With all due respect guys you still don't see the sizing thing correctly.
First the biggest compressor for the power output is not the way to go
at all it invites surge and seldom puts you in the center island of
the map very often. Second a waste gate does nothing compressor wise
it is on the turbine side and bypasses exhaust which does slow down
the compressor by 'wasting energy'. Third a BOV is not used to limit
boost or pressure ratio in the normal sense of things. It is used to
dump boost only during a throttle closing at high rpm. If you rely on
this to limit boost you are dumping inter cooled air out. You now are
wasting inter cooler capacity. The best turbo for the job is generally
closer to the smallest one that will do the job. Done properly the
torque peak is in the center island of the compressor map which will
put peak power up and to the right of it. The compressor needs to be
large enough to avoid choke but no bigger than that does much good,
only harm. Some times it takes testing of a couple of different
compressors and a few exhaust housings to get it right. What you need
is the desired boost and exhaust flow as well to regain the energy
that is needed to drive the compressor at the lowest back pressure in
the exhaust system with transient response that is acceptable. Big
compressors take forever to spool up and then generally over shoot
demand on every transient to boot. It is 'TURBO LAG'.. This stuff is
empirical in nature with some preliminary calcs done at the beginning
when starting with a brand new setup. If anyone believes otherwise i
suspect they have never done the job before. There are a lot of
really smart people on this list but i have to ask the question how
many have actually turbo charged an engine that was not an off the
shelf kit or something some one else did for them?? If you have using
these assumptions I suspect it was a disappointing experience. This is
not something you learn how to do by reading you have get out to the
dyno room and start working to learn this stuff.. You will certainly
not learn by reading some brochures. Start with 'Internal Combustion
Engine Fundamentals' by Heywood, he is or possibly now was head of the
combustion engineering lab at MIT and draws a lot on Taylor and
Ricardo.. Don't let the title fool you this is not for the
mathematically challenged type of person if you want to get all it has
to offer.
Dave
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