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C4 Rear Diffuser

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Old 11-29-2015, 07:59 PM
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l98tpi
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Default C4 Rear Diffuser

I have been working on a rear diffuser for the 91. Made a template, took a bunch of measurements, and came up with a design. So far, I have the main panel installed, not fastened yet, and trimmed for fitment. I will get back on it next weekend or the next and work on the vertical stabilizers.















Last edited by l98tpi; 11-29-2015 at 08:08 PM.
Old 11-29-2015, 08:12 PM
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rsc337
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Looks great and I can't wait to see this done. Great idea. Where's your exhaust going to go? Good luck.
Old 11-29-2015, 09:25 PM
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l98tpi
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Originally Posted by rsc337
Looks great and I can't wait to see this done. Great idea. Where's your exhaust going to go? Good luck.
My exhaust ends just before the rear differential. My theory is that the exhaust gases will help speed up the air flow at the diffuSer and aid in decreasing the air pressure underneath the rear of the car.
Old 11-30-2015, 12:07 AM
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bill mcdonald
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Old 11-30-2015, 07:01 PM
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mxnuke
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Thanks for posting pic's of your work . I have to find the time to build one. good luck
Old 12-20-2015, 08:18 PM
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l98tpi
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Default phase 2 and 3 complete

Here is an update on the diffuser. Close to complete, just need to paint.
Attached Images     
Old 12-20-2015, 08:43 PM
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MatthewMiller
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Looks good! Have you figured out ground clearance when the rear is squatting under acceleration?
Old 12-20-2015, 10:01 PM
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l98tpi
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Originally Posted by MatthewMiller
Looks good! Have you figured out ground clearance when the rear is squatting under acceleration?
1.5 to 2 inches. If it does touch, I can trim them. I used dzus fasteners to attach the strakes so I can remove them.
Old 12-21-2015, 01:42 PM
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BrianCunningham
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Nice
Old 12-22-2015, 01:06 PM
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95wht6spd
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Looks good, nice work. Do you already have a spliter? Doing side skirts too?
Old 12-22-2015, 09:01 PM
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l98tpi
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Originally Posted by 95wht6spd
Looks good, nice work. Do you already have a spliter? Doing side skirts too?
For the splitter, I have the M1 Prowler front spoiler if you are familiar with those. What I did there was, I replaced the factory center bracket for the spoiler with a pipe hanger that is strong enough to hold what bend I put in it. With the bend I control the angle of the spoiler and can adjust it to between 1" and 2" off the ground. It has and is working good for now.

Not sure on the skirts yet. I am going to see how the car reacts with the diffuser. If I was trying to keep as much air from under the car as possible like the NASCAR Cars, then I would go ahead and add skirts. I do already have an idea for rubber skirts, but going to hold off for now.
Old 12-22-2015, 09:29 PM
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95wht6spd
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Skirts will help the diffuser work better. If I was going to do it, I would keep it simple and get some material like the front air dam 2-3", and attach a long piece on each side to the seam that hangs down under the body side. Being black, and tucked under, it would not be very noticeable.
Old 12-23-2015, 11:10 PM
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l98tpi
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Originally Posted by 95wht6spd
Skirts will help the diffuser work better. If I was going to do it, I would keep it simple and get some material like the front air dam 2-3", and attach a long piece on each side to the seam that hangs down under the body side. Being black, and tucked under, it would not be very noticeable.
I will keep that in mind. I have a similar idea, but will put more thought into it after I test the diffuser.
Old 12-24-2015, 05:34 AM
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Churchkey
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This plastic works well for side boards etc. Its light weight & will clearance itself.

https://www.lefthanderchassis.com/v2...dgroup=2512038

Avatar pic shows it, side boards & front fender extensions.

Last edited by Churchkey; 12-24-2015 at 05:40 AM.
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Old 12-24-2015, 01:01 PM
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STEVEN13
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Looks Nice!

I can't tell from the photo-Did you remove the storage box and ABS box (if you car had ABS).


Steve
Old 12-24-2015, 01:19 PM
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l98tpi
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Originally Posted by STEVEN13
Looks Nice!

I can't tell from the photo-Did you remove the storage box and ABS box (if you car had ABS).


Steve

ABS and Storage compartments still on the car. It was getting dark when I took the picts .
Old 12-27-2015, 09:18 AM
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spro2395
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Originally Posted by l98tpi
For the splitter, I have the M1 Prowler front spoiler if you are familiar with those. What I did there was, I replaced the factory center bracket for the spoiler with a pipe hanger that is strong enough to hold what bend I put in it. With the bend I control the angle of the spoiler and can adjust it to between 1" and 2" off the ground. It has and is working good for now.

Not sure on the skirts yet. I am going to see how the car reacts with the diffuser. If I was trying to keep as much air from under the car as possible like the NASCAR Cars, then I would go ahead and add skirts. I do already have an idea for rubber skirts, but going to hold off for now.
Did the car run hotter when you put the front splitter on ? I'm thinking of putting one on my 85.
Old 12-27-2015, 08:21 PM
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l98tpi
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Originally Posted by spro2395
Did the car run hotter when you put the front splitter on ? I'm thinking of putting one on my 85.

No, a splitter should not cause the car to run hotter unless you install something that restricts the amount of air going into your radiator opening under the car. Mine increases the amount of air going in and with the addition of the hood vent the extra air and heat get pulled out from underneath the hood.

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