Any tips you gents wanna include for me? I'd like to do This without cutting the bumper...not sure on exhaust yet either...ideas?

Thanks!

 

First off, I love you .... well your ambition that is lol

For a car thats more than 10 years old, NO diffuser? lol yet the C6 has some already

Ok Down to business...

-Id make The fins probably no bigger than a 3/4 of an inch.
-Try to keep the assembly away from the ground for obvious reasons, sway bar would be a good ref point.

Now what do you like more 2 tip or 4? I myself love the 2 tip design. Its funny how a lot of ppls complain about how complicated changing there system would be cause its soooooo difficult lol.

My advice to you ( if you dont wanna run straight piped like me) Buy a Borla Dual In/Out muffler and choose your own tips! you can actually buy JUST the corsa tips, theyre like $99 a piece and SLP made ones just like them for only $69(checked Summit couldnt find them)

Out of All the diffusers Ive seen(sadly not too many) this one is the best looking, sadly the price is



IMO the Fins are too thin, and I think with a lowered vette they would stick too low. A C6 owner already said they stick below the sway bar...

Good luck!

 

thins fins are good ..less drag..they are usually solid carbon ..on most of the gt cars i have worked on ..
the lower part of the fins should be in plane with the belly pan of the car...they are there to keep the air moving straight and reduce turbulence..and the turn up at the rear of the car crates a vaccum and improves down force on the rear the fins bein low is very impotrant for it to work...street defusers and race defusers are different...breathless performance makes some look at them before you take this on ..i really didnt pay much attension to it when i did the roll cage in his car but i know he makes them ...

find a good fiberglass supplier..get the foam..they use for boat top..it is expensive..shape it how you want it wrap it in glass ..they buy a product called dura tec...it is like a spray primer filler...works very well..smooth and paint ..it is going to take you alot of time...to get it right....lay your fins up on a piece of waxed glass..and glass in..

this is a jet ski hull i built..i have it going alomost 90 on the water...and it is still rec friendly..i went through it all..and currently testing and tweaking ..once it is all done ill make a mold and then make it out of carboin and shave @ 150 to 200 lbs off the boat..that will bring my 0 to 60 times down to @ 1.7 seconds..one of the many things i do in my shop..



this is it in duratec



then gel coat..

 

on my first go, I am just going to use ABS plastic. Its hard and durable.

 

what about alumilite? I used that for my splitter, and if i make a rear diffuser, I'll use it as well. MUCH stronger than ABS plastic, and better (but not great) tollerence to heat.

As for the exhaust, you can bump it before the tranny, and you'll be fine.

 

Look at a real diffuser not a rear fascia they call diffusers. You are in for a ton of work and engineering to do it properly. You really need the entire underside of the car set for a diffuser that works. Good Luck.

 

The angle of divergence (that is the angle of the diffuser relative to the road) shouldn't be greater than 10 degrees. Start at the maximum area (at the exit of the system) and go forward at an angle of 10 degrees or less. I you go below the rear swaybar then reduce your angle. The sides of the diffuser should also diverge. You want to maximize the area of the diffuser and this helps to achieve that end.

The leading edge of the diffuser should be rounded and not sharp and the curve of the leading edge should stick up higher than the bottom of the cradle or swaybar. The surface should extend a bit below the cradle so that the flow can reattach, so there should be a bit of surface that is flat for an inch or so and then it should curve gently up to the 10 degree or less angle.

Suggest that you do some mocking up with cardboard before you start cutting plastic or laying something up.

 

Hum...good tips...I am going to mock something up kinda like the gt2 c6r....there is no fins..just a flat surface and angled up

 

Ahhh... somebody knows about about aero engineering

The one tip I'd offer is to decide what you want it to do. If you want it for looks, then you'll probably be happy with whatever you decide on. If you are building it as part of the vehicle's aero, I think you'll be very disappointed. As John mentioned, you pretty much require a flat bottom all the way along.

Here's a bit of quick info:
http://www.mulsannescorner.com/diffuser.htm
http://www.nas.nasa.gov/About/Educat...odynamics.html

And you'll be wanting to research and know Bernoullis Principal.

A diffuser is a great piece, but it'll only work if done right.

 

Might I suggest a copy of "Racecar Aerodynamics" by Katz.

My experience says 7° of divergence, if it has to be a 'flat' ramp...the ones I've done, have been restricted by the rule set of the series, ie no full under body tunnels with conic profiles, etc.

 

And Dave should know - since he did the ones for Mosler! And I couldn't agree more about Katz' book - it is a must have for aero. I read it cover to cover while on a temporary assignment away from home (for a little light reading). Remember, just cause something looks good and looks like it "should" work does not mean it will, and in reality it probably won't. Aero is too complex for seat of the pants engineering.

 

3rd vote in favor that you read the book above. I have another 2 I studied on aerodynamics, but they are much more technical & very dry (and almost 900 pages each...). The Katz book will give you enough basic examples & info to hit the ground with some basic ideas how it can be shaped without wearing you out by reading it.

 

Thanks! I will pick that up! I'd love to know more...

 

What rules are you designing under? Or to put it another way, are there any rules that would prevent you from doing a biplane diffuser? By that I mean a higher angle diffuser with an airfoil section between the main diffuser face and the road. If that's legal, you could get huge amounts of downforce from a configuration like that.

 

You have a pic of something like that? This isn't for any rules...its run My car I will use as fun on a track...I don't have the time to do real events and such..I just want a c5r for the street to :-)

 

The book is called: "Race Car Aerodymanics: Designing for Speed" by the aforementioned Joseph Katz... I also have read it several times and realized that most rear diffusers are really for looks, not effect. Unless the entire underbody is given the aero treatment, the airflow under the car is too turbulent for a rear diffuser to have a noticeable effect. Most of the "supercars' that have effective rear diffuser aero also have flat bottom panels and mid engines. The mid engine design also makes doing the flat underbottom thing much easier from an engineering standpoint. The picture here is the Brian Glover Design "feeder" panels for the rear diffuser. I'm guessing this is about as good as you could do for a streetable car.

 

I am going to talk to Pfadt since their car is very fast with their diffuser to see what they have done, recommended, etc...I know they modified it many times to get it to work. I do not know what they have done under the rest of the car that is within the rules but with a little work I know I could make most of the stock bottom pretty darn flat. Or, I can cover it with Alumalite for a low cost, super low weight flat bottom.

Maybe I will see if they will sell me the design or build me one like theirs.....since my car is a Vert it is not easy to get proper airflow over the top for a wing and I really do not want to run one on the street. I black painted diffuser would be ok for me

Again, I do not know what they have done but I do know it must work to run against cars with huge rear wings as in the 09 season, at least part of the season, pretty sure no wing at the NASA Nationals. 2010 they ran a wing with the diffuser.

Rick

 

I doubt you will have much fun with a diffuser that works on the street. I think you will doing many repairs. Look at the bottom of a C5 or 6 R

 

If I ran a real diffuser I would have it all with quick releases and just put it on for HPDE, TT, etc......I have a CF ZR1, very well built, splitter and side skirts coming, I will use a less expensive FG splitter, modified for much more downforce, for the track and street and keep the CF one for special events....so I do not have to replace it all the time

Rick

 

http://www.breathlessperformance.com...&productId=911

This is a 100% functional lower rear diffuser. A must for track days or that ultimate racing look. Bolts on in about 1 hour.

Weight is under 10lbs.

It is a easy bolt on. Trim of the lower factory bumper and our rear diffuser bolts in from the back side and has a brace and bracket that attaches to the lower control arm bolt.

Our Diffuser was designed around the B&B 2 tip Exhaust system but other 2 tip systems could work as well.

Can be used on the street or the track!!!