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Project Scion FR-S Suspension part 1 Getting the Basics with KW Suspension, Cusco and Race Comp Engineering

By Mike Kojima

 

With the FR-S engine giving us fits we decided to turn our attention to something different on the car, that we understand fully, the suspension.  We were surprised with the FR-S from the factory, the ride in stock form was pretty darned stiff for a stock car, the car felt oversprung for the amount of low speed damping from the stock shocks but the ride still felt harsh, even without the damping. 

The car was also really tail happy, fun to drive but not the fast way around turns, especially on corner exit.  The stock suspension calibration was biased towards oversteer with electronic nannies keeping things in check for average drivers.  With the nannies turned off, wow, the stock car could actually drift.  This is not what we really wanted as we prefer a more balanced chassis for all around use.  Perhaps the worst fault the stock FR-S had was an odd shimmy on the freeway.  The car felt like it was following the rain grooves much like a motorcycle does.  It was a very unsettling feeling.

This first step in fiddling with the suspension is us laying in the base for more parts to come.  When this story was written, we were rushing to complete the car for the SEMA show.  Parts were just being released for the car and fortunately there were already some quality parts out on the market.

KW was one of the few companies making coilovers for the car at the time and the best on the market.  Even now a few months later, they are still on top of the heap.  Currently KW only offers the street friendly double adjustable Variant III dampers for the FR-S.  For our intended track use we would have preferred something like Clubsports but they are not released yet (They are coming soon, we have seen some of the prototypes).

Want more Project FR-S?  MotoIQ Project Scion FR-S

 

We obtained a very early set of KW Variant 3's for our FR-S.  The development history started with the Greddy FR-S Formula D drift car and the street versions of the shocks were further developed on Ken Gushi's street FR-S.  The V3's are your typical KW good stuff with stainless bodies and independently adjustable compression and rebound damping with KW's frequency sensitive compression foot valve that we so love.  There is enough flexibility in the dampers adjustments for stiffer spring rates and track use once we get to that point.
Our shocks have KW's latest damping adjusters.  The compression adjuster used to be this little  sleeve that you had to put a pin tool into to turn, much like Koni race dampers.  This got the job done but it used to drive us nuts, especially when trying to adjust things quickly in the pits.  The new KW adjusters are these large star shaped aluminum knobs that are easy to turn with your fingers. We love these new adjusters, you can easily make an adjustment from feel.  Pictured here are the rear shocks.
The front struts used to have a hole that you would insert a small 2.5mm allen wrench into, kinda a bitch to do by feel.  The new KW adjusters are this large knob.  Much better!  All new KW applications will use these improved knobs.  Making adjustment easy is a big plus for a performance damper.
The V3 front struts use this conical upper spring seat in conjunction with the stock upper rubber mounts.  This is fine for quiet daily driving but we wanted adjustable camber and more positive spherical bearings without flexing rubber making our geometry change under load.  We also wanted all shock shaft motion to be translated through the damper instead of moving rubber as well. The  upcoming Clubsports will use a spherical bearing upper mount that is camber adjustable.  We could not wait for them to come out and went with the V3's.
The rear perch also reuses the stock rubber mounts with this upper spring seat.  The new Clubsports use a spherical bearing here.  The upper perch does cleanly integrate with the stock upper mount.

 

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Comments
Scott Helmer
Scott Helmerlink
Wednesday, February 27, 2013 6:18 AM
Mike, have you guys looked at DMS (I believe they may be fabricated by MooreSport aka MSI) top mounts? The motorsport-grade ones cost a pretty penny ($495 for just the fronts is the cheapest I've found), and I can't say anything about how they locate the struts vertically, but they seem to be absolutely ridiculously adjustable, and being DMS parts they're made to withstand rally abuse, though for how long I cannot say). Food for thought.

I was thinking about using the street-oriented version front and rear on my Impreza RS coupe after I get some struts for it.
jeffball610
jeffball610link
Wednesday, February 27, 2013 9:49 AM
I was initially surprised you went with suspension parts before tires and wheels. But I see now that you were correcting some deficiencies in the factory design. I'm curious as to why a car would follow the rain grooves. My 350Z tends to do this as well on a stock suspension with wider tires and wheels. I'd also like to see some more math and engineering explanations of what's going on with the suspension and what you guys are doing to make it better.
HudsonMC
HudsonMClink
Wednesday, February 27, 2013 9:56 AM
@ Jeffball610

likely too much static camber, resulting in a narrow contact patch when traveling in a straight line.
Mike Kojima
Mike Kojimalink
Wednesday, February 27, 2013 12:28 PM
Hi Scott, I first looked at DMS but I didn't like all the little holes. They are probably better for no slip adjustment but I wanted to make my own increments. I agree that DMS stuff is awesome though.

Jeffballs, we haven't done a whole lot of development with the car yet. Frankly it's mostly been sitting since SEMA waiting for more parts that are in development that we want to test to come out so we can make the most of track time. We will do some extensive stuff on this car.

HudsonMC, I agree, I think it was a combination of a lot of rear camber and toe in from the factory.
Fly'n_Z
Fly'n_Zlink
Wednesday, February 27, 2013 8:01 PM
The addition of the knob adjusters is definitely a worthwhile improvement! Is there any chance they'll begin retroactively implementing this feature on their existing designs?
Mike Kojima
Mike Kojimalink
Wednesday, February 27, 2013 8:17 PM
KW will be changing over to new style knobs in the latest production runs of older product.
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