Front bumper shape

[sheepdog 44]

Correct me if im wrong, but the most aerodynamic shape is a teardrop right? And when you make a boat tail you use a template like half a teardrop?

But doesnt the rounded edge also increase the air pressure in front of the car as opposed to the nose of an f-22 thats almost ends up like a spike? I would ASSUME the best aerodynamic shape should look like a horizontal mirror image of a teardrop with a "spike" tail at the front and rear to minimize air pressure differences at either end.

I would think the ideal shape for a car would look like a wedge at ground level lifting air over the car and reconnecting the stream at ground level in another wedge and NO air going under the car.

Thats my assumption, but you don't see a car like that. You see a prius designed to look like a tear drop. What is wrong with one of these two theories that i cannot see? obviously one is more aerodynamic than other but i don't see why the conventional model should be better. Please help as this is driving me crazy!

[CigaR007]

Originally Posted by sheepdog 44

What is wrong with one of these two theories that i cannot see? obviously one is more aerodynamic than other but i don't see why the conventional model should be better. Please help as this is driving me crazy!

Well speed is definitely a factor here. A F-22 Raptor can cruise at speeds greater than Mach 2.0 (1300+ mph) with afterburners whereas the Prius will normally cruise at 60-80 mph.

The aerodynamics of the Prius and F-22 are light-years apart.

[Gone2]

I've been kicking this around in my head for a while, and scrapped the huge bumper thing for a more aerodynamic 200sx bumper. Now to fill the holes. Also, sheepdog, if auto manufacturers produced a vehicle that was perfect in aerodynamics, they wouldn't be able to sell newer vehicles with better gas mileage. It is all a big scam, and the biggest reason I can't justify buying a new car. Anyway, off to work on the bumper.

[drmiller100]

Looking at the front only, on a "normal" vehicle air builds up in front of the car and creates its own invisible buffer, and pretty much makes its own aerodynamic shape. Yes, you can help it along a tiny bit, but in general, the air stacks up in front of the car until it is aerodynamic.
For this reason, any thing which is not aero in front of the car, gets filled with stagnant air, and BECOMES aerodynamic.
On the supersonic jets, the jet is going SO fast it is faster then the speed of sound. Faster then the speed of sound means air cannot stack up in front of the jet - it MUST go sideways in order to get "out of the way" of the jet.

So, the jet's nose is pointed to get the air out of the way.

Frontal area is the size of the car going through the air. The coefficient of drag describes how well the air gets around the car, and gets filled in smoothly behind the car. MOST of the gains in aerodynamics are to be found from the widest and tallest part of the car towards the back.

[Gone2]

If that is the case, why is there so much emphasis on aerodynamic shape? I have never heard of air being stagnant at the front of the car. I have heard of being dirty and actually slowing the vehicle down, I experienced this with my bumper off.

[drmiller100]

Somewhere between the front of the car and the back of the car is the "biggest" part of the car. Think of the car driving through a carboard wall. The outline left in the cardboard is the "frontal area".

When you look at the car, pretty much everything in front of the biggest part of the car is pretty meaningless, except for the air going through the grill, and the wheel wells.

Everything behind the biggest part of the car is critical.


another way to look at it. If the air is "stagnant", it is high pressure. An example of high pressure is at the base of the windshield on older muscle cars = hood scoops facing backwards actually pick up better air for the carbs then those facing forwards.

i've been thinking about the air flowing through the front grill. There is a LOT of research showing all the air going through the front grill is pretty much wasted energy. You'd think the stagnant air getting relieved through the grill would lower resistance, but it doesn't.

Maybe I'm wrong. maybe we can all learn something.

[Gone2]

It's proven fact that cowl induction hoods do better than hood scoops, and makes a lot of sense. Ideally the only purpose of the grill is to allow cooling of the radiator. A lot of people get rid of this with relocating the radiator to the top of the engine and closing off the grill. If I understand things then, it is a moot point if you have a round nose, wedge, or dam. So long as everything in the back is aerodynamic, then the front doesn't matter?

[drmiller100]

Originally Posted by Sentraguy

I So long as everything in the back is aerodynamic, then the front doesn't matter?

From reading this site, looking at cars, airplanes, etc, it sure seems to me the back of the car is a LOT more important then the front.

What do the rest of you think?????

[Gone2]

So riddle me this Batman, if we leave the front un-modified, and boat tail the back, will that still dramatically improve gas mileage?

[drmiller100]

I would be curious to consider this:
block off the front radiator openings.
Put a chin spoiler to keep air out from under the car.
Boat tail the back of the car.
Put wheel coverings on.

Is that 90 percent of the potential for the car? 95 percent?????