what do they solenoids do and when do they turn on and off at what rpm? or what condition

 

They control the amount of airflow exiting out of the wastegate and precontrol actuator thus controlling the amount of prespool and boost.

 

They don't turn on/off with rpm. They turn on/off with BOOST.

 

how do they know at what boost to turn on and off where is teh boost preset or where des it read it and go thru ecu?

 

They don't. Everything is preprogrammed by the ECU and it controls the boost like a dummy with its eyes closed.

This is why we have boost spikes. If the ECU actually knew about these spikes, it would compensate in some type of way, but it doesnt....

 

so if u unplug the side that goes to solenid and plug the side that goes to the wastegate actuator u wil see less boost, because it takes some time to fill that space (long hose, that goes from wastegate acutato to the soleniod and this will fix boost spiking)

 

The wastegate and precontrol solenoid are set to run at a particular duty cycle set by the ECU (ie open loop control). By changing the ECU's set duty cycle, the time averaged pressure in the lines can be changed, which in turn changes the turbo boost pressure which is required to open and close the actuators. If you cant change the ECU's fixed duty cycle, you can manually change the effective time averaged pressure by changing the size of the restrictor pills in the lines. These restrictors can be placed on either side of the actuators. If a smaller restrictor pill is placed in the line from actuator to solenoid, the wastegate will open at a lower pressure. Conversely, if a smaller restrictor is placed on the input side of the actuator, the wastegate will open at a higher pressure. Ideally though, changing the duty cycle and leaving the pills alone seems like the best solution (if you can reprogram your ECU).

 

a wastegate doesnt just open and close, it opens a lot or little depending on boost, this will make your turbo spool up slower, if u just take teh pills out.
and what u are saying about reprogramming the ecu to change the boost level? that wont work because u cant boost less then what it already boosts. the solenoids are closed most of the time and i think are only there for a limp mode anyway. and nothing else. i could be wrong. but i will test this out tommorw. spiking could be fixed if those long lines to the solenoids are eliminted. because they will not have to be pressurazed for the wastegate actuator to reach the the desired psi to start opening it and since the stock turbos spool so quickly the air gettign to the wastegate fist passes thru and then pressurazes in the lines and then the wastegate opens and the boost spike has already occured at that point in time.

 

The boost control system does not operate based on the delay time it takes to fill hoses, as I suspect you think. Having longer hoses will of course delay the response of the overall system, but not change its steady state behavior, which is what affects maximum boost level. The solenoid bleeds off air from the wastegate actuator, thus changing the effective pressure seen by actuator. As an extreme example, if the duty cycle of the solenoid is set so it is always venting, then there will be no boost seen by the actuator and the wastegate will not open. Conversely, as you said, if the line from the actuator to the solenoid is completely capped off (as if the solenoid was always closed), the wastegate will see whatever pressure is being put off by the turbos, and be fully open at 7psi.
Having a 'mixture' of these two scenarios by opening an closing the solenoids at a particular duty cycle allows outcomes which are between the above two extremes.

 

i was saying that because there is a lot of space for air to fill before it reaches the solenoids, u can get boost spiking, untill the pressure is stabilized and u are at a constant rate... thats all. so these solenoids dotn do anythign but work off some map that is in teh ecu? and if unplugging these solenoids and puttign a pill on teh solenoid side of the wastegate do a petter job then these solenoids tehn why do peopel not do this?

from a hose routing diagram it seems that the prespool and the wastegate solenoids are also connected to the oil injectors? why is this?

 

If you were to unplug the solenoid and just put a pill in the line, you would overboost. You would need to completely plug the line to get 7psi, but thats the only boost level you would be to run without using the solenoids. The output to the solenoids I believe runs into the intake side of the primary turbo.