More downforce less drag

[Vman455]

Originally Posted by freebeard

On street tires? Elapsed time? 60-foot time? Sanctioning body? Front wheel drive? Whatcha got under the hood?

I've liked the Saveiro since cRiPpLe_rOoStEr introduced it to us here. But here is a Caddy that IIRC did 140mph quarters. Would you face off against it on your street tires?

He said it's an example, not the actual truck. Anyone running 170+ in the quarter isn't doing it on street tires.

[RedDevil]

Originally Posted by Vman455

He said it's an example, not the actual truck. Anyone running 170+ in the quarter isn't doing it on street tires.

That, and RWD or 4WD and >1000 hp.

I had a 135 hp Honda CBR1000F which did 0-125 mph in about 8 seconds, but it was a bike.
First gear went to over 80 mph; front wheel barely touching the tarmac; accelerating at about 25 mph per second.
Second gear took less than two seconds to redline from there.
Third took it over 125 mph.

If that car can spin the wheels at 160 mph it has more than twice the power to weight ratio my bike had. Supposing it is 4 times as heavy (including the driver) it needs 8 times the power.

[cRiPpLe_rOoStEr]

An underbody pan might already help you, but would you be likely to get a newer, rounded-body Saveiro instead of the square-body one? As its design is already flushier, the aerodynamic improvement is noticeable, and there is also more room for further improvements. I already saw some drag Saveiros with acrylic windows attached closely to the door arches in order to not leave that gap between the glass and the door panel.

[some_other_dave]

There's a lot of detail work that can reduce drag significantly. Things like eliminating seams (taping them over or changing to bodywork that doesn't have them) can make a difference.

Rounded corners can make a difference. Though I think at the rear you'd want a small lip to promote clean separation?

Tunnels under the body are one way to get downforce without much drag. Most wings and such will increase drag; a well-designed one will give you more in downforce than you lose from the drag. (At least, on cars that go around corners! Not sure about the straight-line folks.)

Reduce the frontal area of the vehicle. Introduce plan taper at the rear. Vertical taper will not help downforce; plan taper should at least not make it (much?) worse.

Probably the easiest thing is to lower it and put an air dam on it.

Wheelie bars can help keep weight on the front tires, but they will add some drag, though more mechanical drag than aero.

-soD

[aerohead]

Originally Posted by Leonel1995

Hi, im Leonel, i'm looking for different ideas to make a Volkswagen Saveiro (Like a caddy) (small pick-up) more aerodynamic, At same time make it have more grip.why? It's a 1/4mile car, that reaches +-170mph trap speed.
The reason of downforce need is wheel spin all track, i will leave a picture of an example of the pick up.

Here are some trucks which were modified for top speed stability,and legal for their racing class.All the mods are for stability at high speed.




All of these trucks have wheelspin issues right up to terminal velocity,and their mods help to keep them from going sideways.
These mods will cut drag as well as help with stability/downforce.
The NASCAR truck series also uses mods for high speed stability

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From a safety standpoint,you should look at total downforce/lift issues with the truck.
*You have enough rear overhang that with too much rear downforce,the rear axle will act as a fulcrum,lifting the front of the truck at speed.
*Acceptable load at 85-mph,will see 8-X this load at 170-mph.
*I suspect that you'll have to balance the nose with a splitter,as mentioned already by members.
*Without a wind tunnel to develop your 'kit',you may want to bracket your runs,slowly building speed with each run,to make sure you haven't over-designed the rear.You don't want to pop a wheelie at 170-mph

[freebeard]

I'm going with that extreme claims require extreme evidence. The 'example' pic is not that. 60ft and elapsed times would help evaluate the trap speed claimed.

Lots of good advise given; though no-one has mentioned aerocaps yet. Can I be first? An example from ecomodder in 2008:

[Magajgfha]

Ignore this post, it exists to make me able to post links

[Magajgfha]

Do regulations allow something like this or this?
How about wheel skirts and covers, these shouldn't affect lift, right?

[jakobnev]

For more downforce off the line skirts all around and a fan that sucks out is the way to go.

[ChazInMT]

Guh. Again, Page 85, Truck Aero Paper

Put a cap on with a 5° top taper. Or you could go with the 15° angle and enjoy a view of the finish line from 250 feet in the air from all the lift you'd get.