PSA, Renault, Gaz de France and TNO carried out a joint research programme with the aim to develop a CNG vehicle based on a Citroën BX 19 GTI. In order to make optimal use of CNG a optimized engine concept (increased compression ratio) was adopted.
The paper describes the engine testbed work, the vehicle body modifications and the initial vehicle testing. By increasing the compression ratio from 9.3:1 to 11.5:1 the power loss of the engine when running on CNG could be limited to approx. 16%. When running on petrol a similar power loss was observed.
Emissions complied with the 91/441/EEC regulation (CO: 18.9%; HC + NOx = 53.6%).
Software developed by TNO specifically for this purpose enabled TNO the make use of only one control unit (EFI-4 of Delco Electronics Inc.) to perform engine management functions for both fuels.
A good driving range is obtained with a minimum loss of boot space.