1. Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;)

1G Downforce! Wing & Splitter!

Posted by Marchev, Jul 21, 2019

Please Support ExtremePSI
Please Support ExtremePSI
  1. Marchev

    Marchev Proven Member

    340
    63
    Joined Jan 31, 2009
    Niles, Illinois
    Here is something I've been working on over the last week, I did not see much covering this topic so figured I would share.

    Little background:
    This car has been a dedicated road race and some autox machine. I compete in the midwest SCCA time attack/time trial and constantly working to improve the car as there are lots of very fast cars in my class. Beginning of this year I installed custom valved Ohlins suspension built by Muellerized and after some seat time and playing with the settings on the suspension, some problems started becoming very apparent.

    Issues with handling:
    The rear end of the car is very light compared to the front. When I got the car corner balanced it showed how light the rear was. Total weight was 2650 with half a tank. On track that resulted in the rear being unstable in high speed corners, and especially in quick transitions. Racing in rain only over exaggerated the problem and made the car difficult to drive.
    Part 2 of the problem was braking and tire wear. Since the rear was so light, I could only apply little rear brake bias otherwise the rear tires would just lock up. That makes my braking distance longer as 90% of my braking was done with the fronts, which translated into changing the front Wilwood pads every 3 events, yet the rear pads would last me 3 years. My idea was to keep the car as leveled as possible during hard braking so I can put more brake pressure to the rear, which would make my braking distance shorter. So somehow I had to add more weight to the back, without actually putting weight in the trunk.
    Tire wear confirmed the same theory as even with just -1.7* camber in the back, the pyrometer showed that the inner tire edge was significantly hotter than the outer.

    My solution:
    Put a functional wing that would add a few hundred pounds of downforce at speed, and also a front splitter so we keep the car balanced. I chose to go with APR GTC-300 adjustable wing for an Evo 8-9. It was the right size and surface area to be legal in my class. I liked it because the mounts were wide enough to be mounted to the quarter panels of the car (as close to chassis mount as I was going to get) and also it felt way sturdier than one that had the mounts closer together. It is also a 3D Airfoil design, which is way more efficient when mounted approximately same height as the roofline. It also made my rear hatch only able to open about a foot, which I didn't use anyway.

    Here is the progress:
    After removal of the side spoiler trim pieces, I started by grinding the paint off so I can weld reinforcements. That area is sturdy close to the edges, but flimsy in the middle due to thin metal, and all the holes that are drilled for the side spoiler mount, and antenna hole. It is a good area to mount a wing to because it is welded to the rest of the chassis\body of the car.
    20190715_125546.jpg
    Next TIG weld a thicker plate on top
    20190715_125559.jpg
    20190715_170553.jpg
    After welding it complete I was surprised how sturdy the area became. I was able to put my hole body weight on one fist at any point of the plate with no noticeable fluctuation. Exactly what I was looking for.
    Next comes the hard part. Since the body there is at a slight angle, about 10 degrees sideways, and 8 degrees backwards, I had to make a wedge that was multi angled. The wedge had to keep the wing at proper height as well as give it a proper angle of attack (AOA). Onto the bridgeport I went:
    20190716_200539.jpg
    20190716_210007.jpg
    20190716_210033.jpg
    Notice how the wedge has a 10 degree sideways angle as well as an 8 degree forward angle in order to give an approximately straight mounting surface to the wing base. I was aiming to make the wing have more of a forward angle since it had plenty of adjustability leaning backwards.
    20190717_091332.jpg
    This picture makes the angle look extreme but it was actually almost perfectly in line with the middle spoiler when looked at directly from the side. I was really happy how these came out, they sat almost 100% flat. I had to take a grinding wheel to a couple of areas in order to achieve complete contact. The welded plates underneath weren't 100% flat, as they contoured to the curves of the body in that area.
    Next a quick layer of paint, and ready for mounting!
    20190717_173618.jpg
    Next I had to cut holes into the side spoiler pieces, these did not come out the prettiest and I will work on making some kind of a cover for the holes. Shoot me some ideas!
    It was difficult to measure exactly where the wing will sit, but I did the best I can
    20190717_193221.jpg
    I had to bolt the side spoiler pieces to a different location since the original mounting spots were now welded over.
    And final mounting!
    20190717_193241.jpg
    20190717_193306.jpg
    I had drilled holes through the mounting plates and wedges, and had it bolted down with studs and large fender washers on the bottom side. It is surprisingly sturdy. I can rock the car left to right by pulling on one mount with little to no deviation from the mount itself. Great success! Ha



    Now onto the front of the car!
    I started with a sheet of 4'x8' of .5" thick alumalite sheet. Its very sturdy and light material with 2 thin aluminum sheets on each side with plastic weaved like cardboard pattern in between. In my class I am allowed to have a splitter up to the middle of the centerline of the front wheels. Also it can not stick out more than 3" from the front of the car. So I went under and started taking measurements. After having the rough shape moched up, I cut it up. Then I used multiple rivnuts aka threaded inserts, on the subframe to give me a rigid mounting points.
    20190718_153108.jpg
    Then I traced 3" around the bumper, tapering down at the ends and went to work.
    This is the final shape:
    20190720_120001.jpg
    Next I worked on attaching my flimsy bumper onto the splitter. This added rigidity to the bumper as well as eliminated gaps between the bumper and splitter. Rivnuts came in super handy
    20190720_122013.jpg
    I used some thin aluminum diamond plate to curve around the edges of the bumper. The plate is riveted to the bumper itself, and bolted to the splitter with the rivnuts for easy removal of either piece.
    20190720_143521.jpg
    I also utilized the front threaded rods to hold the splitter in the front. Those rods are threaded into the front bumper support and held the air duct that allows cool air to go under the intercooler and directly to the radiator.
    20190720_143538.jpg
    And all done!
    20190720_153858.jpg
    I'm expecting to even see some help in the cooling department with this splitter because it traps the air in front of the intercooler and not allowing it to go under the car. Up next I'll be working on making air dams with ducting through the fog light holes leading to the front brakes. As well as some more ducting from the intercooler to the bumper.

    I will keep this thread updated as the next time attack event is coming up in a week at the same track as before. So that will give me direct comparison since nothing else was changed on the car.

    Anything else you guys think I can improve on?
     
    Last edited: Jul 21, 2019

    Autocross Build 3K  5

    1990 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  2. Mech Addict

    Mech Addict Probationary Member

    26
    13
    Joined Jun 9, 2019
    Jackson, Wyoming
    I’m impressed by both your reasoning and craftsmanship. A wing coming through a spoiler! The weight of your car and symptoms resulting square with a suspicion I have had about others writing about trying to “add more lightness” to their dsm. Much of the low hanging fruit, like spare tire, rear seat, even lighter front seats, etc seems to take more mass from the rear vs. the front. This would seem of less consequence in straight line performance, like 1/4 mile, but extremely important for cornering, and dynamics. Depending on the particular event, adding back some actual static mass to the back could even make the car faster through a course. Effective weight (a force, not mass) using airflow can be a big win in a lot of ways if the event allows for enough speed when you need the grip. You’re obviously committed to continuing to tune things to get it right, but I wonder when folks describe substantial lightening efforts for a street car, and aren’t prepared for the drawbacks you described.
     

    Street Build 186  3

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM
    Loading...
  3. Steve92talon

    Steve92talon Probationary Member

    17
    1
    Joined Jul 3, 2019
    Fernie, BC, Canada
    I would say better heat and air extraction from the hood vents. Make them larger and wider like a cowl from a Camaro or similar. your pushing more air into the engine compartment with the splitter but it needs to flow out or you will pressurize the engine compartment creating lift.
     
  4. Marchev

    Marchev Proven Member

    340
    63
    Joined Jan 31, 2009
    Niles, Illinois
    Thanks! And I agree as added mass to the rear might actually turn faster lap times. The rear ends up being so light, it becomes unpredictable, and if I lift off throttle mid turn the rear snaps suddenly because the weight jumps forward. I need to also tighten up the rear rebound as that should help keep the car from raising in the rear in sudden transitions

    Good point! I will look into larger hood vents. Reason why I went with smaller ones before is because I tried to retain as much of the CF hood as possible for rigidity. It seems to become flimsy as I cut more away from it. I need to come up with some kind of reinforcement for bigger vents
     

    Autocross Build 3K  5

    1990 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  5. Cherry

    Cherry Proven Member

    127
    19
    Joined Jun 16, 2019
    Hull, Georgia
    Street Bandito on youtube had an episode of his race build where he was putting vents in his carbon fiber hood and adding reinforcement out of carbon fiber sheets that he just cut and formed to the shape that he needed and then used a 5 minute epoxy to hold everything in place.



    It might give you some ideas for venting the engine bay. They are basically making a full carbon fiber old 240 for the track.
     

    Street Build 197  3

    1991 Mitsubishi Eclipse N/T
    fwd · manual · 1G DSM
    Loading...
  6. Steve92talon

    Steve92talon Probationary Member

    17
    1
    Joined Jul 3, 2019
    Fernie, BC, Canada
    Possibly adding nacaducts like nascar uses is a more efficient air mover then big holes in the hood. Maybe a few diamond shaped vents for more rigidity then squares.
     
    Marchev likes this.
  7. Steve92talon

    Steve92talon Probationary Member

    17
    1
    Joined Jul 3, 2019
    Fernie, BC, Canada
    Or lift the back of the hood to form a vent like nascar uses for sucking air in the motors. Vent the engine compartment to the base of the windshield. I would check out some pikes peak winners for aero ideas :)
     
  8. GST with PSI

    GST with PSI DSM Wiseman

    1,771
    1,220
    Joined Jul 27, 2005
    San Diego, California
    Awesome work, and I love the craftsmanship.

    Thanks for sharing! You should add posts like these to your build thread so they all get amassed in one central location.
     

    Street Build 23K  15  143

    1991 Mitsubishi Galant VR-4
    12.030 @ 119.39 · Galant VR-4

    212  17

    1982 Yamaha Virago
    rwd · manual · Misc Vehicles

    Street Build 5K  74

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4
    Loading...
  9. Marchev

    Marchev Proven Member

    340
    63
    Joined Jan 31, 2009
    Niles, Illinois
    Thanks for sharing! I wonder if I epoxy the cut out pieces of carbon flat against the bottom of the hood around the vent area, wonder if that will add some rigidity to it. Basically double up the carbon, should work!

    If I remember correctly a while back someone had posted that lifting the rear of the hood doesn't evacuate the air efficiently in our platform. Maybe it was about a stock vehicle, or I could be completely wrong. I will look into more efficient venting

    Thanks! I will put one of those build threads together one day!
     

    Autocross Build 3K  5

    1990 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  10. Marchev

    Marchev Proven Member

    340
    63
    Joined Jan 31, 2009
    Niles, Illinois
    Anyone have ideas how to cover up the holes in the side spoiler pieces where the wing mounts to the quarter panels?
     

    Autocross Build 3K  5

    1990 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  11. greengoblin

    greengoblin Supporting Vendor

    1,104
    371
    Joined Mar 10, 2006
    McKinney, Texas
    I'd square out the trailing edge in front of the front tires adding a splitter end fences and front tire deflectors. The simple sides spats deflector would also double as a air damn. Also add diffuser to the bottom.
    Professional Awesome makes some so you can look at their site and see what I'm talking about.

    Kevin
     

    8K  11  0

    1995 Eagle Talon TSi AWD
    12.830 @ 120.000 · 2G DSM
    Loading...
    Marchev likes this.
  12. Cherry

    Cherry Proven Member

    127
    19
    Joined Jun 16, 2019
    Hull, Georgia
    Doubling up the material might make it a little stronger, but I dont think it would add rigidity or if it does it wouldnt add that much. If you have enough material you could cut out 1/2 to 1 inch strips to go perpendicular to the hood surface, or if you have some aluminum sheets you could do something with that.

    For around the wing I would make a template out of cardboard that fits nice and then using whatever material you want or have access to transfer the cardboard template to the new material and cut it out. I guess it depends on what materials you have to work with. If you just want to cover the cut areas I might use some aluminum, make the bezel out of 2 pieces and use rivnuts so you can take the pieces off if you need to remove the wing. So essentially it would be something like [ ] going around the wing posts. Paint it black and call it a day. I wouldnt know what thickness to make it, but if it is a little thicker you could countersink the screws you use into the metal making it flush.
     

    Street Build 197  3

    1991 Mitsubishi Eclipse N/T
    fwd · manual · 1G DSM
    Loading...
    Marchev likes this.
  13. Marchev

    Marchev Proven Member

    340
    63
    Joined Jan 31, 2009
    Niles, Illinois
    A picture is worth 1000 words! I looked at their website and ideas are flooding my list for the front. Thanks for bringing them up

    I didn't think about using the rivnuts on the spoiler pieces. That would be a good removable solution. Just got to be careful not squeezing the rivnuts too tight as the spoiler will probably crack
     

    Autocross Build 3K  5

    1990 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  14. Cherry

    Cherry Proven Member

    127
    19
    Joined Jun 16, 2019
    Hull, Georgia
    They make a plastic 2 part epoxy that I used to fix my side molding on my car. The JB weld kind is more flexible, but the permatex I think it is, is more of a hard type of epoxy. You could use some of that on the rivnuts maybe since it says it bonds to metal, fiberglass and most plastics. I havent put the molding on yet to see how well it holds up to opening and closing the door but I also used some fiberglass on the backside to strengthen spread the overall connection over a few inches instead of on a small crack. I also used it on my rear bumper that had a split in it on the passenger side by the rear blinker and it has held up to speed bumps, and sun wear.

    You can always do a test on the plastic that you cut out to see if it would hold. I never used a rivnut before so you would be able to make the call there. I would definitely use the permatex stuff to hold in the rivnut though if you do go that route, its easier to work with since it holds its form better when you are using it, smells awful though, like a really bad hair salon.
     

    Street Build 197  3

    1991 Mitsubishi Eclipse N/T
    fwd · manual · 1G DSM
    Loading...
  15. Marchev

    Marchev Proven Member

    340
    63
    Joined Jan 31, 2009
    Niles, Illinois
    You don't need epoxy to hold rivnuts. You drill the right size hole, put rivnuts in, thread the special tool and squeeze. The rivnut expands in the hole and that's what holds it in place. The trick to doing it in the spoiler is to expand the rivnut just enough for it to hold and not spin, but not too tight since it might crack the spoiler itself
     

    Autocross Build 3K  5

    1990 Eagle Talon TSi AWD
    awd · manual · 1G DSM
    Loading...
  16. greengoblin

    greengoblin Supporting Vendor

    1,104
    371
    Joined Mar 10, 2006
    McKinney, Texas
    I figured you would find there stuff helpful and its easier than my typing it all out.
    Also you might find somethings at curiosichi.com useful too. https://curiosichi.com/bondage-a-guide-to-bonding-to-carbon-fiber/
    It's a new site but some good stuff there.
     

    8K  11  0

    1995 Eagle Talon TSi AWD
    12.830 @ 120.000 · 2G DSM
    Loading...
    Marchev likes this.
  17. Cherry

    Cherry Proven Member

    127
    19
    Joined Jun 16, 2019
    Hull, Georgia
    Well, if you crack the spoiler you can use the epoxy then LOL. I was just suggesting if you didnt want to take the chance just basically glue the rivnuts in there. Though all they would be doing is holding a cover on so they probably wouldnt be that much force needed to be applied to the rivnut.
     

    Street Build 197  3

    1991 Mitsubishi Eclipse N/T
    fwd · manual · 1G DSM
    Loading...
    Marchev likes this.

Share This Page

Support Vendors who Support the DSM Community
Archer Fabrication ECM Tuning ExtremePSI Feal Suspension Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications OHM Racing RockAuto SouthBay Fuel Injectors STM Tuned VR Speed Factory WheelWell.com White Shed Speed