James
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| posted on 13/5/04 at 04:31 PM |
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To vacuum or not to vacuum
This is probably a dumb question regading my Pinto... but it's me so what'd you expect! 
Basically, I'm converting my EFI Pinto to run a 32/36 carb. To do this, do I actually need a dizzy with a vacuum advance on a carb'd
Pinto?
The reason I ask is that I have the dizzy from my EFI Pinto.
In addition, Ned gave me his dizzy (from his carb Pinto) and it appears identical. How is it that his could run with no advance?
I read somewhere that fitting a non advance dizzy was a "common conversion" but how does this work?
I'd rather avoid using the vacuum if possible as this seems a pain to fit the vacuum lines etc. if they're not needed.
Thanks,
James
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NS Dev
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| posted on 13/5/04 at 04:59 PM |
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You can use a non vacuum advance distributor but it will still need mechanical advance, which the efi one won't have. (but an electronic
ignition ignition carburettored engine will have) On the top the efi one and the electronic ign ones probably look the same as they both have the
hall-effet trigger wheel inside, but the efi one will have no advance weights.
The mechanical advance gives progressively more advance as the engine speeds up (in simple terms, fuel and air burn at a constant speed, as the engine
speeds up, you have less time to burn the cylinderfull, therefore you have to start the fire earlier in order to generate cylinder pressure at the
right moment)
Vacuum advance increases advance from the mechanically advanced position according to vacuum, which is pretty much inversely proportional to throttle
opening, so will add advance at high vacuum (low throttle opening) for better economy during cruising and "pootling around". If this
amount of advance was maintained during hard driving then detonation would set in, but on opening the throttle the vacuum disappears and the advance
returns to the mechanical advanced position.
There, hope that's all cleared up, basically non-vac is ok but will reduce mpg. EFI dizzy is no good as has no mechanical advance (on the sierra
efi, eec 5/6, some bosch systems like L-Jetronic only controlled the fuel, the ign was still mechanical advance)
Electronic pickup dizzy from Carb model (i.e. mechanical advance one) will be fine, though all the carb ones I have seen were vac advance also!!
Extra complication, you could run with efi dizzy (no mach or vac advance), but engine would make poor power as there would be nowhere near enough
advance at higher revs, if the advance was set correctly at idle!
Phew, what a lot of words!
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ady8077
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| posted on 13/5/04 at 06:09 PM |
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Hi James
You can tell if the one Ned gave you has mech adv by turning the rotor arm whilst holding the gear cog still
I was a bit confused too and was recomended to get a matching dizzy, coil and ign mod from either a very early 2.0 or any 1.6 pinto'd sierra, as
they only have 5 wires to connect up
Adrian
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James
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| posted on 14/5/04 at 09:40 AM |
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quote:
Originally posted by NS Dev
Phew, what a lot of words!
But what good words the were! 
Aah followed by Mmmm followed by Oh I seee!
Well, you learn something everyday! Now I know what advance is for!
So guess I'll be going with the non-vacuum carb' one then. (Although I think you may be suggesting this will not give such good fuel
economy?).
Adrian,
So I hold the gear cog and turn the rotor arm- what should happen?
Good advice about the parts- it's what I originally tried to do- but the bits kept turning out to be the wrong part!
Thanks to both of you!
James
[Edited on 14/5/04 by James]
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theconrodkid
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| posted on 14/5/04 at 01:02 PM |
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grab hold of the gear at the boton of dizzy and try to turn the rotor arm,it should turn a few deg,s in one direction then come back under the force
of the return springs
who cares who wins
pass the pork pies
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