rominl

iTrader: (4)

still 0.03 off

XeroK00L

I guess the same can be said about the new IS. Lowering Cd does often compromise styling at the same time.

rominl

iTrader: (4)

a lot of times actually. it's like you can easily get a car with low drag, but it could look very funny

Gojirra99

Do you think the LS430 look funny(specifically a funny butt) then ?
Some people slammed its boxy style so looks have nothing to do with it. The Ferrari's OTOH, with their aerodynamic looks, have high cd's in comparison.

CK6Speed

iTrader: (1)

When you got the power the Cd mean little For me, if the car performs I don't need to know what the Cd is. Plus, with cars like the LS430 and such, I'd end up putting on a body kit and big 20" rims anyway Ask, most LS400 and LS430 owner if they know what the Cd of the car is and I bet you would get a lot of funny looks. With that said, 0.27 Cd for the IS is still a nice achievemment.

spwolf

low CD owns... GS300 tested in latest Autobild fared the best in fuel consumption - it was around 8%-10% more efficient than A6, 530i, E350, etc.... Some of it was from direct injection and a lot was from low drag too!

XeroK00L

For serious sports cars though, a higher drag may not be a bad thing because it helps maintain the downforce and stick to the road at high speeds.

spwolf

right, which is only good when specifically designed to be that way... Generally speaking, car with good Cd has simply better behaviour at any speed, just because its aerodynamics were thought of much better and more work was invested in it.

F1 cars have an Cd of around 1.00, because they need huge downforce, but this is per design and can be adjusted a lot and you can be sure that aerodynamic packages are #1 priority in any f1 car.

CK6Speed

iTrader: (1)

This is ture, but it also has a lot to do with the rules. Aerodynamic grip is harder and more expensive I believe to achieve than machanical grip. F1 rules are written to heavily limit mechanical grip in an attempt to slow the cars down. Thus why aerodynimics now play a huge factor since they had to make up that grip somewhere else. The problem is now that these cars are so sensitive to aerodynamics that what we see nowdays is cars not able to pass when they get close because they are in dirty air. Low Cd is great, but I bet that most F1 teams would gladly trade some of their aerodynamic grip for mechanical grip if given the choice within the rules.

Spyder187

Yeah, I saw the documentary regarding the side skirts and when one of the teams used the side skirts, they were much faster than anyone else because of how grippy their cars were on the road. They were able to pass other cars with basic ease because they could take the corners at higher speeds. In the end the side skirts were banned.

This Cd on the IS sure is an improvement for wind noise though.

Xanadu350

I have to say that this discussion has been fascinating to read.

Out of curiosity what is the Coeff Drag on the 2005 IS?

Gojirra99

cd of 2005 IS300 is 0.29

XeroK00L

0.29 according to http://www.lexus.ca/lexus/experience...192P&year=2005

LexFather

Thanks for hitting us with the multiple CD facts.

LexFather

Aerodynamic Drag
You Don’t Get Something for Nothing

Mount a wing upside down on your racecar and, when the car moves through the air, the wing will press the car to the track surface, giving more grip. But it’s not free. Just as airplane engines are needed to overcome the drag of the plane, a racecar engine has to overcome the drag of the car, including the wings.

There is a basic equation for the force it takes to push something through air:

Aerodynamic drag = 1/2 D x A x Vsquared

In this equation, D is the density of the air, A is the frontal area of the moving shape, and V is its velocity relative to the air.

For real body shapes, air at standard conditions, V in mph, and drag in pounds of force, this equation becomes:

Drag = 1/391 x Cd x A x Vsquared

This equation shows that to calculate drag you need to know three things: Cd, the drag coefficient; A, the frontal area of whatever you’re driving through the air; and the speed of air past it. This equation shows an important point—aerodynamic forces are proportional to the square of the speed. That means you quadruple the drag or lift when you double the speed.

The drag coefficient, Cd, is important because, in concert with frontal area, it determines the power cost of pushing a shape through air at a certain speed. A small, low-Cd road car will have a higher top speed than a larger, boxier car with the same engine power.

Here are measured drag coefficients for some basic shapes. These numbers come from tests of shapes with known cross sectional areas. You blow air over them and measure the force on the shape. That’s what wind tunnels do. The arrow in front of the shape gives the direction of the air blowing over the shape. The cone shape, for example, would have a lower Cd if it were rotated so the air saw the flat end first.


Notice the difference in the Cd of a long and short cylinder. You probably know that a slippery road car has a Cd of about 0.32. A chunky one is 0.38.