Tony D Posted December 14, 2006 Share Posted December 14, 2006 The Cd effects and top speed effects of the G-Nose are pretty well known. (top speed increases from 200 to 215kph for example...) We don't need to test what we already know works. What we need to test are the imponderables of years of marketing hype have made us think this part is aero or that part is aero... Knowing in the back of our minds full well that they most likely didn't ever test squat! Now, On G-Noses what is not known is the effect of the KNOCKOFF G-Noses. I have seen good ones (Japanese) and very poor ones (Most North American Produced Crap...). The five piece pictured on the body thread is a very near replica of the stock G-Nose, and has the proper tray to the radiator. But many of the knockoff G-Noses use shorter trays because they are one-piece, and the shorter apron makes it easier to pop out of the mold. The aero effects of diffusers within the G-Nose opening, Closing up of the G-Nose opening, lack of the proper apron compared to a properly reproduced G-nose, that popular JDM "Spook Spolier" on the front of a G-Nose... That could be a day in itself, but it's a moot point. The way to make it work like a stock Nissan Nose is to make the apron go to the lower radiator bulkhead and seal properly. Then at least even the cheap noses will give the same aero properties as the more expensive units. What will be interesting to see is if there is a combination of flow alterations people can make to give a near or similar effect as a G-Nose without the high cost. Though I do agree, the 'with or without headlight covers' is a basic test that should prove interesting. I actually have an old, complete one-piece Japanese G-Nose laying around, unfortunately it's got broken mounting tabs... No time to fix >:^( Link to comment Share on other sites More sharing options...
madkaw Posted December 14, 2006 Share Posted December 14, 2006 Well I'm hoping a Kaminari falls into this test somewhere:-) . I would like to think all that money i spent on that expensive air dam was not just for looks. I realize and that all this parts swapping with be cumbersome in one day and wish you all well in this project. Hell , I hate to say how much time i have spent in trying to mount my Kaminari . I will be donating shortly for what i feel is a worth while cause. Link to comment Share on other sites More sharing options...
bjhines Posted December 14, 2006 Share Posted December 14, 2006 Well.. We are going to try 2 very different air dams.. We may find time for the stock valence with the spook... There are a dozen various airdams and I have it on good word that there will be very little difference between them aside from actual clearance to ground.. that can be made up with lawn edging on any of them... The ureflex will provide data on common streetable air dams... We have an MSA type3 that has some unique features that allow for blocking off most of the airflow through the radiator openings... If someone can deliver a G-nose to either Raleigh NC or Greensboro NC.. then we can get it in the plan... keep in mind that we need to drill a few holes and we cannot be financially responsible if something bad happens in all the handling... That is a tough pill to swallow considering the rarity and expense of those G-noses... Link to comment Share on other sites More sharing options...
David Spillman Posted December 14, 2006 Share Posted December 14, 2006 Hi Guys, I look forward to learning of results of all the tests of different appendages for our beloved Zs. I race a ITS SCCA 240z...basically stock car with few variations other then airdam in front, containing brake ducts, lowered a couple or so inches maybe. Over the last couple of years shooting the breeze with other z-guys, the topic of allowing the deck lid to be free to rise has come up from a couple of serious racers "Faster then me"...Now I have used a bungee cord last couple of years in order to free the hatch to "rise" if needed, but I haven't ever really noticed it moving. Does air going into side windows need a way out? Through the hatch? Dosen't make a lot of sense, other then the hatch rising slope, decreasing helps reduce lift? Would be a quick and easy test to prop up a couple of inches or inch. Here is a video of on track racing from a VW Corrado that was behind me, and I can't see any lifting of Hatch.....good look on 3-4 lap coming down front straight.....http://ww2.bildon.com/ARRC_2006_ITS_Race.wmv Good drive on Road Atlanta........If I only had a V-8, the Vettes, or red vette wouldn't have got me....... We need a baseline number starting without rear spoiler anyway I would think....Would be a quick change over. Does anyone know how long it takes this tunnel to cycle off and on? David Link to comment Share on other sites More sharing options...
Sparky Posted December 14, 2006 Share Posted December 14, 2006 Well.. We are going to try 2 very different air dams.. We may find time for the stock valence with the spook.. I would love to see that happen, but can understand if it doesnt. A direct comparison of the stock valance with the spook followed by the typical MSA air damn would be very interesting. I would also be extremely interested in seeing the effects that some front canards attached to the typical MSA air damn would do. Link to comment Share on other sites More sharing options...
Globerunner513 Posted December 14, 2006 Share Posted December 14, 2006 lol i can't believe **** is still flying at zcar.... anyways i'd be interested in seeing what kind a difference a rear bumper ('75+) would have versus a shaved rear end? probably something you could do the math for...but another idea since so many of us are bumperless(including me) Link to comment Share on other sites More sharing options...
Carl Beck Posted December 14, 2006 Share Posted December 14, 2006 Cygnus.. thank you for the ideas... The fact is.. that everytime i get a list together someone pops up with even more good ideas.. and the testing schedule gets updated... It looks like we can cover all the common parts except the G-nose... it is just too valuable and too hard to mount and dismount quickly... that said.. we are still trying to decide if we are going to put a G-nose race car in the tunnel at the end of the day to just get some old school numbers... this would depend on a lot of things lining up with the sun and the moon... We also have a splitter/underpan/rear diffuser all lined up for testing.. as well as roof mods and hood mods and a pantera deck... The facility has the equipment to gather data on airflow through ducts, pressure at many points, much more can be interpolated later... Hi bjhines (everyone): I applaud your efforts and like the idea of spending a day in the wind tunnel with a 240-Z. Exactly why I like that idea, I really don't know! The truth is, I don't know exactly what physical measurements can be taken in the wind tunnel. That is to say, I don't understand what test equipment the car would be hooked up to, nor the type of data that test equipment would report. I'm hoping that you might be able to give me some specifics related to the actual test equipment hooked to the car, that would measure the physical effects of the aerodynamics being applied - as opposed to the intrinsic discussion of the aerodynamics themselves. I noticed that Cygnus - suggested "measuring" lift/down-force at speed. Is that something that is actually measured in a wind tunnel? For the tests conducted by Car & Driver in 73 as I recall - they hooked a car up to a device that measured body deflection from standard ground clearance as the car was driven at speed - and then computed the amount of lift or down force being applied to the front or rear of the car. Is a physical device like that used in a wind tunnel? He also suggested plotting drag, which would imply that it to was being measured, as well as identifying pressure points at key locations vs speed. Is there now some test equipment that actually measures the drag created by an object in a wind tunnel? (I was under the impression that drag was calculated from either frontal area or total surface area) Do they have 3D scanners in the wind tunnels now to provide that data? Or perhaps in a stagging area ahead of the wind tunnel? In your reply above - you seem to indicate that data related to airflow is really all that is "measured" (for lack of a better term on my part)... and perhaps high or low relative pressure points could be measured... Any help you can provide in understanding exactly or specifically what is going to be measured or what is not actually measured, but rather computed or estimated in this project would be greatly appreciated by me. It's not so much a matter of knowing what aerodynamic devices work, as it is a matter of knowing which one's have a positive effect great enough to justify the cost of applying them. thanks, Carl Carl Beck Clearwater, FL USA http://ZHome.com Link to comment Share on other sites More sharing options...
Carl Beck Posted December 14, 2006 Share Posted December 14, 2006 Hi Guys, ...snipped.... Does air going into side windows need a way out? Through the hatch? Dosen't make a lot of sense, other then the hatch rising slope, decreasing helps reduce lift? Would be a quick and easy test to prop up a couple of inches or inch. ......snipped..... David Hi David: As I understand it - the Kamm back design used on the First Generation Z's has the effect of forming a turbulent high pressure area at the end of the car. That high pressure area is what forces exhaust gases into the passenger cabin, when the rear of the car isn't properly sealed. When you roll your windows down, that exhaust smell gets worse. (the opposite of what you would expect) That is because the high speed airflow along the sides of the car create a low pressure area, that is, lower pressure than that in the cabin. So when you roll the windows down - while outside air is forced in and circulates with the passenger cabin - cabin air also actually gets sucked out the side windows. Somewhat the same effect as air flowing over the top of a chimney (heat alone doesn't push smoke up a 20' chimney - ie, Venturi effect). Roll the windows up, and open the Z's Fresh Air Vents in the front of the car - and the exhaust smell gets better (ever so slightly)... because the forced air induction from the front of the car is now creating a slightly higher cabin pressure, but still not higher than the area behind the car... Add a rear spoiler and the exhaust smell is greatly reduced. That is because the effect of the Kamm back's turbulent high pressure area is effectively moved farther rearward, and the exhaust gases are no longer held as tightly against the rear of the car. The pressure differential between that high pressure area behind the car and the lower pressure area within the passenger's cabin, is not as great as it was before the rear spoiler was added. FWIW, Carl B. Link to comment Share on other sites More sharing options...
Mike kZ Posted December 14, 2006 Share Posted December 14, 2006 Welcome Carl!! and great info! Would you happen to know what a Supra style wing does to airflow, and does it help fumes? I've noticed that fume issues are not that bad in my car. Link to comment Share on other sites More sharing options...
Carl Beck Posted December 14, 2006 Share Posted December 14, 2006 Welcome Carl!! and great info! Would you happen to know what a Supra style wing does to airflow, and does it help fumes? I've noticed that fume issues are not that bad in my car. Hi Mike kZ Thanks for the welcome. I know several of the people here and have been a lurker for several years as well. No I don't know what would happen to the air flow with a Supra Style wing added. I've never seen any tests with that type of device on a Z. On first appearance, I would venture a guess that it would have to move that high pressure area at the rear of the car, farther back and perhaps a little higher. That one would be a good "test case" for the wind tunnel. It would be especially fun to move it's mounting position up/down the slope of the rear hatch to find the best position. That being where the down-force it applies is high enough to cancel any lift at the rear wheels, without adding unwanted drag to the vehicle. Is it possible to adjust the angle of attack on that type of wing? I can't recall, without going back to look - but I believe one method of measuring increases or decreases to aerodynamic Drag on a vehicle is a "Cost Down Test". You run the car up to 70 or 80 mph, then let it coast down to about 30 mph. Then you measure the distance it took. Below 30 mph the effects of aerodynamic drag are minimal compared to the physical drag from the tires and drive line. There was at one time a wing type "airfoil" made for the 240Z, but I've not seen one actually on a car for at least 25 years, nor seen one tested by anyone. http://zhome.com/History/Images/72Broc4.jpg 240Z Airfoil Of course the Wail Tail on the 79 280ZX-R's was most effective on the track, at offsetting Lift without adding too much Drag. FWIW, Carl B. Link to comment Share on other sites More sharing options...
bjhines Posted December 14, 2006 Share Posted December 14, 2006 The wind tunnel has a force table... as well as many different sensors for flow and pressure through ducts and pressure at specific points on the body... 32 channels of data... The force table can be raised and lowered as well as pitched while the tunnel is operating... The spin up time for this tunnel is no more than 2 minutes... so we can shut it down.. change parts and fire it up again fairly quickly... Rolling wheels are also an option... Link to comment Share on other sites More sharing options...
David Spillman Posted December 14, 2006 Share Posted December 14, 2006 Hi David:...snipped.... That is because the high speed airflow along the sides of the car create a low pressure area, that is, lower pressure than that in the cabin. So when you roll the windows down - while outside air is forced in and circulates with the passenger cabin - snipped The pressure differential between that high pressure area behind the car and the lower pressure area within the passenger's cabin, is not as great as it was before the rear spoiler was added. ...snipped... . Carl , I agree with your statements, but I'm interested as to why a couple of top drivers of both RX-7s and 240s would make claim of needing hatch to rise, helping to increase top speed....or have I been "misinformed/misdirected" david Link to comment Share on other sites More sharing options...
JMortensen Posted December 14, 2006 Share Posted December 14, 2006 Hi David:As I understand it - the Kamm back design used on the First Generation Z's has the effect of forming a turbulent high pressure area at the end of the car. That high pressure area is what forces exhaust gases into the passenger cabin, when the rear of the car isn't properly sealed. When you roll your windows down, that exhaust smell gets worse. (the opposite of what you would expect) That is because the high speed airflow along the sides of the car create a low pressure area, that is, lower pressure than that in the cabin. So when you roll the windows down - while outside air is forced in and circulates with the passenger cabin - cabin air also actually gets sucked out the side windows. Somewhat the same effect as air flowing over the top of a chimney (heat alone doesn't push smoke up a 20' chimney - ie, Venturi effect). Roll the windows up, and open the Z's Fresh Air Vents in the front of the car - and the exhaust smell gets better (ever so slightly)... because the forced air induction from the front of the car is now creating a slightly higher cabin pressure, but still not higher than the area behind the car... Add a rear spoiler and the exhaust smell is greatly reduced. That is because the effect of the Kamm back's turbulent high pressure area is effectively moved farther rearward, and the exhaust gases are no longer held as tightly against the rear of the car. The pressure differential between that high pressure area behind the car and the lower pressure area within the passenger's cabin, is not as great as it was before the rear spoiler was added. Hi Carl. Welcome. I have to take issue with, I don't think that is right. The turbulence in back of the car is not high pressure turbulence. It's LOW pressure turbulence. The reason the exhaust gets into the cabin is because it is SUCKED in, not PUSHED in. Flow separation, the cause of the turbulence, creates low pressure. Cracking the windows creates suction inside the cabin via the Bernoulli effect, so now you have suction inside the cabin and vacuum at the rear of the car, and that REALLY sucks the exhaust into the cabin. Any little hole allows air back in, and since that air is turbulating all the exhaust, that's what gets sucked into the cabin. I do agree that opening the fresh air vents increases the cabin pressure, and that works against the vacuum which is trying to force air into the holes in the rear of the car. That is why positive pressure works. I am not an expert, I only know what I've read here and elsewhere, but the bottom line for me is that you need some sort of deflector or barrier to create positive pressure, like air hitting the radiator, the windshield, or a spoiler. Just pulling the car through the air creates a negative pressure behind. Why can't you run fast in a swimming pool? Because when you try to move you create a huge turbulent vacuum behind you, and that tries to suck you backwards. Same thing with a car through the air, just a less viscous medium. If you created positive pressure behind, then you'd actually go faster for having it there. We worry about drag, but not about "push". Link to comment Share on other sites More sharing options...
dr_hunt Posted December 14, 2006 Share Posted December 14, 2006 Well, I donated, so there. Link to comment Share on other sites More sharing options...
clint78z Posted December 14, 2006 Share Posted December 14, 2006 Some good info guys, and another great curtious discussion. I plan to donate next month, I just find it intresting with no direct benifit to me. There can be a lot of really great info possiblities here if planned out right. Optimize brake cooling, air inlet temps, cross wind stabilty, rear diffuser, chin splitter. One thing I have always found helpful in dealing air flow is think in terms of absolute pressures instead of gauge. Air always flow from higher pressure to lower pressure, it avoids a lot of confusion. Link to comment Share on other sites More sharing options...
Mikelly Posted December 14, 2006 Author Share Posted December 14, 2006 Well we're just a hair north of $1900 AND I'm buying a SHOWCARs Gnose from Ken Jones and donating $100 of that purchase to the cause, and offering up the loan of the GNOSE for the test SO a GNOSE is available with and without spoiler... AND I have other news... Our Friend Mark Frasier who was known as hybrid77z on both HybridZ and Zcar.com won't be causing trouble on either site anymore... got a note from the GREAT STAFF at Zcar.com apologizing for his bad behavior and letting me know that they INDEED DO support this effort! Gang, we're close to meeting the goal funding-wise... It's up to BJ and the crew from the Triad Zcar Club to finalize the test plan... I have a larger/Taller IMSA three piece rear spoiler, a MSA type 1 and type 3 spoiler/airdam and now this Gnose. I've also got some authentic Japanese bolt on ZG Style flares to offer up! Mike Link to comment Share on other sites More sharing options...
Sparky Posted December 14, 2006 Share Posted December 14, 2006 Well we're just a hair north of $1900 AND I'm buying a SHOWCARs Gnose from Ken Jones and donating $100 of that purchase to the cause, and offering up the loan of the GNOSE for the test SO a GNOSE is available with and without spoiler... AND I have other news... Our Friend Mark Frasier who was known as hybrid77z on both HybridZ and Zcar.com won't be causing trouble on either site anymore... got a note from the GREAT STAFF at Zcar.com apologizing for his bad behavior and letting me know that they INDEED DO support this effort! Gang, we're close to meeting the goal funding-wise... It's up to BJ and the crew from the Triad Zcar Club to finalize the test plan... I have a larger/Taller IMSA three piece rear spoiler, a MSA type 1 and type 3 spoiler/airdam and now this Gnose. I've also got some authentic Japanese bolt on ZG Style flares to offer up! Mike All great news! Can't wait to pony up some funds for the effort, should be coming your way in the next week. p.s. dont forget the canards! Link to comment Share on other sites More sharing options...
Tony D Posted December 15, 2006 Share Posted December 15, 2006 Yesss.... The "discussions" at zc.c.... Er... Anyway, on the discussion of the Kammback design, take close notice of the S130's rear roofline. There is a little trip line to interrupt the flow over the hatch---resulting in less lift compared to the S30. There are some who have argued with me that "such a little thing can't have that much effect" but indeed with the smoke tests published by Nissan, you can see the flow effect of that little dip just before the hatch upper seam. A Small device at the rear of the S30 would probably achieve similar effects of lift reduction without the imposition of a drag inducing spoiler. Dirty the flow off the back of the roof, and the lift is effectively lessened. I know when we got our first record at ElMirage, the car ran almost back-to-back runs of 140 and then 143 mph. The wind was nil, and the temperature was higher on the second run, but other than that the only difference was removal of the smaller style BRE Spolier off the hatch. The car did have traction problems above 100mph, and ultimately adding about 200# of lead shot over the rear axle got us another 10mph due to increased traction! So my estimation is that the BRE Spolier should show 200-300# of downforce on the rear axle, at the expense of drag, at a speed between 135 and 145mph. This tunnel testing will stop estimations of what is observed, and quantify it once and for all. But with just this little test, one could see wether adding a "dip" to the back of an S30 Roof would achieve similar gains as adding a spoiler, without the drag penalty. I can't do it, but you can be darned sure that I'd put such a modification on my turbo street car! I digress! LOL Off to the Group Z meeting, I will pimp the effort, and try to drum up some more donors! Glad I made it home in time for the meeting and resultant whoring of the effort to the membership! LOL Link to comment Share on other sites More sharing options...
madkaw Posted December 15, 2006 Share Posted December 15, 2006 money sent!! Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 15, 2006 Share Posted December 15, 2006 Well we're just a hair north of $1900 AND I'm buying a SHOWCARs Gnose from Ken Jones and donating $100 of that purchase to the cause, and offering up the loan of the GNOSE for the test SO a GNOSE is available with and without spoiler... knowledge is power! Link to comment Share on other sites More sharing options...
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