Unless I'm missing something, it is. So the design goal is to feed the exhaust gasses into the low pressure/drag area directly behind the license plate area, and thus increase wing and diffuser efficiency?

 

6mm plywood and three layers og fibreglass on each side.
A steel table, a 25mm aluminium plate and a ton of sand to make sure it would be straight. wil make ad ons on the side with canards later when the splitter is on the car.







Ready for paint!

 

I like when someone says "ton of sand" and literally means it.

 

Proper splitter. Thumbs up.

 

LOL! I read that while I was looking at the first picture, and I was confused at how a bucket of sand was going to improve the finished straightness/eliminate the inherent warping when added to the fiberglass resin....


And then I got to the sand picture and thought: "Whoa, when he said 'a ton of sand', I never considered the possibility that he used 'a ton of sand'.

 

Question for you guys who have installed a flat floor: I'm planning to go the "angle iron bolted to the pinch welds" route and also bolt in or support the panel to the frame. What I'm wondering is how the exhaust is going to route down around the diff to get to the back without getting in the way of the flat floor/diffuser.

Here is my current exhaust and you can see that there is no way to make it empty behind the bumper without bending lower.

 

put a cutout in the flat floor and leave the exhaust as is.

 

I'd like to avoid putting high pressure air under the car though, not the best for creating low pressure down there. I could run a more aggressive diffuser though...

 

make a vertical wall where the exhaust penetrates the floor. don't make it easy for air to get above it.

 

No, under the car as in where the exhaust dumps out. If I run a splitter, full flat underbody, and diffuser I want as little air below the car as possible to create low pressure. Hence the reason for side skirts on some cars. The exhaust dumping below the car messes all this up, and creates turbulance which just makes more pressure down there.

I'm hoping ThePass or some of the other diffuser-wielding miata people can chime in on their solutions (maybe with pics? )

Thanks!

 

Run the exhaust all the way back and have it exit above the diffuser.

 

That is the plan but how can I do that without dropping the exhaust below the level of the flat floor? If I have to do that I will but I was hoping to have a fully flat bottom.

 

switch to 96+ axles.

 

What would changing axles do?

And are you saying to route the exhaust to one side of the diff and up close to the axles?? I hadn't thought about routing above the axles but it seems like that would put a lot of sharpish bends in the exhaust. Below the axles and above the sub-frame brace seems like it wouldn't fit with the axles at full droop

 

Below the axles but above the bracing, with the 96+ you get a lot more room. I built my exhaust kind of sloppily with the 94 style axles and its scraped below the axles. If I was going to make it again now with the 96+ axles I could raise it up high enough to fit all 3 inches up higher than the cross brace.

 

perfect, thanks!

 

are 96+ the one piece axles?

the one piece axles give a ton more space. I agree.

 

Exhaust Blown Diffuser

 

A blown diffuser is basically a way of using the exhaust gases to interact with the diffuser airflow. There are two main purposes for this;
1. To try to move the wake from the rear wheels outwards where it will cause less disturbance.

So the exhaust needs to add air to the back of car, not under it

2. To re-energize the low pressure air at the back of the diffuser to create more rear downforce.

re-energize the air in the diffuser that is slowing down due to an increase in volume.

I am thinking about using an elise diffuser with the exhaust outlet in the middle of the diffuser for just these purposes. Under the car before the diffuser is not a blown diffuser

 

I love the article though, now I don't know if I want to do a blown diffuser anymore...