For me, I set "PassengerMinInstances".
BTW: Don't copy the rest of what I am configuring, I'm fighting some bugly leaks.
PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-3.0.9
PassengerRuby /home/ec2-user/scripts/ruby_wrapper.sh
#PassengerRuby /usr/bin/ruby
PassengerMaxPoolSize 12
PassengerMinInstances 10
RackEnv production
RailsEnv production
PassengerPoolIdleTime 600
PassengerMaxRequests 2000
[ec2-user@domU-12-31-39-06-40-15 ~]$ pstat
*** Cleaning stale folder /tmp/passenger.1.0.1068
----------- General information -----------
max = 12
count = 10
active = 0
inactive = 10
Waiting on global queue: 0
----------- Application groups -----------
/wildobs/app:
App root: /wildobs/app
* PID: 19471 Sessions: 0 Processed: 1381 Uptime: 13h 5m 26s
* PID: 19453 Sessions: 0 Processed: 470 Uptime: 13h 6m 38s
* PID: 19457 Sessions: 0 Processed: 399 Uptime: 13h 5m 30s
* PID: 19473 Sessions: 0 Processed: 783 Uptime: 13h 5m 26s
* PID: 19459 Sessions: 0 Processed: 1 Uptime: 13h 5m 29s
* PID: 19469 Sessions: 0 Processed: 0 Uptime: 13h 5m 27s
* PID: 19467 Sessions: 0 Processed: 0 Uptime: 13h 5m 27s
* PID: 19465 Sessions: 0 Processed: 0 Uptime: 13h 5m 28s
* PID: 19463 Sessions: 0 Processed: 0 Uptime: 13h 5m 29s
* PID: 19461 Sessions: 0 Processed: 0 Uptime: 13h 5m 29s