It's less to do with having it flat than to do with having good airflow, in fact with a completely flat undercarriage a diffuser would be useless since all the air would escape out the sides. What you want is for as much air as possible under there to be channeled out at the back over the diffuser which cuts the lift.



For less than the price of that diffuser you could buy a few 1mm aluminium sheets, and with a little planning make your own - diffuser and all. The only things you need to worry about is air paths for the radiator/diff/exhaust - which is not hard to get right. There's a good book on all this I can dig up if you want.



Mark

 

So youre saying that that diffuser is useless? but can you say why you think its useless? Like why do you think no air will go over it?



im just trying to understand so i can tell the difference



kevin.

 

On a non-ground effects car, invariably underneath you have high pressure - which creates lift = bad. On a ground effects car with a flat undercarriage and actual air passages, the whole car acts like a wing, the under carriage is made to effectively duct all the air out the back over the diffuser and turning the area of high pressure into low pressure i.e. sucking the car to the ground. Emphasis on the word "duct" - like I said, a perfectly flat undercarriage alone (i.e. without lips to hold the air in) will allow all the air to spill out the sides of the car, and away from the diffuser. So you can then safely assume the diffuser pictured is not doing anything since it doesn't even have a flat undercarriage, it has no hope whatsoever of having any serious air flowing over it.



That's a rough synopsis which is all I can offer, I don't want to get in over my head here . I got this book out of the library, and it seemed really good, I'd reccommend it: http://www.amazon.com/exec/obidos/tg/detai...=glance&s=books



Mark

 

I understand what youre saying better now, good description. So rather then perfectly flat you want air to be able to flow over the diffuser, but you want to make that air go from the front, straight to the back, you dont want it just spilling all over the place. right?



still might get this diffuser and build a full body one onto it, hopefully with the help of that book .



kevin.

 

On a side note, I noticed that Mazda paid more attention to airflow on the undercarriage of the FD. Everything is flat under there!

 

racingbeat made the bottom of their fc flat..... and it took off like an airplane .



kevin.

 

Yeah I don't remember a whole lot to be honest, that was when I was looking at other projects before I started the current one - almost 2 years ago.



I still think the diffuser is the easy part, make it out of the aluminium which would give you that real race car look - the only thing to remember IIRC is not to exceed 17 degrees.



Mark