Aerodynamics of a bug

[Sandeep]

Thanks for the link to the article. It expains alot.

So am I right in concluding that pan modifications (venturi) on a bug will have a negligible effect on downforce ? The article said that the car would have to be very low to the ground for the venturi to work ?

Sandeep

[chigger]

Negative! The car can be high, but the closer to the ground the greater the effect of a venturi. To get around this and have sufficient down force you will have to hang a rubber skirt down to direct the air through the venturi. On a street or race car the rubber will eventually wear. I am going to use what is called industrial wall edging. It goes around the wall where it meets the floor to give a clean look in a factory. It is stiff, cheap, and readily available at Lowes or Home Depot. It is usually vinyl and about 1/8 inch thick.
Think of a venturi )( and then draw it on the bottom of your car.
])([ The )( part goes from the forward two body mounts on each side to the rear of the wishbone. AH crap I wish I could draw this as it is simple as dirt. Anyway you would pop rivet 1/2 inch aluminum angle in to the proper curve to the pan then pop rivet the vinyl to the aluminum letting hang down to the gound. You should trim the vinyl a little, but it will wear down as you drive the car till it is perfect. Warning the waist or narrow part of the venturi must be about six inches foward of the jack mounts. The jack mounts are the CG of the car and the max down force should be before them to keep the front end on the ground.

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])([
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The ][ is the edge of the pan.
This is still not a clear picture, but I hope it is better than before.

[Michael Ghia]

One thing that I have been looking at is wing/fender vents.

These are used in racing on full bodied cars. Holes or vents are placed at the top of the front wings, just behind the centreline of the wheel and then again at the back of the wing close to the bottom to release the pressure which builds up within the wheel well.
Thinking about the air when it is travelling around the front of the car, a lot of it is deflected around the front wings and in behind the wheel creating drag and also a small amount of lift as it has to go down to the bottom of the wing to get out.

At the back, a vent at the back of the rear wings does the same job of lessening lift as the air from inside the wheel well struggles to get out.

One of the big problems I have looked into on my car is how to get air to the engine. I thought about putting naca ducts in the rear windows but the bodyshell starts to taper in from the door pillars and this may create more or a vacuum at the rear windows than pressure if I were to fit ducts there.
Another idea was one I saw on a Bug which had a mid-mounted configuration where rear vents from a T3 had been fitted just below the rear windows to feed the engine. Again this is just after the bodyshell starts to taper in.

Another idea I have seen is from Porsche racing cars. The GT1 uses a duct which runs over the top of the roof, where as I'm not too into the looks of this on my Oval roof! I can appreciate how well this must work. One other idea has come from the 962 where the fan intake is on the roof, it's basically a huge naca duct which feeds only the fan to cool the engine. Looks pretty cool and if almost out of sight although it means cutting a large hole in the roof!!!

Lots of ideas!! Anyone got anymore?

Thanks

Mike Ghia

[Racelook]

Originally posted by Michael Ghia

One of the big problems I have looked into on my car is how to get air to the engine. I thought about putting naca ducts in the rear windows but the bodyshell starts to taper in from the door pillars and this may create more or a vacuum at the rear windows than pressure if I were to fit ducts there.
Another idea was one I saw on a Bug which had a mid-mounted configuration where rear vents from a T3 had been fitted just below the rear windows to feed the engine. Again this is just after the bodyshell starts to taper in.

How about Remmele kinds airintakes that are made in the sidepanels.. I have them too!!!

Another idea I have seen is from Porsche racing cars. The GT1 uses a duct which runs over the top of the roof, where as I'm not too into the looks of this on my Oval roof! I can appreciate how well this must work. One other idea has come from the 962 where the fan intake is on the roof, it's basically a huge naca duct which feeds only the fan to cool the engine. Looks pretty cool and if almost out of sight although it means cutting a large hole in the roof!!!

That's what i maybe are going to make a duct on my roof of my bug!!! But i'm still thinking of it (expescially about making it rainclose..)

Lots of ideas!! Anyone got anymore?

Thanks

Mike Ghia

[Alex]

I am still going to cover my floor as much as possible with 2 venturi channels in the back. I hope to work with Carbon Joe on this so that he can sell the stuff later.
I am also planning to close off the fender as much as possible to reduce air getting trapped there. I hate to cut the fenders and use any kind of spoilers on my split.
Rolf Klaus also told me that there was actually a kit available for the front of a standard to close of the gaps and holes at the front beam. He has an original that he thinks of reproducing.
He also send me a video that I still have to convert to NTSC and then to digital for the site from one of his autobahn cruises with his split.

As for getting extra air into the engine.....Gerd Weiser has a scoop under the pan on his Oval and routes the air into the engine compartment....similar as what Sandeep did for his interior oilcooler.

When I had my bug in Germany with the T1 was not scared to drive at 180km/h. I did it all the time and that was without a fancy suspension. Konis all around and lowered quite a bit without swaybars.
The brakes were the scary part........VW disks on the front and drums at the back.

Alex

[chigger]

I am going to incorporate an air channel at the base of the wing with a slight curve to force air into the top of the deck lip. You want to try not to have it forcing air into the carbs as that can upset the carbs fuel metering.

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If you can figure out this picture you are a better man than I am.

[boygenius]

I wonder if wider fenders would help or hurt handling at high speed. Say 150 mph (240 km/h).

[Richie]

Hello,

Wider fenders would certainly hurt top speed. Take a look at the Ruf CTR, this was at one time the fastest road going car. This was also due to the narrow body Ruf used. If he had used the Turbobody is would have cost him certainly 15 km/h in top speed. But, do you really want to go 240 km/h in a bug?
My racecar lifted almost 10 cm ( about 4") at 210 km/h at the main straight. This was without any spoiler though, and 2" wider fenders. So.....

Cheers,
Richard

[vujade]

on one of Porsche's cars when they changed to a smaller mirror, they were able to go 3 mph faster. So, Im sure wider fenders would have a negative effect.

[Sandeep]

I will be interested in seeing what the difference is going to be when my bug hits the road in spring 2004.

I'm sure my top speed will drop with 18" wheels and wider fenders but by how much will be interesting. I'm sure the weight of the car will increase as well but by how much is the question.

Sandeep

[boygenius]

Well now I have a reason to buy the RUF mirrors. I'll just need more power to push against the wind.

[boygenius]

Originally posted by Richie
Hello,

Wider fenders would certainly hurt top speed. Take a look at the Ruf CTR, this was at one time the fastest road going car. This was also due to the narrow body Ruf used. If he had used the Turbobody is would have cost him certainly 15 km/h in top speed. But, do you really want to go 240 km/h in a bug?
My racecar lifted almost 10 cm ( about 4") at 210 km/h at the main straight. This was without any spoiler though, and 2" wider fenders. So.....

Cheers,
Richard

Yes, yes I do. There are some pretty fast cars around my neighborhood. Supercharged viper w/900 hp. A 9 second grand national. A 9 second mustang who's my neighbor. And one really fast 930 wide body which I have only seen once at a car show, garage queen. And yes I want to go 240 km/h at least just to beat those cars. What can I say, I have high expectations.

[Wally]

Don't forget your death wish either...
Walter

[boygenius]

I don't have a death wish, I just have a lack of rational thinking when it comes to things that are dangerous.

[hybrid_john]

LOL!:hehehe:
I like your way of thinkning, 240k isn't fast enough in my books, when you think of it I'd rather die in a car then in a bed some where!!

Good Call genius


John