bricheun
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| posted on 20/2/07 at 07:20 AM |
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vacuum advance - port or manifold?
On my boggs manifold there is one vacuum take off from cyinder number 4. The vacuum occurs in pulses rather than a fixed vacuum.
I was wondering, because my car did run on a vacuum evened out on all 4 cylinders, will this make a big difference to the ignition advance vacuum if I
took vacuum from just 1 port?
Thanks.
p.s. - there is no other way to tap vacuum across all 4 cylinders...
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macnab
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| posted on 20/2/07 at 08:35 AM |
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I don't think the vacuum advance mechanism can vibrate from the pulses as it usually takes a moment to move and could not keep up. Good point
though as I had never thought about it before.
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matt_claydon
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| posted on 20/2/07 at 08:55 AM |
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I had this problem when I was on carbs/dizzy and the dizzy made a nasty clicking noise. Took advice from the rolling road guy to run without any vac
advance and it was fine.
Also had issues on my megasquirt even with all four inlet tracts tapped for vacuum. Usual solution is to fit a plastic fuel filter in the vacuum line
to act as a damper.
BTW, the actual strength of the vacuum will be exactly the same, it's just that it pulses on and off.
[Edited on 20/2/07 by matt_claydon]
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macnab
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| posted on 20/2/07 at 09:16 AM |
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a small diameter pipe would do the same, say the ink tube of a biro.
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awinter
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| posted on 20/2/07 at 09:27 AM |
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I had the same on a Pug Mi16 engine. Ran it with and without vac advance from 1 port.
You will need to limit the amount of suction to the vac advance on the dizzy or it will kill the diaphram eventually. I used an inline bleed screw to
reduce the vacuum and the same pipe also ran to the brake servo unit.
The Vac advance made a big difference to the idle of the engine, I was able to set the idle on the carbs lower with vac connected. Much better for
emissions if thats a problem.
Also gives much better part throttle MPG if you doing any motorway driving.
Started better with vac advance as well.
It may take a little faffing to get working but it is worth it for the above reasons.
Allan
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snapper
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| posted on 20/2/07 at 09:43 AM |
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4 pipes from the top of my Mikunies to a 10mm tube/manifold this then has a 6mm take off either end for Servo and MegaJolt
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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macnab
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| posted on 20/2/07 at 10:52 AM |
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weird
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jamesbond007ltk
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| posted on 20/2/07 at 11:47 AM |
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What engine/carbs are you running? My manifold for twin DCOE's on a pinto had a vacuum port on one inlet aswell. was advised not to use this as
it upsets the butterfly on that cylinder. If you are running twin webers, dellortos etc you should not run vacuum advance to the dizzy. The only
reason you should use the vacuum take-off is if you were running a brake servo.
Rich
quote:
Originally posted by bricheun
On my boggs manifold there is one vacuum take off from cyinder number 4. The vacuum occurs in pulses rather than a fixed vacuum.
I was wondering, because my car did run on a vacuum evened out on all 4 cylinders, will this make a big difference to the ignition advance vacuum if I
took vacuum from just 1 port?
Thanks.
p.s. - there is no other way to tap vacuum across all 4 cylinders...
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bricheun
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| posted on 20/2/07 at 01:19 PM |
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This is how the vacuum is taken..
I managed to connect 2,3,4 vacuums up by using various sized tubes for experimenting..the idle is alot better..
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