|Wright is making both single-deck and double-deck series hybrid buses.|
Engine development and engineering services provider Roush Technologies is supporting Northern Ireland-based Wrightbus in optimizing its new series hybrid drive which uses a Ford 2.4-liter diesel engine as the genset. An earlier generation of the Wrightbus hybrid drive used a GM 1.9L engine. (Earlier post.)
The Wrightbus program involves optimizing the series hybrid drive systems through a detailed analysis of generator load patterns. Roush engineers have been able to recalibrate the engine to operate at its peak performance throughout the drive cycle by using smart charging and load control technology. Overall engine performance is significantly improved when compared with normal applications.
With the base 2.4-liter engine operating as a generator, Roush engineers have been able to predict load and speed changes in advance, thus allowing greater freedom with injection strategies and EGR (Exhaust Gas Recirculation) rates.
Roush engineers have also been able to utilize some of the existing vehicle-based strategies to carry out functions which otherwise would have required significant software changes. This, coupled with a unique CAN interface module, has allowed the full integration of the engine and its controller into the overall hybrid control system at a relatively low cost.
Having the engine control as a fully integrated part of the hybrid system—and coupled with a unique calibration, has enabled us to achieve exceptional improvements in fuel consumption. During back-to-back route trials in London, these fuel savings have been in excess of 30%. The application works extremely well and demonstrates the real potential for hybrid systems… but we do get a few raised eyebrows when people realise that we are running a full size double-decker bus with a 2.4 liter engine from a light van.—Paul Turner, Roush’s Technical Director of Product Development
Wright switched to the 105 kW 2.4-liter Ford diesel—also used in the Ford Transit and the Land Rover Defender—due to the need to exert greater control over the engine’s performance within the hybrid set up. The hybrid buses uses a Siemens drive and a lithium-ion battery pack.