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Vacuum advance
https://www.ausmini.com/forums/viewtopic.php?f=2&t=74994		 Page 1 of 1
Author:  willy [ Sat Jan 14, 2012 12:41 am ]
Post subject:  Vacuum advance
Hi guys,
the topic that 1098 made me check out what other distributors simonbbc has for sale, as I am chasing an electronic distributor for my engine.
He lists 59D that have vacuum and non vacuum advance.
The engine its going on has a weber but is standard apart from that and a set of extractors. It is a 1275 A+.
The weber manifold has no vacuum take off, so I'd assume I would want a dizzy without the vacuum advance.

What is the reasoning (actual) behind this?
Does the manifold supply some advance to the ignition for part-throttle economy/response?

Confused :D
Author:  drmini in aust [ Sat Jan 14, 2012 7:49 am ]
Post subject: 
1st off, ALL Mini distributors have centrifugal advance. Some have vac advance as well for part throttle economy.

A series cars got the vac signal from behind the edge of the throttle butterfly.
But A+ engines with an HIF carb the signal comes from the manifold side of the throttle butterfly, I believe. There was a how-to on a forum that showed how to redrill an HIF to move the drilling further towards the carb piston and make it work better.

As I said, vac advance is purely an economy device. Cooper S never had it for this reason- in competition they are just something else to go wrong. If the vacuum system happens to jam at full advance you burn pistons.
Weber and Dellorto sidedrafts don't use them, as the vacuum/pressure in the separate ports varies widely whenever engine is running. I have not seen it successfully used on these carbs.
Author:  IndigoBlueCooperS [ Sat Jan 14, 2012 11:28 am ]
Post subject: 
I will probably run the vac advances on the Twini, partly because the distributors have them and also the carbs have the ports. My understanding is as per Docs - better economy at cruising.
Author:  coopar [ Sat Jan 14, 2012 3:19 pm ]
Post subject: 
Dumb question, when you say this you're talking about signal for a gauge?

drmini in aust wrote:

A series cars got the vac signal from behind the edge of the throttle butterfly.
Author:  drmini in aust [ Sat Jan 14, 2012 3:55 pm ]
Post subject: 
no, it's for the vac line that goes to the diaphragm on the side of the dizzy- if it has one.
Author:  simon k [ Mon Jan 16, 2012 3:34 pm ]
Post subject: 
coopar wrote:
Dumb question, when you say this you're talking about signal for a gauge?

drmini in aust wrote:

A series cars got the vac signal from behind the edge of the throttle butterfly.


it could actually be used for an economy gauge (think VB commodore), but it's not a fancy schmantsy electronic signal ;)
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