Just for clarity:
SULEV (N26) = Super Ultra Low Emission Vehicle
ULEV (N20)= Ultra Low Emission Vehicle
The differences are to do with legislation differences across the world, or states in your likely case. From what I recall, it is mainly to do with the aforementioned fuelling system being comprised of stainless steel.
EDIT: Just dug out a reply from BMW UK on this when I asked last year:
Quote:
"The US have strict emission laws that are actively enforced with road side checks forming part of their enforcement agencies daily routine activities. Super Ultra Low Emission Vehicles have measures in place that ensure compliance with the US law.
For example in the rest of the world where it is acceptable, rubber fuel hoses are commonly employed in vehicle fuel systems. However in the US metal pipes are specified as these ensure that fuel vapour and fuel are less likely to be emitted into the environment.
Road side spot checks carried out in the US also mean that emission reducing systems need a robust means of being tested, this not being a requirement in the rest of the world at present. The US version and ECE version of the N20 commonly employ a fuel tank venting system. This system is designed to route fuel vapour formed in the fuel tank in to the engines intake system where it is combusted. However in the US model the system needs a way of being tested for leaks to the atmosphere. Therefore an additional valve is installed in the fuel tank venting system that closes off the venting lines so as a specific vacuum can be applied to them and through this action leaks in the system lines can be detected."
|