Hi, I'm new here and my cD is .37, can you help me get a .30?

[freebeard]

My modding skills are very extensive and radiator relocation would not be out of the question. I can seal the front of that car tight.

Relocating the radiator would be a major modification. How does it presently compare to this?

My question is: before I finish and paint the front bumper, do I want a splitter to keep air from under the car? Remember to account for an imminent 2" suspension drop.

Once again: What will you use it for? Could you live with this or would it be curbed repeatedly?

Also, is it better to port the exhaust out the sides right behind the front tires or directly underneath the headers into the underside. I'd like to make my aero and my engines exhaling mutually beneficial to each other. i.e. low pressure sucks exhaust gas out improving exhaust flow.

The pressure differential in the airflow is much less (by orders of magnitude?) than in the exhaust. More likely you could use the exhaust for a 'blown flap' or Coanda nozzle

But the exhaust is corrosive and will degrade anything it touches.

[NeilBlanchard]

That front splitter is not the lowest drag configuration - it is probably the lowest lift, though.

[freebeard]

Higher drag because it adds frontal area. I picked it because it was handy and the most extreme example I could think of.

I took a moment to look around. It looks like a reasonable example would be the stock Crossfire SRT-6:

[aerohead]

Originally Posted by jeff88

aerohead, are you saying that a grill block and belly pan were good for 7 "points" for the Porsche? Do you think that can equate across the board to 7 points for the Crossfire?

When the 1989 Carrera 4 made it's debut,it came in @ Cd 0.32.CAR and DRIVER mentioned that,compared to the generic Cd 0.39 911 Carrera,all the drag reduction came with these subtle refinements.Porsche probably shared the info.
We don't have a drag breakdown on the Crossfire so it's hard to predict what any specific mod will do.
The AUDI TT has a 'fast' roof kinda like the Crossfire,and it's spoiler help it reach Cd 0.29.

Some grille work,airtight ducting,underbody cleanup,and better spoiler might do the trick.
The cooling system out to at least have as good a duct as NASCAR

[ChazInMT]

For starters, this is a proper application of the template on your car.


Be sure that whatever you do it fits with the look of the car. I question whether the few dollars saved on some weird looking aerodynamic enhancements would pay for themselves in the cost of both time and materials. I also wonder if you'd want to fiddle with the stock look of such a great car, I mean, if it comes down to spending a few hundred dollars more on fuel over the next 5 years or putting some crazy looking stuff like a Kamm on my cool car, I'll pay the money.

Next off, I'm sure that this car has been aero designed to within an inch of its life. I'm guessing that based on its rough shape, MB and Chrysler were scared to death of an Audi TT lift off at high speed, so they made sure there was plenty of downforce. Downforce=Drag.

I'm guessing you have a retractable spoiler that deploys at 45MPH or something, this is meant to break the lift. I see some crossfires have a permanent spoiler which to me looks a lot less prone to having mechanical issues, and has a more efficient shape to it. This spoiler could really help your Cd because it brings the rear end of the car closer to the template. In addition, it will help with what certainly must be a lift at higher speeds. It will probably make your car feel much more planted and stable at highway speeds too. If you can get one of these and put it on you’ll be happy.


There are some hidden things you can do to improve a bit. The grill block and belly pan would be big. Adjust your tire pressure up closer to the highest recommended pressure printed on the tire, I'm guessing that Chrysler wants it at 32psi or so, get it up to 38. That will save you about 1-2MPG alone. Hiding in plain sight would be the factory rear spoiler.

To get the biggest gain in fuel efficiency, you need to adjust "The nut behind the wheel". In other words, your driving habits, this will pay off more than any aero tweaks.

The largest areo drag is caused by the general shape of your car, the air affected by it, and thus the air you need to control extends out many feet around and in front of your car. Worrying about how the air is flowing along the skin of the car has a use in gaining insight on the mass air flow, but tweaking this with anything small is unlikely to have any measurable effect.

So, Block the grill, Add spoiler, Pump up tires, see about cool things you can add to act as air flow diverters around your wheel wells, look into a belly pan. For Petes Sake....Put your dern wipers back on, and never do anything to save a few dollars that can jeopardize your life. Safety First.

[AutoDeutchland]

Thanks for that info. Again, my goal is top speed. Fuel economy is just a bonus. The car is usually only driven to tracks and never in anything less than optimal weather. So I'm just trying to figure out how I can get down to the .29 - .32 range without ruining the car. I don't mind bold mods as long as they don't degrade the aesthetics of the car.

[freebeard]

Again, my goal is top speed... The car is usually only driven to tracks and never in anything less than optimal weather.

Ah, so.... Just leave a little earlier?

[Vman455]

Originally Posted by AutoDeutchland

Thanks for that info. Again, my goal is top speed. Fuel economy is just a bonus. The car is usually only driven to tracks and never in anything less than optimal weather. So I'm just trying to figure out how I can get down to the .29 - .32 range without ruining the car. I don't mind bold mods as long as they don't degrade the aesthetics of the car.

Here's an article you may find useful.

[AutoDeutchland]

That article doubled my understanding of this. It just seems too good to be true that I can dorm my cd from .37 to .33 just by dropping my suspension two inches.

[aerohead]

Originally Posted by AutoDeutchland

That article doubled my understanding of this. It just seems too good to be true that I can dorm my cd from .37 to .33 just by dropping my suspension two inches.

With the Volkswagen Jetta Land Speed Record car,it was reported that dropping the car had zero effect on Cd,it only reduced the frontal area.