rustrocket Posted April 20, 2004 Share Posted April 20, 2004 After reading a recent post on the extremely limited top speed of the Z car, (i have a 260) I did a search on diffusers and belly pans, but i was unable to find anything recent, or with working pictures. Can you guys share some of your experiences with making or using front/rear air diffusers and belly pans? Any pictures would be extremely helpful. Thanks Quote Link to comment Share on other sites More sharing options...
Guest miloz31 Posted April 21, 2004 Share Posted April 21, 2004 I install a aluminum front diffuser on my Z31 Turbo. I did it so it would direct the air flow into the intercooler. Good luck Quote Link to comment Share on other sites More sharing options...
blueovalz Posted April 21, 2004 Share Posted April 21, 2004 Using "diffuser" as the key word in the High Tech forum had about the best information on this subject, which hasn't been visited much since then. For some reason the pictures are not there. Quote Link to comment Share on other sites More sharing options...
TomoHawk Posted April 21, 2004 Share Posted April 21, 2004 I considered adding a belly pan, but then realized how difficult it would be to make. The bottom on a Z isn't that flat, with all the fuel & hydraulic lines, the suspension& driceline, and other frame pieces sticking out, would make fabrication difficult and the resulting bellypan would not be as 'smooth' as it should be. The next best thing would be to add a few deflectors underneath. Quote Link to comment Share on other sites More sharing options...
rustrocket Posted April 21, 2004 Author Share Posted April 21, 2004 Terry, I did try a search with "diffuser" before i posted this, and i did find some old info (with broken picture links) as you mentioned, but i was mainly looking for visual aids to get design ideas. Thanks for your help. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted April 21, 2004 Share Posted April 21, 2004 Yeah, the pictures were pretty good. V8Zed???? Not sure about this, but wasn't he the one that supplied pictures of this subject? Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted April 21, 2004 Share Posted April 21, 2004 Here is the bottom of a R34 Skyline for reference. I think I posted this on the old thread. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted April 21, 2004 Share Posted April 21, 2004 There is a fair amount on this topic. One of them I started where I've been working on a rear diffuser. Search "belly pan" or "rear diffuser" Some of the topics have not been updated for a while. I will add more to it as my car has come out to play for the summer again, and work will resume where i left off. This is my front belly pan. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted April 21, 2004 Share Posted April 21, 2004 http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=14817&highlight=bellypan Here is one of the larger topics. Scott. Quote Link to comment Share on other sites More sharing options...
TomoHawk Posted April 21, 2004 Share Posted April 21, 2004 How big is that (chin spoiler)? Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted April 25, 2004 Share Posted April 25, 2004 Do you mean the black strip? Its about 4 inches... about the same as lawn edging...as a matter of fact, exactly the same as lawn edging found a home depot! hehe Its a very old trick of mine. I don't care if it scrapes the ground. I get the air dam effect with out the worries of damaging my expensive air dam!. Nice and low.. When damged..replace! Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted April 26, 2004 Share Posted April 26, 2004 has your underbelly actually had any effects to the car? good or bad? I'm kinda curious.. i want do mine for protection and to keep air from the ground going up into the engien and out the hood. -Ed Quote Link to comment Share on other sites More sharing options...
johnc Posted April 26, 2004 Share Posted April 26, 2004 Go here: http://www.mulsannescorner.com/ Basically what you're trying to accomplish with a splitter, belly pans, and/or a diffuser is to accelerate the air under the car and creat a low pressure area. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted April 26, 2004 Share Posted April 26, 2004 Well I only have a couple of high speed runs under my belt since I had that pan installed. I've seen the high side of 140mph with the car feeling solid. Heck I even did something very stupid and gave the dude I was racing a thumbs up out the window at 135mph. I didn't feel like I needed both hands on the wheel to keep it straight. Stupidity aside, the car has felt very stable at speed. I have driven my car when it was flat stock, and I know the feeling most Z owners describe at 90mph+ The car doesn't wander at speed either (road surfaces not withstanding) even when passing trucks on windy days. I have no numbers to tell ya though.. only seat of the pants. (BTW the belly pan was my last mod... except for last year.) so I know the effects of the rest of the suspension on the handling. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 25, 2004 Share Posted May 25, 2004 the 76 280Z 2+2 Andy Flagg races at Bonneville has seen 173+mph, and was running a full belly pan. The front radiator grille was completely blocked off, so the comparison isn't really apples to apples, but without the front blocked and the belly pan in place the same car is around 10mph slower. And that's a considerable change, seeing as the engine looses HP by running the exhaust full out the back of the vehicle and not in the shortie dumps that it was dyno tuend with! Quote Link to comment Share on other sites More sharing options...
Guest z1 performance Posted July 1, 2004 Share Posted July 1, 2004 we are about to do one similar to the R34 style (front and rear) on my 280ZX...the car sees the better part of 160 now, but it gets quite twitchy Quote Link to comment Share on other sites More sharing options...
zguy95135 Posted July 1, 2004 Share Posted July 1, 2004 Wouldnt putting on a belly pan make the car body more of a wing? Just curious Quote Link to comment Share on other sites More sharing options...
Guest BigWhyteDude Posted July 1, 2004 Share Posted July 1, 2004 thats kind of the idea. Except your trying to make an upside down wing. So you get down force instead of lift. At least that how i see it... then again i did ride the short bus. Andrew Quote Link to comment Share on other sites More sharing options...
labrat Posted July 1, 2004 Share Posted July 1, 2004 The problem with stock Z's is that the air kinda "piles" up under the body while smoothly going over the top, creating a high pressure area underneath and eventually lifting the front off the ground if you have the nads to keep pushing it. The belly pan helps the air smoothly exit the rear of the car and keeps the pressure from building up. There is still a pressure differential between the top and bottom of the car, it just requires much higher speeds to achieve lift. (or lift-off, if you prefer). I still think the idea that the high-end ferraris use is the best. They use a full front-to-back belly pan with an hourglass shaped depression that tightens near the center, creating a venturi effect under the car, effectively "sucking" it down to the road. Very slick engineering. Bill Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 1, 2004 Share Posted July 1, 2004 actually, the air hits the FIREWALL, and piles up under the HOOD, lifting the front end. This is why both the G-Nose and the S130 have a below-the-bumper-line air inlet for the radiator, and most later vehicles are total bottom-breathers! The lift on the back end is aerodynamic from the shape of the decklid. But the lift up front is from that open maw ramming air against the firewall, where it acts similar to a diffuser turning velocity into pressure. The air speeding under the vehicle acts similar to an "air door" preventing easy exit, adding to the diffuser action of the firewall. By adding a Factory-Style Z432R bellypan, along with the G-Nose, the air admitted through the raidator is at the bare minimum to cool the vehicle (when I partially obstructed my G-Nose inlet, the car ran 15 degrees hotter, removed some of the offending items---teeth if you must know--the temperature went back down. Airflow therough the G-Nose inlet is only what it needs to be, and nothing more!) and this allows the FRP bellypan used on those models to smooth the airflow under the vehicle to almost the rear of the tranmission....where it acts like and ejector due to it's relatively highspeed, "sucking" air out of the tunnel and evacuating the engine bay of it's diffused airload. Clever, those Japanese One of the popular (though styling wise probably would not catch on here in the USA) is the addition of vents through the front wings relieving the pressure along the sides of the body. Holes are cut along the inner fenderwell to allow the pressure to relieve to the inner fender well, or through a duct to the outer fender surface. This is very effective, and if you look at the interiors of may high speed performance cars, you will see louvres near the rear of the engine bay venting to the wheel wells. Most hink it's for keeping underhood heat down---whit IS a function, but that can be accomplished through a simple 4" louvre. But having one square foot of louvres on each inner fender near the firewall (wichi is about the equivalent area of the radiator opening....) there is more to it than simply "heat evacuation". Remember, heat radiates UP... Not sideways. Overheating at speed is rarely a concern, it's in stop and go that underhood temperatures soar. So maybe a bit of "misdirection" is involved in the stated purpose of the vents. But then again, an automobile company would NEVER obscure a speed secret from the general public, would they? Quote Link to comment Share on other sites More sharing options...
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