Autocrossing the DOHC V6 ’88 Fiero – Part 1

On October 13th-14th I participated in an autocross weekend with my DOHC Fiero. This was my first autocross event, but I have participated in RallyCross (in my Outback) and a track day with my old Fiero in the past.
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Setup

Tires/Wheels

  • Front: 17×7 (42mm offset) Raze R-74, 205/50/17 BF Goodrich gForce KDW 2
  • Rear: 17×8 (48mm offset) Raze R-74, 255/40/17 BF Goodrich gForce KDW 2

Alignment

  • Front toe in: 1/4 inch
  • Front camber: -1.6 deg
  • Front caster: Mechanical maximum (I didn’t have time to measure)
  • Rear left camber: -1.8 deg (as much as I could get; the wheel is about to hit the knuckle. I need 18s)
  • Rear right camber: -2.5 deg
  • Rear toe in: 1/16 inch

Shocks/Springs/Bushings

  • Front springs: Stock with 1 coil removed
  • Front shocks: Koni Red, adjusted somewhere in the middle
  • Front swaybar: Stock, with Rodney Dickman’s solid endlinks
  • Front bushings: Polyurethane everywhere except the swaybar mounts are stock
  • Rear springs: 350 lb QA1
  • Rear struts: Koni reds, adjusted somewhere in the middle, flipped strut top mounts for more compression travel
  • Rear swaybar: None
  • Rear bushings: Poly on the trailing links, solid rod end lateral links

Weight reduction/relocation

  • Front mounted Miata battery (23 lbs), mounted behind the front crossmember
  • Corbeau A4 seats on original Fiero sliders
  • Removed jack, wrench, spare, and spare tire tray

Engine

  • Balanced and blueprinted 1993 3.4 DOHC V6, custom intake, 220whp on the Dynapack at Church Automotive

Transmission

  • Fiero Getrag case with later Getrag 282 internals (slighter shorter 5th gear, larger and stronger diff)
  • Clutchnet kevlar clutch, Luk pressure plate

Exhaust

  • Stock exhaust manifolds and crossover, 2.5″ cat, custom 2.5″ single inlet, dual outlet muffler

Brakes

  • Slotted/drilled 12″ Corvette rotors
  • 88 Fiero calipers
  • Porterfield R4-S pads
  • OEM-style rubber brake hoses

Steering

  • 2-turns lock-to-lock power steering rack from a C4 Corvette ZR1 or Z51 package

Initial driving impressions

  • Fiero Getrag gearing is not ideal
  • Easy to put power down
  • The super fast ratio ZR1 steering rack is awesome
  • Brakes could use more rear bias

Power/Gearing

The gear ratios really break the car for autocross. I can go full throttle in second gear when going straight or mostly straight and not loose traction, nor hit the rev limiter, so it needs to be shorter. First gear is only usable for the launch, and the beginning of the course until it opens up. After shifting into 2nd, there aren’t any spots where a downshift (and subsequent upshift back to 2nd) are practical, it scrubs off too much time. I think a Northstar in 2nd gear with a 7k RPM limit would be just right, or a turbocharged 3.4 DOHC with a fast spooling turbo and low boost.

With my motor, the Getrag gears with the shorter 2nd would probably be a lot better. I hated the 2nd to 3rd shift with those gears when I ran them though.

Fortunately (or unfortunately) I can’t drive the car well enough to take too much advantage of the extra speed a shorter 2nd would give me, so it’s not a limiting factor right now.

Handling

The fast ratio steering is amazing. It’s VERY easy to point the car where it needs to go, on even the tightest hairpins. I didn’t have any problems with steering feedback. I can still feel the loss in self-aligning torque when approaching the lockup point during threshold braking.

Speaking of braking, it seems the fronts lock up pretty easily. I feel like the car should be able to stop faster. I think it needs more rear brake bias.

My car tends toward oversteer; if I turn in hard enough it spins out. I can countersteer and recover almost every time, but it scrubs off a LOT of speed when it happens. It’s annoying trying to find the traction limit in a turn only to have the rear step out and then lose all your speed. This is the only serious handling problem I experienced.

Performance

Hard to say. I don’t really have enough driving ability to know how fast the car will run compared to others, and the oversteer problem made it hard to find the limit of the car. My buddy running an AP2 S2000 with lots of suspension mods but stock tire sizes and motor ran about a 2nd faster than me. Both of us are novice autocrossers. Even if I could drive it well, it’s hard to compare right now since I have [i]four year old[/i] tires, and almost every other cars in my class (with the exception of my friend’s S2000) is running RS3s or Z1s. That will change soon if I decide to continue developing this car.

Photos

Click the images for bigger versions.

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I’m running -2.5 deg of camber on the rear right, but you can from the photos that it still goes into positive camber due to body roll. Look at how much the inside is lifting! There’s a lot of roll. I am not currently running a rear swaybar. I was running the factory rear swaybar for some time, but the rear end felt very loose.. probably from shifting too much weight transfer toward the rear to the excess roll stiffness vs the front. Once I get some stiffer springs up front I may consider trying the rear swaybar again.

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