Jump to content


Photo

Vacuum Advance Dizzy


  • Please log in to reply
16 replies to this topic

#1 HUBBA.HUBBA

HUBBA.HUBBA

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,823 posts
  • Location: Sutton Coldfield
  • Local Club: Loan wolf

Posted 06 July 2019 - 01:35 PM

This might be a stupid question, but I can't get my head around something.  If a vacuum advance dizzy is connected to the same pipe as the boost gauge, how can that work? Surely that would make positive pressure go to the dizzy.



#2 KTS

KTS

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,227 posts
  • Location: Herts

Posted 06 July 2019 - 02:12 PM

i'd have thought it would need to be taken off somewhere between the carb butterfly and compressor inlet (assuming a suck through set-up) - after the compressor should always be (constant ..ish) positive pressure which is i assume where the boost gauge is connected ?



#3 Ethel

Ethel

    ..is NOT a girl!

  • TMF Team
  • PipPipPipPipPipPipPipPipPipPipPip
  • 25,379 posts
  • Local Club: none

Posted 06 July 2019 - 02:24 PM

That wouldn't necessarily be a problem - as long as it doesn't burst the diaphragm in vac advance can. They'll have to cope with various pressure variations from weather and altitude anyway.

 

It be better to tap a gauge  in to the manifold itself if the advance tapping it designed to work with the throttle position at idle.



#4 HUBBA.HUBBA

HUBBA.HUBBA

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,823 posts
  • Location: Sutton Coldfield
  • Local Club: Loan wolf

Posted 07 July 2019 - 05:47 PM

Yep it's for the suck through vmax Weber kit. The boost gauge is tapped at the bottom of the charger (after the compression).

#5 Dannyboolahlah

Dannyboolahlah

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 168 posts
  • Location: Wigan

Posted 07 July 2019 - 05:59 PM

I asked Stuart from VMAX about this when I was doing mine. He said the boost won't affect the dizzy. Read somewhere else it could burst the diaphragm, but usually only if it's on its way out anyway.

#6 KTS

KTS

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,227 posts
  • Location: Herts

Posted 07 July 2019 - 06:17 PM

according to the VMAX website the DCOE s/c kit has a vacuum out for distributor.



#7 HUBBA.HUBBA

HUBBA.HUBBA

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,823 posts
  • Location: Sutton Coldfield
  • Local Club: Loan wolf

Posted 07 July 2019 - 08:16 PM

When I was at Stuart's the other day he said put it on the boost gauge pipe. I just wondered how the vacuum advance works being positive pressure

#8 KTS

KTS

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,227 posts
  • Location: Herts

Posted 07 July 2019 - 08:31 PM

..would it work backwards ?

 

may be worth a quick call to Stuart to confirm if you're in doubt 



#9 HUBBA.HUBBA

HUBBA.HUBBA

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,823 posts
  • Location: Sutton Coldfield
  • Local Club: Loan wolf

Posted 08 July 2019 - 04:56 PM

..would it work backwards ?

 

may be worth a quick call to Stuart to confirm if you're in doubt 

Yep, left him a message earlier. I'll get a call back at some stage. 

Maybe the more the boost the less the advance, which would make sense I suppose. Despite what people may think, one thing I have noticed with every supercharged set up I've done is there is still vacuum from idle to about 1500rpm


Edited by HUBBA.HUBBA, 08 July 2019 - 04:56 PM.


#10 Dannyboolahlah

Dannyboolahlah

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 168 posts
  • Location: Wigan

Posted 08 July 2019 - 05:05 PM

My understanding was that it simply wouldn't 'notice' the boost.
You'll get advance at idle and low throttle, but once you get past 0psi it won't retard any further, you'll just get the centrifugal advance.

Edited by Dannyboolahlah, 08 July 2019 - 05:05 PM.


#11 HUBBA.HUBBA

HUBBA.HUBBA

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,823 posts
  • Location: Sutton Coldfield
  • Local Club: Loan wolf

Posted 08 July 2019 - 07:15 PM

My understanding was that it simply wouldn't 'notice' the boost.
You'll get advance at idle and low throttle, but once you get past 0psi it won't retard any further, you'll just get the centrifugal advance.

makes sense to me

#12 HUBBA.HUBBA

HUBBA.HUBBA

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,823 posts
  • Location: Sutton Coldfield
  • Local Club: Loan wolf

Posted 08 July 2019 - 07:20 PM

Just putting the new dizzy on. Nearly 90 deg difference in the rotor arm. The drives are in the same positions. The aldon one on the left and powerspark on the right. Is that normal to have such a difference, or is it just how each one is put together? And I just rotate the leads round one?
Attached File  20190708_201227_resized.jpg   43.81K   1 downloads

Edited by HUBBA.HUBBA, 08 July 2019 - 09:03 PM.


#13 panky

panky

    Camshaft & Stage Two Head

  • Members
  • PipPipPipPipPipPipPipPip
  • 1,776 posts
  • Location: Cheshire
  • Local Club: Northwest Casual Classics

Posted 08 July 2019 - 10:16 PM

I fitted an Accuspark dizzy to my Minor and yes it was a mile out compared to the original. As you suggest I moved the leads round, made a big difference compared to the old points dizzy ( it's now bolted into my Commer camper, well the Minor is in bits and the Commer one packed up :shy: )



#14 nicklouse

nicklouse

    Moved Into The Garage

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 17,900 posts
  • Location: Not Yorkshire
  • Local Club: Anonyme Miniholiker

Posted 09 July 2019 - 01:15 AM

not all aserise had the cap aligned with the dog drive. this required the dizzy drive to be fitted differently. but as you understand how it works you can just take the lead positions differently. UNLESS there is something like a amplifier on the side of the dizzy that means you can.



#15 Spider

Spider

    Moved Into The Garage

  • Admin
  • PipPipPipPipPipPipPipPipPipPipPip
  • 13,845 posts
  • Location: NSW
  • Local Club: South Australian Moke Club

Posted 24 January 2020 - 05:20 PM

Sorry for dragging this up (only stumbled over it just now while looking for something else).

 

I've seen this advice previously from this company regarding the use of Vacuum Advance Distributors in Boosted applications.

 

Be aware, some Distributors will retard when a Positive Pressure is applied to the Vacuum Advance.

 

A friend found this out after burning exhaust valves. He disconnected it, and apart from no longer having issues from burning valves, it actually went better.

 

Later, he had it run on a Rolling Road and had a distributor curved to suit and it goes considerably better.






1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users