Originally Posted By: 4WD
We are already running big buses off CNG - but it will be harder to make the needed torque in some cases.
At least where I live, CNG is going the way of the Dodo.
Not only has the media demonised gas-powered buses (several serious bus fires), but the current fleet of vehicles have continuous issues with ignition system failure and turbo faults. The issues have been so bad these buses are set for a semi-early retirement in the next few years.
Earlier examples in the late 1980's and early 1990s were dogged particularly with performance issues (on-par with molasses, I'm told) and finicky mechanical gas systems that severely damaged many engines. Early computerised systems were still slow (lean burn).
Low floor examples from around 2003-2004 were far better, but still somewhat slow, being N/A. They have been reliable, however.
As I'm told, the newest CNG injection systems are far superior to what has gone before, such that "lean burn" is no longer necessary. Euro VI is met relatively easily, too.