XK / XKR ( X150 ) 2006 - 2014

XKR-Carbon Rear Diffuser Project

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Old Sep 4, 2015 | 01:43 PM
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Default XKR-Carbon Rear Diffuser Project

As you guys may have seen in other posts, I'm working on a various amount of projects for these cars and making headway with each.
Pertaining to carbon projects, (Engine bay panels) the molds for each of the 3 panels are off at Hendricks Motorsports for quoting the tools.
A lateral carbon project I've started is both a functional rear diffuser as well as a front splitter and belly panel. I'm awaiting a few things to start the carbon induction prototype as well. I have one for the 4.2 fabbed in aluminum, now I'm going to move forward to doing a nice carbon design.

As a kick off to this project (Diffuser) I went ahead and reverse engineered the factory diffuser for the mount locations and clearances. I've scanned it both on and off the car to account for flex when install by using reference dots. I'm going to setup the sketches the work on aesthetics, then following that up with proper engineering technology and CFD.
For the CFD, I'll be using a few opensource softwares to support the computation. One being OpenFoam and the other Paraview. This will allow me to study the flow characteristics in both Laminar and turbulent flow. I've scanned the entire car so that I may compare the pressure differentials between the top of the car along with this stock and prototype diffuser.
My plan would be to have the structure run up to the rear diff and incorporate well designed strakes. My setup has a little more clearance with the rear muffler swapped, but I do plan to have a design that will clear the factory mufflers as well.
Here are some basic reverse engineered models of the 4.2 factory design I'll be designing from.
I should have the full car data converted in the coming week, then I'll start with setting up conceptual sketches.







Regards,
Derek Fricke
 
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Old Sep 4, 2015 | 08:56 PM
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Do you have any pictures yet. Doug
 
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Old Sep 5, 2015 | 06:40 AM
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I'd like to see a rear diffuser that covers the muffler with 5-7 channels in it. Real functional diffuser. Something similar to what Difflow Diffusers - Your Source for Rear Diffusers! does but for a Jag.
 
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Old Sep 8, 2015 | 08:55 AM
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No pictures yet as I'm still processing the full car data into a usable model. I should have a design put together in a few weeks, then I'll start with the tool to mold the carbon. I'm going to run CFD on the base design then compare to a final design. I plan to do this so that it is truly functional and not just a visual perk. Thanks for the Diff-flow link. Certainly direction I'm heading, just in smooth carbon and nice transitions.
I'll post up CFD and final design iterations for opinions on final appearance soon.

Regards,
Derek Fricke
 
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Old Mar 13, 2016 | 01:49 PM
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Derek its heartwarming to finally see someone QUALIFIED working on these well engineered cars. So many in this game have no technical expertise. You can be a superstar. Count on my support.

I am in NC often, treat you to a pint and dinner if you are up for it.

Here is a top tip, find a lug nut that meets stress criteria from your engineering perspective, I bet only 2% do. Then market it under your name to all Jaguar owners. Thats the beauty, one part fits all. So the market is big. Its criminal what is going on out there- either garbage from the orient- no wonder they are sold on ebay, or idiots like Gorilla telling folks Stainless is stronger than Hardened. What a joke.

On your FB pictures, I saw that the wheels come out PERFECTLY to the wheel arches- are you using a spacer? if so enlighten us on that too please sir. Thats another car wrecker if you get shady 'alloys'
 
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Old Mar 15, 2016 | 04:02 PM
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Certainly shoot me a message when you are near, I'd gladly meet up.

Not a bad thought on the lug nuts, I will give this some consideration. Certainly Hardened is the way to go with the higher tensile and yield strengths. Thus why NHRA specs these. I run into similar dilemmas on the daily with representatives not know metallurgy and pitching products.

Pertaining to the spacers, I used a 20 mm H&R on the Rear and I have a custom 25 mm on the front. (I tried various dimenisions). This gave me the perfect stance with not really any wheel rub. With the Pirelli's (which have a wider contact pattern than most) on the 20" rim I can get a lite rub when fully compressed with very large bumps in the road. I plan to correct this with a slight roll on the inner side of the rear fenders.
 
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Old Sep 24, 2016 | 06:43 PM
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Fricken - Please clear some pm space. I just tried to pm you and was told that there is no space as your mail box is full.
 
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Old Sep 25, 2016 | 08:19 AM
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Originally Posted by ralphwg
Fricken - Please clear some pm space. I just tried to pm you and was told that there is no space as your mail box is full.
Thanks. Clearing now.
 
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Old Sep 25, 2016 | 08:00 PM
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Any update on this diffuser project?
 
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Old Jun 16, 2025 | 01:39 PM
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Originally Posted by FrickenJag
No pictures yet as I'm still processing the full car data into a usable model. I should have a design put together in a few weeks, then I'll start with the tool to mold the carbon. I'm going to run CFD on the base design then compare to a final design. I plan to do this so that it is truly functional and not just a visual perk. Thanks for the Diff-flow link. Certainly direction I'm heading, just in smooth carbon and nice transitions.
I'll post up CFD and final design iterations for opinions on final appearance soon.

Regards,
Derek Fricke
there’s a couple of good AI apps out there that will literally render some 3-D drawings based on the parameters or dimensions that you put in and can formulate the drag coefficient for different models. It’s amazing how fast and easy it is.
 
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Old Jun 16, 2025 | 01:40 PM
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Originally Posted by Obtuse1
there’s a couple of good AI apps out there that will literally render some 3-D drawings based on the parameters or dimensions that you put in and can formulate the drag coefficient for different models. It’s amazing how fast and easy it is.

Interesting…. Which ones???
 
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Old Jun 16, 2025 | 02:15 PM
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Originally Posted by jahummer
Interesting…. Which ones???
For creating 3D drawings and calculating drag coefficients, several AI-powered tools are available. Meshy and 3D AI Studioare excellent for generating 3D models, while AirShaper is a cloud-based platform for simulating aerodynamics and calculating drag.

Drag Coefficient Calculation:
  • AirShaper:
    This cloud-based platform uses Computational Fluid Dynamics (CFD) to simulate airflow around 3D models, allowing you to analyze drag and optimize designs for aerodynamics.
  • try a free one at first like famous AI that has limited capabilities or even something like ChatGPT. All you have to do is type or talk into the voice microphone with something like “generate me a 3-D model of a rear diffuser fit specifically for a 2012 jaguar XKR”
 
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