why seq. turbo's?
 

I'd like to know why Mazda decided to make the 13b a twin seq. turbo engine. I could see if it was a V6 engine or something. It seems like overkill to me. Any responces would be great! Thanks.

A big turbo (or moderately-sized parallel twins) spools slow, but works great at high RPM.

A small turbo spools up quickly, but doesn't flow enough at high RPM.

A sequential system (or small parallel twins) spools fast and still has enough flow to make power at high RPM.

These are obviously generalizations. Turbos come in many sizes, so you can choose whatever mix of quick spool and high RPM flow you want. Opening up the exhaust also reduces lag significantly, so a big single tends to work better for modded cars than they would in a factory system with a restrictive exhaust. But the basic ideas I outlined are correct -- a sequential system allows you to have quick spool and high flow in a combination that would be impossible to acheive with one turbo or parallel twins, all other things being equal.

Parallel twins work best on V engines because you can run one turbo off each cylinder bank, which is much easier than plumbing both banks over to one turbo. Sequential would be a total pain in the ass to plumb on a V engine. The Supra also has sequential twins, but it is an I6, not a V6.

-Max

Thank you so much! That has to be the best, most informative, and to the point answer I've gotten in a while. When I wrote this question the supra and skyline engines came to mind but since they were inline 6's I thought I'd ask anyway. I forgot that V6's didn't have seq. turbos like the 300z (don't ask how) but your answer makes total sense. Now I know. Thanks again.