Ive made my own out of alumilite. But check out DHP Composites for real aero:



http://www.flickr.com/photos/dhp_composites/

 

So, how does that mount up?

 

thats for you to figure out/fabricate

 

To really generate the downforce from ground effect the splitter needs to be LOW. I ran a custom fabbed alumilite splitter that replaced the stock lip on an Evo 8 bumper and attached to the frame with welded on tabs. It was 2.5" off the ground and with R888s and 500lb springs in front it would rub on severe elevation changes (at Infineon, it rubbed in T1, a little in T3, and in T6). It made a noticeable difference but not really until 80mph. It had no flex problems up to 113 mph (as fast as the car went that day).

So, it can mount to the bumper, but not *only* to the bumper.

 

Properly designed, will provide significant improvements even at autocross speeds. . .

I agree to focus on brakes and reliability first, then start adding parts to allow you to go faster. . .

 

I've only really noticed any benefit from my Aero bits (splitter, canards, wing) on my car above 140km/h or so (80mph) - at those speeds the difference in stability os pronounced, expecially when cornering.

But my car runs pretty high - not a tarmac scraper at all - so I don't think I'm getting much in the way of ground effects.

Question for people - better to run extremely stiff (not skipping over ripples stiff though) but low in order to lower Cg and improve aero ground effect OR would it be better to run at a higher ride height in order to improve suspension geometry but at the expense of Aero?

Or, perhaps, would the best of all worlds to be run higher (better suspension geometry) and extend the bodywork lower to acheive aero effects (airdam, sideskirts etc.)?

Curious to know if anyone's experimented with full, aggressive aero setups on the Evo - i.e. an aero setup designed to dam off the underside of the car to create the best "vacuum" possible (combined splitter + sode skirts + rear diffuser). And if so, what the benefits were/what speeds benefits started to be felt?

 

'Real' aero takes affect somewhere around 60mph. That was the case at least on the single seater Formula Russell cars I drove last year. For any production based sedan, the best you can hope for is to cancel out the lift all sedans generate at around 80mph. To do any better involves installing a working flat bottom which involves a lot of compromises to daily driving/usability. Look underneath a Ferrari or elise for an example.

The other issue with aero on an evo is achieving the right balance. It is way easier to add more rear aero than front. The traditional rear aero upgrades ( rear wing and diffuser up to rear axle) will generally overwhelm any front aero you can reasonably add (splitter, canards). This usually leads to biasing mechanical grip in order to supply the necessary front grip at lower speeds but inevitably leads to compromised performance once aero takes affect. Its been really helpful to have an experienced suspension tuner around when making these choices.

Beyond not being able to add enough front aero on an evo, it is also really hard to add front aero that is adjustable. As an example most prototype class Le mans cars can move how far the splitter extends in front of the bumper and how low it sits.

We have been facing these issues on the Lee Myles Time Attack car and at almost every track, we have to minimize the rear wing effect (take out wicker bill, zero out angle of attack) in order to achieve the best balance.

Next year we're hoping to test a prototype canard systems as well as lowering where the front splitter sits to achieve better overall balance.

Hope this expands the conversation.
-heeltoer

 

If your splitter is not a properly designed 3-d style, then you're only getting about 1/2 of the front benefit you could be making . . .

Because the front is hardest to change, and the front wheels do the most work on the EVO, MAX out the front downforce then use wings, diffusers, etc at the back to even out the aero balance. . .

As far as ride height vs. stiffness - you only have to take a look at your average LMP car to figure out what is best. 1-2" of wheel travel and lots of aero is the way to go. It is also the expensive way to go . . .

 

Great post. The only thing I disagree on is the "if you can't stand on it, it doesn't work" idea.

Think about it this way - you said the Voltex bumper makes downforce. Can you stand on the lower lip/splitter area of it? Can you stand on the center of the stock wing?

If a splitter makes 600# of downforce at 150mph, and is aproximately 60"x30", that is only about 5 ounces per square inch of weight to support . . . and that's ALOT of downforce and a pretty small splitter. Real world the weight per square inch is probably half of that.

 

Not necessary. If you are running wide wheels, they will stick out farther than the bumper.

If you are hitting cones with the front of the bumper you have other problems. . .

That bumper was on my car when it won two Solo2 national championships this year . . . PLUS another splitter that sits below the VOLTEX unit and sticks out 5" in front of the bumper !!!

 

DHP sells one. They are not really "off the shelf", as they don't have them sitting on a shelf - rather they are made-to-order.

Every version of this that has been built mounts to the frame of the car. I will see if I can dig up some old pics of the V1.0 mounts. . .

My latest home-made revision uses part of the Voltex mounting system, and incorporates 4 AEROCATCH latches and a slotted rear mount to make the splitter quick-detach. Goes on in about 30 seconds, comes off in about 5 seconds. . . and still makes downforce. . .

 

Here are some pics of how we mounted the very first version of the DHP splitter. Nuts welded to square tube stock bolted to the frame. . .

 

Thanks for the info!

Do you have a list of those that are or (are popular splitters) and are NOT 3-d style? I'm not sure what you mean here.

Also, are you saying you recommend the Voltex? And what was the additional splitter you used with the Voltex front? Was it the widebody front and using canards?

Thanks again!

 

By 3-d I mean not totally flat. The APR splitter is totally flat. The DHP and Voltex units have angled areas that creates a low pressure zone on the underside of the splitter that "sucks" your car down the ground.

The APR style flat splitters will only create downforce by gathering air on the top of the front lip area . . .

I DO recommend the Voltex front bumper, as well as their splitter and undertray and canards. They are all top notch parts. If you want a moderate track setup while being able to drive around town and not worry about ripping anything off the front of your car get the Voltex street bumper and undertray. This will make a good amount of downforce and you won't have a giant carbon ankle slicer sticking out the front of your car.

If you are independently wealthy and want your car to be as fast as humanly possible and don't plan on driving the car on the street, get the Voltex Cyber Edition front end with giant splitter, giant canards, front wider fenders, some 18x10 or 18x11 wheels and have at it. Plan on around $5K for the Voltex pieces. .

If you want something in the middle, go with the Voltex front bumer and the DHP splitter/undertray.

(they "street" edition stuff is what's on my car, the "Cyber" edition stuff is what's on the Cyber EVO, if you need to look up pics. . . )

 

Not having seen the underside of an DHP (link? can't find these guys anywhere) and using the voltex as a reference
https://www.evolutionm.net/forums/sh...d.php?t=220889
Was this tested before hand? I.e. flat bottom vs. DHP/Voltex "3D" used on the same car and lap times recorded?

I'm having a hard time being convinced that a "3D" front splitter will have any greater effect than a flat bottom'd front splitter. Please explain the purpose of 3D area and vanes if the rest of the underside does not also have a flat bottom.
thx