They are that wide. i plan to run a wider wheel and tyre combo in the future. unfortunately these were what was available for the right price when i needed them. not a perfect offset for racing i know. any lesser offset in the wheel i got woulda had clearance issues. as with most wheels with factory brembos these days

i have voltex guards on the front and a widened front bumper so the front fits them easily just need to pump the rear out a little to fit in the rear. they fit as they are currently just under high load it will rub

Attached a photo of how they fit currently. sorry are linked from instagram so you have to click the image square for them to appear

 

Just an FYI for those Aero nuts out there who have the funds and would rather buy the best in the world rather an build it yourself - the entire 2014 Tilton Interiors aero package from Voltex would cost around $70,000 USD. More than I was expecting, but you have to pay to play! :-) I was really hoping to be the first EVO in the US with this kit but it's just out of my budget right now.


If I can get a breakdown of the individual piece prices I will post it. Right now I am planning on buying a couple pieces and custom fabbing some other stuff to end up with a respectable aero package for my T/A build at a price my privateer/working-man's budget can afford. But looks like it's still going to be at least a year or two before my car hits the asphalt.


Back on the topic of aero, and specifically canards, there seems to be two major thoughts into canard design. First is the vortex generation of the smaller style canards such as the APR or the Voltex street canards. These create vortices down the side of the vehicle, reducing drag a bit and keeping some air from from flowing under the car along the side-skirt area. The second style are the very large units such as seen on Nemo Evo and the TI car during WTAC. These may also create some vortices, but the major effect seems to be to actually act as a wing element and create direct and measurable downforce at the front of the car.


I read a technical article years ago in Racecar Engineering magazine where they tested the effect of smallish canards on a GT-1 style car. I think it was an Aston Martin if I remember correctly. The wind tunnel testing showed that adding the canards reduce total car downforce slightly, while adding some in the front and reducing some in the rear. Basically they were used to shift a bit more traction to the front of the car. So, in theory, if you had a car that tended to push a bit - adding canards in the front could increase front grip while reducing rear grip a bit - thus yielding a more balanced car. However - if you already have a well balanced car - adding the canards could, in theory, make the car more tail-happy. (all this is just my understanding and recollection - feel free to add to or fix any misinformation).

 

Next, in response to some friends who were discussing rear diffusers:


According to my aero guy a good average rear diffuser angle is around 8-10%. Of course this is going to be different from car to car, and even from the same car with different aero treatments. Once you start getting past 10-12% angle you run the risk of flow separation, which can cause increased drag and reduced downforce.


If designed properly - this angle could be increased dramatically. For example - the Lovefab Pikes Peak NSX.



According to some basic and rudimentary testing by Lovefab, despite the huge angle of the diffuser, because of the close proximity of the giant wing and the overall shape of the car the flow stayed attached fairly well. Of course in a real wind tunnel at 100mph the results may have been different.


So, on a boxy shaped car with a wing such as the EVO we normally look at a diffuser in the area of 8-12* angle. The keys in downforce generation are the area of the diffuser, where the air comes from, and where the diffuser starts. Let's start with the last one - the first change from flat undertray to the rear diffuser.


From my research and what I've learned this is the key to making and locating the center of the low pressure zone that creates "downforce". Keeping the whole-car as a unit in mind - where this happens has a significant effect. You can think of the rear wheels as a fulcrum and the DF as a giant weight on the end of a lever arm attached to this fulcrum. If you make 1000# of DF 2 feet behind the rear wheels, you could measure more than 1000# increase in force at the rear wheels, but also a loss of force on the front wheels. Think of it like this - if you put 5000# in the trunk - the rear is going to squat while the front of the car tries to come off the ground. HOWEVER - if you put all that force directly over the rear wheel - the weight on the front of the car is not affected. And, likewise, if you put the weight in the rear seat - most of that weight gets applied to the rear but a bit also gets applied to the front of the car. Likewise where you locate the first angle in your rear diffuser affects the center of lower pressure, and thus the distribution of DF. In my opinion it is best if this is at or in front of the rear wheels. In fact, I say as far in front of the rear wheels as possible is best. Your limiting factor will likely be the rear diff and the rear lower control arms while maintaining that 8-12* slope. . .


I think this idea is why the tunnels on old race cars from the 70's and 80's started so far forward until rules changed. Also I believe the Nemo Evo and to a much lesser extent the Tilton Interiors Evo has rear tunnels/diffusers that start farther forward.


This could all be late night beer induced conjecture - or it could actually work kinda like that. Not sure. But that's my theory. . .

 

Great analogy, Jarrod. From my reading, you couldn't have explained that in a better way.

$70k for the Tilton kit? Not as bad as I was expecting. I opted to build my own and spent no where near that. Obviously quality isn't anywhere close to Voltex, but it will work.

 

here's some picture of my rear diffuser i just finish making.

more details here - https://www.evolutionm.net/forums/pr...l#post11408652

 

i need this.

 

subscribed

 

Looking great Honda Guy! Any other underbody tray or just the Splitter up front followed by the Rear Diff?

 

no flat bottom. but i'm going to make panels under the fuel tank to the rear control arm. there's a large void there that can disrupt airflow.

 

Flat bottom is easier than building a diffuser lol. I have a few attachment ideas in my notebook.

 

^ then you'll have to worry about additional cooling for everything

 

NACA ducts...duh

 

i have a NACA duct for the tcase on the front splitter. you'll have to do something with the exhaust if you going to trap all that exhaust heat in.

 

floor doesnt need to be flush to the bottom of the car. there will always be SOME air above the splitter/floor/diffuser just need to control it/make it useful and most importantly fully seperated from other flow.

as long as the pressure above the floor is higher than below.

 

On my flat bottom I placed guides that divert the air out the rear wheel wells... not sure if it works but the trapped heat hasn't been an issue yet

George