[Mgs] Timing discussion

PaulHunt73 paulhunt73 at virginmedia.com
Wed Apr 24 07:36:16 MDT 2019

----- Original Message ----- 
  > Are you sure that isn't vacuum retard?

    Yea, I wrestled with that for ages when restoring my car. The early Biturbo turbos blow through the carburetor, which is enclosed in the plenum. When boost comes up, vacuum advance fails so the other capsule takes over. Its a nasty, complex system with flow restrictors in various vacum/pressure lines to retard reaction time. It almost destroyed my love of dynamic systems! :-P

  Ah of course - boost kills 'vacuum' advance, so 'pressure' advance takes over.

  ... When preignition or pinking occurs, the computer modulates the waste gates to reduce the boost.

  For a long time I messed around trying to get a 'knock-sensing retard' system onto the MGB, but the engine is so noisy the knock sensor was triggering all the time!  Early BL computer controlled systems used that instead of (or maybe as well as) fixed maps, suddenly tread on the throttle to pull away and you could hear it pink like billy-oh, then rapidly reduce as the system retarded.  Had it worked it would have largely taken the place of centrifugal and vacuum advance, but never mind.

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