Vacuum source for bc solenoid

[LeedsMike]

Please can someone help me to understand the vacuum source for the boost control solenoid? Is the metal hose connection on the turbo body a banjo bolt and the vacuum source is there?

Should the actuator arm move on engine start or is vacuum held in the system?

Mainly curious and trying to understand….. thanks!

[lotusflasherman]

Please can someone help me to understand the vacuum source for the boost control solenoid? Is the metal hose connection on the turbo body a banjo bolt and the vacuum source is there?

Should the actuator arm move on engine start or is vacuum held in the system?

Mainly curious and trying to understand….. thanks!

Should the actuator arm move on engine start or is vacuum held in the system? - Answer is No, it's much more complicated than that. Suggest you download the appropriate Manual from the Manuals tab above - it's 5th across. Lotus cover the topic in a separate Manual as it's that complicated. If you have a UK SE it's Section EMK for Open Loop, if it's an S2 it's Section EMJ for Closed Loop. Closed Loop uses an Exhaust Oxygen Sensor, as Lotus call it, a.k.a. Lambda Sensor, in the turbo. It's easy to tell, SE has a big hex plug in the hole, S2 has sensor and wiring coming away. Some SE's have been converted to Closed Loop as it gives better emissions and passes MOT more easily and better mpg.

You will not see any boost if car is stationary and engine is not under load. The ECU looks at engine revs, throttle position, manifold vacuum and engine temperature, amongst a few other criteria. It will not provide full boost until vacuum indicates the throttle position is above 25% and revs above 2,900rpm ... and full boost is restricted until engine is up to a certain temperature. That prevents damage by idiots who "boot a cold engine". Sections EMK.2-W gives a description of the Turbo Boost Control functionality, and that section is shown in EMJ.2-X for Closed Loop but is still called EMK.2 so was obviously a copy and paste exercise.
Hope that helps... happy reading. I'm happy to answer further questions when I have some idea of the level of your understanding and how to write the answers to assist you ..

[LeedsMike]

Thanks. That really helps.

All questions answered and more. It’s not vacuum, it’s a pressure takeoff.