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Vacuum Advance - Or Not?
https://www.ausmini.com/forums/viewtopic.php?f=2&t=47675		 Page 1 of 1
Author:  slide [ Tue Nov 18, 2008 5:20 pm ]
Post subject:  Vacuum Advance - Or Not?
I came across this quote recently on the merits of using vacuum advance distribuotrs:

"Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for ..."

I always had Cooper S dissy's in my Minis and these don't have any vacuum advance mechanisms, though all other Minis do.

Of course vac advance only works to advance the timing (by about 15 degrees over static) when manifold vacuum is low - at idle and light cruise when the mixtures are leaner and take longer to burn. Full throttle drops the vacuum and the advancing is taken over purely by the centrifugal weights in the dissy.

Anything to be gained, or lost, by going the vac advance route?
Author:  TheMiniMan [ Tue Nov 18, 2008 5:54 pm ]
Post subject: 
exactly what the man suggests,,, but more for a fuel efficiency (economy) thing than anything else
Author:  drmini in aust [ Tue Nov 18, 2008 6:27 pm ]
Post subject: 
I have been told by GR recently that on ANY Mini with a sporty cam (266 duration up)- the vac advance is a waste of time, there is insufficient vacuum at the throttle plate under cruise conditions to do anything.
It will LOOK like it works when you watch the timing marks with a strobe light in neutral, but under way with any throttle at all, it does SFA.
I've disconnected Barney's now, one less thing to break/go wrong.
Economy seems the same (has twin HS4s, Wade 104 cam, 1.5 rockers).
Author:  1071 [ Tue Nov 18, 2008 7:52 pm ]
Post subject: 
I guess I have an alternative view. 1330, big valves, Waggot police grind, 1.5 rollers, twin HS4s. The installation of a Fraud (boo hiss) vac unit on an Aldon Yellow dizzie provided a 33% improvement in fuel consumption - from 30 odd to 40 mpg.

There was no sense in fitting a vac advance system to the S. No one EVER drove an S on a light throttle - and who cared about fuel economy when you couldn't fit $2 worth of Super in a Mini... an S took about $3.50 worth :)

Vac units aren't dear so give one a go...

Cheers, ian
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