http://www.speedhunters.com/2013/06/...-aerodynamics/ Just saw this today

 

I have been wanting to make full undertray and rear diffuser for s2000 for some time now. however, everyone talks about diff and tranny temps. so I am wondering if anybody actually knows what is the optimum temperature range for the two?
I am not sure if NACA ducts under the car can create a good cooling system for the diff and tranny however i do know a better and more efficient way of cooling it if necessary I will be making a kit soon (couple of weeks) and as usual will test it on the track and get some temperature readings on both diff and tranny with no ducting and with NACA ducts.

 

A Big to you..

 

r1rs being what they are - they lost all my respect when they mounted hte NACA ducts with an exposed lip - that is going to totally abuse any attached airflow going over that outside lip and ruin the whole point of a NACA duct.

as to how effective NACA ducts can be under the car - as long as you're running attached flow - aka a flat undertray you should have good success with them under a car. Ideally you'd locate them wherever you have the most attached airflow which may not be by default on an undertray.

I run my trans in a fully contained/closed trans tunnel with the only airflow being transient air leaking through the bodywork and a few errant holes. Temps have been very reasonable and I haven't done anything like boil trans fluid yet. My diff will be covered 100% by a diffuser shortly and I'll know if there are any issues there as well.

Most pure race cars that run very high specific output motors with full tunnels/floors tend to run cooling pumps/radiators for diffs & trans to keep the temps down and those are way more efficient with air use then passive cooling of the outside of a diff or trans.

 

Be careful with the differential cooling--the S2000's definitely runs hot on the track.

 

I added splitter dams to my splitter's outside edge to bumper junction to try and keep the very high velocity air spilling around the splitter/bumper junction from hitting the front tires. The S2000's nose shape will cause even more air to flow around the sides of the car than the Ford Fusion NASCAR in the CFD diagram posted earlier. Running wider than stock front tires will increase the drag caused by this side airflow because the tires extend out into the airstream. I run a square 255 width tire setup (stock is 205) and the front tires extend over three inches outward beyond the front bumper.

In the book, Competition Car Aerodynamics, by Simon McBeath (yea, tell your friends you enjoyed reading McBeath) he discusses how splitter dams (he refers to them as a "vertical fence") increase downforce by creating a high pressure area on top of the splitter in front of the dams--so they are a win-win with less drag than bare tires in the airstream plus additional splitter downforce.

 

Does the book address the pros/cons of those versus dive planes? Since both would direct air around/over the front tire. The latter visually would seem to introduce less drag (as the splitter dam appears to be more of a 90 degree angle), but I am aware that what looks intuitive isn't always actually right when it comes to aero

 

so is it necessary to have splitter Dams and splitter side plate together? Do you think it will creat alot of Drag ?

in progress to build my splitter right now, any word would be help.

Like the pic below from Nemo EVO .

 

McBeath tested 3 different size dive planes with and without a dam. The dam without a dive plane gave the most downforce and least added drag which surprised him. The discussion is on page 256.

For an S2000 the drag generated with a splitter with a dam and end plate might be excessive enough to slow lap times. I would think if you're running 255 or wider front tires then a splitter dam would probably be optimal. The Evo pictured has excessive horsepower so the drag is not as important as the added downforce.

 

Thanks. I am working on revising my front aero now and have been curious about that. That finding (dam without a dive plane) being best surprises me too, so that's very interesting. I'll have to order this book.