Reliable powerpack Opel V8 engine: 10,000 kilometres at racing speed without any trouble When the 2002 DTM (German Touring Car Masters) season ends at Hockenheim this coming weekend, the powerful V8 engines of the Opel Astra V8 CoupÃ©s will have...
Opel V8 engine: 10,000 kilometres at racing speed without any trouble
When the 2002 DTM (German Touring Car Masters) season ends at Hockenheim this coming weekend, the powerful V8 engines of the Opel Astra V8 Coupés will have done 3,500 kilometres and more at racing speed, without any trouble nor revisions. The engines used in the DTM are sealed and there are only two power units available for alternate use in each DTM car during the entire season.
"The DTM engine regulations are working out extremely well. The four-litre V8 units develop high levels of power, but the limit of two engines per car and season puts a considerable cap on costs," says Opel motorsport boss Volker Strycek. "There's a good reason why Formula 1 officials are thinking about limiting the number of engines used. The DTM has shown how effective this rule is."
Even piston weight is prescribed
DTM technical regulations clearly define every relevant engine component. The only permissible engines are eight-cylinder units with an aluminium block and a 90-degree cylinder bank angle. Maximum displacement is set at 4,000 cubic centimetres. The minimum weight of the engine, not counting fluids (oil, water) nor the exhaust manifold, amounts to 165 kilograms. Equally defined are the minimum weights of certain individual assembly components, pre-empting the development of extremely light-weight and thus more costly and less reliable components: Every one of the eight pistons must weigh at least 350 grams, each con rod at least 450 grams.
Such a four-litre V8 powerhouse could easily muster far more than 600 hp, if it were not limited by two air restrictors. The air aspirated by the engine that is necessary for combustion must pass through two air restrictors, each having a diameter of 28 millimetres.
Due to the restricted air flow, the DTM engines hardly run above 8,000 revolutions per minute, at which point the engine's 'breath' is virtually cut off. The concept of restricting the air volume as an alternative to limiting engine speed has been tried and tested over many years and has been used in Formula 3 racing since the nineteen-seventies. "Air flow restriction can easily be verified by measuring the orifice and by vacuum-testing the airbox for any leaks," explains Peter Rühl, engine project engineer with Opel Performance Center (OPC). "There are several of these checks performed at every race weekend."
15 hours of endurance testing on the test stand
Like every year, 'right on the dot', meaning the start to the season in April, twelve Opel V8 engines -- two each for the six Astra V8 Coupés -- had to be handed over to the German Motorsport Federation (Deutscher Motor-Sport-Bund -- DMSB) for sealing. This means that the cylinder head, engine block and oil sump are fitted with special seals in order to prevent the engine from 'opening up' during the season. "Under the supervision of a DMSB engineer, the valve lash of the engine may be checked and adjusted twice during the season," says Peter Rühl.
That this restriction works was clearly shown by the first DTM season. Although in 2000 there were two engines planned per car, only one of them was intended for actual competition use, whilst the other was merely held in reserve. As such, the competition unit was generally run for more than 6,000 kilometres. Counting tests during and after the season, this could even add up to 10,000 kilometres.
"When we opened up the engines at the end of the year 2000, there were no surprises. They were in superb condition, with hardly any wear to be noted," says Holger Spiess of Opel's engine partner Spiess in Ditzingen near Stuttgart, Germany. Spiess attributes this to the clearly 'oversized' dimensions prescribed by the regulations, like those for the crank shaft bearings and con rod big end bearings for example. "If at all, the pistons and valve train are subject to wear."
Nevertheless, these restrictions do not completely preclude the possibility of further refinement during the season. Injection position, air intake system with inlet pipe lengths/diameters and exhaust systems are offering sufficient developmental potential, enabling another hp to be 'squeezed out' here and there. Now and then, an engine will be put on the test stand. If not, servicing by the teams is by and large limited to external cleansing and the exchange of air filters. Before the season, every engine is being run a good 15 hours on the test stand prior to delivery. "If performance deviates by one percent from the standard parameter, the engine will not be delivered," says Holger Spiess.
Spiess Tuning, associated with Opel since 1989, are employing a staff of 40 for producing and maintaining Opel's DTM and Formula 3 engines. The new, 2,600-square-metre hall in which Spiess produce all relevant components in-house, is equipped with four engine test stands.
462 hp and 510 Newton metres
The 2002 Opel V8 engine delivers 462 hp at 6,750 revolutions per minute, whilst the enormous maximum torque of the four-litre unit, developed at 5,500 revolutions per minute, amounts to 510 Newton metres. "The DTM is marked by a precarious ratio between sheer engine power as well as high-level torque and the drivers' desire for good driveability of the engine," explains OPC's engine specialist Peter Rühl. "Camshaft characteristics must necessarily be determined prior to the start of the season, reflecting the preponderance of certain types of race tracks. Consequently, any modifications to engine characteristics during the course of the season must come from the engine's electronic system." The standard engine management system (MS 2.9.2) is supplied by Bosch.
"Different response characteristics resulting from changed program maps of the engine's electronic system, such as a soft response in rainy weather, can be felt very distinctly by the driver," says Opel works driver Timo Scheider. "Of course, a DTM car would be able to handle 600 hp, but even 460 hp require careful 'dosing' by the driver's right foot, especially during the Grand Prix-style start, when accelerating out of corners or when it rains."