I've got a JDM 2002 STi Type RA Spec C bugeye running a factory 2.0L engine aside from a Trust uppipe and turbo-back 3" exhaust. My boost gauge and dyno data confirm that the car hits 21psi boost at 3950RPM and then progressively tapers off to 14psi at redline.
While I fully plan on getting the ECU remapped in the next few months, and that the remap can get the factory boost control solenoid to hold higher boost to redline, I figured that I might as well go for a more effective option. Hence I've just purchased a used Blitz DSBC-R dual solenoid intercept type electronic boost controller. I'm hopeful it should build boost more quickly than the factory single solenoid, and hold it stable at 21psi to redline.
I've got the installation manuals, but I have a couple of questions:
1) Should I run the DSBC in series with the factory restrictor pill, or am I better off to remove this and allow the DSBC to manage everything unaided? I realise that this will involve increasing the gain, but will it give an advantage in preventing boost spiking and increasing the finesse with which I can influence boost onset/level with gain?
2) It's quite clear on my dyno plots where the ECU transitions from closed loop to open loop fueling, as the AF ratio drops off fairly significantly around the threshold of factory boost. I don't know whether or not the ECU determines this switchover point based on boost pressure feedback or based on engine RPM (or both), so presumedly I am better off being conservative with my gain and matching boost onset with where it kicks in factory? Of course once the ECU gets tuned, the gain can be adjusted to match the new fueling maps.