15psi...Miata performance
Manual Boost Controllers (MBC)
Manual Boost Controller
Spring & ball manual boost controller, that you adjust to the desired psi. The spring holds the ball, so that the wastegate doesn't open before the desired boost level. Same units are offered on the net for $42+ Instructions included. 5 minute install time. Sports Compact Car (SCC) tested this against 'electronic' Boost controllers and found this held a more constant boost level.
$24 & s/h
Note that there are 2 types of MBCs. "Bleeder" and "Ball & Spring"
Pic #1 is a bleeder. Note the knob. This adjusts the air valve, that determines the amount of air that leaks out. It is always leaking and thus wastegate opens early.
Pic #2 is my Ball & Spring 'insides'. You compress the spring by tightening the casing. A lock nut secures it when you are finished. The ball blocks the passage until the desired boost is attained. In turn the wastegate is closed longer and better spool-up.
Pic #3 is a release vent so that the you have less boost 'overshoot'. The hole is just slightly thicker than your hair.
Pic #4 gives you a rough representation of how both MBCs control the wastegate as boost increases