IRL: Olds Revs Up for New IRL Rules

OLDSMOBILE REVS UP FOR NEW IRL ENGINE RULES GM Engineers Developing New IRL Aurora V8 Components for 3.5-Liter Formula in 2000 While the impending arrival of Y2K has sent computer programmers searching for software bugs and survivalists ...


GM Engineers Developing New IRL Aurora V8 Components for 3.5-Liter Formula in 2000

While the impending arrival of Y2K has sent computer programmers searching for software bugs and survivalists stockpiling rations in preparation for the collapse of civilization, General Motors engineers are focusing on the year 2000 for a different reason. The new year will bring the first major revision in the Pep Boys Indy Racing League engine rules since the introduction of the series' naturally aspirated engine formula in January 1997.

Oldsmobile's 4.0-liter IRL Aurora V8 racing engine has been a roaring success in the IRL open-wheel series, winning 26 consecutive races, three straight Indianapolis 500 titles, and three consecutive Engine Manufacturer Championships. Now GM Motorsports is developing a new 3.5-liter version of the IRL Aurora V8 for the new formula that will take effect in January 2000.

New Formula for 2000

On November 17, 1998, IRL Executive Director Leo Mehl announced that the rules package for 2000 through 2004 will require a maximum engine displacement of 3.5 liters (214 cubic inches), a reduction from the current 4.0-liter (244ci) formula. Engine speed will continue to be controlled by a programmable rev limiter, and 180-degree "flat" crankshafts will be optional.

In addition, the new IRL regulations will no longer require manufacturers to base their racing engines on production powerplants. This will allow manufacturers that do not have DOHC V8 engines in their showrooms to produce purpose-built engines for IRL competition. All approved engines must meet minimum size and weight requirements, must be interchangeable between IRL chassis, and must be generally available to IRL teams at a specified price.

"Any automobile manufacturer in the world can now compete in the IRL and the Indianapolis 500 if it produces an engine that meets the series' requirements," noted Peter Lagenhorst, Oldsmobile brand manager, Silhouette. "We will continue to base Oldsmobile's motorsports program on the architecture of the production Aurora V8 because we believe that is the best way to spotlight our powertrain technology - and because we think the Aurora V8's basic design is good enough to compete with purpose-built racing engines."

New IRL Aurora V8 Components

GM Motorsports is responsible for the design and development of the IRL Aurora V8. Key components such as the engine block and cylinder heads carry factory part numbers, and are distributed through selected engine builders. GM specifies a basic engine package, but independent builders are free to experiment with different components and configurations within the limits of the IRL rules.

"GM Motorsports is currently developing a revised IRL Aurora V8 engine package for 2000," said Joe Negri, GM Motorsports IRL/Road Racing Group manager. "The reduction in displacement from 4.0 liters to 3.5 liters will be accomplished by shortening the crankshaft stroke and lengthening the connecting rods to compensate. Crankshafts and connecting rods are routinely replaced at regular mileage intervals, so this change will not be a hardship for IRL teams.

"We will maintain the IRL Aurora V8's 93mm cylinder bore diameter and 8.1-inch deck height, allowing builders to use the same block, cylinder heads, and many other components that are included in our current 4.0-liter engine package," Negri explained. "The IRL Aurora V8 already meets the IRL's maximum bore size, minimum block height dimension, and 340-pound minimum weight, so there is no need to produce an entirely new engine package for the new formula.

"We do not anticipate that a significant redesign will be required to optimize the IRL Aurora V8's power level as long as the maximum rpm limit is not set too low. We also do not foresee the change to a 3.5-liter formula affecting the competitive advantage of the Oldsmobile engine versus Nissan's Infiniti Indy."

Power Predictions

According to IRL officials, the scheduled reduction in engine displacement will reduce horsepower and rein in rapidly escalating speeds. Since the 4.0-liter formula was introduced in 1997, the output of a typical IRL Aurora V8 assembled to GM specifications has increased approximately 50 hp, producing an average 7 mph gain in speeds at most IRL tracks.

"An IRL Aurora V8 engine produces nearly three horsepower per cubic inch, so a reduction in displacement of one-half liter, or about 30 cubic inches, would be expected to reduce output by 90 horsepower," Negri reported. "However, we anticipate that the maximum engine speed will increase from the current 10,000 rpm to a higher redline in 2000, although the new rev limit has not yet been announced. Faster engine speed, combined with improved efficiency, should offset the reduction in piston displacement to some extent.

"We foresee an initial net loss of approximately 50 horsepower with the change to 3.5 liters," he predicted. "Most importantly, IRL officials can control speeds in the future by adjusting the rpm limit throughout the life of the 3.5-liter engine formula.

"The reduction in engine size will also enhance reliability," Negri commented. "Shortening the crankshaft stroke will decrease piston speed by more than 400 feet per minute from the level used in 1998. Since piston speed is a major factor in engine durability, we expect this change to improve overall reliability and reduce expenses for IRL teams."

The New Sound of the IRL

Engines competing in the IRL series will have a dramatically different sound next season with the introduction of an optional 180-degree "flat" crankshaft design.

"The difference in the exhaust note is due to the timing of the exhaust pulses," said Roger Allen, lead design engineer for the IRL Aurora V8 program. "With the 90-degree crankshaft currently used in IRL engines, two of the cylinders on each bank fire in succession, and two cylinders have longer intervals between firings. These irregular intervals between exhaust pulses produce the low rumble that's typical of the racing V8 engines used in the NASCAR stock car and the IRL Indy car series.

"With the 180-degree crankshaft that will be used next year, the cylinders fire alternately from bank to bank in even intervals," Allen continued. "This regular exhaust note is like a musician beating rapidly on a drum - the note almost becomes a continuous tone. These even bank-to-bank exhaust pulses, in conjunction with higher engine rpm, will produce an exhaust note with a higher, more 'exotic' pitch.

"The 180-degree crankshaft design offers several advantages," Allen added. "It can be lighter and stiffer than a comparable 90-degree crankshaft. The lighter weight reduces the crankshaft's inertia, so there is a potential for quicker acceleration on a short-track. The 180-degree design also has the potential to improve engine output by optimizing the exhaust tuning."

The change to a 180-degree crankshaft will also require a revised firing order (the sequence in which the cylinders ignite) and corresponding changes in camshaft timing. Several different firing orders are possible with a 180-degree crankshaft. GM Motorsports engineers selected the 1-8-5-4-7-2-3-6 firing order because this configuration uses common camshafts for the right and left cylinder heads and is capable of producing equivalent power to other firing orders.

The Tingle in the Driver's Seat

The chief disadvantage of a 180-degree crankshaft is that it is inherently unbalanced. A V8 engine equipped with a 180-degree crankshaft is essentially two four-cylinder motors joined by a common crankcase. And like other inline four-cylinder engines, the movement of the pistons up and down in their cylinders causes a perceptible vibration. In contrast, virtually all production V8 engines use a 90-degree crankshaft, a design that is inherently balanced and produces the smoothness that is characteristic of a V8 engine.

"Inline four-cylinder engines have a vertical shaking force," explained GM Motorsports engineer Ed Keating. "Many production four-cylinder engines use dual balance shafts that run at twice engine speed to counteract this vibration. In a racing environment, the additional weight and packaging requirements of these systems make balance shafts impractical."

The Aurora Advantage

"One of the areas where the IRL Aurora V8 has a clear competitive edge is the infrastructure that we have created to support Oldsmobile teams," Negri commented. "We have developed an international network of suppliers, an efficient parts distribution system, and a talented group of ten independent engine builders. GM has produced over 600 IRL Aurora V8 blocks and more than 1,000 cylinder heads to date. We have parts in stock, and we are continuing to improve the quality of the components on a regular basis.

"We recognize that under the IRL rules, all of the engines competing in the series will eventually arrive at a similar performance level. GM Motorsports is focusing on customer support as well as on the hardware. We believe that customer service will be a key factor in continuing the success of the Oldsmobile motorsports program."

With an aggressive engine R&D program already underway for the 3.5-liter engine formula and a strong commitment to providing exceptional service to IRL teams, Oldsmobile is determined to maintain the IRL Aurora V8's standing as the absolute power in the Indy Racing League.

1999 vs. 2000 IRL Aurora V8 Specifications

1999 2000 Change

Displacement 4.0 liters (244ci) 3.5 liters (214 ci) -.5 liter (-30ci) Maximum RPM 10,300 11,000* +700 Est. Horsepower 700 650 -50 Bore 93mm (3.66") 93mm (3.66") No change Stroke 73.4mm (2.89") 64.4mm (2.53") -9mm (-.36") Max. Piston Speed 4817 ft./min. 4657 ft./min -160 ft./min. Deck Height 205.7mm (8.10") 205.7mm (8.10") No change Rod Length 138.6mm (5.46") 143.3mm (5.64") +4.7mm (+.18")

*Estimated - maximum rpm TBA

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