> But the NOX issue is due to the sulfur content in the fuel, no? And 
> the
> newest small diesel cars even filter that out and will have lower 
> NOX as
> well as lower everything else.

NOX levels are affected by fuel compositions but burning air, with 
it's nearly 80% Nitrogen content, is the major source of the NOX. 
Internal combustion processes which are only reasonably controllable 
across the reaction can not totally eliminate NOX production. External 
(ie continuous constant conditions) combustion allows better control. 
While you can never totally eliminate NOX by-products when you burn 
air, it's far easier to make them much lower with external combustion. 
But it will be a wee while yet before the other issues related to 
automotive external combustion engines are solved :-)


        Russell 

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