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240, 60, 80 Z Aerodynamics


EMWHYR0HEN

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Yeh, Nissan did a lot of aerodynamic work with the S130, for that and other reasons it is significantly a more stable car than a stock S30. One point concerns the headlight scoops, Nissan left them much as on the S30. Guess why?

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The best s30 would be around .38 this is full bellypan gnose all the works... that is where a stock s130 starts!!!! so' date=' to set the title straight ... it is not the 80's z! it is just the s30 that has the same basic aerodynamics as a piece of plywood ( ~.48 for plywood and something like .46 for a split window Microbus..) and the Z is somewhere in between !! I have to look up exact numbers...

 

The s30 is poorly designed in that matter .... if you look at the small lip where the hatch starts on a s130..... it is not there for no reason... those are the secrets that make it so much better than the s30 in this department (not talking looks here)

 

so if you want some good aerodynamics a s30 will not do the trick… that is why TonyD is going to use an s130 on the saltflats!

 

However how many times do you get upto 120 on a windy mountain road or even a track anyway ;)[/quote']

 

If you get the reaction research 280YZ body kit, it pretty much solves most of the problems.

img_49812_std.jpg

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Then, if you're interested in reducing the windshield problem you can lower your roofline and rake the windshield! ;)

 

I'm doing some extensive aero mods to my 240-Z to try and turn it into an open road racer that can still drive on the street (theoretically). I'm implementing a lot of the above advice to try and make the car as sleek (aerodynamically speaking) as possible. Here's what I'm doing.

 

1. - lower the roof and rake the windshield. There are some pics posted of what I did at... http://forums.hybridz.org/showthread.php?t=101672&highlight=chop+top (look at bottom of first page of thread)

 

2. - underbelly of car - I'm lowering the floor of the car (partly to give headroom after lowering the roof), and creating a completely flat bottomed floor. This underpan will extend from front to rear (under the engine, trans and differential). I may also integrate a 1/2-3/4 length diffuser as well.

 

3. - air management - The engine bay will be completely sealed... all air going in will pass through the radiator and come out through a hood vent. Separate ducts will provide air for the engine and brake cooling.

 

4. - front end body mods - I've created a new front one-piece nose with a smaller grill opening. It will dam air from going under the car. Also, because it is one-piece, there are fewer seams in which air can be trapped or "leak" into places I don't want it. Also, headlight covers are a must...

 

5. - anything else? - There will be a few other things... changing side view mirrors... trying to vent air out of wheel wells as best as possible... etc.

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Just visited your site

 

I love the roof line … however why are you going so wide on the rears.. this wil not promote aerodynamics… and even worse… how wide are you planning your rims to be ? The YZ kit witch by far is more subtle even uses 12 j rims to fill out nicely.. you would need.. well doubletires ..

 

However I like the Dearing approach…However IMHO you went a little over the top with flares ;)

 

I widened my zx aswel I just have to reproduce the front fenders and hood in glas or carbon

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No windshield yet. Haven't had much time to work on the car... I'm finishing up law school right now. Hopefully I'll be able to start doing a little more work on it starting late this summer.

 

Frank,

 

Yeah, I might have gone a little over-the-top on the flares... I may eventually trim them down a little if need be. I wanted to increase the track width quite a bit though.

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Actually i have no idea, so enlighten me, and us in that matter... as it does not strike me as being Ãœber effective in the aerodynamics department...

 

Apparently filling in the headlight scoops had a negligable effect on drag so Nissan left that area pretty much alone with the final production version of the S130, although they did consider a couple of alternative smoother looking designs. It is surprising, perhaps air blocked in front of the lights acted as a filler, directing air flow in a curve over and around the guards?

 

The 280ZX book published by Nissan at the time has quite a bit of info on the S130's aero development.

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Apparently filling in the headlight scoops had a negligable effect on drag so Nissan left that area pretty much alone with the final production version of the S130' date=' although they did consider a couple of alternative smoother looking designs. It is surprising, perhaps air blocked in front of the lights acted as a filler, directing air flow in a curve over and around the guards?

 

The 280ZX book published by Nissan at the time has quite a bit of info on the S130's aero development.[/quote']

I see, good to know. Wouldn't putting vents behind the wheel wells fix that problem? Oh wait production cost, lol.

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a proper air dam, vented or a louvered hood, and even venting the fenders (would require vents on the fenders AND through the support) would greatly reduce high pressure in the engine bay, and would help cool the engine..

 

a small hatch lip will stretch the vacuum or low pressure out a bit further behind the car

 

 

Now guys... we are not flying an airplane or doing a land speed record...

 

its a street car.. so everything is soo minute, it wont cause such a huge improvement..

 

wide tires for example.. wont make much of a difference

 

Hell .. it's 1970's technology... it looks good, and handles superbly..

 

what else do you want?

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wait.. I have an idea to reduce the pressure in the engine bay...

 

and its soo simple its dumb

 

 

Pop the hood open a bit... since it pops in the back, the hood still stays latched, and wont fly open like typical hoods that open in front..

 

 

The boundary layer, and air flow flowing OVER the hood, will actually SUCK the air out of the engine bay, therfore reducing engine bay pressure..

 

on top of pulling the high pressure air out of the engine bay, it will also help pull the HEAT out, and the fan will be more effective, and the car will cool faster.

 

Now the hood opens by the windshield.. which would be dumb, since there is an area of high pressure along the windshield...

 

depends on what you consider "high pressure" though..

There is a higher pressure gradient in the engine bay, that along the windshield.. soo in addition to the airflow over the e-bay sucking the air out, the higher pressure from the engine bay will flow to the "lower" pressure built up along the windshield.

 

 

 

also consider the turbo 'vent' on the 280zx's..

now technically your bringing cooler forced air into the turbo which would help cool some..

BUT.. what is happening at high speeds?? the RAM AIR effect... so your ramming even MORE pressure into the engine bay... at slow speeds it helps aiding in the escape of the pressure... but when your moving quickly.. it actually hinders the effect

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I think the widespread use of cowl induction hoods tends to point to the conclusion that the area of high pressure between the hood and the windshield is higher pressure than the area under the hood.

 

To my understanding this is why the vents on the 280 hood are so far forward of the rear edge of the hood. Because there is a high pressure area at the front, a low pressure area towards the rear of the middle (about a foot from the rear most part of the hood), then a high pressure area caused by the air hitting the windshield at the back.

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Because there is a high pressure area at the front, a low pressure area towards the rear of the middle (about a foot from the rear most part of the hood), then a high pressure area caused by the air hitting the windshield at the back.

 

Jon is right. It's an easy experiment to prove with yarn tuft testing. Cut some pieces and tape it to the hood and see how the air moves with the hood open and closed. I used to think this would help until I watched the yarn go into the engine compartment.

 

On my race car I put holes in the inner fenders in front of the strut tower to allow air to escape. I then added gurney's to my fender flares that could be moved out if I needed more airflow. And in front of the radiator I used a box to help slow the air as it hit the radiator face. Also make sure to use the stock belly pan or add an upgrade.

 

If I wasn't in FP at the time I would have made a duct that came out the hood for the radiator. Louvers in the front section of the hood would probably have a similar effect.

 

Cary

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wait.. I have an idea to reduce the pressure in the engine bay...

 

and its soo simple its dumb

 

 

Pop the hood open a bit... since it pops in the back' date=' the hood still stays latched, and wont fly open like typical hoods that open in front..[/quote']

Norm [the 12 second SU dude] said he would unlatch his hood, run the quarter mile and the hood would raise up like 12" or so, if I remember correctly.

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Well I havent pulled out any photos for a while. This is my take on aero mods. I dont have any recent ones but the hood is now vented before the struts to benifit from the low pressure there. I am just about to put the final undercoat on and sand it all back this weekend hopefully. The under tray goes as far back as the steering rack and the rear "diffuser" picks up on the angle of the petrol tank so I had to cut out some of the rear valence (spelling :wink: ) to get it all to fit.

 

http://album.hybridz.org/showphoto.php?photo=948&cat=500&ppuser=8086

 

Douglas

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Well I havent pulled out any photos for a while. This is my take on aero mods. I dont have any recent ones but the hood is now vented before the struts to benifit from the low pressure there. I am just about to put the final undercoat on and sand it all back this weekend hopefully. The under tray goes as far back as the steering rack and the rear "diffuser" picks up on the angle of the petrol tank so I had to cut out some of the rear valence (spelling :wink: ) to get it all to fit.

 

http://album.hybridz.org/showphoto.php?photo=948&cat=500&ppuser=8086

 

Douglas

do have any more pics? The front looks like a 350z kinda from the photo. The back looks to be an improvement.

 

Well would the belly pan that darius put on his be a big improvement?

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I think the widespread use of cowl induction hoods tends to point to the conclusion that the area of high pressure between the hood and the windshield is higher pressure than the area under the hood.

 

jmortensen .... you are correct, since cowl hoods pull the high pressure from the windshield and suck it down into the carb or engine bay...

 

However, this is true on some cars, and not necessarily for other cars...

 

the 240Z has that nasty firewall, which builds up tons of air...

 

YES there is HP on front of the windshield and HP inside the engine bay..

 

but which is higher?? Lets just say.. im just throwing random number out here.. but lets just say the engine bay has 25 pounds of air pressure at 100MPH .. and the front of the windshield has 18 pounds of air pressure at 100MPH..

 

The lower 18lbs of pressure on the windshield is lower than the 25lbs of pressure inside the engine bay.. High Pressure always flows to Low(er) pressure area's.. therefore ... there would be some suction going on..

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