Ten-cylinder engines breathe easy
The module weighs more than 7 kg (15.4 lb) and goes into BMW 10-cylinder engines for M5 and M6 sports cars. The two-piece module is made from Ultramid B3WG6 GP, a 30% glass-fiber-reinforced PA6. The material comes from BASF Corp., Florham Park, N.J. The dimensionally stable PA6-GF30 features a bursting strength almost twice that of conventional PA grades. High-burst-strength materials create smooth, highly structured surfaces, says Nicole Berg, production engineer at the Mahle Co. in Öhringen. It also features a flame-retardant UL 94 HB rating (at 1.6 mm), an Izod-notched-impact strength of18 kJ/m2, a heat-deflection temperature (1.8 MPa) of 210°C (410°F), and a maximum service temperature (short-cycle operation) of 200°C (392°F).
Mahle designers also spec'd Ultramid B3WG6 GP for BMW four and six-cylinder engines. Intake manifolds for eight-cylinder engines posed a major challenge for designers because they have a variable length. Secure joining of the seven individual parts calls for five welding procedures. Manifold material mustn't warp much, important because individual parts are stored for different lengths of time. An accurate fit is also crucial for the 10-cylinder module because the two part halves must affix to the engine close to each other during final assembly.
Injection-molding cycles for each side of the intake module are about 4.5 sec at temperatures of about 280°C. The modules feature wall thickness of between 1 mm for small ribs and 3.5 mm at the "wings," to better resist inside pressure.