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View Full Version : Carbon diffuser? You can make too! Here's how with pics.



Chairs with flares
27th February 2009, 08:27 PM
The plan was to make a carbon/fiberglass rear diffuser for downforce as an adjustable wing would look too funky on a small hatch.

Here's how it all started;
http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7469.jpg

The first thing to do was to determine the size and curve of the main diffuser panel. The optimum trailing-edge angle was determined to be 10*-15* up from horizontal over a fairly gradual radius. The diffuser creates downforce by helping the higher pressure air flowing under the car transition into the low pressure area directly behind the car. As a result, the vacuum behind the car essentially 'sucks' the air out from under the car, creating downforce. Any steeper angle on the trailing edge and the air won't follow the diffuser and it won't be as effective (unless it's really close vertically to a wing; e.g. Formula Ford cars)

Using cardboard, we made a rough template of the curve and size available within the dimensions of the car's floorpan and rear bumper cover.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7470.jpg
http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7471.jpg

Using this template, a mold was made up to allow the carbon and fiberglass to be laid to the right shape. I just made more of the above template and used them as 'ribbing' to bolt together a wooden frame topped with MDF board then aluminum sheeting from Bunnings. Aluminum is chosen for it's ability to de-mould itself from carbon cleanly.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7472.jpg

I also made a smaller form purely out of cardboard to mark the cut-outs needed in the main panel to allow clearance for the exhaust muffler and factory tow-point.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7473.jpg

Time for the fun and stinky stuff! I'm gonna skip the stuff on laying down fiberglass as that's fairly simple and there are many tutorials through google. For carbon, make sure the weave is even at right-angles, as any imperfections will show up. Also, make sure you have enough material to cover your mould with a little hanging off the side and really wax the mould with mould release agent (4+ coats).

First layer of carbon/resin.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7474.jpg

Then 2 layers of rough fiberglass matting, a sheet of 3mm MDF board, and another layer of fiberglass to seal it all up. The MDF board gives a stronger base to mount through, reducing the risk of any mounting bolts pulling through the diffuser.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7475.jpg

After leaving it 48hrs to cure, pop it out of the mould by going aroudn it with a spatula. Here is when you find out whether you used enough release agent.

Use you cut-out template to mark and cut the main panel to shape and make sure it all fits around everything.

I then glued a strip of rubber 'U-section' with silicon around all the edges to hide imperfections and well as sticking a single layer of dry carbon on the top where it sticks out past the rear bumper cover.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7476.jpg

Now is when you decide how you mount it on the car. Being a FWD hatch, I had the luxury of simly bolting it to the floorpan in the spare wheel well. If everything went well, this will be where the MDF in the diffuser sits. The rear of the diffuser was decided to be bolted to the bottom of the rear bumper cover. Once the mnounting holes were mocked up, design for the strakes/fins can be done.

The strakes stop the diffuser drawing air from the sides, only allowing it to draw air from under the car. Ultimately, they should taper out towards the rear slightly. I used scrap dry-carbon to use as I had some lying around, mounted with 'L brackets' for shelving
through some of the holes used for mounting to the car body.

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7477.jpg

All mounting hardware was stainless steel, using 6mm allen-key bolts with Nylock nuts to prevent vibration induced loosening.

Finished product;

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7478.jpg

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7479.jpg

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7480.jpg

And everyone's happy!

http://www.ae86drivingclub.com.au/dcimages/1/1/6/7/7481.jpg


BIIG cheers to Busby (User ID: Mike86) for the inspiration and help through this shoddy weekend backyard project. He's the man to see for carbon blanking panels (radio delete/ac vents/speaker holes/etc).


Oh, and it seems to help with high speed stability on the track. Combined with front canard spoilers, cornering at previous speed felt much more stable and less 'floaty' allowing faster cornering. In short, it was a success!

:jdmsmile:

carbonae86
27th February 2009, 08:42 PM
Nice when are you making ones for toyotas

Or maybe that should be for toyota that arent cut up since thats the rage now :hehe:
http://img3.imageshack.us/img3/3927/reardifundershot2.th.png (http://img3.imageshack.us/my.php?image=reardifundershot2.png)

biggo
27th February 2009, 08:45 PM
Hahaha thats cool. I noticed they now make carbon weave look fibreglass now too. Might have a go at something like this oneday.

mack 10
28th February 2009, 04:06 PM
i enjoy resin

buddyparts
28th February 2009, 11:04 PM
thats awsome

mike i never new your skill well done

James86
16th March 2009, 12:56 PM
hahahahaha..........hahahahahaha

squish_m8
22nd March 2009, 05:00 PM
that's great

KKUSTOM
29th March 2009, 08:12 PM
saw this today awsome job dude. helped him grip like a beast. lol

The Human Panda
22nd February 2010, 08:04 PM
when r u putting this into mass production 4 us all

ArbPotatoes
16th March 2010, 05:46 PM
Make diffusers for 86s and KEs and sell them haha

KePanelVan
23rd June 2010, 05:32 PM
agreed and make one for a ke panelvan :D

takai
24th June 2010, 01:14 AM
Needs moar double venturi diffuser.
http://i35.tinypic.com/2lmt9x3.jpg

Oh and flat undertray....
http://www.gurneyflap.com/Resources/WILLIAMS-under2.jpg

keiichi
10th July 2010, 11:22 AM
^ and splitter