Question: what is the difference between a bmw n51 and n52?
Answer: The N51 engine is a SULEV version of the N52 that was sold in parts of the United States that had SULEV legislation. Differences to the N52 versions include a variable-length intake manifold ("DISA") with three stages instead of one, and a compression ratio lowered from 10.7:1 to 10.0:1.