11 replies to this topic

[RalphyBMW]

I want to know more about the vacuum system, boost control valves, what they do, and what is connected to what, etc. Does anyone have any kind of schematic? Thanks!

[Ormes]

Sorry, I have requested a schematic before and there isn't one. The end points are... 2 x solenoids Actuator Turbo Recirc valve Intake manifold FPR Vacuum box (probably others I have forgotten) You can check most of the tubing by taking the trays off, jacking and dragging yourself under, but easiest to check the boost solenoid/actuator/turbo from above by removing the intake pipe.

Edited by Ormes, 25 November 2012 - 10:07 PM.

[RalphyBMW]

No prob, thank you!

[Ormes]

http://www.astraowne...ad.php?t=290382

[RalphyBMW]

Fantastic, thank you!

[Nev]

I understand it all, but the diagram is in my head.

[siztenboots]

recirc is vacuum operated , waste gate is boost operated

[Nev]

Does anyone know if the recirc is opened by the ECU/vacuum box solonoid just when the clutch is pressed in (for any gear) or is it gear depenedant ?

[Ormes]

My understanding is fairly limited but I thought that the vacuum in the intake manifold combined with boost against the diaphram opened the recirc whenever closing the throttle butterfly? I had assumed that the ECU uses the vacuum box (via the solenoid) to feed vacuum to the recirc when there is no vacuum from manifold (butterfly open). I was under the impression that this "overiride" is used when coming off the throttle (to part throttle?), to keep the turbo spinning? I may be out of my depth here

[Nev]

I think you are right Alex, but I was wondering if this happens in all gears or just 1,2,3rd for example.

[siztenboots]

My understanding is fairly limited but I thought that the vacuum in the intake manifold combined with boost against the diaphram opened the recirc whenever closing the throttle butterfly?

I had assumed that the ECU uses the vacuum box (via the solenoid) to feed vacuum to the recirc when there is no vacuum from manifold (butterfly open). I was under the impression that this "overiride" is used when coming off the throttle (to part throttle?), to keep the turbo spinning?

I may be out of my depth here

yes, to improve driveability when coming off the throttle or clutch active the ecu opens the recirc (using vacuum source A or B ) to keep the turbo rpms high ready for the next use, ie. to stop the compressor wheel stalling working against a closed throttle.

primary vacuum source A is the intake manifold
reserve vacuum source B is the vacuum storage box under the IM.

[Ormes]

Cheers Nev/Sizten... It's nice to know that I am along the right lines

Edited by Ormes, 28 November 2012 - 06:55 PM.