Cd and blunt front ends

[EngineeringStudent]

Originally Posted by MadisonMPG

Show me one car that has lifted off of the ground going 80 mph.

cars can't lift off the ground at 80, but you'll have less control if your car has aerodynamic lift. everyone knows that lol

as long as the front end isn't completely flat, a more rounded blunt end is fine, unless you're coming close to the sound barrier. blunt front ends will give more resistance because you're pushing more air out of the way, but if done right, that can be beneficial. air dams are a perfect example.

the mclaren and saleen s7 are made to go 200 plus mph, so they need to be sleek and offer as little wind resistance as possible while having enough downforce to keep control at speed. on mass market cars, you rarely see that level of aerodynamic engineering.

[Cd]

Originally Posted by thatguitarguy

I don't understand your question. Fit, Ferrari, or F'n Hummer, they all have to pass the same impact standards. But crashing any car into a wall, and crashing the same car into a post, or an identical car, or an SUV, will yield different results.

In other words, what I am asking is this : The Fit has a sloped front end that has an attractive look to it.

The Yaris, Prius, Civic etc, , have front ends that are bulbous.

Why ? Is there a design reason behind it ?

[Christ]

I'd be inclined to think that it fit their form, and still stood enough in the face of function to be used.

It seems with automakers that function nearly always takes a close second to form, when in reality, the most beautiful designs are the things that just work. Reliably, safely, and just WORK.

[winkosmosis]

The other day I saw a Boxster at 65mph with the rear spoiler popped up. Apparently lift does matter at normal speed.

[Christ]

I'd be interested in the actual numbers produced at 65MPH by that car... Just cuz the "engineers" programmed the BCM to put the spoiler up, doesn't really tell me that it's anything more than a nicety.

[thatguitarguy]

Originally Posted by winkosmosis

The other day I saw a Boxster at 65mph with the rear spoiler popped up. Apparently lift does matter at normal speed.

That was to keep his toupee from flying off. Toupee lift is always bad.

[aerohead]

Originally Posted by Cd

In other words, what I am asking is this : The Fit has a sloped front end that has an attractive look to it.

The Yaris, Prius, Civic etc, , have front ends that are bulbous.

Why ? Is there a design reason behind it ?

I would presume that the car reflects as close as possible,what the stylist rendered,what the manufacturing engineer said was possible to build,any compromises the wind tunnel guys could beg,and finally,a committee which made the final decision for production approval.
All the noses operate in a positive pressure regime and can enjoy a wide variety of creative license and still maintain attached flow.
That cannot be said for downstream of the max. cross-sectional area location.

[Cd]

So it's a style thing and nothing to do with crash test height legislation ?

Personally, I think that the sleek lines of the Prius would have looked better with a sleek looking nose ( especially the second generation cars. ) even if they function the same in the windtunnel.

O.K. I was just curious.

( Let's talk about something else now )

[aerohead]

Originally Posted by Cd

So it's a style thing and nothing to do with crash test height legislation ?

Personally, I think that the sleek lines of the Prius would have looked better with a sleek looking nose ( especially the second generation cars. ) even if they function the same in the windtunnel.

O.K. I was just curious.

( Let's talk about something else now )

Cd,I found my timing slips from Bonneville for another thread and wanted to post the data for you on its nose.
The original nose I built was only good for 0.47 mph additional top speed.
By adding a chin spoiler of about 1.5 inches to limit air under the nose,I gained another 1.056 mph,for a total 1.526 mph.
The tail got me 5.51 mph.
The entire kit got me a top speed of 97.339 mph,compared to 89.77 mph( 85.5-degree DB,62.5-degree WB,27% RH,4,300-ft elevation) with the car stripped of everything but rocker panels and partial bellypan which I had no way to remove at the track.
Later,the car was tested by CAR and DRIVER's Don Schroeder at Chrysler Proving grounds.At a cold 42-degrees F DB, she went 98 with the kit.
At warmer temp and lower elevation she pulled an even 100-mph on four occasions,up from the original 93-mph when tested under similar conditioins at Tochigi,Japan.
The cardboard and duct tape mods stayed on the car until I got back home,and I averaged 60.6 mpg compared to 52.0 for the "naked" car.
I had hoped the nose would do more,and was very surprised to see most of the "speed" and " mpg" from the tail.

[aerohead]

Originally Posted by Hermie

Obviously, cars can't really take off, because the power needs contact with the ground. However, that doesn't stop them from flying from lift:

But if you're so intent on ignoring the Cl and be so narrowly focused on Cd and nothing else, I'll be laughing my ass off when you wreck on the freeway because your skinny, no-grip tires slipped when you tried to swerve.

I'm not a drag-nazi. I'm seeking a balance between economy and performance. Just because I don't have tunnel vision doesn't mean you've got to be a jackass.

At normal posted speed limits the lift won't be an issue.And a skinny no-grip spare tire was tested on a Corvette with virtually zero loss of cornering force.