這個不是H-4 engine。這個叫flat-4，又叫boxer engine。H engine是2個flat engines。

這個不是H-4 engine。這個叫flat-4，又叫boxer engine。H engine是2個flat engines。flat engine的好處是重心低。

From Wikipedia
"The H-4 and H-6 engines produced by Subaru are not H engines at all, but boxer engines."
http://en.wikipedia.org/wiki/Engine_configuration

"An H engine (or H-block) is an engine configuration in which the cylinders are aligned so that if viewed from the front, they appear to be in a vertical or horizontal letter H.

"An H engine can be viewed as two flat engines, one atop or beside the other. The "two engines" each have their own crankshaft, which are then geared together at one end for power-take-off. The H configuration allows the building of multi-cylinder engines that are shorter than the alternatives, sometimes delivering advantages on aircraft."
http://en.wikipedia.org/wiki/H_engine