Project Evo IX – Part 10 – Track Tire Explosion
By Joey Leh, Photography by the author & Peter Tarach
After the last two time attack events at Willow Springs International Raceway, two things have been bothering us – how can we make Project Evo IX faster and how can we do it without spending a lot of cash? By optimizing the car as much as we could with M1 Fabrication & Development, we’ve been able to take a class win and a podium with a nearly stock car.
We’re talking stock turbo, cams, air box, intercooler, ECU, bushings, arms, full interior, stereo and air conditioning. Off-the-shelf JIC coilovers are still being used (with custom rate Swift springs) along with a Progress 27mm rear swaybar and Whiteline Automotive front roll center kit. Beyond that, we focused on good brake pads, good tires and solid aerodynamics.
But we’re not about to kick back and sit pretty. Not while the competition stockpiles horsepower and nuclear arms. Time attack is, unfortunately, an arms race and we don’t want to be stuck bringing a knife to a tank fight anymore. Project Evo IX needs more power, more stability and the ability to get on the throttle as much as possible.
We don’t have the budget for a custom built engine and we’re not interested in the upkeep that comes with a turbo snail so large, you can’t use the stock exhaust manifold anymore. We’ve been eyeing the bolt-on Tomei ARMS and FP Green turbos but we’ll wait and see. For now, we need to refine our base.
Our first order of business is to choose our tire. Tires are one of the most important things on a car. Those four precious contact patches provide the only connection between car and pavement and a tire’s characteristics will affect all other aspects of drivability. There’s no point in adding 500whp and then slapping on Pep Boys remanufactured specials. We need grip.
We’ve already tested Toyo’s Proxes R1R and Yokohama’s AD07 Advan Neova in competition. Both are fantastic tires but each comes with a downside. The R1R has a UTQG rating of 140, which is unfortunately below the 180 treadwear limit placed by the Super Lap Battle series.
The Neova has a higher 180 rating but is incredibly expensive for a street tire. We went looking for a high performance street tire that had a 180+ UTQG rating (to be legal for both Redline and Super Lap Battle), the size we needed (255+ width) and had loads of grip. Nitto had just the tire for us.
We’ve followed along with the NT05 maximum performance summer tire since before it was released to the public. Infused with design elements from Nitto’s NT01 racing tire, the NT05 is designed to be a high grip street tire that still provides long life. It’s not a super soft one lap special, but time attack cars have broken the hallowed 1:58 barrier at Buttonwillow Raceway using it. The NT05 also comes in wide performance sizes like 255/40/17, 265/35/18 and 275/35/18. With a UTQG rating of 200, the NT05 was the tire for us.
We currently have a set of 18×9.5-inch +35 offset 5Zigen FN01R-C wheels on Project Evo IX. Since the 255/40/17 is the NT05 size to have for the Redline Time Attack series, we’ll be securing a set of 17×9-inch FN01R-Cs as well. Our 18-inch wheels clear the front Brembo calipers without a spacer; we do use hubcentric 15mm Eibach units when on track for better rotation. The rears clear perfectly, although our fender lips are rolled for clearance.
With our rubber figured out, it was back to the drawing board with the suspension. We decided to go ahead and try out new spring rates with our JIC Magic FLT-TAR coilovers. Our dampers are off-the-shelf and have not been revalved or rebuilt.
We contacted Swift Springs, who claim the design of a material they call H5S.TW. Stronger than standard spring steel stock, the H5S.TW allows a spring of the same rate and length to be lighter and have fewer coils, which should help with stroke. We were just glad to work with a spring manufacturer that prints length, rate, useable stroke, maximum stroke, maximum load and weight data for each spring.
Swift Springs also stocks more springs than anyone else, with rates ranging from 3kg/mm up to 34 kg/mm. Swift also stocks direct replacement lowering springs, swaybars, helper springs and standard lb/inch rate springs. If you do change out your coilover springs, be sure to double-check the measurement on the inner diameter of your spring.
Coilover manufacturers use rates that are 2.25-inch, 2.5-inch, 65mm, 70mm, etc. Many springs also have a large variance in their diameter; some 65mm springs are actually 64.75mm. We think it’s all designed to confuse and make sure you were paying attention in class.
To test the Swift Springs, we used a set of the exact same rate springs from a competitor brand. We kept the ride height and alignment the same, as well as the driving route. The Swift Springs were a true surprise, riding smoother and soaking up bumps with more ease. Oscillations and undamped movements were reduced, leading us to believe that the new Swift Springs units and rates were a much better match to our JIC dampers. Our next test day for Project Evo IX would be at Buttonwillow Raceway and we were interested to see how the supple Swift setup would absorb the bumps and curbs of the desert circuit.
We were also planning on testing out some new aerodynamics and the Gruppe-S ACD ECU reflash. Since the last event, we added on an APR Performance carbon fiber rear lower diffuser and a GTC-300 carbon fiber wing. Our APR unit is solidly bolted down and feels at least 2.877 times more secure than the Voltex wing we borrowed last time.
We’ve been planning on altering the drivetrain to get more of a rear-wheel drive feel from Project Evo IX for some time. We even did our aero with such a setup looming in the future. For now, our compromise setup has been based around a huge 27mm solid Progress rear swaybar.
Project Evo IX definitely does have rotation and the right behavior but it also has massive wheel lift and spins the inside rear wheel when driving on the street. This isn’t good for the rear LSD and is garbage unless you enjoy going slow. We don’t like going slow.
The Gruppe-S ACD ECU is a service that Gruppe-S provides to 2005-2006 Lancer Evo 8 and 9 owners. Simply remove your factory ACD ECU (it’s high, next to the glovebox on the right side of the passenger footwell) and bring it in to Gruppe-S. They’ll flash some programs on your ECU and you just plug it back in. Available programs include street, race and rally. The programs differ in how quickly they tell the center differential to ramp up its locking behavior.
The ACD doesn’t have an effect on front/rear torque split, so don’t go thinking that you’ll have a full drift rear-drive Evo with this flash. What you will have is a drivetrain that promises to allow you to get on the gas sooner and more easily manage the slip angle of the four drive tires. Logically, we got the most aggressive race map. In the future, we’ll be looking at combining this ECU with a stronger locking rear limited-slip differential.
With Project Evo IX all buttoned up and ready to test, we hit the road for Buttonwillow Raceway. Despite being only two hours north of Los Angeles, logically we would arrive late and spend the first session swapping tires and brake pads. With summer in full swing, the air was hot and the ground temperature even hotter. Without space to fit a canopy, we took refuge (like all good moochers) by bumming off everyone else at the track.
Warming up with the later half of the second session, Editor-in-Chief Joey Leh reported back about the car’s behavior. Project Evo IX was slow to react in transitions and was scary when loading up in the high-speed turns. As it turns out, the dampers were all set to full soft still and were poorly matched to the high grip of the Kumho V710 racing DOT slicks. Since this was just a testing day, the 91-octane street ECU tune was retained.
With the tire pressures checked and the JIC coilovers set to their correct damper settings, Project Evo IX headed out for the next session. From its outlap, the OR project car shined. With lots of stability and grip, Project Evo IX refused to be unsettled by surface undulations, curbing or triple-digit sweepers. Traffic was thick in the run group however and a Porsche, Corvette, Miata or S2000 was caught on each and every lap. Still attempting to find a single clean lap, Joey came on to the front straight about ¾ of the way into the session and slowed with a sudden vibration in the steering. Sandwiched between a Spec Boxster and a Corvette during a hot session, he apparently didn’t slow enough. Midway through the Buttonhook turn, the front left tire let go with a shotgun blast.
Un-dramatic to the core, Project Evo IX simply coasted up the hill a few feet to a paved run-off zone away from the course. NASCAR fans would have been disappointed. There wasn’t a single door flying off or air flap opening. The front left Kumho V710 had exploded, ripped apart, stripped and whipped around the wheel well. The casualties also included the wheel speed sensor / ABS line. With the ABS light on and all three ACD lights now fully lit (so this means that it’s not working three times as hard? – Ed.), our testing day was done. We didn’t even get to try out the Gruppe-S ACD ECU.
With just a handful of hot laps and no clean laps under its belt, Project Evo IX ended the day with a time of 2:05. After speaking with other Kumho users, we discovered that our failure was not a rare occurrence. The Kumho V710 race tire doesn’t like a lot of camber and has a tendency to overheat its inner sidewall when heavily loaded during hot days. Our test day was hot and, in a clockwise configuration, put a lot of load on the front left tire. Makes sense and we’ll have to make a few changes to keep running these. Regardless, our aim is to hit the 1:58 mark or lower on NT05 street tires at the November Super Lap Battle finals event. With a few drivetrain tweaks, bigger turbo, 100-octane race gas and less weight, can it be done? A few more testing days are definitely going to be in our future.
Sources
ENGINE
Tuning Technologies – Custom ECU flash
(909) 783-1200
www.tuningtechnologies.com
GReddy – SP2 catback exhaust, PRofec B-spec II electronic boost controller
www.greddy.com
Works – O2 housing, downpipe, high-flow catalytic converter
(415) 226-2500
www.worksevo.com
K&N Engineering – Drop-in air filter
(800) 858-3333
www.knfilters.com
SUSPENSION
JIC Magic – FLT-TAR coilovers
(626) 576-0900
www.jic-magic.com
Swift Springs – Coilover springs
(909) 923-9788
www.swiftsprings.com
M1 Fabrication & Development – chassis setup/alignment, carbon fiber front splitter
www.m1fd.com
WHEELS
5Zigen – 18×9.5” +35 offset FN01R-C wheels
(310) 608-5575
www.5zigenusa.com
TIRES
Nitto – NT05 high-performance street tires
www.nittotire.com
BODY
APR Performance – Front airdam, rear carbon fiber wing, carbon fiber diffuser
(909) 594-3796
www.aprperformance.com
DRIVETRAIN
Gruppe-S – ACD ECU flash
www.gruppe-s.com
Continue to Project Evo 9 – Part 9
Continue to Project Evo 9 – Part 11
