The Indy Racing League's evolution brings more fans, more interest, and the most technically advanced cars yet.
Firestone tires lined up during practice for the Yamaha Indy 400.
Though 2003 will see more big changes at Indy, things certainly aren't standing still this year. GM Racing introduced an all-new small block Chevy V8, Infiniti honed its powerful 35A engine, and Toyota's designing a new purpose-built powerplant to compete in 2003. Chassis builders continue tinkering with current models to get more aerodynamic gains, all the while designing next-generation chassis. A new, significantly smaller gearbox is also in the works. With so much new, one thing stays the same; Firestone continues as the League's sole tire supplier.
One thing is clear; the Indy Racing League (IRL) is gaining popularity. The League's roster continues to grow as new teams and suppliers swell the ranks and old favorites return. Key to everything is the IRL's goal to maintain high technology and intense competition within a tight financial framework. Making it all come together is a host of talented engineers, pit crews, and drivers.
GOODBYE OLDS, HELLO CHEVY
Oldsmobile's proud 98-year history in motorsports came to an end last year when the checkered flag fell at the IRL's season-ending Chevy 500 at Texas Motor Speedway. In its place comes a more-powerful, lighter, and more-reliable Chevy Indy V8. The new engine marks the first time Chevrolet powered an Indy-style car since 1993. Before the hiatus, the automaker was quite successful, winning 86 races, 80 poles, six Indy 500s, and five series championships.
The Chevy Indy V8 for 2002 is based on GM Powertrain's Premium V engine platform and on the series' current technical requirements, says Joe Negri, GM Racing IRL/Road Racing Group Manager. IRL engine rules in 2002 specify a maximum engine displacement of 3.5 liters (214 in.3), a maximum engine speed of 10,700 rpm regulated by a programmable rev limiter, and a 180° flat crankshaft.
The new powerplant preserves the architecture of its predecessor, the Oldsmobile IRL Aurora V8, but is significantly upgraded to better fit the League rules, explains Roger Allen, lead engine designer for GM Racing's Chevrolet IRL program. Carrying over only the oil and water-pump assemblies, the all-new design is smaller, lighter, and has a lower center of gravity (CG) than the Oldsmobile engine. Unlike the Aurora, designed on paper by draftsmen, the Chevy has been completely solid modeled and FEA analyzed with the latest high-tech design tools. Key objectives were more horsepower, less overall engine weight, low CG, reliability, and better chassis integration. According to Allen, CFD, computer simulation, and FEA made these goals a reality. "Using these tools we were able to boost horsepower by cutting frictional losses and reciprocating weight, increase engine airflow, and improve combustion chamber shape and valve-timing events," he says. The software also helped designers cut engine weight from high CG components which, in turn, lowers the CG.
At full throttle, the new Chevy small block puts out 20 to 25 more horsepower than last year's Oldsmobile engine. "Chevy getting back into the competition gave us a great opportunity to take the basic architecture of the IRL Aurora V8 and evolve it into an engine that fits the current rules better," says Allen. "Nissan brought the game up last year with the Infiniti Indy 35A; it's very competitive. Sitting on our laurels would have put our teams in a position that's tough to compete with. And it would have given them an opportunity to switch over, because at the end of last year, we believed the Nissan was better than 645 hp, the last spec of the Aurora engine. The new Chevy produces about 670 hp."
One way to boost power was to cut frictional losses in the engine by trimming the main and rod bearing diameters. Less reciprocating weight was another, so designers cut piston mass. Another target, getting more airflow through the engine, was trickier. In most series this is easily handled by increasing the bore diameter. Not so in the IRL where bore size is limited (93 mm). "Getting more airflow is difficult, but achievable," says Allen. "To do it, we improved the valve positions in the chamber by reducing bore shrouding." Designers used CFD to optimize the intake port shape by increasing its cross-sectional area. Changes to the combustion chamber also helped boost airflow. Designers also shaved engine weight, cutting it from 326 to 315 lb.
"Some engine parts are more important than others when cutting weight, such as the crankshaft, for instance. A lighter part helps the car accelerate which improves performance at the track by cutting lap times. We took 4 lb out of the crankshaft itself," adds Allen.
Using computer simulation, engineers were able to design a more reliable engine. The water jacket in the cylinder head, for example, was configured to get better cooling and to cut the risk of combustion-chamber cracking at extreme temperatures. Valve reliefs in the pistons were revised to improve durability. Designers used FEA to substitute steel for titanium in valve retainers. Problem was, the titanium valve retainers were coated with chrome and the chrome was flaking off and getting distributed through the engine. "With FEA we were able to make a steel component the same weight as the titanium one and not have to use the chrome plating. This reduces wear on many engine parts," Allen explains.
Like the engines, chassis evolve year to year and designers work side by side to ensure the best set up. One example is water exiting from the engine. In 1996, water exited both sides of the engine as radiators were located on each side of the car.
"After engineers found that feeding the water to the left side of the driver improved weight distribution of the car, we developed a passage in the engine to run water out the lef side to match the new radiator location," says Allen.
This year engineers also upgraded the intake manifold with a new throttle cable location and enhanced fuel-line routing. "This took about 1 lb out of the manifold and helped cut CG," says Allen. With airflow testing, CFD, and analysis tools, Chevy engineers were able to improve pressure distribution in the airbox, sending more power to the engine.
In initial testing, the Chevy Indy V8 ran more than 500 simulated miles at Indy, including pit stops, on a water-brake dynamometer at the company's testing facility, Katech Inc., Clinton Township, Mich. The new engine passed early validation tests with flying colors. Since then, the results speak for themselves: At press time, Chevy engines have been in the winner's circle in three out of three IRL races.
GM Racing is simultaneously designing an all-new "Gen 3" Chevy Indy V8 to meet new IRL engine rules for 2003. Next-generation engines will be even lighter and smaller than this year's model. "The 2002 Chevy Indy V8 will provide a benchmark as we move toward an even more refined engine package for the 2003 season," Allen explains. "By combining real-world test results with powerful engineering tools such as CAD, FEA, CFD, and 3D solid modeling, we are rapidly developing the next-generation Chevy Indy V8."
MORE POWERFUL POWERPLANTS
Challenging Chevy is the Infiniti Indy 35A which debuted last spring. Getting the engine ready to race took some doing by the Infiniti team but was well worth the effort. The powerplant's prime champion Eddie Cheever Jr., #51 Red Bull Cheever Racing, gave the new engine its first win at Kansas Speedway last July. By the time the season ended, Infiniti engines earned more top-three finishes than ever before in the series and led a record number of laps. "When the 35A came out last year we were very late due to reengineering required for the engine to be competitive in 2001," says Cheever. "We only did about 200 miles of testing before we went to Phoenix for the race. Now we are far ahead of the curve. Since the end of last season we have a new electronics package, and we've done some modifications to help engine reliability, making it a very strong package."
The Infiniti team was indeed working hard in the off season. Engineers put the 35A through a complete design review and teams tested more than 5,000 miles, concentrating on the new electronics package and durability of core engine components. Add to that many more miles of simulation races on the dyno at the TWR engine facility in Kidlington, England. The result: lower CG, more horsepower, and better reliability.
"We lost some opportunities last year because of electronic problems," explains Charlie Bamber, chief engineer, Infiniti Motorsports. "The new Magneti Marelli MR5 engine-management system is more adaptable to the rev limits and it gives us better speed control in the pit lane. If we are able to keep the speed closer to the limit we'll lose less time entering or leaving the pits. Our drivers might then gain a few car lengths that could make the difference at the end of the race."
Last season showed Infiniti engineers other opportunities for improving engine reliability. For example, the team experienced exhaust-valve head failures so it redesigned the camshaft profile and changed the sealing velocity of the exhaust valve. Another key change is the way the engine mounts to the car, says Bamber. "The engine mountings are now integrated with the camshaft cover whereas before we used a three-piece composite assembly including a camshaft cover, mounting plate, five studs, and five nuts.
The change helped us improve the overall stiffness of the engine/chassis combination, making the engine a stronger stress member of the chassis. It also let us cut engine weight."
Much of the durability testing took place on the dyno. Basically, Infiniti engineers used data from Cheever's car during last year's Indianapolis practice and race and derived what would be a "typical lap," then replicated it. In simulation tests, the throttle position moves as the driver would move it, engine revs go up and down through the corners, and even atmospheric conditions, such as wind speed and direction, are replicated. Says Bamber, "The dyno lets us validate engine reliability before we get to the Indy 500 as long as we are close enough to the pace, and we believe that we are."
Actual loads on the chassis are another matter. Bamber says engineers can input GT cycles the engine experiences in terms of rpm, load, and speed. These are good indicators of stress on the rotational and reciprocating components. But what they can't add is the torsional moment in the car between the front and rear axle that transfers through the cylinder block. "For that, we use a static-rig test and hydraulic jack. It's a pretty crude-looking device — essentially a big plate that bolts on the front of the engine to simulate the chassis, and one on the rear for the gearbox — but it shows us the durability of the engine and gearbox mountings."
Infiniti engineers also rely on design software, though not as extensively as Chevy. In designing and updating the Infiniti Indy 35A, the team runs mechanical simulations and works with CFD and FEA but mostly to verify a design in its early stages. "It's only recently that engine designers have begun using these tools to their full extent," says Bamber. "It definitely speeds the process. Spending 10% input time on these programs gets you about 90% of a result."
In its sixth season of IRL competition, Infiniti looks stronger than ever. The engine maker powered just three cars last year but doubled its ranks thus far, and expects more teams on board by the Indy 500. At each IRL race to date, Infiniti cars have given Chevy a run for its money. In fact, the team earned its first IRL pole position for the Yamaha Indy 400 at California Speedway when Cheever clocked a 221.422-mph qualifying lap.
The competition heats up even more in 2003 as a new contender enters the race: Toyota announced its plans to join the series last spring. According to Lee White, group vice president and general manager for Toyota Racing Development (TRD), discussions with the IRL began more than a year ago. "Brian Barnhart and I agreed on some fundamental things: First, neither of us see potential for a merger between the IRL and CART. Second, I see a lot of merit in the cost control and controlled technology, and the development rate of the IRL formula. Last, we both agreed the potential is there to modify that formula so it can have applications in both oval-track and road-racing series'," he explained.
TRD, based in Costa Mesa, Calif., has built race-winning engines for many series including IMSA, CART, Nascar Goody's Dash program, and the Pikes Peak International Hill Climb, to name a few. So, what's their expectation coming into the IRL? Formidable competition, according to White. "TRD will have its work cut out for them competing with GM and Infiniti. It won't be a cakewalk."
All three engine makers will start from a clean sheet of paper designing 2003 engines. The new formula is essentially the same as the current package: Purpose-built 3.5-liter, 32-valve dual-overhead cam, normally aspirated V8s. Teams will see the biggest changes in the camshaft drive and injectors. The camshaft drive can be chain or gear-driven and a second injector will be added. The current formula restricts the engine to one injector, but manufacturers believe a second one will improve the engine's midrange drivability and help in making the engine dual purpose. These changes will also help cut engine size and weight. New-generation engines will lose about 30 lb, with the minimum weight dropping to 295 lb.
Toyota's new powerplant, called the RV8I (Racing V8 Indy), is well on its way to fruition. Engineers started with a design last June and spent about seven months working on the detail design. Currently, engine parts are coming in for assembly, says TRD, and the team plans to do some track testing this July in a modified 2002 IRL chassis.
Leading the design effort is TRD's Philip le Roux, senior manager, engine design. le Roux is no stranger to race-engine technology; he and his team designed the winning RV8F CART engine, a 2.65-liter aluminum-alloy V8 that puts out more than 800 hp. But the IRL engine is a completely different animal. "With the IRL engine we have extra constraints. It has to be cheap and very efficient. Normally, to get more horsepower we can boost rpm to push more air through the engine. But in the IRL rev-limited formula we can't do that so we have to make the engine more efficient by cutting friction and so on," he explains. "I took a completely clean-sheet approach to this engine and in comparison to the CART engine, we cut out about 45% of the parts. It's completely fresh, completely different."
le Roux and his team are designing the IRL engine almost entirely in PTC's Pro/Engineer. The software has helped them boost engine volumetric efficiency and reliability. "When analyzing a component we go straight to Mechanica, the Pro/E finite-element package," says le Roux. "Here, we can put loads on the parts and learn how they carry the load, and see if any high stresses crop up. We can then make changes and measure the improvements before we actually make the parts.
"When an engine runs for a long time, fatigue-type failures are common. It really comes down to details," he adds. "We need to have nice corner radii in the parts and no stress raisers or sharp edges where cracks can initiate. We also must have enough bolt stretch so the bolts don't vibrate loose." The team uses other software for mechanism simulation and fluid-flow simulations.
Engine care doesn't end in the assembly shop. TRD engineers make sure engines are easy for teams to install. "Some of these engines are taken in and out in less than desirable conditions by guys that have been on the road a long time," says Pete Spence, TRD vice president and technical director. "We make handling and part ergonomics a big priority." Engineers also are on hand at the track to help teams adjust fueling, ignition timing, and so forth, making sure drivers and chassis engineers get the most out of the engine, says Spence.
So far TRD's new engine has generated a lot of interest, but the first IRL team to officially sign on with Toyota power is Kelley Racing. "We're thrilled to partner with a corporation as successful as Toyota," Team co-owner Tom Kelley says. "The combination of our IRL experience and Toyota's successful history in open-wheel racing will create a partnership that lets us achieve our goals of winning the Indianapolis 500 and the IRL championship."
At press time, Toyota announced it will also supply IRL engines to Penske Racing in 2003. Penske said goodbye to the CART FedEx Series in favor of running exclusively in the IRL series, including the Indy 500, this year. Twotime defending Cart champion Gil de Ferran and last year's Indianapolis 500 winner Helio Castroneves will drive the Marlboro Team Penske cars. The team will test the new Toyota Indy engine later this season.
CHASSIS CHANGES COMING
This year is the last for the current IRL chassis formula enacted in 2000. New-generation cars, though similar to existing models in appearance and aerodynamics, will be "the most technically advanced in terms of car construction and driver safety ever used in open-wheel, oval racing," according to Tony George, IRL president and CEO. "We could have easily frozen the rules package for the next few seasons and continued to put on exciting, competitive races," he adds. "But with the data we continually record from crashes and other tests, we are confident a new generation of chassis can be built that will be safer and stronger, yet still provide the level of competition for which the League is known."
This year, chassis makers Dallara Automobili SRL and G Force Technologies Ltd. produced update kits with new undertrays, sidepods, and radiator boxes. Dallara also has a new speedway front wing while G Force cars sport new speedway and short-oval noses and new front-wing assemblies. "The car design was set in 2000, so there aren't many opportunities for big chassis changes," explains G Force's Chris Rushforth, senior technical
engineer for the IRL car. "Structurally, the shape of the chassis doesn't change or the components wouldn't fit year to year. Changing the shape of the nose this year was both a safety issue and an aerodynamic advantage." Another performance update to the G Force chassis was the new water-radiator installation with a different left duct. "Last year, our cooling was marginal so we went for a longer duct and different, more-efficient radiator core." Updates this year will give both camps small gains in downforce and less drag, as well as better overall efficiency.
The new chassis package for 2003 through 2005 is geared, as always, toward driver safety. While still in the planning stages, the design calls for adding three inches between the pedal bulkhead and front bulkhead, and wider, longer sidepods to put more distance between drivers and the wall. Other items up for discussion include cutting car weight to lessen impact mass, and establishing a minimum chassis length. Additionally, a bulkhead must sit directly behind the front-suspension mounting points, and the chassis' aluminum honeycomb core must meet a minimum density.
The IRL will also add more energy-absorbent foam around drivers' legs. Dallara is ready. "Our car has panels inside with about one-inch dead space on the sides and above the driver's legs to help eliminate any sharp edges. These areas can be filled with foam," says Sam Garrett, Dallara's U.S. technical representative.
The aluminum honeycomb core of the chassis is, on it's own, a good energy absorber. However, to add to driver safety, G Force engineers can make the aluminum honeycomb thicker or add to laminate thickness. "Another area to consider is the wishbones," explains Rushforth. "At the moment, the lower wishbones actually mount inside the chassis and the drivers' legs sit just above them. Sometimes in accidents, the lower wishbones punch out the brackets inside the chassis. If they break through, the wishbones can touch the driver's legs. To avoid this, G Force places a special carbon pocket inside the chassis, around the wishbones."
To nip potential problems in the bud, both chassis makers put cars through rigorous impact and load tests. New rule changes in 2003 will beef up the tubs even more. One targeted area is the nose. Nose-impact tests measure how much energy is needed to collapse the nose box. New rules call for increasing energy in both the first and second nose-impact tests. Moreover, the chassis can't be damaged during either test. "For the nose-box test, we actually build a tub, bolt a real nose box on it, and then slam it into a wall," says Dallara's Garrett. "We measure its deceleration rate and g-load. The nose box is designed to collapse in a controlled manner so that it keeps the g-loading on the driver down to something survivable." It's a delicate balance: If the nose box is too soft, it'll collapse without taking any energy and when the tub actually hits the wall, it'll be too big of a hit. On the other hand if the nose box is too stiff, initial impact is too high.
The nose-impact test is severe. Once the nose box slams dead on into a wall at a certain load, it gets reimpacted a short time later. The IRL specifies how much the nose can deform. There's also a nose push-off test to measure how much force it takes to push the nose box sideways off the front of the car. "We put a block onto the side of the nose then give it a push. This lets us check the mounting from nose cone to chassis," says G Force's Rushforth.
Another component under scrutiny is the roll hoop. In a roll-hoop test three simultaneous loads are applied from the top, front, and sides, says Garrett. "The roll hoop has to withstand minimum forces in all three directions." The test gets even more stringent in 2003 as the IRL ups the applied load on the roll hoop. Manufacturers also must boost side-intrusion absorption levels, and apply a new impact test and side-load test on a new rear-crash structure.
There's also talk of side-impact tests to the monocoque. "The idea is to develop ways to make it more difficult for one car to penetrate the side of another, as when one car T-bones another," says Garrett. "We are working on changing the standards for the lay-up on the side of the car. We are also changing the nose boxes a bit. Right now, the nose box comes to a small radius point. In initial impact, the loading area is small, so the forces are high. There will be a new IRL rule saying the first 5 or 6 in. of the nose box must be less strong than the rest of the nose box so that it collapses more easily and is less likely to go through another car."
The rear of the car will also be safer thanks to a new shorter gears-forward transmission from England's Xtrac Ltd., the IRL's gearbox supplier since 2000. "We've just started designing the new gearbox," says Xtrac's Jon Marsh, senior designer. "The objective is to cut the overall length of the assembly, thus improving the weight distribution and safety of the car. The longitudinal orientation will stay the same with the cluster of gears inline with the engine but mounted further forwards, below the axle line." The shorter gearbox is less vulnerable to damage and less likely to hit the wall. Its compactness makes room for a larger impact attenuator on the rear. Yet the design still offers the same servicing features as the current transmission — a cassette-style ratio change for quick cluster removal and replacement.
"Right now, the gears sit behind the differential output shaft which means the car has a high polar moment-of-inertia at the back," says Rushforth. "Bringing the gears forward significantly changes the way the car handles. Instead of having a lot of weight out the back, it'll be brought more inside the wheelbase of the car and should improve handling." G Force also is looking at redesigning the bell housing to suit the new gearbox for better weight distribution.
"The new gearbox is a nice design and it'll be a big improvement over the current transmission through weight distribution and lowering the polar moment," adds Rushforth.
To stabilize costs, the new transmission assembly will use many existing internal parts. Xtrac will work with chassis manufacturers to design the new rear-crash structure.
Another enhancement is to the Suspension and Wheel Energy Management System (SWEMS). Mounting points for the restraint system, consisting basically of small Zylon cables that keep parts from flying off in crashes, will be integrated into new-generation chassis.
Changes such as these take place year to year, but others happen race to race. Chassis bodywork, for example, stays the same but engineers specify different aerodynamic configurations for the cars depending on the track. Basically there are four different packages, says Garrett: The short oval, mile-and-a-half high bank, mile-and-a-half low bank, and super speedway, such as Indianapolis.
Teams can't alter the main structure of the chassis but such things as suspension geometry and aerodynamic settings are fair game. G Force offers three different suspension options: Standard wide track, narrow, and ultranarrow, featuring different top and lower wishbones, antiroll bars, springs, and so forth. Dallara offers three track widths (narrow, standard, and wide) and three wheelbase options (standard, –2 in., and –4 in.). At faster circuits where corners are tight but long, for instance, teams may run a narrow-track suspension which means less drag, though the car's a bit more unstable. At a slower circuit, teams might run a wide-track suspension to get better corner stability.
"Three different suspension sets give us a good spread of performance and let teams tailor their cars," says Rushforth. "They also can change aerodynamic settings. For example, they can use cross weights to alter the amount of oversteer or understeer. Drivers also can adjust the antiroll bars using a series of levers on the side of the car. This gives them better balance and control in the corners." During tire changes, quick adjusters on the front and rear wings let teams change the wing angle to get less understeer. A quick adjuster on the nose changes the balance of the car in seconds with just a couple of turns.
NOT TIRED OF THESE TIRES
All 59 IRL events thus far have run on Firestone tires and that won't change anytime soon. Bridgestone/Firestone Inc. signed on as the IRL's exclusive tire supplier through 2005. Firestone will also serve as sole supplier to the new Infiniti Indy Pro Series.
"The Firestone Racing program has consistently demonstrated it can supply the quality tires needed for our high-speed, oval-track competition," says IRL's George. "With such continuing involvement, we believe our series will continue to grow and prosper, and that we'll have tremendous competitions in the years ahead. We wanted one tire supplier for safety and cost-control benefits and we're pleased Firestone will be that supplier."
Besides maintaining its presence in motorsports and strengthening consumer confidence in the Firestone brand, the company's contining relationship with the IRL boasts other advantages. For example, the series provides an excellent test bed for new technologies.
"The Firehawks must be thin enough to allow heat buildup to dissipate, but thick enough to shoulder the enormous stress placed on them during practice, qualifying, and race sessions," said Al Speyer, executive director of Bridgestone/Firestone Motorsports, in a recent IRL interview. "It's a balancing act, really, with the Firestone race-tiredevelopment engineers and chemists constantly looking at new technologies, new materials, and new methods of construction." At Indianapolis this year, in fact, teams will run all new tires in all four positions. Not new construction-wise, but rather, incorporating a new compound. "Right now, there's not a tremendous amount of construction activity going on because our construction is very durable, and there's no real need to try and get additional speed out of the tires," explains Firestone's Page Mader, manager of race-tire development. "We are, however, updating a number of our sets this year with a new compound. Obviously, after supplying tires to this spec series for several years now, we are pretty stable in what we do. But when the series makes aerodynamic changes where speed goes up or the load on the tires increases, then we would determine if we need to bring in a different tire," he adds.
Firehawk racing radials endure punishing conditions during each race. Consider, for instance, the downforce created at race speeds: At more than 200 mph, the centrifugal force of the components combined with lateral forces in the curves can quadruple the weight tires carry. Factor in track temperature and friction where rubber meets road, and treads can heat to water-boiling temperatures. "If we're racing on an oval and it's going to be hot outside, we try to control the tread gages so tire temperatures don't get much higher than 200°F," explains Mader. "Anything above 230°F concerns us." Firestone techs take tire pressures and temperatures throughout the race weekend and run comparisons.
Another consideration is ambient temperature. Track to track, temperatures can range from 50 to more than 100°F, and track surface temperatures can get even hotter. These variables and others, including track length and speed, are considered when preparing for a race. "If we know how fast the track is, we have a pretty good idea of what tires to take. We test multiple compound lineups and a couple different-stiffness constructions to confirm which one works best for a particular aeropackage and speed," explains Mader. "To determine course speed, we generally look at average lap speed rather than maximum speed at any given point on the track." Richmond International Raceway, for instance, is only a three-quarter-mile oval track. Cars run about 165 mph. The 1.33-mile oval at Nashville Superspeedway, and the 1.25-mile oval
at Gateway International Raceway in St. Louis, on the other hand, push drivers to about 200 mph. According to Mader, the same tire construction can be used at each track but the compound must be changed for better heat resistance.
Which tires to race becomes a little trickier for road versus street courses because the cars run on so many different types of surfaces. Firestone often turns to more durable compounds for grooved street surfaces where the concrete is brushed to add grip. An example of this type is Cleveland's Burke Lakefront Airport where Cart runs the Marconi Grand Prix. "The grooved runways are tough on tires so we use a harder compound than those used on some of the other permanent road circuits," says Mader. Not surprisingly, Firestone has varying road com-pound line ups for each type of circuit, from street course to superspeedway. "Typically, street courses are slower than road courses and require a softer tire with more grip. Road course tires are a bit stiffer and stronger because the cars go faster with more downforce."
Firestone engineers work closely with teams, taking valuable information from dataacquisition systems. Most Indy cars use Pi data recording systems, from which tire engineers watch steering angle, g-loading, and downforce on each corner of each tire position. "That also helps us determine track-to-track severity," says Mader. "We can see how much loading is in a corner and for how long, and from that, determine how severe a track is."
This year, the IRL clamped down on how many sets of tires teams receive for testing and race use. For races 200 miles or less, each car gets seven sets. The IRL determines how many sets teams receive for longer races but generally the rule is, eight sets for 300-mile races, nine for 400 miles, and about 28 sets for Indy. Also, teams can't swap sets between those marked for testing and race use. Firestone and the IRL keep tabs on the tires using bar codes and a hand scanner. "We bar code every tire," explains Mader. "Teams are only allowed to use tires mounted at that event. The IRL is very precise in tracking this." The tires, approved by IRL officials and given an external code, carry bar codes assigned by Firestone Racing. "Using a hand scanner, IRL track officials can scan a tire quickly and verify that its code number matches the car's code. With bar codes we can follow a tire from beginning to end."
In competition, each car starts the race on the tires used in qualifying. After that run, usually the length of a fuel tank, teams can switch to any of their other sets. Firestone highly recommends teams scuff or "scrub" their tires to take the shine off and heat them up. Scuffing/heat-cycling the tires acts like a curing process, making the tires slightly more durable. "Teams wouldn't want to heat-cycle the tires too many times, however, once before the race can only be a good thing," says Mader.
Future IRL stars may be born from a new open-wheel support series set to debut this July. The Indy Racing Infiniti Pro Series will serve as a training ground of sorts for the 650-hp, single-seat winged cars of the IRL. The inaugural season, which opens July 7 at Kansas Speedway and culminates Sept. 14 at Texas Motor Speedway, consists of seven races run on 1.25-mile and larger tracks. Infiniti Q45 engines will power allnew Dallara chassis riding on Firestone Firehawks.
"The events will be 100 miles long and will run the same weekend as the Indy Racing League feature event," explains IRL's Brian Barnhart, vice president of operations. The V8 engines will produce 450 hp, run on gasoline, and have a minimum fuel capacity of 25 gallons. Pro Series cars will include nearly all the same safety features as IRL cars including 19-in. cockpits, larger headrests, long and high sidepods, and the SWEMS system on all four corners of the car and the rear wing. Cars will use a Ricardo six-speed sequential gearbox mounted forward of the differential.
"The purpose of the series is to be a development series for young drivers, particularly those out of USAC Sprint cars, Midgets, and Silver Crown cars," says Barnhart. "At a very young age, those drivers learn to race wheel-to-wheel in close competition in probably one of the best training and proving grounds in today's racing world. They get oval, high-horsepower, and wide-tire experience, but it is still a drastic change to step into a 650-hp, rear-engine Indy car, and experience its aerodynamics."
IRL plans to expand the Pro Series season in 2003 to a full schedule of 12 races.
The various surface shapes of an Indy-style car produce tons of downforce. More downforce inevitably means faster cornering speeds and quicker lap times. The underside of Indy-racing car sidepods accelerates air through the venturi, creating a pressure differential between the upper and lower surfaces of the sidepods. This produces downforce. Airplane wings do the same thing except in reverse, creating low air pressure over the wing, causing lift.
"The downside of downforce is that it almost always comes with the penalty of drag," says Kevin Bayless, chassis and aerodynamics consultant for GM Racing. "At a high-speed track like the Indianapolis Motor Speedway, cars are trimmed out to produce 1,700 to 2,000 lb of downforce with minimum drag. At a one-mile track like Phoenix International Raceway, the cars are set up to produce as much as 4,000 lb of downforce."
The increase in corner speeds produced by the extra downforce on such short ovals compensates for the speed penalty produced by additional drag on the straight runs, Bayless explains.
Another source of drag is the open-wheel design of Indy-style cars, as a rotating wheel creates both drag and lift in a moving air stream. The spinning tire piles up air at the bottom to produce lift while air turbulence behind the tire creates drag.
"The turbulence disrupts the airflow around the rest of the car, affecting aerodynamic performance of the sidepods and wings," says Bayless. "Ramps in front of the rear wheels deflect the air to minimize the lift and drag effects.
Information courtesy of GM Racing