Group 25 Intake and exhaust systems. Turbo
- 250 General
- 251 Intake and exhaust manifolds
- 252 Silencer and exhaust pipe
- 253 Exhaust brake, exhaust pressure governor
- 254 Catalytic converter and emission control
- 255 Turbocompressor
- 256 Air filter, shutter housing
- 257 Crankcase ventilation
- 259 Miscellaneous