The Baron
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| posted on 13/6/06 at 07:59 PM |
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Twin Webber 40 DCOE's & Vacuum Advance?
I have a standard 1600 pinto in my seven; I have bolted on a pair of Webber 40 DCOE's.
The manifold I have has no vacuum advance take off.
Obviously on the original manifold, the vacuum draw was the result of 4 cylinders sucking, if I were to dill my manifold I would only have 1/4 of this
original draw.
So my question is..........
Do you have to have vacuum advance?
Would 1 cylinder provide enough draw?
Do I have to alter my timing to compensate?
Any advice is welcomed.
Cheers in advance.
The Baron
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andyharding
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| posted on 13/6/06 at 08:37 PM |
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No you don't need vacuum advance. With 12deg static and the standard dizzy your motor will run fine but not make as much power as it could. This
is how mine is at the mo while I'm building a new dizzy.
One manifold runner would suck enough but the only advantage would be 10-15% economy. No performance.
The best solutions is a non-vacuum modified dizzy that gives 38deg total advance at 3500rpm. I'm just building one for my motor.
Are you a Mac user or a retard?
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Nighthawk
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| posted on 13/6/06 at 08:40 PM |
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It is not good practice to take a vac from a single cylindr as it will pulse giving erratic timing particularly at tick over. There are some vac
advance less dizzies out there check Ford performance dealers, they are likely to have a different mechanical advance curve to compensate. If you want
to try yours without vac advance you may well have to increase idle speed a bit to get a steady tick over and maybe advance the timing a bit, remember
though that the best advance is found from getting a bit of pinking on full throttle with the engine working ( try high gear up a hill ) then backing
of just enough to lose the pinking.Once you are set at that deal with idling issues at the carb as far as you can.
Just to check you aren't using the Pinto dizzy that has a vac connection to the electronics box are you? If so you need to change to a
mechanical points type or the electronic version that does not have the vac to the electronics.
Good luck!
NIGHTHAWK
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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rusty nuts
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| posted on 13/6/06 at 08:42 PM |
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Suspect some would say Magajolt might be the best solution.
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jacko
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| posted on 13/6/06 at 08:47 PM |
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Hi i have a dizzy from Hand H ignition solutions on my bike carbed engine and it work very well it is modifided to the spec of my engine give them a
ring
no 1384 261500
Jacko
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DIY Si
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| posted on 13/6/06 at 08:57 PM |
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Or if you really want to keep the original manifold, take a feed from each inlet runner, plumb them into a common small vessel, and plumb that into
the dizzy.
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mookaloid
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| posted on 13/6/06 at 09:15 PM |
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quote:
Originally posted by DIY Si
Or if you really want to keep the original manifold, take a feed from each inlet runner, plumb them into a common small vessel, and plumb that into
the dizzy.
doesn't work sorry
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DIY Si
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| posted on 13/6/06 at 09:18 PM |
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Does this mean you've tried it and it didn't work, or that there's some reason it doesn't work in general?
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andyharding
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| posted on 13/6/06 at 09:22 PM |
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Taking a vacuum from one runner won't work well with electronic systems with a MAP sensor but works OK on the Pinto dizzy as the advance
mechanism has to move a huge chunk of metal so it can't react quick enough to pick up the inlet pulses and cause huge fluctuations.
Are you a Mac user or a retard?
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mookaloid
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| posted on 13/6/06 at 09:27 PM |
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Well I can't see any good reason for it to work, mainly because when one cylinder is sucking another cylinder in the bank of four won't be
so the vacuum effect will be lost at that moment, by the time the next cylinder is sucking there will be another cylinder that isn't and so on.
basically the air will take the path of least resistance to equalise the pressure, and it is not likely to want to pull against a vaccuum operated
diaphram?sp when it can get air from a cylinder that isn't sucking.
its like if you want to lift a ping pong ball by sucking on a drinking straw you can .... but not if there is a hole in the side of the straw.
I had this discussion with Jacko (above), I suggested he try it but measure the vacuum obtained with a vacuum guage. He was able to confirm that there
was no vacuum obtained using this method.
HTH
Mark
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mookaloid
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| posted on 13/6/06 at 09:31 PM |
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quote:
Originally posted by andyharding
Taking a vacuum from one runner won't work well with electronic systems with a MAP sensor but works OK on the Pinto dizzy as the advance
mechanism has to move a huge chunk of metal so it can't react quick enough to pick up the inlet pulses and cause huge fluctuations.
Sorry Andy but I have to disagree with this
I initially connected a vacuum dizzy to one runner on the pinto inlet manifold. The dizzy sounded like it had a little guy with a jack hammer inside
it. the pulses of vacuum were hammering the vacuum advance constantly.
It sounded terrible and certainly wasn't working as it should.
Cheers
Mark
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DIY Si
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| posted on 13/6/06 at 09:36 PM |
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Fair enough. Thinking about it more, it probably won't work. Best just get a vac less dzzy then, eh?
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mookaloid
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| posted on 13/6/06 at 09:48 PM |
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Yep non vac dizzy or megajolt.
Aldon are another supplier of these.
Cheers
Mark
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MikeRJ
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| posted on 13/6/06 at 09:54 PM |
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quote:
Originally posted by mookaloid
Well I can't see any good reason for it to work,
Better tell that to Suzuki, Kawasaki etc, as that is how they have MAP sensors plumbed into throttle bodies...
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andyharding
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| posted on 13/6/06 at 10:01 PM |
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quote:
Originally posted by mookaloid
quote:
Originally posted by andyharding
Taking a vacuum from one runner won't work well with electronic systems with a MAP sensor but works OK on the Pinto dizzy as the advance
mechanism has to move a huge chunk of metal so it can't react quick enough to pick up the inlet pulses and cause huge fluctuations.
Sorry Andy but I have to disagree with this
I initially connected a vacuum dizzy to one runner on the pinto inlet manifold. The dizzy sounded like it had a little guy with a jack hammer inside
it. the pulses of vacuum were hammering the vacuum advance constantly.
It sounded terrible and certainly wasn't working as it should.
Cheers
Mark
I guess it depends on the cam. I tried it with the standard cam which is very cool. I have a Piper 285 in my new engine and that is hot enough to spit
a nice mist of fuel out so it would probably play havoc with the dizzy.
Are you a Mac user or a retard?
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mookaloid
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| posted on 13/6/06 at 10:02 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by mookaloid
Well I can't see any good reason for it to work,
Better tell that to Suzuki, Kawasaki etc, as that is how they have MAP sensors plumbed into throttle bodies...
Well I was only talking about vacuum advance mechanisms on Pintos. maybe MAP sensors are designed to cope with this and are more sensitive .....I
dunno
Cheers
Mark
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mookaloid
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| posted on 13/6/06 at 10:06 PM |
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quote:
Originally posted by andyharding
quote:
Originally posted by mookaloid
quote:
Originally posted by andyharding
Taking a vacuum from one runner won't work well with electronic systems with a MAP sensor but works OK on the Pinto dizzy as the advance
mechanism has to move a huge chunk of metal so it can't react quick enough to pick up the inlet pulses and cause huge fluctuations.
Sorry Andy but I have to disagree with this
I initially connected a vacuum dizzy to one runner on the pinto inlet manifold. The dizzy sounded like it had a little guy with a jack hammer inside
it. the pulses of vacuum were hammering the vacuum advance constantly.
It sounded terrible and certainly wasn't working as it should.
Cheers
Mark
I guess it depends on the cam. I tried it with the standard cam which is very cool. I have a Piper 285 in my new engine and that is hot enough to spit
a nice mist of fuel out so it would probably play havoc with the dizzy.
i guess that's possible
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MkIndy7
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| posted on 13/6/06 at 11:33 PM |
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Well here's our Experiences.
With the Twin 40's on 1 Vacume take off they appeared to make little advantage over the standard carb other than drink fuel!
With 4 takeoffs reduced in Y pieces 4-2-1 (rather than into a common chamber) then fed into the Sierra ECU Advance type Dizzy it did make an
improvement.
With the above 4-2-1 setup and Megajolt it did make an acceptable measurable vaccume, although over a reduced range probably 40Kpa compared to the
80Kpa range of the original Sierra setup. But this is still mapable on an electronic system and maybe why the Bikes can use this method.
This made the car so much more driveable it was unbelievable, exactly what were were looking for with the 40's (they were just too damned
thirsty! and we'd decided on TB's by then)
On the Sierra I would deduce that maybe with the 4 Vacume takeoffs and the reduced range that it would maybe manage to make 1/2 the advance with the
Vacume Dizy/ECU setup, or maybe the full advance but at higher revs,(maybe 4500 rather than the standard 3500?)
Well there's my 2pence worth
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jollygreengiant
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| posted on 14/6/06 at 03:50 AM |
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quote:
Originally posted by MkIndy7
Well here's our Experiences.
With the Twin 40's on 1 Vacume take off they appeared to make little advantage over the standard carb other than drink fuel!
With 4 takeoffs reduced in Y pieces 4-2-1 (rather than into a common chamber) then fed into the Sierra ECU Advance type Dizzy it did make an
improvement.
With the above 4-2-1 setup and Megajolt it did make an acceptable measurable vaccume, although over a reduced range probably 40Kpa compared to the
80Kpa range of the original Sierra setup. But this is still mapable on an electronic system and maybe why the Bikes can use this method.
This made the car so much more driveable it was unbelievable, exactly what were were looking for with the 40's (they were just too damned
thirsty! and we'd decided on TB's by then)
On the Sierra I would deduce that maybe with the 4 Vacume takeoffs and the reduced range that it would maybe manage to make 1/2 the advance with the
Vacume Dizy/ECU setup, or maybe the full advance but at higher revs,(maybe 4500 rather than the standard 3500?)
Well there's my 2pence worth
Works even better if you put a one-way valve in three of the individual vaccuum lines.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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02GF74
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| posted on 14/6/06 at 08:32 AM |
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quote:
Originally posted by mookaloid
Well I can't see any good reason for it to work, mainly because when one cylinder is sucking another cylinder in the bank of four won't be
so the vacuum effect will be lost at that moment, by the time the next cylinder is sucking there will be another cylinder that isn't and so on.
basically the air will take the path of least resistance to equalise the pressure, and it is not likely to want to pull against a vaccuum operated
diaphram?sp when it can get air from a cylinder that isn't sucking.
I follow the reasoning but am confused.
So how come the advance works for a standard manifold? The sort that have 1 carb with all 4 inlets connected together?
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mookaloid
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| posted on 14/6/06 at 10:12 AM |
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errr it could be because it is one large chamber through which air is pulled through a small hole (carb) causing a low pressure vacuum chamber inside
the manifold which air is always trying to get into. this vacuum is enough to power a brake servo.
If there is no chamber in the manifold as with bike carbs or 45 's etc then this effect is not there.
I guess
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