May 2004
DEDICATED CNG CONVERSION PROGRAMS
By DieselGas of New Zealand
Overview
For the past several years DieselGas, have been aware of the severe pollution problems experienced in many cities and the aim of the Governments to reduce this problem. It has been quoted that 70% of the atmospheric pollution in many large cities is caused by diesel exhaust emissions. DieselGas is an alternative fuels, equipment, development company that specialises in technology for operating diesel engines on dedicated compressed natural gas (CNG) and dual fuel (Diesel/CNG).
Benefits of Experience
New Zealand engineers have converted more than 20 different diesel engine models to dedicated gas operation.DieselGas possesses expertise, which includes a diverse mix of skills, knowledge and experience as well as a unique Engine Management System and Technician Interface Software program. When this technology is implemented, by DieselGas in co-operation with local engineers and technicians, Project Objectives are assured.This experience means DieselGas can offer well established and proven procedures for carrying out the conversion of diesel and petrol engines.
Diesel Engine Conversion Process
1 Application Engineering (AE)
1.1 What is Application Engineering
Application engineering incorporates all of the mechanical changes, electronic changes and additions to each engine to allow it to operate successfully on gas. It also includes the testing and documentation required to confirm the engine performance and to allow the conversion kit to be released for production. Full design drawings, specifications and manuals of the vehicles and engines will be required for preliminary study at the beginning of the project.1.2 Diesel Engine Conversion to Dedicated Gas Operation
Diesel engines to be converted to dedicated gas operation require major component changes:
? Instrumentation and thorough testing of the engine on diesel prior to conversion to obtain accurate performance ratings. This is used as the benchmark rating with which to compare the performance of the engine in gas operation.
? Establishment of a Performance Specification to be agreed to by the engine owner and DieselGas.
? Design the conversion system including the mechanical changes such as head and piston redesign, gas control, ignition system and the engine management system.
? Remove the diesel injection system and replace with an ignition system.
? Install a gas carburettor or gas injection system as required to deliver the CNG.
? Modify pistons to reduce the compression ratio or replace with new pistons of a selected design and material. The new compression ratio will normally be between 11 and 15 to 1 depending on the gas composition.
? Modify the cylinder head to accommodate a spark plug or design and manufacture a new gas head as required. This new head may be available from the factory or may need to be specially engineered and manufactured for the conversion.
? Inlet and exhaust valves and seats from the diesel engine may be used providing the materials are compatible for the use of gas otherwise they must be replaced with valves and seats of selected material. This is especially important on a turbocharged engine.
? Turbochargers on dedicated gas engines encounter higher exhaust temperatures than for diesel engines. A water cooled turbocharger exhaust housing may be required or a new turbocharger incorporating selected materials to withstand the higher temperatures. Control of the inlet manifold air pressure may be required using a waste gate or air bypass.
? Implement the DieselGas engine management system to control the variable parameters of the engine including ignition timing, air/fuel ratio, inlet manifold pressure and temperature, knock sensing and various safeties.
? Install catalytic converter as required.
? Dynamometer test engine and develop operating parameters to meet Performance Specification.
? Implement the Engine Management System Technician Interface software program, which uses MS Windows from a laptop computer. This includes automatic Fault detection, self-diagnostics and Fault Logging with graphing program to analyse Fault Logs. The Fault Log records the 15 seconds of engine operation prior to the Fault being logged. These Fault Logs can be easily sent electronically to the factory for analysis and rapid diagnosis of problems.
? Once the Performance Specification including emissions standards have been met; carry out a 1,000 hour endurance trial. Dismantle the engine and check that wear patterns are within expected limits.
? Repeat any of the above steps as required to meet the Performance Specification.
? Acceptance that the engine meets the Performance Specification and is signed off by the owner, engine manufacturer and DieselGas.1.3 Gas Quality
Gas composition will have a significant affect on performance of the engines on gas. Accurate reporting of the gas composition and any variations to the composition is vital to the success of the project.Failure to accurately report gas composition can put the conversion program success in doubt. 2 Other general conditions
2.1 Local Facilities
It will be the responsibility of the local supplier to establish facilities suitable for the conversion of engines and vehicles.
2.2 Engine Conversion
It is anticipated that the local engineers and technicians will be involved in conversion of the diesel engines to dedicated gas.
2.3 Engineering Support
Engineering support for all facets of the project will be available directly from DieselGas New Zealand. This includes fax, phone and electronic mail as well as personal visits. The DieselGas Technician Interface Software supports the DieselGas Engine Management System. The System is designed for use with dedicated gas engines and dual fuel engines. The Technician Interface Software is a user friendly program which uses MS Windows on a laptop computer. It includes Automatic fault detection, Self diagnostics and Fault Logging with Graphing program to analyse Fault Logs. It includes extensive Help files to assist with correcting faults. The Fault Log records 15 seconds of engine operation prior to a Fault being Logged. These Fault Logs can easily be sent electronically to the factory for analysis and rapid remote diagnosis of problems.Initial and ongoing training will provide technical staff with a full understanding of the system designs, service and maintenance techniques.
2.4 Training
The transference of training techniques and expertise by DieselGas will be aimed at tutor training. These tutors will train local technicians. A good training program is essential to the success of the project. The training will include vehicle conversion techniques, service and maintenance

2.5 Refuelling Facility
CNG must be readily available for refuelling vehicles for dynamometer and road trials. Gas composition must be recorded at least weekly for the first year to gauge the variation in the gas supply. 2.6 Standards
All equipment and engineering services supplied shall comply with the following New Zealand standards for CNG conversion equipment and systems unless otherwise stated. NZS 5422:Part 3:1991 Code of practice for THE USE OF LPG AND CNG FUELS IN INTERNAL COMBUSTION ENGINES Part 3 IN HEAVY VEHICLES. 2.7 Engine Performance.
The converted engines shall have performance ratings similar to the performance of an equivalent diesel engine, or according the requirements specifications, in terms of the power and torque developed providing the natural gas meets a minimum specified standard and consistency.2.8 Exhaust Emissions.
The requirements specification will establish the emissions specification for the exhaust emissions from the converted engine. Either lean burn or stoichiometric combustion technolgy may be used. This may be from Euro II or III.
2.9 Initial Vehicle Conversion
Once a kit has been released for manufacture and supply, a prototype engine or kit may be road trialled locally. The initial conversion and road trial will involve:2.10 Car Conversion
It is anticipated that car manufacturers will be involved in designing the installation of cylinders and pipe work to the new cars. This will also apply to the installation of the dedicated gas engines and Bi-fuel conversions for new cars. Retrofit car conversion facilities will require:
? Production line type facilities for the installation of the cylinders, gas engines or BI-fuel kits and other components as required.
? Full dynamometer test cell with emissions test facilities to allow testing to the standards set in the Performance Specification.
? Full and comprehensive workshop testing of the equipment, including all necessary adjustments and fine tuning will be carried out, to achieve optimum vehicle performance.2.11 Engineering Support
Engineering support for all facets of the project will be available directly from DieselGas New Zealand. This includes fax, phone and electronic mail as well as personal visits.
2.12 Training
The transference of training techniques and expertise by DieselGas will be aimed at tutor training. These tutors will train local technicians. A good training program is essential to the success of the project. The training will include vehicle conversions techniques, service and maintenance
2.13 Initial Vehicle Conversion
Once a kit has been released for manufacture and supply, a prototype engine or kit may be road trialed. The initial car conversion and road trial will involve:
? Design and installation of storage cylinders systems and interconnecting pipe work, valves etc. to the car.
? Installation of conversion kit or installation of converted engine to the car and commissioning of the vehicle.
? Initial road and dynamometer trials to prove the engine and vehicle operation.
? Full dynamometer testing to confirm the engines meet the standards set in the Performance Specification when in the chassis.
? Modification and adjustment if required and acceptance by client.
? Begin extended road trials.
2.14 Engine Performance
BI-fuel engines are expected to retain at least 85% of the original power of the engine on petrol. Dedicated gas engines, where the compression ratio has been increased, shall have performance ratings similar to the performance of an equivalent petrol engine in terms of the power and torque developed providing the natural gas meets a minimum specified standard and consistency.