These pictures are of my rear diffuser. First off let me say I like how the Mopar rear diffuser looks though it's not a diffuser, it's more of an air blocker, it does not help air get out from underneath the car as a true diffuser would. I'm not saying what I have made creates any kind of huge downforce (and a true diffuser would), I do think it straightens up and aids the air flow under the rear of the car. It also fills that gaping void under the back of the car that already has a pretty decent diffuser-looking shape. The car also has an SRT front fascia and Koni shocks as the the only other non-stock items.

The material it's made from is called Tegris and it's 5/8th thick. I believe it's a type of modified polyurethane. I bought the material from roushyatesparts.com, it was a NASCAR COT splitter in it's former life and was only $40 used, though what I got had not been used and was unpainted.
It looks pretty much like carbon fiber, the gray weave is part of it though it's only on the outer surfaces, it works pretty much like wood and is easily painted.
The surface texture can be seen after it's painted. I painted the fins, the panels (behind the rear axle-in front of the rear fascia) and the indented area of the rear fascia around the exhaust flat black.

Picture A: This was a mock up for position and fit, the size of the fins got a lot smaller at their final size, raw material with unpainted panels.

Picture B: Close to final size and painted, with an additional fin outboard that is at the edge of the inside of the rear tire. Left side panel shown with the fins attached, right side panel (on the left in the picture) with the fin unattached and showing the 3M double sided adhesive tape that sticks (only the fins) to the rear fascia.

Picture C: How it attaches to the under side of the OEM rear panels, long sheet-metal screws and washers. Fins at final size, one attached, and the raw material unpainted.

 

I don't see how your diffuser is any different than the Mopar piece. How is the Mopar Diffuser an air blocker and yours are not? Now the fin next to the exhaust pipe needs to be lengthened to match the one you added.

James

 

I agree, the larger fins look out of place next to the smaller original ones on the trim panel. I have serious doubts on their looks, functionality and ability to stay in place with just the adhesive. I highly doubt these will catch on....

But thats just my opinion

 

I could be wrong, but I always thought of the diffusers as more of an aesthetic thing rather than functional. I just don't see them as adding to the aerodynamics of the car.

 

On our cars and at our level of speed, I would say they are purely aesthetic. I always thought the purpose of them was too keep the rear straight at high speed and keep the car from getting squirrely. Like multiple rudders in the straight ahead position. Maybe, maybe not.

James

 

I don't think they add too much performance on the xfire as that rear section is already shaped and works like a diffuser (gradual rising slope) but there are probably some benefits when getting closer to top speed. If we had a full flat panel underneath they may work a lot better. Basically they just channel the low pressure accelerated air from under the car out the back end in a way that allows it to decelerate/decompress smoothly. This should increase downforce if done correctly (from my understanding) the little vertical pieces are mostly there to prevent turbulent/slower moving air from getting in the sides and mixing in with the low pressure stuff. In this application they are not really long enough to do so (they would need to extend well under the center of the car) so they just help smooth out / direct airflow.

If I remember correctly it took them a while to get the rear end designed right to be stable at speeds. The mopar piece basically just adds strakes to what is already essentially a diffuser built into the back.

 

I just want to say great work! customisation is alwyas fun! Do you have a pic straight from behind?

 

The whole point was with "rear section is already shaped and works like a diffuser (gradual rising slope)" to have more than just a "void" as the Diffuser. The tape merely holds the rear most few inches against the fascia, the rest of the big fin is very firmly secured to the panels ahead of the fascia. It's not going anywhere, and hasn't. I'm not saying it gives any great performance advantage, but it doesn't do nothing. A louver flows more air than a hole.

And yes it is more for aesthetics than function, though it does function, the longitudinal fins (in any diffuser) are there to straighten the airflow, and yes you want them as long as possible but on road cars they don't extend forward of the rear axle. These fins are as long as those on an OE diffuser on a Viper. Look at pictures of other diffusers such as http://www.roeracing.com/productcart...154_detail.jpg

The Mopar diffuser (described by them as an appearance accessory) just hangs stubs of material at the very end of the "rear section is already shaped and works like a diffuser" that are about an inch and a half wide, stick down a few inches and extend toward the front of the no further than the fascia.

 

There is just something about the wording of your post that makes it unbelievably hard to read.

 

Understandable. Helped me write Yoda did.

 

Haha! After closer inspection, I understand what you're saying now. Sorry about that!

 

I have mine on just for the look, however this might explain how it should work.

Diffuser (automotive) - Wikipedia, the free encyclopedia

 

Anyone know where to find the Crossfire rear diffusers these days (other than Hot Car Accessories, whose product lacks the quality I'd like)? Just acquired a 2006 limited roadster and would like to dress it up a bit. Thanks.

 

I got tired of waiting and bought the ebay ones. Should arrive soon...

 

Well, I have been 160 with them and without them... I am just glad they stayed on every time. Saturday, I will try to shake them loose once again.... It's always fun to mod something up. Not everyone will like what you do, but if you like it, keep it, 'cause you won't find any diffusers for sale unless I roll mine this weekend....

 

Don't recommend rolling, it's hard on the head! If you run across anyone who is trading in their car, let me know (they don't offer any more money for one with diffusers). Otherwise, I'm searching the wrecking yards, I've seen plenty of Crossfires but none with diffusers.

Remember to follow the advice of my airline pilot friends: BLue side up, green side down and keep off the grass!

 

I was considering the ones from Hot Car Accessories. What exactly is low quality about them? Just curious before I purchase them.

 

Here's a past post of mine:
1-26-2012
There have been quite a few members wanting these. I did finally receive the Rear Fascia Panels from hotcaraccessories.com that I originally order from their ebay listing that was delayed about three weeks. These are not the original Mopar Panels made out of plastic. They used an original to make a mold to have fiberglass reproductions made in China. Actually, they turned out looking fairly good and I could have made them work. However I returned them for some of the following reasons:

1. After checking the form and fit I wasn’t totally satisfied. The fiberglass is very stiff with no flex, and I didn’t think I could get them to fit in the area as tight as I wanted. My car is in cold storage. Actual final installation was not possible.
2. After seeing the product, I decided I wasn’t willing to pay the amount for what I was getting.
3. They were willing to pay for the return shipping, so that was another incentive to return them.
4. One more thing. On the originals, the hollow fins that stick down have weep holes drilled to let water out. The reproductions that I receive did not, but you could see the indents where the holes should be. I could have easily drilled those out. I discussed that issue with the supplier. They will be drilling the holes in future productions.

The owner (Chris) was very agreeable to the return. He said that he had received and delivered 5 of these, and due to demand has ordered more. He is going to make it ‘more clear’ in his listings that these are not the original Mopar product. I want to make it clear that I probably could have installed these with decent results, I just decided not. I commend this vendor for making aftermarket parts that are no longer available. I think he realizes, that he should have been clearer in his advertisements. If someone receives these without weep holes, I recommended they be drilled. If they fill up with water and freeze, they might break. I've attached a few pics of what I received.
Attached Thumbnails

 

Thanks for the info! If I can't come up with a factory set somewhere, I think I am going to mock up my own design and see how it turns out. I've worked in fiberglass for years, so this shouldn't be an insurmountable task.

 

At one point, I took to searching eBay and messaging anyone who was selling a car with diffusers to see if they were OEM and if they would sell them separately.. didn't get a lot of bites and I ended up with an OEM set from someone here on the forum who never installed theirs (which I haven't installed either, ironically)