A Chiltern Railways Class 168 DMU refitted with a Rolls-Royce MTU hybrid drive system is undergoing testing ahead of entry into passenger service later this year.
The HybridFlex unit, No 168329, is owned by Porterbrook and is one of a series of trials the company is undertaking to improve the environmental credentials of diesel trains. Testing is taking place on the Ecclesbourne Valley Railway following fitment of the new underframe equipment by Gemini Rail Services at Wolverton.
The aim has been to convert the unit to a self-charging hybrid, meaning it can operate emissions-free in stations and in low emission zones. An MTU power pack has been fitted in the underframe, which incorporates a diesel engine with a Category V after-treatment system. A new electric air compressor has twice the capacity of the previous version, with a new cardan shaft and solid-state alternator also fitted. A new ZF six-speed gearbox, similar to that on more modern Turbostar DMUs, improves efficiency when operating below 60mph.
