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Aerodynamic data for 240Z needed & cooling idea


pparaska

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DOH!!!! A guy less than 2 hours from me just sold a G-Nose for $100! In good shape too apparently. Someone on the other side of the US bought it and he's now got to box that sucker up and ship it to him (sob). I've told him that if it falls through I'm ready and willing to take it off his hands :-)

 

Has some other good parts too - seems he's about to build an SCCA racer from a car he dragged up from New Orleans. He should've used my '72 shell instead but I never advertised it anywhere (smack again!).

 

ah well, he's got some doors, I'm buying his NEW steel hood, and maybe a good bit of the interior for spare parts too :-) The G-nose is what I really wanted, we'll see what happens. I've got a glass hood on the way already, I really am not sure I want to do a ton of bodywork on this car - I'd like to actually DRIVE it with a V8 someday (smile).

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I read a Road&Track acticle from the late 70's or early 80's that said the ZX's improved aerodynamics was most do to the front windshield having a more sloped angle. In SpeedRacers article about his beautiful 250 GTO he states that Ferrari did extensive wind tunnel testing resulting in a very slippery design. Mark

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Has anyone found aerodynamic information on the IMSA GTU cars?

I'm interested in a belly pan. It seems like you could really "shoot yourself in the foot" if you did it wrong. You could end up with a really good airfoil.

Any information would be greatly appreciated.

Thanks,

Al

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I used to have contact with a guy who ran the Nevada SSC and he had given me some very interesting info on aerodynamics. His car was an L6 motor pushing about 12 PSI boost and he was getting into the lower 170s on a regular basis. He say and average speed increase of 4 miles per hour in the top end sections of the run when using headlight covers AND he noticed that the steering became a little more precise at speed.

 

I have had my previous Z into the 160s and the car floated even with road race suspension and side skirts and spoilers. The way I plan to attack this is with a chin splitter, belly pans, and some sort of rear end difuser. Problem is that youcan do more damage than good if you aren't carefull. How will I get to know if the mods work??? I'm gonna try to get some sponsore support as I get closer to actually heading out to Nevada so I can get to a wind tunnel. We'll see.

 

As for the G-nose.. the nose was designed to combat the exact issue of the nasty reverse angle grill/ sharp edge of the hood. The only way to use that nose visually and make it work is with fender flares, which I have. I'd be up for putting one on if it made the car handle better at speed.

 

I to am extremely interested in all the info you guys find. I'm shooting for an 2001 appearance in Nevada, but my impending marriage may push that back yet one more year.

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

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Mikelly wrote:

quote
I to am extremely interested in all the info you guys find. I'm shooting for an 2001 appearance in Nevada, but my impending marriage may push that back yet one more year.

 

Woah, so you decided to tie the knot! Congratulations to both of you!

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Guest Anonymous

hey mike, congrats on getting married. now the hard question. who's first: car or wife. well if wife see's this then it's her of course. ha ha. congrats again, chris

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Can someone educate me on (chin splitters and rear diffusers). What do they do and how do they do it?

Is there any aerodynamic info available

for the assorted rebody kits,some of them look very slippery, but so does the stock Z

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The chin spliter... a good example is on the Red 2003 concept Viper on the cover of this months road & track. A chin spliter is mounted to the front spoiler and lats horizontal and sticks out forward of the car as much as 8 inches depending on the need..,. What it does is catch air that forces the nose down towards the ground. A rear difuser helps the air that collects at the back of the car better exit the shape of the vehicle.. That rear difuser is what got the Mercedes in trouble last year at road atlanta... You know the one that took flight.. Oh, wait, that was in 1998. Anyway, you have to be real carefull with those.

 

As for Belly pans, equal attention must be given to them and veins, and channels must be properly designed within them as well or the car will again act as a foil.

 

What we are ideally trying to achieve with aerodynamics is to really cheat the wind and get air flow to assist in forcing the car to the ground. Figure that out, and HP is a non issue. Botch it and you might look at getting your pilots license because these babies will take flight with out any aerodynamic assistance. Monkey with the dynamic airflow around one of these and you can do more harm than good.

 

People thought I was crazy when I first put a whale tail on my Zs back in the late 80s, but I had data from this old racer I knew and it proved that those big wings (Some of them anyway) really worked and created as much as 2000# of downforce.. They work at speed. Now, the front chin spliter can achieve the same effect. There are some who think that you should A: Leave the rear of the car slightly up in the air, and have the front closer to the ground, creating a wedge. Run coil overs up front, run a chin spliter and a belly pan under the front of the car, only up to the firewall. And then run a big wing on the rear. Side skirts are also desired as is a nose extension of some sort, usually a g-nose. Supposedly this is the recipe for getting the car to behave at 180mph. I'll find out...

 

The sad thing here is that this guy I used to converse with... Years ago I thought I knew everything.. I was 23 or 24 and he critiqued something I built and it pissed me off, and I threw his number away... I was young, and very stupid, and his assistance was invaluable to what I wanted to do. The pride of a young man can be dangerous. Wish I had his number today..

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

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  • 3 months later...

woohoo! i get to drag up an old thread! wink.gif

 

i was wondering if anything new had been determined about either cooling or (more importantly) aerodynamics in the past... three months.

 

also, while you all talk about 160, 170, 180mph, i am more interested in speeds half that. how stable is a z at highway speeds? would the g-nose improve anything in that speed range? i'm still in my "excessive planning till i can afford anything" phase here, so i must know! wink.gif

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quote:

Originally posted by pauli:

also, while you all talk about 160, 170, 180mph, i am more interested in speeds half that. how stable is a z at highway speeds? would the g-nose improve anything in that speed range? i'm still in my "excessive planning till i can afford anything" phase here, so i must know!
wink.gif

 

 

I'm also interested in this. I've noticed that driving an early Z above 85mph can be unnerving, especially with a crosswind.

 

Any info on how lowering or body kits affect this?

 

BTW, has anyone noticed that a raised pickup truck can be a greater aerodynamic "obstacle"

than an 18-wheeler?

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Michael (our resident aerodynamicist) will hopefully chime in soon. I'm sure raking the windsheild would help some, but the slope of the back window is important as well. Now changing THAT would be a bit of work!

 

The way it was explained to me was a good rule of thumb is that asking the air to turn more than about 7 degrees is asking for flow separation. I'm sure I've missed some nuances here or totally messed this up, but I think the idea is sound - decreasing the angle the hatch makes with the horizontal-ish direction of the air coming over the roof would keep the flow attached and get rid of the large vortex behind the roof/hatch line (or a bit further down the hatch).

 

Actually, the way Michael explained this to me (while sitting at my kitchen table drawing some sketches), a spoiler creates a stagnant vortex at the lower end of the hatch that serves to let the flow separate up higher on the hatch and do away with some of the vortices at the back of the car.

 

Man, I know I've screwed this up now. confused.gif

 

Michael, help!

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Guest Anonymous

I hate really really long messages. This should be a normal message board damnit! smile.gif

Any s30 is just a pathetic example of aerodynamics, as is any other car from the 70s.

A spoiler, in addition to helping create a light high pressure area in front of it, more importantly, breaks the flow over the top of the car cleanly as it spills off the trunk/hatch lid. That's why all modern cars have subtle spoilers or a raised lip in the trunk!

The door sills are no good, they're nice and rounded which helps encourage airflow out from under the car(which is bad). Ever notice how all newer cars have much more angular transitions from the side of the body to the undercarrige between the wheels?

The rear of the car is too blunt(Note how much less blunt it is on 280ZXs - much flatter hatch and also longer hatch)

The grille opening is waaaaay too big - my 300ZX with much more power gets by with an opening of something like 10x50cm or so and runs nice and cool on 100% 105F days with the AC on! I think the 30x60 chimney sized opening on an s30 is a major killer and also totally unecessary. But damn it looks cool!

but regardless, with an air dam and a tiny spoiler my car feels fine at 100-110mph even with the gimp worn out suspension! Once I get new tires and suspension it should be fine at any speed I think.

For whatever it's worth, I've made a manometer and am going to toot around with it this evening and take pressure readings all over the hood, cowl, and nose area. Also inside the front wheelwells and between the grille/radiator just FMI (for my info!). I also conned a pair of friends into helping me tape lots of string bits to the front of my car and take pictures at various speeds... film should be back from developing soon.

 

 

 

------------------

Morgan

http://z31.com/~morgan/s30

http://carfiche.com

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I'll be especially keen to hear pressure's from the front wheel wells fwd of the tires and rearward as well:-)

 

Their's a reason rads and airboxes have been tucked in their on some v. 'neat' cars smile.gif

 

I'd quite enjoy an airbox up front behind my drivers headlight in the wheelwell;-) I've heard it can be quite a high pressure zone, be curious how it measures on a 240 but especially on my ZX. How'd you make your manometer Morgan? I have a digital temp guage with a 3' lead on it but haven't got to using it yet:-(

 

------------------

Of all the things I've lost, I miss my mind the most.

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i'm glad i'm not the only one interested in normallish highway speeds smile.gif

 

something occured to me the other day: would the aerodynamics improve if you chopped a few inches off the top of the car? how about if you chopped it, and took the opportunity to lay the windshield and rear windows down to slightly more sedate angles?

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Guest Anonymous

Wheelwells are always high pressure, that's why rain spray blows out around the wheels and gets the side of your car so dirty!

On a 240 though, the area in front of the radiator is great - clean air, easy to plumb things up there, and lots of room!

I thought about putting an intercooler in the engine bay with air ducted from a wheelwell many times, but it would get real dirty in the rain and pick up leaves and general road garbage and really isn't worth the trouble to me.

 

 

------------------

Morgan

http://z31.com/~morgan/s30

http://carfiche.com

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Hey ross, i do think an airbox behind the headlights is a good idea. Just think about the mounting position of the oil cooler on a zxt! Pass side, kinda hidden in the front of the wheelwell.

 

Evan

 

PS i thought of putting an oil cooler in my wheel well, and still mighty. Corky bells maximun boost shows ICs in wheelwells with a thick mesh screen over them to keep rocks from turning them into swiss cheese!

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