Suspension
We want the ability to adjust ride height and to cornerweight our car, so coil-overs are a must.
When HKS's Hyperdamper II suspension system became available, we grabbed it. From previous experience, we knew the Hyperdamper would have a huge adjustment range and a base valving that was firm, not rock-jarring solid. This is the exact daily-driver-friendly setup we're looking for.
The Hyperdampers feature 30-way damping adjustment, which increases both compression and rebound damping externally with an easy turn of a knob. They come with pillow-ball mounts, allowing adjustable camber up front and eliminating all the gushy rubber in the stock mounts. This ensures that all wheel motion will be damped instead of dissipated in flexing rubber, letting the car bob.
The front struts use an inverted shaft, a feature that's compatible with the EVO's WRC DNA. The inverted shaft has the strut shaft upside down inside the strut tube and the shock body appears to be the shock shaft that attaches to the upper pillow ball mount. This method of building shocks is many times stronger than the normal conventional way with the body down and the shaft up.
The Hyperdampers feature hard-anodized and stainless hardware to eliminate rusting and sticking of the adjustment collars. They bolted in easily like stock factory pieces. The Hyperdampers featured a reasonable 30-percent stiffer spring rate, which wouldn't break our teeth. The front springs are rated at 5 kg/mm, up from the stock 3.8 kg/mm. The rear springs are 6 kg/mm, up from the stock 4.8 kg/mm.
One of the coolest things about the Hyperdampers is they have a 1.5-inch shorter body and thus lower the car without reducing wheel travel. This is a huge advantage for both ride comfort and handling.
We demanded that all of our suspension elements have racecar-like adjustability. To further reduce body roll and give us more tuneabilty, we called upon Nukabe products for a set of Cusco anti-roll bars. The Cusco bars are currently the stiffest EVO bars on the market. They fit like a charm. The front bar installation, however, required we remove the lower engine and transmission crossmember, steering linkage and exhaust. The front Cusco bar is 25mm, compared to the EVO's stock 23mm, and offers a 123-percent increase in roll resistance over the stock bar.
The rear Cusco bar is 23mm, compared to the stock 18mm, and features three-way adjustment, which allows fine adjustment of oversteer and understeer. The adjustment range is 108 percent, 122 percent and 138 percent more roll resistance than stock in each of the three positions. We expect to use the adjustable feature to help us set up the car rapidly at the track.
The EVO's suspension is amazing. The suspension links are all constructed of strong, light and stiff forged aluminum. The rear suspension is multi-link and most of the rear suspension pivots in a spherical bearing that are sealed against the elements and float in a thin layer of hard rubber for noise isolation.
There's little "sticksion," little flex in the wrong direction and long life to boot. It's just about impossible for the aftermarket to improve on these pivots. However, the rear trailing arm bushings have a huge gushy rubber front pivot and the front lower control arms pivot in soft rubber. These bushings are probably concessions toward ride comfort.
To help hold our wheel geometry in line with our newly installed, bigger, stickier tires (while avoiding a spine-compressing ride), we replaced the non-bearing gushy rubber pivots with hard polyurethane parts from Energy Suspension. The urethane bushings were used for both lower control arms bushings, the rear suspension trailing arm and the front anti-roll bar.
When installing the big front lower control arm bushing, it's necessary to chamfer the lower control arm hole with a .200-inch radius, or it's almost impossible to press the bushing in. The instructions say to merely chamfer the control arms' hole's lead in. We lightly chamfered the hole, but weren't able to get the bushing in. We slowly removed more and more material until the bushing popped in.
We also installed Energy's bushings in the differential carrier and differential moustache bar. These hard bushings will help prevent any wheel hop our sticky tires may create on launch or when powering hard out of a corner, by greatly reducing differential movement and wind up. Getting rid of this will greatly extend the life of other drivetrain components. Unlike other hard differential bushings, Energy's urethane parts didn't transfer any more noise or vibration into the cabin.
Once we installed our suspension, we drove Project EVO to West End Alignment to have Darren Nishimura align the car. Darren is well known in the local So. Cal. road racing scene as the guy to set your chassis. Darren set our front camber at -2 degrees, and the front toe slightly out. The rear camber was set at -1.5 degrees with 0 rear toe.
Darren also set the corner weights for 0 cross weight with 200 pounds in the driver's seat. We also set the front Hyperdampers at 25 clicks, nearly fully stiff, and put the rear shocks at 20 clicks. We set the rear Cusco bar in the middle setting as well to keep close to the stock balance between front and rear roll stiffness.
We're very impressed with this setup. The Hyperdampers ride with less harshness than the stock suspension, yet still resist roll. The easy compliance of the EVO's rally-bred suspension is still there, since the dampers' short bodies have ample wheel travel, but body roll is reduced by more than 50 percent to slightly less than stock, even with the sticky tires.
The EVO's precise steering is now razor sharp; turn-in is fantastic and the car only understeers with the most ham-fisted wheel motions. The EVO's natural balance is about neutral. Our setup will work for both autocross and road course work, which is unusual.
EVOs outfitted with fat R compound tires that are the same size as ours may desire a stiffer, more race-oriented suspension, but our setup can't be beat for total street and weekend warrior track dominance. We can't wait until the next NASA HDPE open track event to see how many supercars we can embarrass with this little giant killer.
The only downside is the car's cornering limits are so high, perhaps higher than any street car we've ever driven, that we can't safely probe the car's capabilities on the street. The final setup will have to be determined on the track.