Little update...

Next 2 feet are done bringing me back passed the front tires. Also finished up one side blade that runs all the way back to the rear tire. Now just gotta copy this piece to the passenger side and install a center section.

Sadly the W brace hangs lower than anything. If I installed the panels to the brace the flat bottom wouldn't be flat. Instead of tapering up going back it'd actually taper down which would make the bottom 100% want to take off like a airplane and that wouldn't be good. So everything will be flat down there but the W brace. It'll just have to stick out some.



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Well the outside fins do run up to the tires, does that count?

No idea what I'm seeing but I'll get a ground height measurement once the flat bottoms done and I go back onto the ground.

Looking good .............

BTW, I have some photos of the diffuser I will be using for my Z34 here as well ......

I don't have images of the front splitter yet but will post them in my engine thread in due course

Nice!

So as long as the fins closest to the wheels run close to the wheels thats good?

Ill also make this diffuser piviot where its attached to the rear spash guards if you will and make it height adjustable with aluminium plate screwed to the rear bumper beam. Ill use some 1-2" x 1/8" plate with holes drilled it in like every 0.5" so if 15* dont work ill just move the plate down 0.5" at a time.

Takjak, that article was really good, but went over my head a few times. The key points I took from it (correct me if I'm wrong) were: volume of air entering the diffuser dictates optimal rake; to reduce delaminating and/or increase efficiency, create vortices; and the suspension setup can create the same effect as a diffuser - without using a diffuser.

As for the turbulent air from the tires, as I understand, ideally you want to isolate it so it doesn't slow down the air from the diffuser.

Did it say how to do that?

where's the pics of flat bottomed girls?

Don't see any. Reported for lying.

:icon23:

A couple things that come to mind are:

1) You probably want to attach the rear diffuser REALLY well or it will just get pulled right off. Overbuild the attachment points like you wouldn't believe. A lot of rear diffusers are only there for cosmetics, or as a cover to smooth the underside of the rear of the car. But with your design, you're hanging it as a wing, so really make sure it's securely mounted.

2) If you clam-shell the whole bottom of the car, you'll have to make sure you have enough room for hot air to leave the engine compartment. A vented hood might do it, depending on the vents, otherwise you might want to look at venting the front fenders. I suspect the factory aero blows the hot air under the car at the firewall, and you'll be blocking all that off. So with less throughput through all your coolers, they will be less efficient.

3) Don't forget you need to be able to get air to the brakes. There isn't much from the factory, but when you really streamilne the evacuation of the air under the car, ducts are a necessity. Make sure you have room for them under the clam-shell.

These are pretty rudimentary points that you probably already considered, but that's what's popping up in my mind when I see this. But great work so far! Can't wait to see how it turns out!

1. Thanks

2. Yes im gonna run aluminium 1/8" plate to the diffuser like the front spliter and will be going to the body under the trunk and stuff and also the rear bumper beam.

3. The hoods cut and vents very well.

4. The front has 2" brake ducts already but im planning on adding a 2nd 2" that'll get air from the front end grill mesh vs the velocity stacks attached to the front bumper already. Also the rear gets air from the window scoops.

5. The rear bumper oem fake fog light and cutouts for the exhaust is gone so a nice 3" gap is missing from the bumper to the splittter. So any engine heat should go under the car between the body gaps and the flat bottom and exit out the rear bumper gap. The rear diff cooler has the window scoops also feeding it air to the cooler so sadly it'll get a mix of extreme hot and ambient. I might add a naca duct on the flat bottom and run a hose there also to the diff cooler so its being fed 3 ambient tubes.

6. I do wanna add fender vents. Martin makes some but im thinking more of a STI 207 long skinny vent.

Both sides done. I've decided not to use the same material to cover the center section. I'm going to try and save weight. I used the dibond for the sides for strength as they stick out pretty far but the center will be just thin aluminium. I also did access holes for my jacks and I'll be using the same thin aluminium to make removable plates for these holes. Last I had some black vinyl around so I wrapped the sides to blend into the side skirts.

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Back to the topic. How far out does the side blades protrude?

The are equal with the rear tires which are 285's on 10.5" wheels with +15 offset but then I have a 45mm spacer back there. So talking wheels it's 79mm extended over oem plus the tire.

It's not done yet, all the self tapping screws will be replaced with rivets holding the fins on. Also going to paint it black with the tips of the fins painted red.

Also cut the fins back 5.5" as it was to low and now I have 2.75" clearance just like my front spitter.

There's a diff cooler under there with a cage I built thats bolted to the underside of the car at the same angle, there's 4 self tapping screws to that. Then I have 4 brackets with 1x1/8" plate holding the back end and sides up which is bolted to the rear crash bar and the side body of the car. Then I have a bunch of self tappers into the bumper and stuff holding it all down snug.

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