Photo Credit: Alejandro Aviles
THE GURU:
Brian Karwan is a Honda extraordinaire out of the Washington DC region, and is on his 10th year of SCCA Solo. Running his own parts fabrication business, Karcepts, Brian is extremely knowledgeable about what it takes to set up a car to win. His decals can be seen on many top-national cars at National Solo events.
His driving isn't too shabby either, claiming two SMF national championships in his 1994 Honda Civic, and that's out of the only two years he’s made the trip to the big show. He has since spent the last couple years running a Honda S2000 in the very popular Street Touring Roadster class. If you're thinking about joining in, we got the run-down from Brian so we could tell you all about what it takes to run at the top.
THE PITCH:
Being one of the largest classes in all of SCCA Solo, Brian describes STR as a "Super fun and extremely competitive RWD street tire class with cars that have just enough power to weight to get you into trouble." It contains some of the most iconic sports cars of the 21st century, and is a great way to get yourself an extremely fun Autocross car that can also be used for daily use.
THE SCOOP:
STR features the best Japan has had to offer from the 21st century, and while it is predominantly a class for the Honda S2000, fully prepped Mazda MX-5s can just as easily vy for the championship. The Toyota MR-S has too proven to be quick, but being the least powerful of the trio it seems to need a little help from the course designer to run at the front.
Two generations make up the Honda S2000, the AP1 (2000-2003), and the AP2 (2004-2009), and it’s important to know the difference between the two when making a purchase. The AP2 S2000 is the clear choice for the class, because while being similar in weight, the AP2 makes 15lb-ft of torque more across the entire RPM range. Gearing can be an issue for the AP1 on the Solo course as well, being significantly taller and harder to keep in the S2000’s peaky power band.
The Mazda MX-5 can make more power down low than the AP1s, and comes with a substantial weight savings of 300lbs to the S2000s. However, if you want the simple, no-excuse formula, Brian says just grab any AP2 S2000 and call it day.
THE PRICETAG:
For the initial starting price, the AP1, MX-5, and MRS can all be found under a $10k price tag. To get into an AP2, plan to spend $15k, but with lots of searching, they can be found cheaper for earlier high mileage ones. They can also get as expensive as $25k if you come across the CR package. However, with the Street Touring modifications allowed, a CR is definitely not a requirement to win nationally. An '04 AP2 shares the same power plant and gearing as an '09 AP2 CR.
The street touring classes offer enough modifications to keep any tinkerer satisfied, but there are still many limitations. While very much a driver's class, minute details can be the deciding difference between National Champ and first loser. Sometimes those small peculiarities could substantially add to the cost of the build, such as the quality of shocks, and degree of weight savings, as well as extracting as much power as possible. Regionally, most can get into STR with a basic budget setup and be 90% of the way there. That last 10% is what really affects the cost of the build. The overall price of modifications can range from $3-4K on top of the vehicle cost if done as conservatively as possible. If you are looking for National level full prep, plan to be spending around $10k after the price of the car. While that may seem rather pricey for a toy, these cars can dual-purpose as a daily driver and a weekend warrior.
WHEELS/TIRES: $1,000-$2000
Most cars run a "square" tire set up of 255s, the 200TW street tires cost about $650 a set. 9" wheel width is likely, and wheel expense can greatly vary. The more you pay, the lighter the wheel, which means less unsprung weight.
SWAY BARS: $300-$1200
A larger front sway bar is valuable towards helping with stability after the newfound front grip from bigger wheels and tires. While all sway bars will be similar in design, you're paying the premium for adjustability and weight loss.
CAMBER KIT: $150-$300
Most chassis will require more camber adjustment to acquire the 3+ degrees desired around corners. Most kits are not very expensive, but prices will vary based on the vehicle.
SHOCKS/SPRINGS: $1000-$6000
At the minimum, multiple sets of springs and rebound adjustment will be desired to make appropriate handling changes to properly balance the car for your driving style. Higher-end, more expensive brands such as MCS, JRZ, and Penske, make high-pressure nitrogen-filled shocks that allow for incredibly easy compression and rebound adjustment. If adjusted properly, these could save you lots of time on course with the capabilities of adapting your suspension to each location.
INTAKE/HEADER/HIGH-FLOW CAT/EXHAUST: $1000-$2000
Intake modifications (pre-throttle body) and exhaust modifications (post-head) make up the majority of ways to increase power in the Street Touring category. The exhaust system can also be a major source for weight savings, and what you’re willing to spend determines whether you’re sporting one in stainless steel, or the lighter aluminum and titanium.
ECU PROGRAMMING/DYNO TUNING: $500-$1500
ECU tuning can be critical to optimizing power output of your car, because even if you have the best intake and exhaust money can buy, the factory ECU parameters are programmed to operate with OEM components, unless told otherwise. Tuning in STR may be performed by either "re-flashing" the stock ECU, reprogramming a modified ECU, or utilizing programmable "Piggyback" hardware. A 10% overall power increase could be noticed if done effectively after the STR bolt-ons are added, and cost will vary based on brand of hardware/software,customization of tunes, and dyno tuning time.
LIMITED SLIP DIFFERENTIAL: $600-$2000
Most of the cars competing in STR already come with some form of a limited slip differential, and as long as it's functioning properly it will not be the factor holding you back from a National Championship. You can opt to either run a Torsen or clutch-style LSD, and added expense can get you active adjustment in their locking characteristics, and clutch-style LSDs are known to change handling characteristics and may make the car easier to drive. All S2000s come with a Torsen LSD from the factory, and it is/was an OEM option in the MX-5s and MRSs. If you’re on a budget, make sure you purchase a car with a LSD so you don't have to worry about installing a new one.
WEIGHT SAVINGS: $0-$6000
Racing seats, lithium battery, lighter wheels, and aftermarket exhaust are where you'll see the largest weight savings, and from there it's a matter of how much you’re willing to spend to shave every pound from things such as the braking system, pulleys, and bushings.
THE HONEST TRUTH
"STR is a driver's class. To compete nationally, plan on at least $8K in parts on top of the base vehicle cost to be competitive. However, all the money in the world will not win you a championship without the driving skill required. Additionally, even with the talent and parts required to win, they mean nothing without proper chassis setup. If you chat with any of the top STR car owners, one would think you are speaking to super geeky physics majors." -Brian
