The Nissan E engine was a major redesign of the Nissan A engine, specifically to fit Front-Wheel Drive vehicles. The first variation, E15, debuted in the 1982 Pulsar (N10 "Datsun 310"), replacing the A15. it has an identical bore & stroke.
From Nissan Product Bulletin Vol 75.
Quote:
The E-engine is an extensively improved version of the A-engine...
The E-engine provides higher power and greater torque than the A-engine. Its dynamic performance, as in standing start, passing acceleration, upgrade driving, etc. has been increased by 5 to 10%. A summary of the major improvements is as follows:
1. The E-engine is approximately 10kg (22 lb) lighter than the A-engine
2. An O.H.C., cross-flow engine design provides high torque as well as responsiveness to acceleration.
3. The cylinder pitch is identical to that of the A-engine, which has already been proven to be both duarable and reliable
4. The overall length has been shortened by 48mm (1.89 in) to accomodate the in-line transaxle design.