He's correct that's how they work. But to the original poster how do you know how much each turbo is boosting do you have two different boost gauges??#1 boost less then #2, that is why it is called sequential twins. first one boost around 2500-300 and then second one boost after that. so you go fast and then you go faster.
if you just want to go faster you can turn it into true twins where both turbos boost at the same time but the #1 turbo will still make less boost that the othet one.
OK, that is starting to make sense then. At WOT boost should rise to approximately 11 to 12psi and at approximately 3800-4000rpm should reach 17psi or there about? So basicly there is no possibility of hitting 17psi on the 1st turbo before 4k rpms?When I turn up my boost controller, my first turbo seems to boost to about 11psi then full boost is around 17psi. I don't know if there's a way to turn just my first turbo down and it seems to me that 11psi is probably bad for it.
Mark,yes, while the first one is online alone, it cannot make the volume so the pressure is lower, but once they are running toghether, they make the same pressure, just each has 1/2 the volume that is required to produce the pressure.
Which part of my explination did you disagree with?nope...
There is a wastegate (WG) that dumps exhaust to control boost pressure, an exhaust bypass control vale (sort of a reverse wastegate that is used to prespool the number 2 turbo) and an exhaust gas control valve that closes off the exhaust tract of the number two turbo so that all exhaust flow is routed thru #1.
At low boost pressure, all three are closed. All exhaust flows thru #1 turbo. As you increase pressure, the bypass opens up to spool #2, spinning #2 up gently. As you increase pressure, the EGCV opens up and exhaust flow is shared fully between #2 & #1. Once you start making enough boost that the computer wants to limit boost, the WG opens up. #1 does not spin #2 in reverse because there is a one way checkvalve between them (the reed valve that makes that elephant sound sometimes).