From track to road and back to track again. That is the path for gasoline direct fuel injection. In the late 90s Audi added direct injection to its R8 Le Mans prototype in order to get more power while consuming less fuel. In racing reducing fuel consumption is important because it allows cars to run farther between pit stops spending more time on the track. Direct injection eventually migrated into most of Audi's production engines along with those from parent company Volkswagen. After adding direct injection to the Cayenne GTS and 2009 911, Porsche is now migrating that same technology back to its own race program. The Porsche RS Spyders debuted a new direct injected version of the 3.4L V8 two weeks ago at Mid-Ohio and won the LMP2 class. The output of the DI engine went from 476 hp to 503 hp while fuel consumption dropped. Porsche is not saying how much it went down, but they are evidently still developing the system and optimizing it. For example the engines now run extremely lean under light loads greatly reducing consumption in a manner that would not be possible with a port fuel injection system. In coming years we will be seeing virtually all gas engines migrating to direct injection.

[Source: Porsche]

Direct Fuel Injection Lowers Fuel Consumption and Increases Performance in 3.4-Liter V8 for 2008 Porsche RS Spyder in the American Le Mans Series
ATLANTA - July 31 - Following in the footsteps of the street Porsche Cayenne and 911, the sports prototype Porsche RS Spyder now profits from direct fuel injection technology (DFI). The new engine, with which Porsche underlines its role as technology leader in energy efficiency, celebrated its race premiere with an LMP2 victory in the American Le Mans Series as Timo Bernhard (Germany) and Romain Dumas (France) took the class win at Mid-Ohio earlier this month. The power output of the successful 2006 and 2007 championship winning Porsche, which has so far claimed victory from four of the six races run in this year's ALMS, increased with the new engine from 476 to 503 hp (370 kW) at 10,000 revs per minute. Maximum torque rose from 370 Nm (273 ft. lbs.) at 7,500 revs to 385 Nm (284 ft. lbs.) at 8,500 revs. The most compelling feature of the DFI version of the successful Porsche 3.4-litre V8 motor is its improved energy efficiency - an important element in endurance racing. Despite an improved power output, fuel consumption was significantly reduced.

After reaching a very high level with the previous engine we raced, we had to put considerable efforts into the development of the direct fuel injection unit in order to significantly improve performance and efficiency," says Thomas Laudenbach, Head of Motorsport Development/Power Train. "In order to achieve revs of up to 11,000 with DFI technology it meant stepping into totally new territory." During the design and development of the engine, synergies of product areas and motorsport departments were utilized to a large extent. "Right from the beginning there was a lively exchange," reminisces Thomas Laudenbach. "We had already recognized the advantages of this technology at the start of the RS Spyder project and adapted them to the very special requirements of motorsport, always in close consultation with our colleagues in the standard development department. The methods and insights we obtained from our co-operation are of considerable value for future development projects involving DFI technology."

Normally an increased engine output is in conjunction with a rise in fuel consumption. This is not the case here. "Thanks to the substantial increase of energy efficiency there's no rise in the absolute fuel consumption despite the significant hike in performance. On the contrary - we're even a bit lower," said Laudenbach. Another advantage of the new DFI engine: At partial load - for example during the many caution phases of long distance races - the engine can be run extremely lean. This further reduces fuel consumption and was not possible with the intake manifold fuel injection which was raced previously.

Moreover, new options open up for the controlling of highly dynamic processes like, for example, gear shifting at full throttle. Such options were not fully utilized before. After the successful premiere in Mid-Ohio, the new DFI motor will power the two Penske Racing RS Spyder cars for the next round next week at Road America in Elkhart Lake, Wisconsin. With this, Porsche intends to strengthen its top position in the American Le Mans Series. "Competition in the LMP2 class is at an extremely high level and it gets tougher race by race," says Hartmut Kristen, Head of Motorsport at Porsche. "Therefore now is exactly the right time to race the new engine."

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