INDYCAR DW12
the lives of racecar drivers, designers and engineers. As the IZOD IndyCar Series
Under pressure P
The introduction of the new DW12 Indy car is beset by problems
ower, weight, downforce, drag, grip and balance. Those are the six key elements that dictate
BY MARSHALL PRUETT
has found with its new Dallara- built 2012 chassis, miss any one key by a small margin and the overall package will suffer. Miss the key in two or more areas and, like a guitar with multiple strings out of tune, no one will want to play the instrument. With IndyCar acknowledging a
few areas that require immediate attention (weight / weight distribution, balance and drag), and others pointing to the need for a major re-think on the levels of power, downforce and grip needed next season, it’s clear a lot of tuning and tweaks will take place before 28 March, the first race on the 2012 calendar.
DESIGN PHILOSOPHY The general design philosophy for the Dallara DW12 centres on achieving a level of performance that would surpass the previous Dallara IR07 package through two main factors: a significant weight reduction and an even greater drop in aerodynamic drag. The DW12 was conceived
to be lighter on its feet and more slippery through the air, to be nimble on road and street courses, as well as on ovals, and to do all this using a smaller, more efficient engine. But, as recent tests have shown, a discrepancy between the expected lesser weight / lower drag figures in Dallara’s digital world and what the DW12 has so far delivered has been a cause for concern for all involved. For IndyCar teams, the new car price tag came with the promise of greater performance, but so far, the DW12s have been
10-15mph slower at Indianapolis, and just a few tenths faster on road courses. For the series, which expected Dallara to achieve its performance targets from the outset, the need to rush fixes into place has led to non- stop work at the IndyCar offices and at Dallara’s base in Italy.
PROBLEM SOLVING For those who’ve driven the DW12, general praise has been offered on its low to medium- speed handling traits on road courses, but in almost every other performance category, the positives have been sparse. To make matters worse, as each problem area is changed going forward, it affects the others, creating a cyclical loop of problem solving. The DW12’s problems are solvable with time and money, of course, but who will pay for the fixes? As IndyCar and its partners embark on those multiple rounds with the DW12, and with the clock winding down, they can ill afford to make more mistakes. The biggest problem for the
DW12 is an excess of weight, and specifically, where that weight is found within the chassis. Originally expected to weigh 1380lb (626kg), 185lb (84kg) less than the 2011-spec car, the DW12 has only shed in the region of 100lb (45kg). According to Will Phillips, IndyCar’s vice president of technology, the DW12’s unexpected rearward weight bias (according to sources, it was delivered with a staggering four per cent rearward shift) can be attributed to a number of vendor- supplied items being delivered well above their specified weights, meaning most, if not all, of that weight falling on or behind the rear axle. ‘Dallara did not go out to put
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www.racecar-engineering.com • February 2012
[the weight distribution] where it is now,’ said Phillips. ‘They were expecting it to be closer to where it was [specified]. Now, obviously, as you go from the wheel centreline towards the back of the chassis, any weight saving change will be helpful. So if we can pull weight out of the gearbox, if we can pull weight out of the diff, there’ll be much more benefit than the same amount of weight coming off the engine, for example.’
When pushing the car hard
at Indy, drivers noted the DW12 exhibited dangerous handling traits on corner entry and exit. With the rear-heavy car wanting to spin once they began to turn, drivers found it like a pendulum, swinging back in the opposite direction as they left each turn. Calls for the DW12 to be
harder to drive notwithstanding, “the oval
equivalent of a dragster“
its test pilots found that to safely negotiate Indy’s four corners, lifting off the throttle and coasting was vital. With the oval equivalent of a dragster on its hands, immediate action was required by the series and the car’s manufacturers. Quantified numerically, the 2011 Dallara-Honda had a delicately balanced but safe weight distribution of approximately 45 per cent front and 55 per cent rear, while the DW12’s numbers as it first appeared are closer to 41 / 59.
SHEDDING WEIGHT IndyCar has worked with Xtrac to reduce the weight of the gearbox and has progressively shed some 8.8lb (approx 4kg).
Beyond paring weight from the aluminum housing, a change in philosophy on the internals was made in an effort to aid the DW12’s oval handling issues. ‘For the speedways, we were, for reason of economics, just going to put a blocker inside the road course differential and so save componentry,’ Phillips explained,
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