Hello, I am bit lost in the vacuum lines of my DDS V12HE engine (JP spec), which to some extent seem "too much tubing" plus slowing the engine down.
Currently I found either my car or my mechanic made its first attempt to get rid of this blue system. Can anyone let me know what this "denso"label blue switch does? :-)
Please let me know what vacuum management would you normally recommend for the V12 HE engines.
Pictures and schemes highly welcome!!
Seems I was not able to find the V12 information and the XJS guys are too shy to share - anyone who knows a thread with such details, please, feel free to step in.

 

I suspect it's the 'solenoid vacuum valve' for the vacuum advance system, part number EAC4100 or EAC7935 (depending on connector type)

I don't know the exact function of this valve within the system....and different markets had different systems which adds to the confusion. I'm familiar (barely) with the USA-specific system.

A lot of V12 guys discard the advance control system and route a vacuum hose directly from the distributor to a vacuum nipple on the RH throttle body. At the moment I can't remember which nipple, as some are ported vacuum and others are constant vacuum. Others will chime in on that.

On general principles, and since we're talking about advance systems, make sure your vacuum advance capsule on the distributor actually works (they often don't) and that the mechanical advance system inside the distributor isn't stuck (they often are)

Cheers
DD