Just after 4pm on 5 October, the first of two Opel Astra two-litre CDTi hatchbacks crossed the start line on the Millbrook Proving Ground's high-speed bowl. Precisely 24 hours later it crossed the same marker, having covered nearly 4800 kilometres at an average speed of 200km/h - including pit stops - and set 12 World and six British speed endurance records.
Twelve drivers - three Opel staff and nine motoring journalists - each drove a total of four hours, split between the two cars. Only one tyre change was required per car, no engine oil was used at all and, despite completing nearly 1500 laps of the 3.2-kilometrwe banked circuit with the cars' go-fast pedals nailed to the floor, each car completed the run with only 22 minutes downtime, other than for refuelling and driver changes.
CHALLENGING THE BENCHMARKS
The 24-hour flat-out blast was an attempt to challenge to challenge two sets of speed endurance records: the world records in the 1600-2000cc forced-induction diesel production car class and the British records in the 1500-2000cc forced-induction diesel production car class.
There were existing world records for one, six and 12 hours but nobody had yet cracked the 24 hour benchmark - and the British time and distance records had stood for more than two decades, with the 24 hour record set at 160.32km/h in 1992.
Nearly a year before D-day, Astra engineers began compiling data that simulated the cars being driven at full tilt boogie for 24 hours on a banked track.
“We'd never run one for 24 hours at full throttle before.”
Chief engineer for Astra Mariella Vogler said: “We had a lot of faith in the two-litre CDTi engine but we had to be sure of the powertrain before the record attempt, and it passed with flying colours.”
Unlike the Gerotek high-speed test circuit north of Pretoria, which has two banked curves, one larger than the other, and two short straights, Millbrook's high speed bowl is a 3.2 kilometre, constant radius track, steeply banked towards the outside lane all the way round.
In addition to the pounding on cars' powertrains as the drivers constantly maxed out at about 210km/h, the centrifugal force exerted by the track's banking on thr cars’ suspension and tyres was intense.
STANDARD PRODUCTION TYRES
Former DTM race driver and now GM Europe director of performance cars Volker Strycek said: “We worked closely with Michelin right from the start to ensure that the Astra's production-spec tyres could run the course.
“We did 800km of testing in an Astra at Millbrook in July, and it was clear that the Michelin Pilot Super Sports we were using would last at least six times that distance.”
Strycek put his money where his mouth was - he was one of the three 'works' drivers - and also brought his four-man professional pit crew from the Nurburgring to help the UK press-fleet garage staff with quick and efficient re-fuelling and drivers' changes throughout the day and night.
“Believe me, two more standard production Astras don't exist!”
PR maven Simon Hucknall said the FIA was, quite rightly, concerned that carmakers should use genuinely standard vehicles for record attempts, rather than 'specially prepared' cars.
“Official observers visited the Ellesmere Port plant, where the record Astras were built, and tracked their assembly from body-in-white right through to final audit,” he said.
“Then the cars were fitted with roll cages, Corbeau race seats and Luke harnesses, sealed and locked in a secure compound until the record run.”