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Koni & BMR Fabrication Suspension Upgrade - Shock And Awe - TechThe Sti Killer Cuts 3 Seconds Off Its Lap Times And 3-Tenths In The Quarter With A Simple Suspension Upgrade, Courtesy Of Koni And BMR Fabrication From the March, 2011 issue of GM High-Tech Performance By Justin Cesler Photography by Justin Cesler, Scott Parker
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After a full year of hard work, blood, sweat (not my sweat mind you, but the sweat of quality mechanics, builders, painters, and tuners) and tears (those were mine), the STI Killer is finally ready for us to begin heavily testing suspension, tires, wheels, brakes, and anything else that makes it haul the mail around a road course the quickest. Built specifically from the ground up to allow us to test anything we, and by extension you, want, the STI Killer is not only a fun car to drive but it is a car with a purpose and a mission: to dominate all other cars in its class on any road surface, including the auto-cross, road course, dragstrip, and street. If you have been following along with our progress, you have already seen our '01 Camaro receive a new GMPP LS6 engine, a D&D Performance T56, a full host of bolt-on parts, a built rear-end and a set of awesome 6-piston CTS-V Brembo brakes. Until now, the Killer has been good at making noise and spinning the dyno rollers, but its stock suspension has made it difficult to get around a road course and do what it's supposed to do. During our first round of testing ("A Killer on the Loose," Jan '11), we found several things wrong with the Camaro, as lap after lap we blew through braking zones, lumbered heavily into corners and generally just fought to make a clean road course lap. As our friends and critics watched on, the Killer did what it could, mustering several 1.10-second lap times and spinning its way to a 12.996-second quarter-mile pass. However, this month, the STI Killer was on top of its game and we left the track with much, much better results. As you will see on the following pages, this month's project was all about suspension. With help from BMR Fabrication, Koni North America and our trusty pals at AntiVenom, we were able to install several key suspension components, including BMR's all-new 1-inch hollow front sway bar and re-designed lowering springs, and the results were impressive. In just a couple of laps around Gainesville Raceway's 1.6-mile road course, we were able to drop lap times into the 1.07-second range, running a new best of 1.06.707-a gain of 3.289-seconds from our previous endeavors. The Camaro felt smooth, predictable, and fast, especially during post-apex power-on cornering. With the 1-inch hollow front sway bar and the Koni shocks set 4-turns from soft, the Killer exhibited zero understeer, even when intentionally pushed too hot into heavy corners. This was one of the most surprising aspects of our install, as we initially expected the 295/30/18 Nitto NT05's up front to object to heavy turn-in, but the combination proved to be almost perfect. At no point did we feel the nose fight our inputs and the steering response was excellent, even in the low speed, heavy turn-in corners. Out back, however, well, that was another story. Once our speed picked up, the rear was quick to rotate, although it remained predictable. We're not talking about hit the brakes, turn in and spin type of rotation, but just a slight drift to the outside of the corner. Once settled and turning, the Killer was a beast, with great mid-corner grip and a stable feel. The BMR sway bars certainly worked well, taming the Camaro's roll center and keeping the car flat and planted through the turns. On-throttle exits were, well, awesome. It seems that our 295/30/18-inch Nitto NT05 rear tires are simply no match for aggressive throttle application and many a corner became a dance of throttle modulation, counter steering and smiles, as the rear tires went up in smoke. We must take a minute to praise the Eaton differential we installed earlier this year ("10-bolt Basics," August '10), as it applied power evenly throughout the entire test session and showed no signs of slipping or one-wheel peeling.  The STI Killer was in for...  The STI Killer was in for a treat, courtesy of BMR Fabrication and Koni North America. From front to back, you can see Koni's highly touted single adjustable shocks, BMR's lower control arms, sway bars, Panhard rod, and re-designed lowering springs.  To gain access to the suspension,...  To gain access to the suspension, we loaded the Killer up on our in-house lift and removed the 18-inch OE Wheels and Nitto tires from all four corners. Then, the AntiVenom crew got to work on the front suspension, removing the spindle from the upper control arm, unbolting the factory sway bar and removing the two shock-to-control arm bolts.  Up in the engine bay Kyle...  Up in the engine bay Kyle Miller removed the master cylinder from the brake booster and slid it towards the center of the bay. This gives just a little bit of extra clearance to access the four strut-top bolts. Two of these are held in with traditional bolts, while the rear most mount holes are fixed with Torx head bolts.  The upper strut mount, A-arm,...  The upper strut mount, A-arm, and factory shock come out as one unit, although the upper A-arm isn't held in place by anything at this point, so be careful while removing it and don't drop it on your toes!  Using a spring compressor...  Using a spring compressor (you can buy one from Summit Racing or rent one at a local parts store) Greg safely compressed the stock spring and removed the top nut, to free the stock strut top. We were reusing these, hence the removal.  Our BMR 1.25-inch, 550-lb/in...  Our BMR 1.25-inch, 550-lb/in front springs slipped right over the new Koni Sport (Yellow) front shock. With the single-adjustable Koni shocks and the improved, stiff front springs, our '01 Camaro will ride great and handle like it is on rails.  Adjusting the Koni shocks...  Adjusting the Koni shocks is a little different, as you have to rotate a small disc within the top of the shock body. On a fourth-generation Camaro, this adjustment is made through the springs, which can be a little tricky out on the road but nothing to worry about.  With the strut top bushing...  With the strut top bushing and A-arm back in place, Greg slid the entire assembly back in place and, since he is skilled, tightened the top nuts with his other hand. If I were attempting this, I would need a friend in the engine bay to do this and I suspect you might too. In a straight line our new suspension helped out as well, even with the rear Koni shocks still set at 1-turn from full stiff. Using the same tires as always, we laid down a 12.64 at 114.5 mph in the quarter, a gain of .348-seconds and 4.5 mph, which we attribute to the suspension transferring weight better and planting the rear tires, as we could finally use wide-open throttle in first and second gear. Overall, we were impressed by the new changes to the STI Killer's suspension and we can't wait to spend some more time in the driver seat. Going forward, we might even need to rename out project the C6 Killer, but that's an entirely different story that we're going to save for another issue!  Time to turn our attention...  Time to turn our attention to the front sway bar. Since we removed the endlinks earlier, dropping the sway bar only required removal of the four bolts attached to the sway bar mounts.  The bright red, 35mm sway...  The bright red, 35mm sway bar may look like a heavy beast, but thanks to its hollow construction, it actually weighs less than 15-lbs. Combined with the rest of our suspension, this sway bar will really help keep our Camaro planted, level, and in control.  BMR also supplies new endlinks...  BMR also supplies new endlinks with the sway bar kit, which attached through the stock lower control arms. It's best to leave these loose for now, you can tighten them down fully once the car is back on the ground and at ride height.  As with the front sway bar,...  As with the front sway bar, the rear removes easily as it is bolted to the 10-bolt rear end with four bolts and the two endlinks.  Like the front, you can install...  Like the front, you can install the endlinks now, but keep them loose until the car is at ride height. Also, take note of the new BMR sway bar bushings, which need to be lubed in order to work properly.  Time to remove the rear suspension...  Time to remove the rear suspension pieces, which come off much easier than the front. To start, Kyle removed the single shock-to-rear bolt and slid the shock out of the bracket. Then, using a jack, the rear can be slowly lowered and the spring will drop right out.  Since the STI Killer doesn't...  Since the STI Killer doesn't have rear seats, removing the upper shock nut was a simple procedure. For you full interior enthusiasts, you just need to fold the rear seat forward and move the carpet and foam block to access the nut.  With the rear end still supported...  With the rear end still supported by a jack, Greg slowly raised the 10-bolt while Kyle slid the Koni Sport (Yellow) shock in place. The new BMR 1.25-inch lowering springs slid in place effortlessly as well. With a 160-lbs/in spring rate these rear springs are also stiff, but built to complement the 550-lb/in fronts, giving a predictable feel front and rear.  Back up in the air, with the...  Back up in the air, with the shocks completely installed, Kyle slid a new pair of BMR Lower Control Arms in place. For all out track abuse, you may opt for a "double rod-ended" LCA; however, we went with a poly/rod combination, which is still adjustable and strong.  Last but not least, Kyle installed...  Last but not least, Kyle installed the BMR Panhard bar, which we also received in a poly/rod combination. Per BMR's directions, you want the rod-end on the rear end bracket and the polyurethane against the chassis, to help reduce noise and vibration.  With our install complete,...  With our install complete, we loaded our Camaro and drove over to our favorite test track at Gainesville Raceway. Within the first 30-seconds of track time, we knew we had made major progress, as the Killer felt solid, flat, and capable of big speed around the course.  Of course, nothing ever goes...  Of course, nothing ever goes completely as planned. After a couple of laps, we noticed our rear tire rub issues were getting worse. Luckily, we were able to remove the wheel and use a BFH (big, well-you know) to gain some clearance. Unfortunately, this is just one of the necessary evils of running a large 18-inch tire on a fourth-gen.  Using our Racepak G2X GPS...  Using our Racepak G2X GPS datalogger, we were able to record and compare lap times from this test session to last. On the right, you can compare our Main lap (this session) to our Reference (our best lap from last time out, on the stock suspension). Up top, you can see the mph difference exiting turn 3: 75.84-mph vs. 66.06-mph, an exit speed difference of 9.78 mph!  In the low speed, super frustrating...  In the low speed, super frustrating 180-degree turn, you can see how much harder we were able to brake (23.46 mph vs. 45.15 mph) into the corner, as well as how much faster we were able to exit (51.55 mph vs. 26.53 mph). These amazing differences in speed were due to the suspension allowing much more traction during braking, cornering, and accelerating.  To put those numbers in perspective,...  To put those numbers in perspective, our new suspension allowed us to cut 3.289-seconds off our total lap time, with entry and exits speeds that sometimes doubled our previous efforts. Whether on the track or the street, such drastic changes in the car's handling are obvious and highly recommended!  We didn't do any formal skidpad...  We didn't do any formal skidpad testing during this outing, but since turn 4 and 5 use the skidpad section of the track, we were able to extrapolate the data from our runs. Check out the Lateral G difference from stock (.94) to our modified suspension (1.13). As you know, anything above 1.0 is sticky and 1.13 puts us in a small percentage of really great handling cars.  We left Gainesville Raceway...  We left Gainesville Raceway feeling great; the new suspension worked well, looked fantastic, and the Killer felt ready to do serious battle with other cars. Next time, we'll test it head to head with a real Subaru STI, but we may have some other tricks in store before then!
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