JMortensen Posted November 9, 2013 Share Posted November 9, 2013 Don't we already know that the cabin is a low pressure area when the windows are down? Isn't that why the exhaust into the cabin gets much worse when the windows are down? If you have a reference port and a test port, try putting one of them in the engine compartment and one on top of the hood where the vents won't affect it. That way at least you would be measuring the pressure relative to the hood itself. If you have the same pressure top and bottom, you know that you have no lift or downforce (which would be a pretty big deal). If there is a pressure differential, then you can see if you have net lift or downforce. Two or three other quick easy tests you might try, all involving your existing hood vents. The louvers look relatively small. 1. Put a simple angle gurney in front of the louvers to try and get more turbulence over the vent to improve their effectiveness. 2. Remove the louvers and try the open hole. 3. Try open hole with the gurney in front. Could also test the top and bottom of your splitter. Yeah. I can see how this would get addictive. Quote Link to comment Share on other sites More sharing options...
duragg Posted November 10, 2013 Share Posted November 10, 2013 I had been having hood blow-open problems at real high speed. Added a second vent to the hood and cut out all the little fingers to make a more bigger opening. No more hood popping. Temps that were 210 dropped considerably (even tho I was running at lower altitude). Pics to follow. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 10, 2013 Share Posted November 10, 2013 (edited) So I think the cabin is influencing the numbers. When I checked above and below the pic right behind the Z emblem I should be at 1.5" lift. When measured both together its only ~0.7-0.8". Moved and tested delta pressure right behind the vent in the pic above and got only <0.1" lift. Still unfortunately havent measured any downforce When I stopped to make the last change a cop pulled up and checked my license. Guy I shouldnt have stopped near a railroad track at night but that put an end to my testing for the night. Was hoping to check the splitter but oh well. Jon - I tried 280Z vents, then just open hole, , then open hole with trip strip at leading edge, and now these louvers and to be honest seat of the pants didnt change although I never measured it precisely with the pressure gauges. Edited November 10, 2013 by heavy85 Quote Link to comment Share on other sites More sharing options...
Sideways Posted November 10, 2013 Share Posted November 10, 2013 So I think the cabin is influencing the numbers. When I checked above and below the pic right behind the Z emblem I should be at 1.5" lift. When measured both together its only ~0.7-0.8". Moved and tested delta pressure right behind the vent in the pic above and got only <0.1" lift. Still unfortunately havent measured any downforce When I stopped to make the last change a cop pulled up and checked my license. Guy I shouldnt have stopped near a railroad track at night but that put an end to my testing for the night. Was hoping to check the splitter but oh well. Jon - I tried 280Z vents, then just open hole, , then open hole with trip strip at leading edge, and now these louvers and to be honest seat of the pants didnt change although I never measured it precisely with the pressure gauges. Might I suggest a magnehelic gauge ? I bought me off ebay for peanuts. Quote Link to comment Share on other sites More sharing options...
duragg Posted November 10, 2013 Share Posted November 10, 2013 These are ZX Turbo vents I think. With little fins cut out Great lengths to ensure they cleared STBs Quote Link to comment Share on other sites More sharing options...
AZGhost623 Posted November 10, 2013 Share Posted November 10, 2013 (edited) Well you could always go with a reproduction Datsun Competition hood scoop like mine. =) That should definitely alleviate any kind of pressure buildup under the hood. Cut the middle hump out, and bolt this guy in. Hood does not lose any rigidity... http://i801.photobucket.com/albums/yy299/77s30/ZdayZ%202k10%20trip/DSCN0846.jpg http://carphotos3.cardomain.com/images/0016/52/25/16172552_large.jpg Edited November 10, 2013 by AZGhost623 Quote Link to comment Share on other sites More sharing options...
ZT-R Posted November 11, 2013 Share Posted November 11, 2013 Once Beta makes a 1 piece hood mold ill buy it... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 11, 2013 Share Posted November 11, 2013 No more beta motorsports. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 11, 2013 Share Posted November 11, 2013 No more beta motorsports. Really? What happened? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 11, 2013 Share Posted November 11, 2013 http://forums.hybridz.org/topic/115508-betamotorsportscom-is-no-more/ Quote Link to comment Share on other sites More sharing options...
260DET Posted November 26, 2013 Share Posted November 26, 2013 (edited) Pic of open Road Registered class winner at Phillip Island recently. Against a R35, GT2 and a couple of GT3's so his aero is worth noting, RB26DET helps of course. Edited November 26, 2013 by 260DET Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 27, 2013 Share Posted November 27, 2013 Cameron, thought you might like to see this; interesting testing using magnahelic guage and manometer to quantify the downforce. It's more about the underside, but note that there is NO tray in the middle, and he still gets pretty awesome results... http://www.e90post.com/forums/showthread.php?t=629051 Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 27, 2013 Share Posted November 27, 2013 Cameron, thought you might like to see this; interesting testing using magnahelic guage and manometer to quantify the downforce. It's more about the underside, but note that there is NO tray in the middle, and he still gets pretty awesome results... http://www.e90post.com/forums/showthread.php?t=629051 Interesting. Reads like a lot of assumptions go into converting pressure to downforce so its hard to believe those numbers but maybe? Hes definitely on the right track. Something I've thought a lot about but find basically zero tech on is how to best flow air from the rear wheels to the diffuser. Should you have full inner fender or poke a vent out the side behind the tire or ?? Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 27, 2013 Share Posted November 27, 2013 (edited) Pic of open Road Registered class winner at Phillip Island recently. Against a R35, GT2 and a couple of GT3's so his aero is worth noting, RB26DET helps of course. I need max downforce force hill climbs (ave mid 60 mph with top speed just over 100) and wonder how effective thise vertical fences on the side of the spliiter. Pikes peak style so Im sure they do something just again have trouble finding tech on it. Edited November 28, 2013 by heavy85 Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 28, 2013 Share Posted November 28, 2013 Interesting. Reads like a lot of assumptions go into converting pressure to downforce so its hard to believe those numbers but maybe? Hes definitely on the right track. Something I've thought a lot about but find basically zero tech on is how to best flow air from the rear wheels to the diffuser. Should you have full inner fender or poke a vent out the side behind the tire or ?? What he did is what I'd expect to see. Area multiplied by pressure drop to determine overall load. Ideally that would be backed up by load cells or suspension displacement but as long as the pressure drop is real then the downforce should be there. For your rear tires if you want the best possible sealing there should be a wall that all the suspension passes through for the rear diffuser. This is typical of tunnel cars from FA to IMSA GTP. The ALMS GT level cars do different things based on the class because the rules are different. Where they can a wall runs along the tire. If the rules don't allow it then the tire sidewall is treated like a wall in the diffuser. Another interesting car to look at that has some different ideas is the Mighty Mouse CRX. It's running 1320 lbs at 100 MPH according to what has been shared. He also shared the lateral acceleration number for the AIM data logger showing 2.65Gs so I'd guess the downforce number is very real. Barry Lock designed the aero for the car. They have enough shared on their facebook page that you could probably come up with something very close. Here's a link to a speedhunters articel on the car (http://www.speedhunters.com/2012/12/giant-killer-the-mighty-mouse-crx/) Cary Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 28, 2013 Share Posted November 28, 2013 I need max downforce force hill climbs (ave mid 60 mph with top speed just over 100 and wonder how effective thise vertical fences on the side of the spliiter. Pikes peak style so Im sure they do something just again have trouble finding tech on it. Racecar Engineering has done a few aerobytes columns on splitter side fences. It doesn't always translate but it seems that a rectangular flap up to around hub height generates max benefit. You can also use a device called an S-flap that's essentially a vertical gurney on the leading edge of the front fender. This helps to increase the extraction of the fender and lowers overall pressure connected to the splitter (i.e. a powerful tuning device). From Jeff Braun (https://www.facebook.com/AutoRacingTechTips) S FLAP - This is a small aero bit you will see on many sports cars. See the picture here. Its the small black vertical tab right in front of the tire. It is a super effective way to make downforce on the front of the car. As the air flows along the side of the nose it encounters the S Flap and is tripped outward much like how a Gurney flap on a wing trips the air. So the air is forced outward and that creates a low pressure or suction right behind the S Flap. Hold that thought. Inside the wheel well there is a high pressure from the air under the car and inside the wheel. This air is trapped in the wheel well and can't get out. It pushes up on the inside top of the wheel well and tries to lift the nose off the track, reducing the grip of the tire because it makes less downforce. You see louvers on top of the fenders on may sports cars to vent this high pressure air and restore the downforce and grip. So adding the S Flap and its low pressure right behind it "sucks" more of this high pressure "bad" air from the inner fender and helps make more downforce. Its very efficient (lots of downforce for little drag) and simple and cheep. Why is is called a S Flap? Not exactly sure but sort of looks like a S shape from the side. I prefer to think its after Sam Garrett the designer of the Kudzu GTP Lights cars. Sam and I used them on the cars back in the day and we found how great they were in the Lockheed tunnel in Atlanta in the very early 90's. But I am sure they date way earlier than that. Have a look at all the sports cars and see if they have S Flaps. You will even see them on a Funny car. Cary Quote Link to comment Share on other sites More sharing options...
260DET Posted November 28, 2013 Share Posted November 28, 2013 (edited) I need max downforce force hill climbs (ave mid 60 mph with top speed just over 100) and wonder how effective thise vertical fences on the side of the spliiter. Pikes peak style so Im sure they do something just again have trouble finding tech on it. Without a wind tunnel all us amateurs can do is read stuff and try to apply aero principles. I have a similar setup to what you are talking about but mine started off as a vertical plate to cover that part of the front tyre that projected past the airdam, looking at it from the front. It then developed from there. They are becoming fairly common on time attack cars particularly. The S flap Cary mentions could possibly be incorporated into the design too. The red Z pictured also has front and rear diffusers, he has developed that car over a lot of years so even without a wind tunnel my guess is that his aero all works. The lap times he does could not be explained otherwise. Edited November 28, 2013 by 260DET Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 28, 2013 Share Posted November 28, 2013 Is there anymore info on the red Z in the pics? It looks like an interesting car. Cary Quote Link to comment Share on other sites More sharing options...
260DET Posted November 29, 2013 Share Posted November 29, 2013 Above is about all I know about the red rocket Cary, it does have a big rear wing which can be glimpsed in the pic. Front diffuser is central, not one each side exhausting into the wheel wells. Quote Link to comment Share on other sites More sharing options...
Gareth. J. Posted November 29, 2013 Share Posted November 29, 2013 (edited) Here's a rear shot of the Z Edited November 29, 2013 by Gareth. J. Quote Link to comment Share on other sites More sharing options...
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