Isn't a 2"x24" brake duct going to pretty much kill the effectiveness of the splitter either way?

 

It's going to rob downforce, yes, but it's going to also direct a lot of air to my brakes, which is a bigger problem than front downforce ATM.

God, they're all problems, why isn't building a racecar easy? LOLOLLOLROFL

 

Something to consider, brake flow has two sides. Getting air to the brake area, but also getting warm air out of the wheel wheel to let more cool air in.

Observe what a lot of high end production cars do for ducting. Few (if any) actually duct air directly to the rotor. Most just point air AT the rotor (and caliper) while keeping the flow path very straight and open. I wonder if all these duct kits using 3" drier duct tubing and calipers mounts to force the air into a limited amount of area are the wrong approach?

 

The production cars aren't race cars. The high end race cars all use ducting

 

I was under the impression that these cars generally route the duct into the vicinity of the rotor but leave it up to the end user to install the actual ducting. That way, those who need it can easily route the ducting into place without doing all sorts of plumbing through the front of the car like we do with the Evo. This way, those who don't need the ducting (probably 90+% of owners for a lot of these cars) don't have to deal with the ducting wearing out, coming loose, etc. Or I could be totally off base here.

 

I drilled new holes and moved it forward another 1", I also used bolts/nuts through the bottom of the bumper as studs and wing-nuts for easy removal and angle control; in addition to adhesive back bulb seal to seal the gap.

 

So after a month of being under the car, removing and installing the lip and front bumper at least 2.6 million times this is what I came up with. I'm pretty happy with it, and This weekend's NASA event at Pacific Raceways let me know the ducting is working as intended quite well. I managed to make it thru the day without warping the rotors.

Center section of aluminum is not attached to the bumper, but only the splitter. This allows the turnbuckles to adjust the angle of attack on the center section, while the outer sections remain in contact with the splitter keeping the edges sealed. Duct inlets are from a go-kart trimmed to match the Evo bumper curve. I used Binary (JID2) caliper mounts, and exhaust ducting from House of Hose. I added some supports for the rear of the splitter on both sides as well to help with the weight. (No pics )

Fender quick releases for the bumper I machined out of aluminum myself.

Future Modifications possibly include:
Tow Hook (!OOPS!) Minor oversite
Upsizing to 2.5 or 3" duct
Using the factory caliper dust shields to adapt 2.5" or 3" duct
Discard the APR splitter in favor of Alumilite and extending it to a flat bottom (thanks EVOizmm for your build thread, I referenced it at least a dozen times thinking and looking at your rear supports)












(Crushed ducting to be replaced)

 

my splitter is sitting my parents basement. had planned to run it next month but i may miss the event to get a new clutch/trans. i managed to run my brake ducts to the bumper openings on either side and even with regular driving haven't torn a hose! on a 60ish ambient temp day my oil temp was up about 180...we shall see what it does in hotter temps to come since im blocking the cooler a tad (although its on my list to move it up front...)

how far is the lip protruding from the bumper?

 

Approximately 1". I know SCCA won't like that, but for Hillclimbs I got an OK from our director. NASA doesn't care except for TT3

Hillclimbs are the only event I do that follows SCCA rules luckily.

On Evo's the front bumper is the farthest protruding part, which makes any splitter illegal. It's the way the bumper/lip was designed unfortunately.

I was able to leave the oil cooler ducting in place from the factory and run the ducts below the oil cooler / ACD on the driver's side. Once the splitter was level, I still used the factory lower under tray mounting bolts with fender washers, and I was able to pull the plastic down low enough to put the brake ducts in place in the bumper, clear the oil cooler shroud, and get the hoses past with no issue. I could probably get some pics if anyone was interested.

The sad part was that I spent easily 6 weeks looking at, fitting, aligning, supporting buying the wrong stuff, replacing the wrong stuff, getting different parts, modifying and getting it to work, and only about a week actually building the finished product.

 

i ran my duct up into the oil cooler ducting with an inlet ziptied to the grill. i need to come up with a clean way to make the tube disconnectable in the middle tho so i can remove the bumper instead of having to cut 38 zipties off lol.

 

Just an update on front splitters. After a very frustrating weekend in Seattle, The June 1/2 event at the Ridge Motorsports park came up. With new 265/35-18 BFG R1's, a new alignment of -3 camber up front, -2 in the rear with 0 toe front and rear.

Day one the car was still feeling very twitchy in the rear. Under braking it was very difficult to keep the rear of the car in line on high speed sections.

At a last second point by, I decided to pass a 911 just before the turn, and I felt out of my element and off my line coming into the turn. After clearing his front end I pulled back onto my race line (turning right) and came in too hot to the left hand turn 1, sucessfully scandinaving flipping the car off the inside of the turn. The splitter stuck in the ground, broke in half and ripped the lower lip off the front bumper, trashing the splitter, the turnbuckles and brake ducting.

I spent the rest of the day checking for broken suspension components, and anything that looked out of place under the car. Luckily it appeared everything was OK.

Coming out Sunday, on the first session I went out a little mentally shaken, and just decided I'd put around the track, and just give anything a point by that got even close to me. After taking a 5/10 first session, I went to the scoring board and found I ran the same exact time, down to the 0.01 as my fastest time on Saturday before the spin.

Session 2 I started feeling my groove again, which was so important I can't put into words. After 3 major spins at the last 3 track sessions I've done, I was starting to take some mental fatigue trying to figure out what was wrong, why my car wasn't feeling right.

End of the day, I ran my best time of a 1:55.615 putting me second in TT2, and 10th overall for the weekend.

I think I've finally got my finger on what was wrong as well. The front splitter was giving too much downforce, especially into braking off high speed straights, and the car was unbalanced in the rear still running my factory wing. There's been a lot of debate over the years in the Motorsports section here about front splitters without GT wings. I can vouch from personal experience now, that yes, adding a splitter without a wing can be very bad news. I was lucky I ripped it off, as I spun at 100+ MPH, and it was all the damage that took place.

My brake overheating issue came back as expected, but the car felt solid again, and responded to my inputs much more how I would expect, instead of being an unpredictable twitchy b***h.

EOD Saturday was rough... My confidence was very low, to the point of giving up racing for a few seconds, but my brain new better... I had to get back into the car again or I might of walked away forever at this point.

 

the zero rear toe isn't helping to prevent spins...

 

Good to read, as I've been considering running stock wing, but building a splitter just to give myself a project, but this seems to be a repetitive statement of just giving too much downforce up front.

 

What do you run on rear toe? I don't really know all of the suspension tweaks that people do. For every thread on alignments, there's crowds of 'internet' experts. Other than talking to Evo drivers that are faster than I am in my area (very few, Evo's aren't hugely popular in the NW for actual track cars, most owners around here prefer to stand next to their cars looking cool.)

I'm not trying to come off as a smartass, but rereading what I wrote could be interpreted like that. I'm honestly looking for valid advice. From what I understand toe on the rear helps make it rotate even more.

 

Which is fine if that's what the car needs. If the car is already feeling a bit loose in the rear you probably don't need any extra toe to make it rotate. For my particular setup and driving style I ran zero toe and almost put my car into the wall rear facing at BMP a few years ago at well over 90MPH. A little toe in, smaller rear bar, spring changes at the rear etc and the car felt much better. Note all of this was against a lot of the internet advice you get on this very same forum. The key is to adjust the car to your particular suspension/tire/aero setup and your particular driving style.