U.S. company aids in "greening" of London bus

Diesel Progress North American Edition, August, 1997 by Peter Mullins

The converted diesel was supplied by Power Torque Engineering, of Coventry, England, under an agreement with Vinyard Engine Systems Inc. (VESI), San Antonio, Texas. Designated VT10, the 10 L, six-cylinder in-line engine is rated 290 hp at 2100 rpm.

Vinyard was formed by Shannon Vinyard, chairman and president of the company and a former director of engine research at the Southwest Research Institute (SwRI), also of San Antonio. An independent applied engineering and physical sciences R&D organization, SwRI has close links with VESI, which is promoting and developing some of the gas-fueling technology pursued over recent years by the institute.

Vinyard Engineering Systems has "Clean Power" conversions ranging from 40 to 450 hp. They are extensively used in several states for school and city buses, tractor trailer units, electric hybrids and refuse trucks, said the company. The conversions can be engineered to operate on LPG, CNG (compressed natural gas) or LNG (liquefied natural gas). The first two fuels would normally be used for city vehicles and centrally fueled transport fleets, according to VESI, the latter for dedicated long-haul vehicles.

The Clean Power line includes replacements for Cummins 4B, 6B, L10, 855 and N14 engines, with the Navistar DT466 and Cummins C series shortly being added. The conversion includes full electronic, closed loop control based on Ford's advanced engine management technology. Each conversion is engineered to produce equivalent power and torque to the parent unit and is optimized for low emissions and fuel economy. Conversion components are sourced from a variety of high-volume automotive manufacturers, with many being made specially to VESI specifications to simplify diagnostics and product support.

The London Pride tour bus installation is fairly typical of VESI's customized approach. Major modifications were made to the Cummins L10 engine. The cylinder head was completely reworked and the compression ratio dropped to around 10.5:1. Valves, conrods, pistons and turbocharger are completely new. Piston rings have different profiles and land areas.

Brian Longley, engineering director of London Pride's parent company, Ensignbus, said he was impressed by the way the new engine has been tailored to suit his needs - even to the. computerized monitoring of performance. The management system incorporates a tamper-resistant design data logger able to record operating conditions on a second-by-second basis to analyze vehicle operation and quantify fuel use. It is thus possible to obtain an operating profile, which records driver activities, instantaneous speeds, fuel flow, temperatures and other critical data. The package includes fuel, ignition, wastegate and speed controls. Single-point fuel injection at moderate pressure is used.

Longley explained the need for the specially-designed engine. "The Metroliner was originally designed for longhaul use. Engines and gearboxes were intended for much higher sustained speeds. Crawling, stopping and starting frequently in London traffic did not suit them. Nevertheless, the Metroliner had basically the right layout with some modifications - for instance, we arranged more seats upstairs on the open top deck, since that is where sightseers prefer to sit."

Longley also emphasized that drivers preferred the gas-powered unit since it has good, clean acceleration and is quieter and smoother in operation. Development has taken place over some three years and has now entered a final phase. Based on the success so far, Ensignbus has ordered nine additional conversions with the possibility of 15 more during 1997. This would equip the entire Metroliner fleet.

For its part, Power Torque is obviously anxious to offer the gas-powered VESI engine to other bus and truck operators. The company said it has extensive experience in gas conversion. Its parent company was formed in 1920, and Power Torque emerged in 1960 as a separate division. Since that time, the company has been a market leader in the development and conversion of engines for running on natural gas, biogases and LPG. Currently, Power Torque holds franchises to supply Ford, Iveco and New Holland diesel engines from 1.8 to 25.8 L (40 to 1210 hp).

Power Torque was introduced to Vinyard Engine Systems by Robin Tilden-Davis, a consulting engineer representing Vinyard in Europe. Tilden-Davis is a party to the agreement between VESI and SwRI and is handling the marketing of the VESI-based units throughout the U.K., continental Europe, Africa and the Middle East. A VESI engine is scheduled to be sent for detailed emissions testing at a major independent research facility in the U.K. It will be tested on a typical diesel cycle and is expected to meet and exceed Euro 2 emissions specifications.

Peter Mullins is regional editor for Diesel Progress International.