Holbert-Porsche 928 History- The Land Speed RecordThis is the page that will document the history of the Porsche 928 used by Al Holbert and Porsche of North America to establish a land speed record in August of 1986 at the venerable Bonneville Salt Flats.This 1987 model vehicle was not destined for the streets of America. This particular car was an early, pre-production European model pulled off the assembly line for its special duties. Originally slated to be built as an automatic transmission vehicle, it can be plainly seen where the firewall has been modified to accept the clutch master cylinder assembly. Other small changes include the addition of a clutch interlock switch and the needed brackets for a US market ABS system.There is also some documentation of a non-standard engine control unit, see this thread at Rennlist : http://forums.rennlist.com/rennforums/928-forum/191945-phase-1-of-the-holbert-928-archeological-dig.htmlThe car arrived at the Holbert Porsche dealership in Pennsylvania and the exterior was quickly painted red over the white body. In the available pictures and videos, the lighter original color can be seen in the door jambs and under the hood. (Record run video link).Here is a great story by Christopher Korody that gives some insight into the mind set of Porsche at the time, and his experience on the production of the soon-to-be-famous commercial feauring the Bonneville record run- Christopher Korody's WebsiteExcerpt follows from "Excellence Was Expected" Second Edition, Karl Ludvigsen, pg 1082-1083:
Porsche claimed a top speed for the new model of 270 km/h. The objective was to achieve an officially timed speed at Utah in excess of 170 mph, equal to 274 kp/h. The attack would be made with a 1987 prototype modified slightly as a result of wind tunnel testing. Changes included an underpan that extended back to the transaxle, omitted exterior mirrors, reduced ride height and subtle additions to the bottom of the nosepiece, where brake-cooling inlets were blocked. A cockpit switch gave the air-inlet louvers three positions: shut, 30 percent open and fully open. In the 30-percent position the Cd was 0.29 while with the louvers open it rose to 0.30.
The versatile Walter Naher engineered the Bonneville effort. Seven-inch-wide rims at all four corners were to be fitted with Pirelli P700 tires that were scuffed to provide a minimal tread depth and pumped up to 64 psi. Bilstein dampers were specified and a stiffer (30 x 5 mm) front antiroll bar installed. Although it was not ready for the preliminary tests, a new 2.54:1 ring and pinion was installed for the Utah runs, replacing the 2.64:1 ratio that had been the highest previously available.
Prototype G18 was readied for testing in March and in early April Naher took it to the Nardo circular track in Italy. Ideally the runs would be made with the 30-percent-open louver setting but this turned out to be unfeasible when engine-water exit temperature rose to 106 degree C. With the louver fully open the exit temperature fell to an optimal 98 degrees C. Even with this added drag the 928S4 romped around Nardos bowl at 176.2mph clockwise and 181.8mph counterclockwise. The difference was attributed to roadway unevenness and wind effect.
After these successful tests on April 5 and 6, 1986, the 928S4 was fitted with its higher rear axle ratio, which was aimed at matching peak power with peak speed. At Nardo the engine had been bumping up against its controlled limit of 6,500 rpm. By the end of April the car was ready for shipping to the United States, where Walter Naher supervised the runs. Al Holbert took the wheel at Bonneville in August, when the salt was at its best. On August 7 he was officially timed by USAC, under the auspices of the FIA, at an average of 171.110 mph for the flying mile and 171.926 mph for the kilometer. It was official; Porsche could declare the 928S4 the world's fastest catalyst-equipped car.Porsche decide to loan the car next to IMSA as a track support vehicle, and it traveled the country for several years in this role. It was outfitted with safety gear and a new paint job at Fabcar Engineering in Indianapolis.
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