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Vacuum Advance Dizzy


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#1 HUBBA.HUBBA

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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


#13 panky

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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

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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.






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