Nissan introduced the 3 valve heads in 2 engines the K and G series engines (ka24e and g16i).

For the Ka24e 12 valver it has been recognized as having a better
low speed and midrange than the 16v ka24de in all sort of tunes by
enthusiast in the states. The 3 valve head is now used by Mercedes Benz
throughout the latest engines for their road versions.
Low response and midrange is in favor by the use of a 3 valve chamber by
Mercedes and supercharging is added for higher spec versions.

Im not saying the Ga16i is better than a 4 valve head for all out performance
but some have expressed the 12v head has response and torque that makes smooth
driving and overtaking whereas the 16v head has little down low and makes you rev
the engine in order to do the work its supposed to.
I a world of more complicated architecture employed in engines you only have to
look again at Mercedes Benz and see that its not a cost cutting feature but as the
company with the largest holder of patents in the world, a logical one.
Even F1 has gone from 5 to 4v per chambers, so its no surprise 3v chambers with the
right manifolds instead of the nasty single point injection restrictions they came
out with by Nissan (not to mention Toyota, Mazda, Honda and Mitsubishi) could be the
ultimate heads to use for the best overall street/track setup.

The 3v architecture was an intermediate technology before the use of variable valve
technology 4v chambered heads and for lower spec fuel usage.

Compression is a big issue also with these 3v heads as many of these engines came with
low comp to use low quality fuel so piston design is critical to achieve its potential.

Attach file:

---

  ga16-12v.JPG (21.95 KB)