Quote:
Originally Posted by NHB
Those numbers were taken from Mercedes website (german). Most likely they are for basic model without any extra trim or spoilers. AMG-model has a bit different shape for outer decorstion for sure, but that doesn't explain a difference that huge.
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I was trying to illustrate that each of those cars has a "base model" that is different. Some of them, seem to be far different from one another in terms of aerodynamics and the generation of down force. I mean one of them has radiator blocks to increase aero, but I could be entirely wrong
. And simple exterior differences can make a large imapct on CD... Sometimes an increase and sometimes a decrease. Generating down force is not the same as reducing drag for FE. I don't claim to know what causes the difference in CD on these Mercedes, and you may be entirely correct, but here are some examples of how "little" differences make a big impact one way or the other. This is on the front of the car.
Data from modeling...
1. Stock 1990-1997 Mazda Miata
2. Stock 1990-1997 Mazda Miata at a 4in Ride Height
3. Small Front Air Dam at 4in Ride Height
4. Small Air Dam with Splitter at 4 in Ride Height
5. Large Air Dam at 4in Ride Height
6. Large Air Dam with Splitter at 4in Ride Height
Note: The air dam and/or splitter is 2 inches off the ground in study 3-6
The models illustrate how "simple" changes can drastically impact down force and drag at 100 mph... Much less 200+ mph. Creation of down force can cause a lower OR a higher CD value depending on how it is done. Taken from
Splitter or Air Dam – Which Design is Best? | Hancha Blog.
Similarly, rear diffusers that are designed for down force, often have the opposite impact of those designed for better FE via lower CD. Most designs increase drag exponentially as the angle of the diffuser increases (gets steeper), and the angle is often quite steep in order to create more down force.
Read the following description, the diffuser only created 55lbs of downforce @175mph with an increase of .002 in CD... How much would the CD increase if it was to generate 200 or 300lbs of down force on the same car? A modern F1 race care produces over 1000lbs of down force via the rear diffuser alone, just as an example of how race cars and super cars are designed differently from normal cars.
"The Werks1 diffuser was designed using the most state of the art engineering and computer modeling techniques available today. Using these processes, a functional prototype was created and wind tunnel tested in order to verify the effectiveness of the part. During testing, it was proven that a stock 997.2 (with wing raised) produced over 40lbs of lift at the rear axel, at 175mph. With the rear wing raised and the new Werks1 diffuser installed, that number was completely eliminated, and the test vehicle not only showed no signs of lift, but it now produced 14 lbs of usable downforce, again at the rear axle. When measured at both the front and rear axles, the stock 997.2 showed nearly 110 lbs of total lift. Once the Werks1 diffuser was added, total lift was reduced to just below 75lbs. Best of all, the addition of the Werks1 rear diffuser increased the vehicle's coefficient of drag (or Cd) by only .002, from .313Cd to .315Cd. What this means is that the downforce created by the Werks1 rear diffuser is essentially "free", with no negative side-effects to be found."
From
Werks1 - Porsche 997.2 Carbon Fiber Rear Diffuser
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I didn't say that it's only cooling. Wide tyres have also a major effect. And of cource there are many other thing but those two are always major reasons for high Cd values.
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Sorry if I implied that you thought it was only cooling, I was just trying to illustrate that little aerodynamic differences can create big differences to CD and the generation of down force at high speeds. Whether that is the case with the CLA, is unknown to me... But I feel like it would make sense
Quote:
Originally Posted by freebeard
Whatever the reason, 400mph (644kph) cars *don't*.
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But do they turn at 400mph???
~C