Compact Heat Exchangers". The book explores (among other things) two different but equally effective philosophies of inlet and outlet ducting. Kucheman and Weber's research led to a long inlet with a small front inlet that expanded smoothly until it got to the face of the radiator, and an exit that contracted as the ductwork merged with the body. Kays and London's design had the radiator laying nearly flat with a wedge shaped inlet. Both designs sought to slow the incoming air to create a high pressure region across the entire face of the radiator. Additionally both design philosophies accelerate the air in the exit duct to minimize drag. If I were to do mine again, I would probabbly lay my radiator down even further to more fully approach the London and Kays design. In fact, I would arrange it such that the top of the radiator was even with the top of the bumper and just behind it. If you are serious about designing a cooling system, read Paul Lamar's book. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted July 31, 2008 Share Posted July 31, 2008 I'm not sure how much impact this has on downforce but this picture is of a vintage race car that is running a V8 in the rear of the car and the little hole at the bottom in the front is the inlet for the radiator and it keeps that engine from overheating. Just guessing on this part but I think the low pressure created above the radiator helps to pull the air through at a volume that is somewhat proportional to the speed of the car. Dragonfly Quote Link to comment Share on other sites More sharing options...
g00kb0i Posted July 31, 2008 Author Share Posted July 31, 2008 isnt there a venturi effect that occurs 45* angles as well? so, the mainstream air that passes over the hood would draw out the air from front area of the car through the ducted radiator. kinda, sorta, maybe? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 31, 2008 Share Posted July 31, 2008 You're thinking Bernoulli Effect. It doesn't have much to do with the 45* angle though. Search on the web and you'll see it applies to all sorts of things from carburetors to airplane wings. Quote Link to comment Share on other sites More sharing options...
260DET Posted August 1, 2008 Share Posted August 1, 2008 For practical reasons some airflow under the car is required to cool the transmission components etc, unless additional coolers are used. But such airflow should come from the front via an undertray. If an undertray is designed to take advantage of the Bernoulli effect then such airflow generates downforce, not lift. This takes advantage of the situation often found with a road car where the front spoiler is located higher to avoid damage from speed bumps etc. Quote Link to comment Share on other sites More sharing options...
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