Chrysler LLC with MAHLE


In 2004, Chrysler's Street and Racing Technology (SRT) team faced a challenge to the Dodge Viper. Like many big, high performance engines, this one displayed combustion instability at light loads due to aggressive valve timing for high-speed power, and did not meet EPA standards.

Variable valve timing (VVT) would mean a new, taller, overhead cam engine, hence investment, delay, and styling changes. However, a never-implemented 1908 patent described an intake camshaft mounted inside the exhaust camshaft, so intake and exhaust timing could be advanced or retarded independently. The UK engineering firm, Mechadyne, had introduced the concept to Chrysler and built a prototype, which was too complex.

MAHLE engineers, already involved with the SRT team, saw that independent rotation up to 40º between intake and exhaust cams was possible using assembled camshaft know-how. The MAHLE design featured an inner shaft that allowed the CamInCam® VVT camshaft to fit into the space of a single standard one.

Next came phasing the angle between intake and exhaust to accomplish variable valve timing, giving the V-10 both smooth idle and extreme power at speed. Chrysler brought in INA of Germany, a leader in phasing dual overhead camshafts in high performance engines. Bench testing and non-fired engine testing occurred at MAHLE, while Chrysler performed fired engine and vehicle testing, with data collection and correlation between the two parties. Working closely with INA and MAHLE, Chrysler introduced a 600 hp Viper engine for 2008 production, with no major chassis or body changes.

The Dodge Viper V-10 engine now has 60% better combustion stability, full-range OBDII mis-fire detection, part-load fuel economy improved 14%, increased exhaust gas recirculation, and 18% higher peak power. Working together, MAHLE, INA, and Chrysler accomplished what had not been done in the century since the first Cam-In-Cam patent in 1908: independent timing of exhaust and intake valves in one camshaft.