More downforce less drag
 

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.

http://ecomodder.com/forum/attachmen...7&d=1459900869

I guess fuel savings are not on the top of your priorities, but anyway, do you already use a tonneau cover or eventually race it with the tailgate down?

The author poses a good question. How to get more down force and less drag? So I guess something like a bed cover that went from the roof top down past the tailgate at a 15 degree angle and tapered in from the sides toward the rear for aerodynamics, maybe ending in a Kamm type tail. Then add a wing on the back for the down force.

I've never understood the purpose of downforce for 1/4 mile runs. The moment when tires are most likely to spin is from a dead stop when there is zero downforce. By the time the vehicle has enough speed to produce downforce, isn't there enough traction?

That said, fuel economy and downforce are at odds. The ideal shape for fuel efficiency on a vehicle represents an airplane wing, which actually produces lift.

It reaches 180miles per hour in the track, this car is really ppwerfull and it hace wheel spin from 0 to 180 mph, we did use once a cover and a free tailgate (open) but it closes by itself when reached 100mph a wind effect. No, haha no fuel saving here, we have more power but we cant use it

An air dam and side skirts would be the way to go. That would lower the pressure under the car, creating downforce. And it would be relatively simple.

If it is a pure track car you can get them really far down to the tarmac.
Get the dam as far forward as the regulations allow for.

Red devil, yes, i think that too, but also i would Like to optimize the shape of the car to decrease drag in all the car, and at dame time increase downforce.

Then a raised tonneau cover of some sort?

You might have found this link already. If not, enjoy :)

From that link:
http://ecomodder.com/blog/wp-content...ckupAero1.jpeg

The effectiveness of the simple wing + cover is remarkable, considering how easy it would be to make one that would still be 200+ mph resistant.

This is front wheel drive, right? A splitter on the front, as low as possible, will give you downforce in the front. But I'd want to match the rear downforce to the front at 180 MPH! Wheelie bars will help keep the front tires gripping too.

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?

http://ecomodder.com/forum/member-fr...1-p1010050.jpg
http://ecomodder.com/forum/member-fr...0-p1010049.jpg

Here is how you get downforce without drag. How you apply it to your situation; I don't know. This has 10% less drag than a flat bottom and rear by CDF analysis, done by a member here. The downforce wasn't reported.

http://ecomodder.com/forum/member-fr...14-1-42-00.png

It is like having a rake, without the downside.

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.

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.

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

downforce
 

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.
http://i1271.photobucket.com/albums/...2/HPIM1921.jpg
http://i1271.photobucket.com/albums/...itled21_13.jpg
http://i1271.photobucket.com/albums/...itled17_16.jpg
http://i1271.photobucket.com/albums/...titled28_6.jpg
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
http://i1271.photobucket.com/albums/...itled24_10.jpg
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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 :o
http://i1271.photobucket.com/albums/...titled1_29.jpg

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:

http://www.upcountry4x4.co.uk/images...navara-top.jpg

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

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

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

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.

http://i68.tinypic.com/25z1l3l.jpg

More info on the truck is needed. Has it been converted to rear wheel drive? Are you using a conventional radiator cooling system or an ice box? Have you already moved dead weight to the rear by putting the battery in the bed? Have you scaled it to know weight distribution of the vehicle?

I'm sure you've already done most of the race car mods but us knowing what you have will give us a better starting point.

[IMG]http://s29.postimg.org/5fsp3wut3/Sin_t_tulo.png subir fotos gratis[/IMG]This saveiro is AWD and it uses 4 slick 25x8x15 tires, also we tested M/T (mickey thlmpson) 4 26x10.5x15 but it had less traction, the track is without treatment, no glue, no vht.

In my country we made 8.38 sec 1/4 mile at 288km/h (gps) 60' is around 1.50 sec, 1/8 mile around 5.6sec. With other saveiro stock chasis, now this is a street legal saveiro, and we are trying to low that number.
One of the problems to work underside, is that the truck have susp. travel, also with the air dam

Looks pretty good to me.

Click on the links in my signature to see my project.

Trading out the rear spoiler for a wing as you have is shown the lower drag option.

I'm looking at this:

http://truestreetcars.com/forums/drag-racing/22346-60-ft-times-interesting-read.html

1.5sec 60 foot time isn't that great for cars that run at the speeds you claim. Either the AWD isn't hooking up or someone is napping at the Christmas tree. :)

We don't know the weight yet. We don't know the sanctioning body. Would they tolerate this difusser:

http://ecomodder.com/forum/member-fr...80-silver4.jpg

Or this one?

http://ecomodder.com/forum/member-fr...bonnevette.jpg

[QUOTE=freebeard;510812]

1.5sec 60 foot time isn't that great for cars that run at the speeds you claim. Either the AWD isn't hooking up or someone is napping at the Christmas tree. :)

60' time has nothing to do with R/T. Timers for 60' don't start until the R/T sensor is tripped (car starts to move). If he is really having traction issues, he may be nursing it off the line to try and keep traction. Remember, he said the track is not prepped at all. As much as drag racers would love to say that their car hooks well, it has just as much to do with track prep that will pull your shoe off your foot as it does suspension and tire technology.

I still can't really believe that AWD is roasting all 4 tires at mid-track but I've never driven a car with that kind of power. Drag radials and slicks won't help becuase they stick best when warm and (usually) AWD has trouble with warm up burn outs. I'm thinking tires need to be super soft summer high perf summer tires that grip when cold.

https://youtu.be/rO8uSNzb0bQ
That vídeo is an example on a 1/8 mile track boost is controled all race, not mid track, in 1/4 mile too.
1.5 aprox without R/T (reaction time)(driver business) At 60'ft (18meters) the car starts with 30%power and reaches 90% power to the end of the track of 1/4 mile we control it to be driveable, imagine too muchas power and the car goes like soap on wet floor.
Wheight around 1100 kg at race
We do 2nd gear bournouts 4wheels smoke 60meters, pretty hot slicks, no bournout problem.

Now that's movin! Great job building a truck like that that you can still drive on the street.

A front bumper should help keep the front end from lifting at speed. Also, consider fender vents to evacuate some underhood pressure which also causes lift. If you don't want to cut the fenders, cut the hood...back by the windshield but on the outer edges. If this wasn't a street car your best bet would be a 1 piece, solid front end with an a/w intercooler in the bed. I'd grab a sheet of plywood to make a 1 piece tonneau cover and pro-stock spoiler. Use the template feature on this site to see how far off the back the spoiler should reach. Pro-stock spoilers usually have "fences" on the sides which kind of channel the air flow and help to keep the vehicle going straight. It's a nice truck I wouldn't blame you for not wanting to ruin the lines or the body with speed holes or big wings off the back. I think you'll notice a big benefit by fitting it with a larger front bumber/air dam.

Are all 4 wheels given 100% of the power? Or is it biased to the front or rear?

I've already seen some drag-racing Gols with the hood slightly tilted forward. That may help in case you don't wanna cut the hood or the fenders.

Are you allowed to fold the mirrors, replace them for smaller or delete them altogether?
Little details like that can help.

If you go to the roof wing link in my signature you can see where I theorize about the function of an air gap and the affect on air flow.

If you do an all flush (no air gap) roof wing and side pillar, maybe test in both configurations in the name of science.

Gaps between body panels and doors could be taped up as they do at Bonneville.

Aerodynamics by George Kachadoorian | Photobucket
http://i184.photobucket.com/albums/x...psspjtyl3n.jpg

Cool truck!!!!

I don't have to much to contribute about down force and aerodynamics, I will leave that to our local experts. With that said I think your going to have issues no matter how much down force you have have on a no-prep track with the power your making. On my my car running around on the street running with my QTP Hoosier's it will spin the tires and move around on me and my car is only a mid 9 second street car. I have two friends that have the fastest AWD Talons in the world both in the 7's at 180+ and there is no way they can hook on a no-prep track.

I also think your 60' is what is hurting you the most. You should be at least around a 1.40 60'. Even on a AWD you have to hit the tires hard off the line and keep them planted.

The hood is raised on the back part, the air of engine and intercooler exits there yo the windsshield, cant remove mirrors or change them, its 50%rear 50%front all time traction
Pgfpro: the real problem is the track, se hace tested all kind of launch, but the 1/4 mile track we have is old and even worst at the first + - 30mts theres even sometimes oil on it, so you can imagine, any street road have better grip

I just wanted to say 'napping at the Christmas tree' because I thought it sounded funny. That was an awesome 1/8th-mile run. Is anyone at the track competitive with you or do you 'own' the place?

I suppose massive wings are out too then. I think it's going to come down to what is allowed, and the choice of tires for those track conditions.

Sorry, i can change them, cant remove them, At same time i dont think it help much, cos idk if with this body air goes close to sides of car. I can add everything i want except wheelie bar. We race against the time, thats what we care about

Folding the mirrors back would make much less difference than a diverter, bellypan with wheel spats and difusser.

Is there any way you can dial in more anti-squat in the rear suspension? I watched this video as well as a couple older videos that youtube conveniently linked up to it. Looks like you have a lot less squat now than you used to, but it still looks like it sags and then pops up when the tires slip.

What tires do you use exactly? What tire pressure? Doesn't seem like the sidewalls give enough, but it's hard to tell with the camera angle.

Proping up the back of the hood is a popular tuner thing to do, but my car has a cowl induction hood that is designed to pull air into the engine. I wonder how much the propped up hood helps, becuase I would think it would hurt more in the aero department.

Less, but still some. It does not exclude the other stuff, so why not have it as well?

But maybe you can move them?