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Diffusers and belly pans


rustrocket

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Again,

 

They don't call aero a black art for nothing......

 

There are two concepts that address under body aero.....

 

1. Block as much air as you can from going under the car to minimize lift caused by the air being slowed down by obstructions (suspension transmission, exhaust, etc....

 

2. Guide airflow purposely under the car through smooth ducts which create downforce

 

Option 1 is much more common, but option 2 is what is used on professional race cars.....

 

For the Z car, well, probably option 1 since not everyone has computation fluid dynamics capability on his or her PC

 

a splitter is nothing more than a horizontal surface below the stagnant high pressure air right in front of the car.. this increases front downforce, which could make the car tail happy at high speeds........

 

for street cars, the general rule of thumb for the minimum speed the aero is effective is 60mph and above, although I designed an aero package for a specialized race car that needed downforce at speeds as low 25mph (it's top speed was about 70mph, so it's a different animal

 

as far as how low is too low, full bodied race cars have between .5 to 1 inch of ground clearance and computer generated aero packages specifically designed for the car. for a street car, I would not run less than 3 inches

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Well this thread has really gotten into a life of its own.

 

Does anyone have pics of their belly pans, diffusers, ground effects, sheet metal work etc?

 

I still only have seat of the pants feel, at 220kph the car is rock solid...problem is.. it was solid before.

 

Well at least it hasen't ripped off, doesn't hit the road in driveways, speed bumps etc. It doens't make any weird hums, thrumms, vibrations, etc. So I don't think it is negatively affected by the air traveling around it.

 

My areo experience derives from a lifetime of sailing experience, 5 years of sailing theory and practical training, 20 years racing catamarans, and one design mono hulls.

 

Anyone planning aero mods? I've seen very little on street Z's the few I have seen are friends that have copied my front pan.

 

Anyone interested in experimenting? I'll explain with some pics this weekend.

 

Scott.

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i have tons of ideas to help the aerodynamics but its most likely going to require heavy body style changes to get good aerodynamics. i don't really mind though as i'd rather have performance over style.

 

once i get my Z going i'll start throwing on a bunch of stuff using the ideas of others, if everyone is cool with that, and i'll try talking to some people at that school to get it in the windtunnel.

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normal_roof%20aero%20mod.JPG

 

 

This is an idea talked about in another thread here. I used my new 280zx as my model.

 

This is a pic of the roofline of a Z. The theory is similar to that of a rear spoiler on the back of the car. It is to spoil the smooth air flow over the car to reduce lift.

 

I'd like to see this effect alone on a car to see if it works or not. I'm sure it doesn't need to be too big to have some kind of effect on the car besides worse fuel economy. hehe

 

might reduce the dead air behind the car? I thought it may even reduce some of the fuming smell in the car. who knows.. I just thought I'd post it and see what you guys thought. It is super easy to build and test. A small piece of aluminum sheet would be enough. Test that in a wind tunnel.

 

or am I just nuts?.... don't anyone answer that last one...hehe

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3" it is for street(maybe four :roll: )(and lower for track :twisted: ). Add a small camera into the front fascia :) , customize the driveway :wink: and avoid speed bumps :? , and all should be good. :D

 

Super stiff coilovers and walla (yeah right like its that simple)

 

yeah I was wondering that, what about side skirts, what is the most beneficial design?

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Wouldnt that mess up air to the rear wing? I am guesing that vortex g's make turbulent air fill in behind the rear window and then make the rear seem a lot more tapered to the air flow so you woulndt get as much lift..?

Tell me more.

 

Douglas

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Is that what those are? They certainly don't look like any I've seen, but perhaps VG design has changed lately (like everything else these days). These simply look like nubs stuck along the top of the car. Perhaps these operate much like the ubiquitous supply of the so-called "ground effects" that can be stuck on any car.

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I would think that if one were successful in creating a pan, tray, sheet, etc, under the car that met all the characteristics of "ground effects", that it would require quite a bit of rigidity and a strong means of attachment. Otherwise, higher pressure above the pan, tray, sheet, would force it to separate from the unibody. A very small amount of pressure difference over the broad bottom panel's area would seem to make for easy separation.

 

Please see my comment about Andy's Underpan coming off at speed! :shock:

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