Volvo Buses has received its first bus order for its new gas engine, the G9A. Bernmobil in Switzerland has placed an order for 32 Volvo 7700A articulated buses using the G9A, with an option for 39 more.
Bernmobil is the local public transport company in the city of Bern, and is gradually replacing its diesel-operated buses with gas buses. The new gas buses will run on biogas rather than compressed natural gas.
The first 10 buses will ship during summer 2006, with the remainder scheduled to follow in the autumn.
The G9A engine, announced in June 2005, is a 9.4-liter in-line 6-cylinder engine for CNG or biogas operation, and offers either 260 hp or 300 hp. It has a common cylinder head with overhead camshaft and four valves per cylinder. The new engine is primarily intended to meet the growing demand for gas-fueled buses in city traffic.
Volvo’s earlier gas engines, just like most others on the bus market, are designed according the lean burn concept, based on combustion constantly having a surplus of oxygen.
The Volvo G9A is a Lambda 1 engine, meaning it delivers a constant stoichiometric mix of air and fuel, burning neither lean nor rich. This is made possible due to a highly advanced engine management system that receives input data from a multitude of sensors.
The Volvo G9A uses a three-way catalyst, and emission levels are below the levels defined in both Euro 5 and EEV, Enhanced Environmental Vehicle. In addition, according to Volvo, the engine concept makes it possible to fulfill future requirements following Euro 5 and EEV.
The advanced electronics governing the engine also measure the quality of the gas fuel and adapt combustion accordingly.
To offset the higher exhaust temperature, Volvo uses an exhaust gas recirculation system (EGR)—possibly the first such use by a manufacturer of gas engines. (EGR lowers exhaust temperatures but also further reduces emission levels).
Volvo Buses has delivered more than over 1,000 gas-operated vehicles delivered since its starting producing them in 1992.