How does the ECU determine WG/PC solenoid duty cycle?
 

I read somewhere that the ECU duty controls the wastegate and precontrol solenoids based on fixed maps. Fixed maps based on what?

That suggests to me that there is no feedback (ie: boost pressure feedback) used in determining the duty cycle for each solenoid.

My reason for asking is that I would like to know if the stock turbos could provide lower boost as they wear wtih age, assuming a perfectly functional stock control system. If there was no boost feedback, I would imagine this to be the case.

Cheers Guys!

Map Sensor I'd Guess..... but that's what it is a Guess..... I don't know any other place where the ECU has access to Manifold pressure, and that's what It would need to know together with RPM's.... to activate the prespool actuator... to spool the secondaries.

Actually, these solenoids are controlled not by MAP feedback, but by pre-programmed open loop mapping based on RPM, throttle position, etc., but NOT actual boost pressure. That's one of the main reasons that boost controllers are necessary, even for relatively (Modified intake + DP + aftermarket CB) stock setups.

There are several explanations around describing how things work. Here's one:

http://robrobinette.com/boost_note.htm

So, bottom line, yes, it is likely that if the turbos are in less than optimal condition, you could see a reduction in response and peak boost.

Yep that's what I was lead to believe. Cheers for the link.

So a perfectly operating control system could give boost patterns less than 10-8-10 on an old set of turbos then. So if I can't find a boost leak or problem with my stock controls, I might end up grabbing a manual boost controller and see if I can regain some boost. Although if the turbos are just old and I use a boost controller to work them a bit harder, that's probably not going to be good for them.

That solution is still a long way away, plenty of troubleshooting left to be done.

Awesome thanks for that :)