Chewievette Posted March 5, 2006 Share Posted March 5, 2006 I dont see how the wheel wells are a low pressure area on these cars. Unless my car is missing some parts, very likely, then there is a huge pocket where air gets traped directly behind the front wheels. Cutting a hole in the exterior metal and venting it outboard will promote smooth airflow. That or install an inner fender shroud like most modern cars have. Another idea that I had was to reduce the drag created by the headlight buckets. If you can move the acctual headlight foreward by an inch or so that will allow air to flow around the light and into the inner fender. This air can then be vented overboard through the wheel well or just aft of it. Or if you really want to get creative duct it down to your brakes, the more air on those the better. btw, moving to a smaller diameter light in combo with this mod will get more of that air out. The only way you will be able to get your car up to and past 200mph and not feel like it's going to fall apart is to completely rebuild it from the ground up, new suspension, up to date aerodynamics, basically redo everything. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 10, 2006 Share Posted March 10, 2006 Interesting drawing. If you'll look at the 280ZX windtunnel effect you'll note the air flow across the rear hatch. It does appear to breakaway midway up the glass because of the small flatter area extending out to the rear of the car. That area is actually the low pressure area as well as the rear panel of the car. It seems that the S30 holds the high pressure tightly to the hatch until it reaches the rear of the car because no rapid change to the rear hatchbody exists. As it exits over the rear panel it pulls the low pressure air upwards. Opening the windows accentuates the induction of fumes into the interior. Look at it like this...a pickup truck with the tailgate shut creates a fixed low pressure area with stagnant air. Items in the bed aren't tossled around. If you drop or remove the gate then high turbulance is created and everything is sucked out forced against the back of the cab as high pressure tries to fill the void. Back to the S30, the rear spoiler helps to create a low pressure area helping to reduce fume induction. The problem is it happens too little and too late. You need to get the high pressure air off the body much sooner. I have a window louver and BRE spoiler and still deal with fumes (lots of other work in progress to reduce this). Someone mentioned in another post that affixing small tubular pieces perpendicular to this air flow could induce early tubulance and creat that low pressure area we long for. No one would likely care for it as it wouldn't be appealing visually. For experimental purposes I am going to affix half-round tubing or small spoilers to the upper half louvers of my car and test that theory. They will be in the range of 1/2" to 3/4" to hopefully promote some measurable effect. Painted black they should not be too obtrusive to the eye. If it actually worked then maybe two or three could be be attached across the top of the hatch glass to promote the same affect. These could be made from half-round plexi stock and glued with clear silicone again to reduce the visual impact and possibly pass state inspection too. Just another thought... Quote Link to comment Share on other sites More sharing options...
scott19 Posted March 10, 2006 Share Posted March 10, 2006 I had thought that adding a spoiler or small wing (similar to the 80's Supra) at the top of the hatch would be beneficial, but TonyD ripped me a new one over at Zcar.com when I posted my intentions to do so. Still don't quite understand why it wouldn't help break the air away from the hatch, but oh well. Ezzzzzzz, can you do a yarn test on your idea when you do it? Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 10, 2006 Share Posted March 10, 2006 I'll try to yarn test when it's back on the road (hopefully soon!). My idea is that the use of a tubular deflector or a small spoiler(s) would help create more of this valley with the aid of the rear deck spoiler. It certainly doesn't fix the inherent problem but might help diminish it to some degree. If you look at any car today you'll see that there is always a valley or subtle V shape from the top of the roofline to the rear lip of the vehicle. This valley creates a low pressure area (look at the 280ZX again) allowing the high pressure (read high speed) air to break away from the vehicle near the roofline and straighten out. Without that valley the high speed air wants to hug the body. On our S30 this high speed air is only detaching off the surface at the rear hatch lip. As speed increases this creates lift and also sucks the low pressure air (and exhaust) behind the rearend up to meet it. A spoiler doesn't really help push the rearend down but does help create an inverted airplane wing effect. That low pressure effect aids in pulling the car downwards as the air passing over the vehicle (longer distance) attempts to keep pace with the air flowing under the vehicle (shorter distance). Look at the 280ZX again. You can see this effect as the higher speed air is several inches above the trailing edge of the car, not hugging the sheetmetal. That same low pressure extends outward off the back of the body. The way I see it is you are reducing the difference in hi/low pressure at the trailing edge. This difference reduces the tendency of the exhaust being pulled back against the rear panel but instead allows it to move more easily away from the vehicle. I'm no engineer but it seems reasonable to me when I look at wind tunnel photos. Lastly, think of a golf ball. The dimples aren't there to look pretty. They create a multitude of low pressure areas that allow the high pressure air to more easily slip over, under and around. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted March 10, 2006 Share Posted March 10, 2006 Try adding a vortex generator to the back of the roof similar to the EVO MR. I've been wanting to experiment with this. It should create a vortex and keep flow attached down the hatch. There was a little bit of discussion on this in an ealier thread. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted March 10, 2006 Share Posted March 10, 2006 A vortex generator creates a small vortex (in this case) which mixes stagnant boundary air (on the surface) with moving air helping to keep the high speed air attached to the body. I was thinking you would want to prevent this on the S30 body. On the EVO MR it helps move more air onto the rear wing aiding in downforce. It would be interesting to see a windtunnel smoke test of a stock S30 and then additional photos of spoiler, vortex generators, etc. Anyone got access to one? Quote Link to comment Share on other sites More sharing options...
Chewievette Posted March 11, 2006 Share Posted March 11, 2006 If you were to attach a piece of "L" channel to the top just ahead of the hatch perpendicular to the air flow it would act as a mini spoiler and separate the flow from the hatch. Simple, effective, and not too visually revolting. I think you can go two ways with this, attach a small spoiler like I just said and separate the air before the hatch or use vortex generators to stick the flow to the hatch then use a BRE spoiler to create downforce at the tail end. Personally I would go with the latter but I'm no aerodynamicist. You will need something to create downforce on the back end so either go with a spoiler or a wing. Check out the Lamborghini Jota it uses a wing on the roof and a small integral spoiler on the back. I have never seen complaints of lift on those, of course I've never seen one on the track. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted March 11, 2006 Share Posted March 11, 2006 I've just noticed. On the wind tunnel pic, they are only testing the area fromt he leading edge upward and not testing the lower portion. Quote Link to comment Share on other sites More sharing options...
scott19 Posted March 11, 2006 Share Posted March 11, 2006 There was a bit of discussion on an earlier thread concerning the vortex generators sold on http://www.airtab.com , but I think they be too large for our use. If you're right Ezzzzzzz, these ( or any vortex generators) wouldn't work on the roof. However, what about a spoiler on the rear deck lid with generators affixed on the upper surface? Any chance they might dissipate the invisible cloud following a S30? Quote Link to comment Share on other sites More sharing options...
Chewievette Posted March 11, 2006 Share Posted March 11, 2006 Aircraft use very small pieces of what look like "L" channel arranged in a "V" pattern on the leading edge of their wings, I'll try to find a pic right quick. Go to the hardware store and pickup some aluminum 1/2" "L" channel, cut it into 1" sections and attach to the roof, seems pretty easy to me. Quote Link to comment Share on other sites More sharing options...
scott19 Posted March 11, 2006 Share Posted March 11, 2006 Chewie, would the "V" shape be pointing toward the front or back of the car? Quote Link to comment Share on other sites More sharing options...
Chewievette Posted March 11, 2006 Share Posted March 11, 2006 doesnt much matter, its the angle that the air hits them that is the key to creating the vortex. In the pic provided the leading edge is to the left. Quote Link to comment Share on other sites More sharing options...
Synlubes Posted March 11, 2006 Share Posted March 11, 2006 Chewie, would the "V" shape be pointing toward the front or back of the car? If you go to the Air Tabs link posted earlier you would see that the air flows into the v-shaped section not the pointed end. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted March 11, 2006 Share Posted March 11, 2006 Acctually on aircraft they are usually arranged in pairs with the point of the V foreward. check out this link it shows this clearly. Also if you read through, instead of them "providing the control surfaces with more power" they allow the rear mounted spoiler to create more downforce. Think of an airplane's aileron in the up position, same idea. http://en.wikipedia.org/wiki/Vortex_generator Quote Link to comment Share on other sites More sharing options...
Oleh Posted March 11, 2006 Share Posted March 11, 2006 offtopic what book is that scan from ? and were can i get one ? /offtopic Quote Link to comment Share on other sites More sharing options...
scott19 Posted March 12, 2006 Share Posted March 12, 2006 Hmmm. Well, correct me if I'm wrong, but it seems that Vortex generators are NOT the way to go, because the problem with the S30 is lack of separation, and vortex generators essentially ( if I'm reading right) promote adhesion of the air to the surface on which they are mounted. Quote Link to comment Share on other sites More sharing options...
Hypertek Posted March 12, 2006 Share Posted March 12, 2006 http://www.rs-watanabe.co.jp/underpage/photogallery2/dai.htm Quote Link to comment Share on other sites More sharing options...
Chewievette Posted March 12, 2006 Share Posted March 12, 2006 Either way you go you are creating drag so it depends on what you want the air to do. I was saying to use vortex generators to keep the air stuck therefore increasing the downforce that a rear spoiler can provide. Unless you are planning 100mph+ on a regular basis I wouldn't worry about it. If you are, I would suggest consulting an aerodynamicist who specializes in race cars. Quote Link to comment Share on other sites More sharing options...
scott19 Posted March 12, 2006 Share Posted March 12, 2006 Yeah, I was thinking the opposite: breaking the air loose to dispel the fume cloud following the S30. I'm gonna go buy some yarn today and do some experiments myself. I've got part of a set of louvers from a 280ZX that I'm going to take apart into separate pieces. If I can think of how to attach it temporarily, I'll try my makeshift wing/spoiler in diffrent spots and see how it affects things, if at all. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted March 12, 2006 Share Posted March 12, 2006 The new HOT ROD magazine with a cuda on the front has an article in it about areodynamics. even though it is on a 32 ford there is a lot of information of what causes lift and how to decrease it. they have several test results and pictures from a wind tunnel Quote Link to comment Share on other sites More sharing options...
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