EMWHYR0HEN Posted October 18, 2008 Share Posted October 18, 2008 The S30 roll pan looks like it catches a good bit of air under the car. I was thinking of cutting out this parachute to help reduce the drag. My car is far from show quality so I don't have such a problem doing so. I was thinking of cutting it out something like this: My roll pan is out of shape... and I don't think it looks too bad.... Anyone think this will actually work? Quote Link to comment Share on other sites More sharing options...
ihavearustedz Posted October 18, 2008 Share Posted October 18, 2008 I would keep it, and maybe make like a deflector? I dunno but it looks better with it. Quote Link to comment Share on other sites More sharing options...
CArFAn Posted October 18, 2008 Share Posted October 18, 2008 Cut it out and make a diffuser. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted October 18, 2008 Share Posted October 18, 2008 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 18, 2008 Share Posted October 18, 2008 Could you make that picture bigger please? Myron, I had considered doing the same and there was a picture of a Japanese car that had the roll pan cut off that was posted a couple years ago. If you're serious about this, I'd start checking out NASCAR photos, as they use the same basic principle to try and get a bit of diffuser effect. Now my intention is to do a diffuser. I set my fuel cell in the car so that the bottom of the cell lined up with the bottom of the roll pan and also the fenders. I figure a flat bottom should be pretty easy to make. One thing with diffusers is that they need to be close to the ground. Even though Darius's diffuser is very pretty, I don't think it is going to do much. There was an article in Race Car Engineering where they tested a Lotus diffuser and it wasn't doing much at all until they got the side fences down to about 2" off the ground. That's not going to be very street friendly... Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted October 18, 2008 Share Posted October 18, 2008 Here is what I did. http://album.hybridz.org/showphoto.php?photo=6309&limit=views The photo is about 4 years old. It looks a bit better now. With the 2+2 there is a kick up at the rear of the stock fuel tank and I just continued that angle up to the "roll pan". I am not ecpecting any down force but am hopeing the air wont get caught up in there anymore. Douglas Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted October 18, 2008 Share Posted October 18, 2008 Myron, Personally, I highly doubt the roll pan is contributing in any significant way to the amount of drag on the car. By the time the air gets back there its all completely turbulent and crap anyway. IIRC, the lower edge of your fuel cell is at or below the level of the bottom of the roll pan, so cutting it out isn't going to gain you much where the fuel cell exists. What could provide some benefit I think, it creating two channels on either side of the diff/fuel cell that head forwards and down to the front pivot of the rear LCA. Combined with a flat undertray all the way from the front splitter this I think would have positive effects. BTW, I have two quite good books on aerodynamics I could lend you if you don't have them already. J. Katz's `Race Car Aerodynamics' and S. McBeath's `Competition Car Aerodynamics'. Lemme know and I'll bring them over sometime. Dave Quote Link to comment Share on other sites More sharing options...
EMWHYR0HEN Posted October 18, 2008 Author Share Posted October 18, 2008 . There was an article in Race Car Engineering where they tested a Lotus diffuser and it wasn't doing much at all until they got the side fences down to about 2" off the ground. That's not going to be very street friendly... I've been browsing around and all the diffusers that claim to be functional are super low to the ground. Like this one for a C6 Vette With the S30's relitively high rear end this is going to be hard to achieve without making a super huge ricey looking diffuser. I think Jons right looking into the whole Nascar thing. Quote Link to comment Share on other sites More sharing options...
EMWHYR0HEN Posted October 18, 2008 Author Share Posted October 18, 2008 BTW, I have two quite good books on aerodynamics I could lend you if you don't have them already. J. Katz's `Race Car Aerodynamics' and S. McBeath's `Competition Car Aerodynamics'. Lemme know and I'll bring them over sometime. Dave That would be great! Surley, I need to get schooled on this topic. Quote Link to comment Share on other sites More sharing options...
260DET Posted October 19, 2008 Share Posted October 19, 2008 Cut mine out, left enough metal to bend in a flange to keep some rigidity there. In the pic the black stock fuel tank can be seen below the green bodywork. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted October 23, 2008 Share Posted October 23, 2008 Well I ended up doing the opposite. I have lowered my rear fascia (rollpan) to cover my fuel tank, and I will construct another rear diffuser (more for looks than anything else) I originally had another rear diffuser that I built, that curved up after the fuel tank. Understand though that my fuel tank is the 280 style, and hangs a bit lower than a 240 tank. The original use for the diffuser was to combat fumes getting into the cabin by reducing the turbulence under the car and reduce the vacuum effect/dead zone just behind the car. No the diffuser did not perform as intended, but neither did it turn the car into an airplane or other such unstabling factor. I did however install aluminum mesh in the lower fascia in the effort to let trapped air escape. Time will tell once the new diffuser is made whether it does its intended job, though I am not worried about the car getting less stable. I also intend on extending the front belly pan to cover the tranny tunnel from frame rail to rail, but that is a whole other thread which I will keep separate. As for cutting your roll pan, I do not think you should do it, unless you really want to getting into fabricating something along the lines of Darius's diffuser. If you want to do it "just because"..to experiement..to learn and have fun, then go for it, don't let any of us slow you down. I am enjoying watching your build. Scott. Quote Link to comment Share on other sites More sharing options...
janaka Posted October 23, 2008 Share Posted October 23, 2008 My $.02 input for this thread comes from other forums I'm on. Much like how Scott has cut a small section and put a grill over it to allow the air to flow through the rollpan many high-hp civic's and other imports do the exact same thing as seen below, albeit much more extreme in some cases. I've seen some people report decent improvements in ET's with them due to not having the 'parachute' effect... apples and oranges to our cars I'm sure. Babysteps - I'd say try this first, and when it doubt, cut 'er all out and see what happens. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 23, 2008 Share Posted October 23, 2008 Here's my "opinion" on this subject without any actual data to back it up, but with the knowledge I've gained in the two cars I've owned that have pretty decent bottoms and looking under a bunch of race cars that have incorporated difusers... Adding a difuser will likely negatively impact the performance, unless you do more to clean up the rest of the cars undercarriage. When we were at the tunnel the engineer commented that the bottom of the datsun is so ugly that you really do have better areas to focus on... Tom's Redbird has a diffuser and I'll wait until he gets it in a tunnel to confirm or prove wrong my thoughts on this. But I think ZR8ED has the right idea... Install a couple panels where air can escape and call it a day! Mike Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted November 8, 2008 Share Posted November 8, 2008 Just thinking out loud - but what if you constructed an entire underbody that you could bolt to the underbody of the Zed? Make it out of fibreglass possibly, So it looks something like this! That would fix up those aerodynamics underneath the Zed wouldn't it? Incorporate it so the front is bolted to the underside of a big spoiler and as mentioned previously, should be low enough at the back for the rear diffuser to do something! Lay down some really thin sheet metal, cover all areas, make a mould out of fibreglass, than make a final version out of fibreglass or carbon fibre and your away - timely as hell, but would this work? Quote Link to comment Share on other sites More sharing options...
Whittie Posted November 8, 2008 Share Posted November 8, 2008 tonycharger, I believe that would ultimately be the best thing to do, and if you look at a car like the Mk.4 supra they actually have cowling under most of the car. I believe its for legal reasons in Japan, however it does work to allow smoother flow of air under the car. The only glaring error i can see however is that if youve got the exhaust tucked up under that thing what are you gonna do to cool it down? And what about all that big air pocket youll be creating in the engine bay if the air doesn't have anywhere to vent. It would be interesting to see what they did on rally or even GT cars to deal with these issues. GT more so because i would think they're more aerodynamically orientated however i believe a solution on the Z would look more like something on a rally car. Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted November 8, 2008 Share Posted November 8, 2008 "The only glaring error i can see however is that if youve got the exhaust tucked up under that thing what are you gonna do to cool it down? And what about all that big air pocket youll be creating in the engine bay if the air doesn't have anywhere to vent." Yeah that floor pan is from a Ferrari 360, so engine is at the back -so no drama's with the exhaust, don't know how you would get around that one with a zed, be good to look under a mk.4 Supra see what is done there! For venting the air in the engine bay you could do something silly like this !!! http://album.hybridz.org/showphoto.php?photo=19602&limit=recent Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 8, 2008 Share Posted November 8, 2008 I have some pics of a 360 spyder underside to use as examples. Notice that the area under the driveshafts is only crossed by the wing shaped lower crossmember. The suspension pickups are outside the framerails. This leaves a nice "Tunnel" area under the Ferrari. Our Datsuns don't have this kind of space for a tunnel. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 8, 2008 Share Posted November 8, 2008 A better idea for the S-30 may be to simply smooth out the underside of the car and keep air from getting caught behind the rear roll-pan. Maybe you could figure out how to get the rear filled-in better ... Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 8, 2008 Share Posted November 8, 2008 Most modern sports cars have smooth undersides. I can take some pics of a Porsche, E-46 M3, Minis, and a Lancer EVO, etc. None of those cars have tunnels or diffusers, But they have near-perfectly flat undersides. The tunnel areas are covered and the lower control arms have plastic inserts to smooth them out. There are often trip-strips right before the suspension components(front and rear). I have also seen scoops or turnouts near the control arms to divert air into the wheel wells(brake cooling). Quote Link to comment Share on other sites More sharing options...
tonycharger72 Posted November 9, 2008 Share Posted November 9, 2008 I would love to see pics if you can get your hands on them? Particulary the M3! "I can take some pics of a Porsche, E-46 M3, Minis, and a Lancer EVO, etc" The M3 would probably be the only one that would bear similarity to the Zed, nice big straight 6 rwd car - be interesting to see if the exhaust is run up in the tunnel underneath the transmission and tailshaft and then covered!!! "The tunnel areas are covered and the lower control arms have plastic inserts to smooth them out. There are often trip-strips right before the suspension components(front and rear). I have also seen scoops or turnouts near the control arms to divert air into the wheel wells(brake cooling)." I would love to see pics of how the factory does this mate!!! Quote Link to comment Share on other sites More sharing options...
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