Designs on the winner's circle
This Memorial Day weekend, Indianapolis again becomes the center of the motorsports universe with the running of the 87th Indy 500. This year's race shines the spotlight on a new three-year engine and chassis specification package. The new plan, as always, focuses on driver safety and more competition. Look for a shakeout among engine providers -- GM, Honda, and Toyota are in, Nissan is out -- as well as more robust chassis and redesigns galore from nosecone to powerplant to gearbox.
A brand-new bow tie
Competition in the IRL has never been more fierce. This year three engine makers will battle it out on the track. GM Racing, Detroit, returns with an all-new Chevy Indy V8, the second new IndyCar engine produced by the team in just two years. Toyota Motorsports threw its hat into the ring last spring, announcing Toyota Racing Development (TRD), Costa Mesa, Calif., would design and build an engine to compete beginning this year. And American Honda Motor Co. Inc. is making its initial foray into the IRL IndyCar Series. Leading its engine design and development effort was the company's racing subsidiary Honda Performance Development (HPD), Santa Clarita, Calif., and technical partner Ilmor Engineering Inc., Plymouth, Mich. Long-time IRL engine supplier Nissan Infiniti pulled out of the IndyCar Series, instead focusing its efforts in 2003 on the IRL Infiniti Pro Series.
GM Racing has been powering IndyCars to victory since the IRL introduced naturally aspirated engines in 1997. The powerplant producer is working around new and carried-over IRL specs. The IRL engine formula still calls for a maximum displacement of 3.5 liters (214 in.3), and a 180° flat crankshaft. Maximum engine speed, however, has dropped from 10,700 to 10,300 rpm, regulated by a programmable rev limiter.
The IRL rev limiter is basically the "policeman" of the race -- its limit is inviolable. But, within the GM engine-control module (ECM) is another limiter, there to avoid triggering the IRL limiter. It has "hard" and "soft" limiting features used at the engineers' and engine builders' discretion. According to GM, two "hard" limiters within the IRL Chevy Indy V8 shut down the engine's ignition system when it hits 10,300 rpm. A third "soft" limiter progressively cuts spark to the cylinders as engine speed nears the limit.
"The IRL limiter is called a hard limiter because when it activates, it shuts down the entire ignition system," says GM Racing engineer Ned Baker. "It's like an on-off switch. When the limiter is activated, engine output drops to zero. The limiter doesn't restore current to the ignition system until is has determined the engine is below the rpm limit, so there is a period when the car is essentially without power." The rev limiter figures engine speed by measuring intervals as four teeth on a flywheel pass a block-mounted sensor. It also contains a data logger that IRL officials can access any time during an event. According to Baker, the hard limiter is extremely harsh so the second rpm limiter is set just below the IRL limit threshold. "The ECM calculates engine speed just as the IRL limiter does, but uses its own sensors and logic," he says. When activated, the internal electronic-control-unit (ECU) limiter shuts off the signal to the ignition module. The interruption may only last a thousandth of a second, but it is usually enough to keep the engine speed below the point where the hard limiter kicks in, says Baker.
Physically, the 2003 Chevy Indy V8 is 3 in. narrower, 3 in. shorter, and 35 lb lighter than the 2002 version. It has an aluminum cylinder case, aluminum cylinder heads with four valves/cylinder, dual-overhead camshafts, and sequential electronic fuel injection. At 280 lb, the powerplant puts out more than 675 hp.
According to GM, the new engine went from concept to dyno cell in just nine months, thanks to both sophisticated design tools and old-fashioned know how. "The 2003 Chevy Indy V8 builds on the experience GM Racing has gained with two previous IRL engines," says Lead Engine Designer Roger Allen. It also takes advantage of regulation changes as the IRL IndyCar Series has moved from production-based to purpose-built racing engines, says Allen. "For example, the new Chevy Indy V8 has a precision-gear camshaft drive instead of chains, two fuel injectors per cylinder instead of one, and removable light-alloy wet cylinder liners instead of cast-iron dry liners that were used previously," he explains.
IRL specs again call for a maximum cylinder bore diameter of 93 mm. This requires a 64.4-mm stroke crankshaft to produce 3.5 liters of piston displacement. The stroke yields a mean piston velocity of 4,385 ft/min, and a maximum acceleration of nearly 7,000 times the force of gravity at 10,300 rpm, according to GM Racing. GM engineers pay special attention to the piston, pin, pin lock, and connecting-rod design so that reliability isn't compromised during a 500-mile race.
The engine, a dry-deck design, uses cylinder sealing rings and O-rings between the block and cylinder heads instead of conventional head gaskets. Camshaft timing, valve sizes, and port volumes have all been tuned for peak power at the 10,300-rpm limit. Four camshafts operate 32 titanium valves on the new V8.
GM engineers also developed a new-generation brain box for the engine. The system includes two modules. The ECU calculates how much fuel to deliver and monitors the ignition timing. A second module then processes the ignition signals, explains Baker. "We start with a 12-V battery signal, charge the capacitor to 400 V, and then the transformer winding in the coils produces the 16 kV that the spark plugs require to ignite the fuel mixture."
The IRL keeps a tight reign on the use of engine electronics but one of the few approved automatic functions is a pit-lane speed limiter. Also new this year, IRL rules allow "shift without lift," basically full-throttle electronic gear changes, and traction control. All three engine manufacturers are taking advantage of these functions.
Honda back at Indy
Honda's last showing at the Indy 500 was in 1995, but this will be the engine maker's first run there as part of the IRL IndyCar Series. Honda's decision to join the IRL ranks after pulling out of the CART Series last year surprised more than a few because the engine producer at that point had no plans to continue in North American motorsports. "We had put a lot into the CART program," says Robert Clarke, HPD president and general manager, "and once the emotions settled down, we began to realize the equity that we had in the program and how important it was for American Honda to have a continuous motorsports program in the U.S. At the same time, we re-evaluated HPD and envisioned it as a true racing engine-development company rather than just an assembly and trackside-support operation. Looking at the IRL, and what we as HPD could do to develop in that Series, we felt it was a perfect match."
The Honda engine is designated the HI3R Series Indy V-8. The company's partnership with Ilmor Engineering made it possible to get the new engine up and running in time for the 2003 season. Current plans have the two working together for at least three years, with HPD taking over full engineering and development work thereafter.
Though Honda got a late start to the IRL program, fans would never know it from race results thus far. At press time, Honda-powered Andretti Green Racing with driver Tony Kanaan took the pole at both the Toyota Indy 300 in Homestead and the Copper World Indy 200 at Phoenix International Raceway. Kanaan also gave Honda its first IRL win in Phoenix.
Victory is nothing new to Honda, whose turbocharged V8 powered six consecutive CART drivers champions between 1996 and 2001, but working under the IRL's tight design constraints is. "The design philosophy of the IRL engine is different than with the CART engine because cost is a bigger consideration," explains Trevor Knowles, HPD senior engineer. "Also, the engine life and life of the major engine components are expected to be much longer than that of the CART engine. It's important to minimize costs and part of that is not scrapping as much of the engine as you would on a rebuild if you were doing a CART or Formula One engine."
IRL rules take many design decisions out of engineers' hands by dictating such things as the angle between the banks, minimum engine length and deck height, engine-mount locations, and so forth. "A lot of the decisions that you'd be faced with if you had a clean sheet of paper are already set for you, which makes life simpler in some respects and difficult in others because there are limits on what you can do," says Knowles.
Ilmor engineers used 2D CAD to initially lay out the major sections of the engine such as the gear train, pump positions, water passages, and fueling philosophy. The next step was creating solid models. HPD and Ilmor ran extensive durability tests on the dyno using a 500-mile run at Indy. Durability tests based on other tracks can be tried on the dyno, too, says Knowles. "At California Speedway in Fontana, for instance, there may be less lifting in the turns and drivers may run flat out most of the race. That's a different situation than at Indy where drivers are expected to lift heavily in the turns. This puts a different strain on the engine."
Though engineers learn a lot from the dyno nothing can take the place of actual track testing. "You may do your best to simulate the track but it's never an exact replication," says Knowles. "Gear shifting, for example, is difficult to simulate properly because you may not be able to get the right change in engine speed and load on the dyno." General driver abuse from revving the engine or suddenly stepping off the clutch is something else not easily simulated. Another unknown variable is air temperature.
Toyota starts strong
Toyota began its inaugural IRL season with a bang by capturing the checkered flag at Homestead, and grabbing three of the top four finishes in Phoenix. Like Honda, Toyota is no stranger to open-wheel racing. The engine maker has a string of victories and pole positions in the CART Series but racing in the IRL presents new challenges for the hardworking design team at TRD. The bulk of the team is eight engineers headed by a chief designer. According to Senior Design Engineer David Weiss, each has specific responsibilities, some of which include the design of the crankcase, cylinder head, intake manifold, throttle mechanism (including fuel distribution), and pumps, as well as the initial layout of the short block, which includes the block, sump, and rotating components. The chief designer is, among other things, responsible for shaping the engine. "It is his judgment, experience, and philosophy that determines this," Weiss explains. "For example, one question with the IRL engine is, should the gear case sit up front or in the rear? Last year's rules didn't allow using gear drives for cams. That has changed so our engine has a set of gears that drives the auxiliary pumps and camshaft."
Other things to consider are more obvious, such as how the engine fits into the available space. "The first step is identifying the geometric constraints and familiarizing yourself with the engine rules," says Weiss. One rule, for instance, says engine makers must be able to install their engine in all the chassis. "That leads to a common interface," he explains. "The bolt pattern on the front of the engine to the bulkhead of the chassis are specified, as are the bolt pattern on the rear of the engine to the gear case."
TRD engineers roughed out a 2D design to establish the location of such things as the gear case and pumps, as well as a concept for the cooling system. They then moved quickly to a 3D model using Pro/E, says Weiss. CFD also helped design the water jacket and block, so engineers could study and balance flow among all eight cylinders. TRD used its own in-house software for the cam-profile design and a dynamics package to analyze impact stiffness of the components. TRD uses a transient dyno to test durability. It uses inputs such as engine speed and the distance around the track to simulate actual operating engine speeds from an Indy lap.
Other telling performance indicators come from the ECU. Under IRL rules, engine makers can choose from a variety of engine-input sensors to measure certain parameters such as crank speed, throttle position, or airbox pressure. This information often leads engineers to a diagnosis of other problems. For example, says Weiss, "We measure crankcase pressure to judge the performance of the scavenging system. But if there's rapid step-change increase in pressure it's likely we have a cracked piston."
All this design work and testing leads to one inescapable fact: Everything that happens on race day, good or bad, is on display for the entire racing world, especially competitors. "In this industry," says Weiss, "you might have an advantage at one race, but the competition moves so quickly that it might be gone at the next race. So by no means can we rest on our laurels."
Stronger sides, softer noses
Driver safety and competitive racing have always been the hallmarks of the IRL. Each year chassis get a little stronger and testing gets a little more rigorous. This year is no different. Particular interest was paid to the nosebox and side-impact safety. Side-impact safety was brought to the attention of the racing world when driver Alex Zanardi lost both legs in a broadside crash during CART's American Memorial 500 race in 2001. The impact, at 200 mph, cut Zanardi's chassis in two. The IRL took steps with its new chassis regulations to guard against a repeat tragedy. Responsibility for building the chassis fell to long-time IRL manufacturers Dallara Automobili, Parma, Italy, and Panoz G Force, Braselton, Ga., and to newcomer Falcon Cars, Concord, N.C.
Meeting the new side-impact regulations wasn't easy, says Dallara's Sam Garrett, U.S. technical liaison. "We had to try a dozen different layups before we got one to meet the specs," he explains. "In a side impact, one car basically T-bones another, so the pointed nose of one is trying to punch a hole into the other. That causes a structural failure. The design challenge was trying to make the side of the car, which is basically a big flat panel with very little curvature, resistant to a pointed impact." Crash testing of the sides is done by pushing a truncated cone through a panel that represents the side of a tub. Engineers measure the load versus deflection to see how much energy it takes to penetrate the chassis sides. Unlike side-impact tests, nosebox analyses are run on actual cars. "The forces that the nose must withstand when it crashes into a barrier are both higher and more gradual than in the past," explains Garrett. Like the stronger chassis sides, the purpose here is to lessen the chance one car will punch a hole in another. "The tip of the nosebox is actually a little bit softer so it gives up easier until it gets to a blunt shape and becomes stronger than previous years' versions," says Garrett. "As a result, the noseboxes on most of the cars are slightly longer too." Also new this year, the tub can't be damaged in the nosebox test.
In another step toward added safety the IRL raised the front wing to slow the cars. "In short-oval trim that hurt us quite a bit," says Garrett. "We lost a lot of downforce and we are struggling to get that back." Testing in the wind tunnel has helped Dallara recover most of what it lost with the change. The ability to completely redesign the car hasn't hurt either. "In a three-year cycle, there are a limited number of things you can change," explains Garrett, "The underwing and shape of the sidepod and engine cover can change, but rules prohibit changing the tub, bell housing, or gearbox. Something like tub shape, for example, has a big aerodynamic effect. We are also limited with the way the suspension mounts. A new chassis cycle lets us move the suspension around and reshape the tub, which might let you do something different with the body work." Chassis engineers spend hours upon hours in the wind tunnel testing thousands of chassis add-ons that might boost downforce or cut drag. "For this new car we've probably tested 3,000 hours in the wind tunnel and that number could be up to 4,000 by the time Indy gets here," says Garrett.
Unique to the Dallara chassis is a pull-rod front suspension. Typically, according to Garrett, the front and rear suspensions are operated by push rods: A push rod, attached to the lower wishbone on the outboard side, pushes up toward a damper and spring unit mounted high on the tub. "We mounted our damper down low," he explains, "so we have a pull rod running from the upper wishbone outboard that actually pulls against the rocker, which pushes against the spring." The layout, different than anything Dallara has used in the past, has advantages and disadvantages, Garrett explains. "It is mechanically more complex because all the loads go through the lower part of the tub, which is already heavily loaded because it takes most of the load from the tires." So why use it? Simple -- less drag, says Garrett.
Like the Dallara chassis, the new-generation Panoz G Force car also spent significant time in the wind tunnel. "There are promising numbers coming from the wind tunnel in regards to reducing drag but maintaining or increasing downforce," says Chief Designer Simon Marshall. The cars last year were carrying too much drag in certain configurations, according to Marshall, so the Panoz team is going with a low-drag approach this season. Some of the ways they cut drag are fairly visible such as high sidepods and long leading edges to the sidepods.
Another subtlety that makes a big difference is rear-wing configuration. The IRL has specified three different packages: Single-element, two-element, and three-element rear wings. The single-element setup is a basic package that includes the mainplane with no flaps. This setup, used at the Indy 500, creates enough downforce to go fast through the turns and enough drag to control speed on the straightaways, says the IRL. The most commonly used setup, however, is the two-element wing with a mainplane and one flap. The purpose of this design is to limit speed at tracks with a larger turn radius and higher banking, such as Homestead for instance. According to specs, the wing is fixed at -2.5° and the top flap sits at an IRL-specified angle which may vary track to track. To add downforce, the two-element rear wing has a 1-in.-tall wicker bill along the trailing edge -- essentially a long, narrow, removable spoiler made of steel, aluminum, or carbon fiber. The three-element rear wing has two vertically stacked flaps added to the mainplane. Though this design creates maximum downforce, the added gs take a physical toll on the driver. The specs say the wing's mainplane must be fixed at -2.5° and the first element to the mainplane must remain as designed, with the top flap having an IRL-designated minimum angle.
For meeting the IRL's new antipenetration standards, the 2003 Panoz G Force cars have a one-piece construction. "Current cars are two halves that are cold-bonded together, which leaves the joint by far the weakest part of the car and absolutely susceptible to intrusion in a T-boning-type accident," explains Marshall. "We've gone to a one-piece construction, which means that the side of the car will represent the criteria imposed by the IRL in terms of side penetration." The Panoz team juggled carbon types, core materials, and layup methods and orientations in its effort to get the most strength and stiffness while also minimizing weight and cost.
"The regs are challenging and have made competition tight over the last few years, and tighter still this year," says Marshall. "There is a lot of compromise in race-car design. The clever part is knowing which areas can be compromised on paper but won't compromise the car on the track."
Firestone back for more
Long-time supplier to the IRL IndyCar Series and now its feeder Infiniti Pro Series, Firestone returns as sole tire supplier for the 2003 season. Firestone Firehawk racing radials have carried more than their share of IRL cars to victory since the League's debut in 1996. And from 2000, the white letters of the Firestone name have been the only ones to grace IndyCar tires since Goodyear's departure in 1999. But surprisingly, this year is the first that Indy 500 tires were built stateside (Akron, Ohio) since Firestone's return to IndyCar racing in 1995 instead of at Bridgestone's Technical Center in Japan.
For the second year running, the IRL has put a number on how many sets of tires teams can use for each race. Full-time IRL racers receive 153 sets per driver for use in all 16 races, with 35 sets allotted for the weeks leading up to and including the Indy 500. Full timers also get 24 sets of tires per driver for open tests and 21 sets for private testing throughout the year. Tire allocation is part of the IRL's strategy to control costs and equalize the competition. "The policy was regarded as being very successful in 2002 and I expect it to continue to be a useful tool in 2003," says Brian Barnhart, IRL senior vice president of operations. "The numbers in 2003 were chosen as a result of balancing the need to control costs and making sure there is adequate track time available for the teams to test the new chassis, engines, and gearboxes." According to Firestone Race Tire Engineer Dale Harrigle, the new chassis are faster this year with more downforce and less drag. That puts more load on the tires. Before the first race at Homestead, the Firestone Firehawks saw quite a few miles of pretesting without any problems, says Harrigle. Firestone plans to run at least 26 different tire specs this season including some new compounds and constructions.
Xtrac is back
Xtrac Ltd. , Thatcham, England, will again supply transmissions to IRL teams. The new contract meant Xtrac engineers had to redesign its gearbox, a chore in itself, but made more difficult because the new unit had to cost the same as the old.
The new-generation gearbox, called the 295, carries about 70% of the same internal parts as the first-generation 195 model IRL teams ran from 2000 to 2002. Such parts carryover means lower inventory costs for teams, always a concern with the IRL. Even so, the redesign incorporates a host of new features to improve safety and performance. The 295 is 13.9 in. shorter than its predecessor, pushing a car's center of gravity forward to improve chassis dynamics. The length reduction also increases the deformation length of the car's composite rear-crash structure by 400%. This gives the rear of the car a crushable structure similar to that in the nose. The shorter gearbox also shed 14.3 lb.
Enhancing safety, the 295 features integral crash-structure mounts and integral wheel-tether pins as well as a new driveshaft-retention mechanism. Also, the 295, to accommodate differing needs among the three engine and three chassis manufacturers, offers a choice of gear-lever position and a range of clutch shafts -- shorter than those in the 195. As was the case with the 195, the IRL wanted the 295 to provide space for a conventional differential. That would allow IRL cars to run on road courses. And added this time around is an option to fit a reverse gear.
Xtrac had to package the gearboxes for each of the three chassis suppliers to the IRL, and worked throughout 2002 to assess and accommodate their needs and also to receive the position and shape of the gearbox front faces early on so design could be completed and real testing could begin. That communication paid off, as is the case with the 195, the 295 boasts ease of maintenance and relatively simple change of gear ratios, say Xtrac officials.
The new gearbox includes an aluminum-allow-cased transmission with six forward gears -- located below the axle line -- and the reverse option designed in. The drive feeds from the gear ratios -- carried in a cassette for simple maintenance -- through two drop-gear sets at the front of the transmission and into a spiral bevel. The 195 carried the drop gears at the rear of the transmission to allow easy access for maintenance or gear changeout. Now located at the front, which helps Xtrac in its goal to bring weight forward, the gears can be accessed through a cover in the transmission bell housing. Engineers believe that, with enough top-gear choices available to fine-tune maximum speed, accessing drop gears will be less critical, and changing these gears will be a job at the shop rather than the track. A spool with output flanges is standard on the 295 as part of a one-piece spool arrangement, unlike the 195. Provisions allow for spool changeout to a plate or viscous differential.
Another major layout change in the 295 gearbox is position of the main shaft, which now sits alongside the layshaft, resulting in a lower center of gravity. The sequential change selector barrel and selector rod, parts carried over from the 195, fit in the same position in the 295, above the shafts. Besides the normal sequence of neutral followed by six gears in the gear-change mechanism, an optional ratchet body allows for a second neutral above the sixth gear. This safety feature lets drivers quickly engage neutral in case of engine failure.
Another design change, the 295 offers two sets of connections to provide options for placing a remote oil cooler. The 195 oil cooler plugged only into the top of the gearbox. Xtrac engineers made the change to increase aerodynamic efficiency.
With all these new features, Xtrac will have a presence at the track to make sure changes run smoothly and to assist teams without dedicated gearbox technicians.