Increasing downforce while reducing drag?

[MadisonMPG]

You will have trouble turning in "evasive" maneuvers at 180mph.

[tanjulio]

I was also contemplating decreasing lift to my 1990 civic hatchback, or at the very least reduce drag; because i wanted to 'road course race". At Laguna Seca, this little car only was able to do 70 mph on the straight (vs. porsche 110 mph,corvette 130mph, ferrari 430 142mph).
I read both these articles...
1: confirms vent...
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2: says nothing really works...
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3: Vortex generator.. claims it works ?
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between all articles, we can see that I may not get the result of a decrease in drag or lift?
aero seems very confusing...So what to do???
NOTE:
I would like to reduce lift and drag, I have read "Katz" and the recommendation is to lower the car... but what about some Vortex generators.. they look like a Naca Duct???.
VORTEX


vs.
NACA DUCT

[aerohead]

Originally Posted by tanjulio

I had a question?
Do you have pics of your Hood Vents?
I wanted to do the same thing with my 1990 Honda Civic hatchback because
a mechanical engineering student mentioned "NACA Ducts" for more downforce but will a vented hood do the same?

NOTE: other websites stated that a "vented hood" would add downforce to the front wheels IF placed before the wheels, BUT is this wise?

A: Will a vented hood add downforce to the front wheels?
AA: How do you "test for downforce" without windtunnel to place the vent in the best location for Both reduction of lift and reduction of draft?

B: and is there an efficiency cost? MPG goes down??
BB: NACA Ducts are useful for what????

thanks.
PLEASE Help..
tanjulio@hotmail.com

tanjulio,I recommend you hunt down a copy of the book,RACE CAR ENGINEERING,by Paul Von Valkenburg.There is a large chapter devoted to race car aerodynamics.I believe that it would be an invaluable resource to you.
It's easy enough getting killed on a race course.You need competent advice.I would be VERY CAREFUL about WHERE you get your advice.

[NeilBlanchard]

Those vortex generators do NOT work (on a car anyway). I bought a bunch of 'em and they lowered my FE, and their drag could be felt -- you would go even slower with them.

http://ecomodder.com/forum/showthrea...ds-2969-6.html

[smokeyj]

I have the solution. Make a Kammback and belly plate, but instead of using the wimpy cardboard and coroplast (sp?) that others use. Use something a little more solid, like 1/4 inch steel.

Now you will have improved drag caused by a better shape and increased downforce at the speeds you should be driving due to the weight.

[tanjulio]

Originally Posted by NeilBlanchard

Those vortex generators do NOT work (on a car anyway). I bought a bunch of 'em and they lowered my FE, and their drag could be felt -- you would go even slower with them.

http://ecomodder.com/forum/showthrea...ds-2969-6.html

NEIL??
I see in your profile that your car is a 'Hatchback", am i correct?
The article stated that on the Honda Insight (a sort of 'hatchback') the vortex gens did not work when placed "the trailing edge of the rear hatch", and Their car had similiar results of increasing the fuel consumption of the car, just as Neil.

SO 2 questions.
1: Do Vortex Generators only work on 'sedans or coupes' when placed on the end of roof????

NOTE I: From my uneducated view; Hatchbacks seem to have a difficult time with Vortex Gens when placed on the top of the car

NOTE II: But under the Honda Insight they had better results in the handling department?? confusing article...

2: What about Vortex Generators under the bumper leading edge of the undertray as stated in the Second article: ' Blowing the Vortex, Part 4'
I am sure that they are reducing lift in the front and possibly back.

[tanjulio]

Originally Posted by smokeyj

I have the solution. Make a Kammback and belly plate, but instead of using the wimpy cardboard and coroplast (sp?) that others use. Use something a little more solid, like 1/4 inch steel.

Now you will have improved drag caused by a better shape and increased downforce at the speeds you should be driving due to the weight.

I have been looking for a guidelines to follow: How to make a Kammback" which will give me downforce or reduce lift...

METRO MPG, Andrew J, page 8-9 or specific TomO's 'my Kammback VX...etc.
have made a Kammback and had great result with fuel efficiency..
BUT can i have both???
FUEL EFFICIENCY AND DOWN FORCE/REDUCED LIFT??
IF anyone can give me a few links OR Guidelines to follow on the DIY section
my car is a 1990 honda civic hatchback. I think this needs to be addressed for people like me who have No clue as to what to do...a DIY Section!!!
I FOUND THIS FROM METROMPG BUT THERE IS NO CONSENSUS ON A SPECIFIC ANGLE TO STRIVE FOR?????
http://ecomodder.com/forum/showthrea...sion-3518.html

[tanjulio]

Originally Posted by smokeyj

i have the solution. Make a kammback and belly plate, but instead of using the wimpy cardboard and coroplast (sp?) that others use. Use something a little more solid, like 1/4 inch steel.

Now you will have improved drag caused by a better shape and increased downforce at the speeds you should be driving due to the weight.

2 questions for smokeyj or anyone

1: Will this give me downforce for the entire car or just the back??

2; what about engine tempertures? I would like to block the grills and vent the hood ,

but how to vent the hood???

[smokeyj]

Tanjulio I am sorry my post was meant as a joke. Don't take me too seriously.

Now from my pitiful understanding of aerodynamics, I get the impression that a belly pan might be the answer for both reduced drag and increased downforce.

Reduced drag is obvious as it is smooth rather than bumpy under the car.
Downforce is increased because with the smooth belly pan air velocity under the car is higher and this means lower pressure, increased downforce. Side skirts should also help keep undercar pressure low.

A front airdam should help, but I think at this point you are getting into the "it depends" regime.

My real point is that at any of the velocities you should be driving downforce should not be your primary concern.

As far as venting the hood, their is an Australian web site ( I think it is Autospeed) sometimes linked to from this site. They have lots of good info on how to determine where to site vents.

They use a tool called a Magnahelic gauge to determine small pressure differences.

The high pressure point on the front of the car tends to be the center of the grill at bumper level or a bit lower. There is a low pressure zone just after the turn of the hood. So this explains the hood design of the Lotus Elan the high pressure air comes in through the lower grill flows through the radiator and exhausts on the top of the hood into the low pressure zone.

The grill block should improve drag. As regards engine temps ;you have to pay attention. Your car is designed to work well from Siberia to the Sahara from the factory. You are going to be using it only a fraction of its capability and can trade off the design margins that are built in for improved performance in a narrower operating range.

I for example have a 90hp Volks TDI but that same Golf body (and grill) is available with a 180hP gas motor. So already I know I probably have 2x the cooling capacity that I need, not including the effect of higher diesel efficiency. So it should be safe for me to block half the grill no problem.

[kach22i]

3-years later update

Car Art

But the following year he tried an even more aggressive development of the ground effect concept on the Lotus 80. His plan was to use underbody aerodynamics to generate all the car’s downforce, doing away with front and rear wings to reduce drag.

Wind tunnels testing showed the car generated twice the downforce of its predecessor. But on the track the immense power of the ground effect couldn’t be controlled. The car would ‘porpoise’ – sucking itself down at the front, then bouncing back up.