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Prepared All Wheel Drive Build for 2005 STI

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  • Prepared All Wheel Drive Build for 2005 STI

    I own a 2005 STI. I am currently running in prepared and I am looking for suggestions on how to make the car more competitive. I have the following mods currently. (updated 11/2016)

    Suspension
    Stock Springs
    Feal Suspension Gravel STI replacement struts
    KartBoy Endlinks
    stock rear swaybar
    stock front swaybar
    Turn-In Concepts Suspension Bushings throughout in the back.
    Whiteline Front lower control arm bushings
    Front Stut Tower Brace
    Kart Boy Camber offset top mount
    Kartboy Shifter bushings
    Kartboy Steering rack bushings
    Primitive Racing Skid plates front and back

    Wheels and Brakes
    2006 WRX 4pot/2pot Calipers
    KNS Rotors to fit small calipers on 114.3 hubs
    Enkei 15x7 Rally Wheels (17.1 lbs)
    Maxxis R19 195/65/15 Gravel Rally Tires - Soft
    IndySport BR 185/65/15
    Bridgstone Blizzak 225/50/17
    Stainless braided brake lines
    Hawk Performance Pads

    Engine and Transmission Mods
    Killer B equal length headers and up-pipe
    Cobb 3" Turbo Back Exhaust with high flow Cat and Trust Titanium catback exhaust
    Custom Cold Air Intake with Cobb box and 3" flex going to area behind fog light cover.
    Custom Tune by Modified by KC
    Grimspeed 3-port boost controller
    Perrin Turbo Inlet tube
    Group N - Motor Mounts
    Group N - Transmission Mounts
    ACT Clutch and lightened Flywheel
    LI3 Lightweight battery (7 lbs)


    Next Steps I am thinking of.

    Clutch type Differential in the front
    Racing Seats to lighten the car and keep me in the seat


    I think I am close to the full extent of items I can change and still be in prepared all. Is there better setup/mods? The issue I typically have is I have to shift between 1st and 2nd or the car will either hit the rev limiter on fast portions in first of bog in second in slow corners. I am trying to avoid shifting more than once by increase the power band, bringing the power on earlier, making more power, reducing unsprung weight or rotational mass.


    Thanks,

    Mark
    Last edited by gsxnut; 06-24-2017, 04:23 PM.
    Mark Macoubrie
    RXB
    Kansas City Region
    2005 STI 41 PA

  • #2
    So how do the King springs compare to the stock springs?
    Charles
    RXB
    RX Rule Committee chairman
    MR 1986 Mazda RX-7
    SA 2000 Subaru Impreza 2.5RS

    Comment


    • #3
      The only thing that would help is to put an old geezer in an Evo.
      Winner of five national championships in a row.

      Comment


      • #4
        Originally posted by slowautoxr View Post
        So how do the King springs compare to the stock springs?
        I have never had the stock springs. When I bought the car it had a Tein Coilovers that were super stiff. I drove a friends car that was 2005 STI with stock shocks and springs and it was fairly similar. I have only driven it twice and once without the front sway bar connected but it seems to handle well.

        The King springs are a progressive rate spring. They start about the same and end up being about 30% stiffer than the original springs. One thing I like is that I have only bottomed out the car once. I do not get the sense I have ever lifted a wheel in a corner so and the car does not bounce in bumps so I think it is a good fit. I also think the cars turns in pretty well compared to when I had the really stiff coilovers but this is the only car I have driven so I don't have much to compare it to. They also weigh less than the original springs which helps a little on reducing the overall weight. I think the do work well with the Feal shocks.

        I am not sure I would used them on a lightened Mod car.


        Mark
        Last edited by gsxnut; 03-10-2016, 11:02 PM.
        Mark Macoubrie
        RXB
        Kansas City Region
        2005 STI 41 PA

        Comment


        • #5
          Originally posted by Fivetime View Post
          The only thing that would help is to put an old geezer in an Evo.
          That is probably the best fix but for now I am going to push forward with trying to make the STI as competitive as possible. I still believe that with the mods allowed in Prepared the cars will be close but the 1st gear speed difference still concerns me and there is little I can do about that. We will see what happens.

          Mark
          Mark Macoubrie
          RXB
          Kansas City Region
          2005 STI 41 PA

          Comment


          • #6
            If PA allows it ( I think it does), you need to ditch your sway bars. try running a rallycross or a test day with no sway bars. the car will loos a bit of "rotation" but you will gain a lot of grip.
            It is a little odd to get use to, but it allows a lot more independent wheel travel. You scrub speed much quicker, that allows you to enter corners faster and brake later.

            You may even want to consider softer spring rates. Stock sti springs are a bit stiff from the factory, King springs are stiffer IIRC.

            -Scott

            Comment


            • #7
              Originally posted by tsidreams View Post
              If PA allows it ( I think it does), you need to ditch your sway bars. try running a rallycross or a test day with no sway bars. the car will loos a bit of "rotation" but you will gain a lot of grip.
              It is a little odd to get use to, but it allows a lot more independent wheel travel. You scrub speed much quicker, that allows you to enter corners faster and brake later.

              You may even want to consider softer spring rates. Stock sti springs are a bit stiff from the factory, King springs are stiffer IIRC.

              -Scott
              I was running last year with no front connected and rear connected. I could try to go to none. I was getting a little tire rub on the front left from suspension travel last year. I have gone to stock sway bars. I am going to try this for a while and see how it works. We do not have test days so I have to do it in live competition. I try to compare my times against my closest competition. The first race of the season was supper tacky.

              I am thinking that if you leave the sway bar connected or not may be a function of the track conditions. Super messy and sloppy - no swaybar connections. Super tacky or hard surface - Go with swaybars because it is more like concrete.

              I have never had stock STI springs so not sure how much it is changing the car. I went from super stiff coil-over that the car came with to the King Springs.

              Mark
              Mark Macoubrie
              RXB
              Kansas City Region
              2005 STI 41 PA

              Comment


              • #8
                Originally posted by gsxnut View Post

                I was running last year with no front connected and rear connected. I could try to go to none. I was getting a little tire rub on the front left from suspension travel last year. I have gone to stock sway bars. I am going to try this for a while and see how it works. We do not have test days so I have to do it in live competition. I try to compare my times against my closest competition. The first race of the season was supper tacky.

                I am thinking that if you leave the sway bar connected or not may be a function of the track conditions. Super messy and sloppy - no swaybar connections. Super tacky or hard surface - Go with swaybars because it is more like concrete.

                I have never had stock STI springs so not sure how much it is changing the car. I went from super stiff coil-over that the car came with to the King Springs.

                Mark
                I still think you should try it with NO sway bars. I took mine off a year ago and haven't looked back. Even on the tacky clay days, I still don't regret removing them.

                Comment


                • #9
                  Update

                  I got a custom tune and the car picked up a ton in the lower RPM. The turbo comes on a lot quicker than it did before.
                  I also got the three port controller at the same time.

                  I have moved to Maxxis tires because the Yokohama's are harder to get. The Maxxis tires seems comparable to the Yokohama but I will what to see as I use them more. I also picked up a set of IndySports for mud and they work very well in the mud but give up a lot when it dries out.

                  I am swapping out the Carbotech brakes and going to Hawk HP pads. I don't think I get the pad hot enough in RallyCross to use the pads I have been using. I have heard good things about the Hawks so I am going to give them a try.

                  I also picked up a Perrin Turbo inlet tube. Per Perrin and a local autocross guy the turbo will spool 200-300 RPM sooner with the Perrin inlet tube. I have not got it installed yet so not sure if that is true or not.

                  I had to swap out my Feal rebuilt struts for a set of Feal replacement struts. They have adjustability and seem to work well for RallyCross. The car is more compliant.

                  I moved back to stock springs that came from a used STI. The springs rates were 180 in the front and 140 in the back per my measurement.

                  Mark
                  Last edited by gsxnut; 11-03-2016, 10:47 PM.
                  Mark Macoubrie
                  RXB
                  Kansas City Region
                  2005 STI 41 PA

                  Comment


                  • #10
                    I love your mod list!

                    I have the Perrin inlet tube but it came with the car so I can't say I notice a difference. I can say that the TD04 on the car spools insanely low (I'd say it's at full boost around 2700-2800 RPMs) but it is a pretty tiny turbo. I had to remove and reinstall it when replacing the short block and it was kind of a pain to install but not as bad as the forums led me to believe. I mistakenly disconnected the wiring harness in its entirety and that was about 100 times worse to put back together (lesson learned).

                    You mention a clutch-type front diff may be a future mod. We had a helical diff installed in the front of our 04 WRX and I can't honestly say I could tell much of a difference. That said, my installer Dan Quiet also put one on his Legacy and says it was a massive improvement. In hindsight I do believe a clutch-type would have been a better choice but funds weren't available at the time to make it happen.

                    When you say you got the Feal replacement struts are you talking about the full-on rally struts they sell? I'm very interested in possibly getting a set in a year or two if/when our Bilsteins fail.

                    I'm sure you'll be happy with the Maxxis tires. I've only run the hard compound but found they've worked pretty well in muddy conditions as well as the firmer stuff. I did manage to qualify for contingency tires at nationals and am thinking of getting softs when I finally get the tires.
                    Max Lawson
                    2006 Mitsubishi Evo IX MR
                    National Champion 2015 PA
                    2nd Place 2016 MA

                    Comment


                    • #11
                      Max,

                      Feal Suspension recently came out with a new product to replace the fixed perch struts. http://fealsuspensionstore.com/wrx-sti-struts/#FPS-1

                      They indicated they were having a hard time finding good used struts to rebuild to started to make their own and that is what I purchased. They still have the rebuild service but these are nice because they have some adjust-ability in softness. I am running right in the middle of the settings currently.

                      So far the Maxxis Tires are good. I was not able to work the magic you did at 2015 nationals but I still think they are a competitive tire. I am going to go with Hard compound next time around to see what the difference it.

                      One of the real problems I have is not being able to test. I cannot tell how much difference changes are making. The tires seem to be very similar to where I was with the Yokohama tires I was running.

                      Mark
                      Mark Macoubrie
                      RXB
                      Kansas City Region
                      2005 STI 41 PA

                      Comment


                      • #12
                        Testing back to back certainly gives you data you can use. Shelton and I were trying to decide between snow tires and IndySports for our Saturday AM runs. The course looked like it was taking rubber so we elected to go with snows. For whatever reason, the Saturday afternoon course was not taking rubber so we went with IndySports and remained on them for Sunday.
                        Charles
                        RXB
                        RX Rule Committee chairman
                        MR 1986 Mazda RX-7
                        SA 2000 Subaru Impreza 2.5RS

                        Comment


                        • #13
                          Max, TD04 was a WRX turbo. I believe Mark's car has a VF39 or VF43 or something like that.

                          Sway bars.

                          I disconnected the front bar on my PF Mazdaspeed3. That transformed the way the car turned in, and was the only mod I did to it's suspension. I coned myself out of a Championship in 2013 on that setup. I disconnected the front bar on my MF Escort too. That setup would power drift on command. Not fast w/o power to the rear wheels, but tons of fun, especially in the fluffy silt or mud. I disconnected the rear bar too and the car became much more balanced. I took the bars completely out of the Escort and haven't looked back.

                          My RX sway bar theory: Softening up the front end prompts better turn in and promotes slip angle and/or oversteer, especially in FWD. The RWD cars tend to turn in well, sometimes too well. They can need a stiffer front OR softer rear to tame down their responsiveness. Which can be accomplished by disconnecting the rear sway bar. The car usually has a weight bias to the front on AWD cars so the sway bar tuning should better mirror FWD.

                          Power tuning.

                          The previously mentioned MS3 was tuned to launch off of a rev-limiter, in 2nd gear. Not very feasible in AWD, but it brings up the topic of using what the car has. My Escort and FR-s can't do that type of start, especially with their light weight flywheels. You could try extending the rev-limiter in your tune. The STi is intended to operate best at the high end of it's RPMs. But you can't extend the rev range too far without modifications that are not legal for the Prepared class. Would 500-700 extra rpms do it for you Mark?

                          Tires

                          Most important part of the car setup in motor sports, but also one of the most expensive. It sounds like you already have multiple sets of rally tires. You could try intentionally running mis-matched sets of tires on different axles. Again, for me and FWD, it worked great on the MS3. Rally tires on front and snows on the back allowed me all sorts of liberties to make the car turn. They were sized the same at 205/55r16 so most of the grip difference front to back was due to tire type rather than size. It is a free experiment and something you can easily change at an event between runs. I've done that on the FR-s too. Again, mis-matched snows/rallys and a two year old set on one axle and a new set on the other. Similar results.

                          And on the topic of easy changes. If you have adjustable shocks now, you could mess with those between runs too. Of course, only change one thing at a time to be able to see what effect each change is having. And all of that is getting you experience feeling your car as you drive.
                          Last edited by So Close; 02-15-2017, 03:28 PM.

                          Comment


                          • #14
                            I have decided to disconnect the swaybar front and back to see how it goes. I will also play with the stiffness settings over time. It is currently set in the middle. I will not be able to swap tires. All t he tires are different sizes and rolling diameters so I don't want to have that much difference. From what I have seen it seems the IndySport BRs are best for mud and lots of loose material. Gravel rallies are good for gravel, some loose material and some mud. Snows are best for hard packed surfaces and really tacky surfaces where you want to maximize contact patch.

                            I got the turbo inlet tube installed. I also got new front lower control arm bushings installed. I have been chasing a low speed clunk and cannot find it. I will see if this helps. I have already checks the struts bolts to make sure it was not a loose strut.

                            I think the car is now ready for competition.

                            Mark
                            Mark Macoubrie
                            RXB
                            Kansas City Region
                            2005 STI 41 PA

                            Comment


                            • #15
                              First RallyCross with swaybar disconnected. the car seem to have more oversteer. The back end was wanting to come around more easily when getting on the power and I almost spun the car a couple times.

                              The conditions were dust on a hard surface so the conditions were slick. I also had the rally tires om. It may be that I am over correcting because the car had more understeer before and so I am turning in more than I need to. It may have been the slick conditions and level of power and I was just on the throttle to hard coming out of corners but overall it felt a little harder to control.

                              I am going to go to another RallyCross and try it again but right now I do not think removing the sway bars has reduced my times based on the gap between competitors I have raced several times.

                              Mark
                              Mark Macoubrie
                              RXB
                              Kansas City Region
                              2005 STI 41 PA

                              Comment

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