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post #961 of 1034 (permalink) Old 07-06-2019, 09:01 AM
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Originally Posted by PS70 View Post
the diameters of the tubes are quite big (that is not a good news because the solution I image is bases on a pair of 8 or 9 mm diameter tube.
Since there is virtually no air flow to the float bowl (except for compensating for the variation in fuel volume in the float chamber) we're talking mostly about pressure variation, not air flow. I would guess the diameter of the tubes probably has to do with acoustic resonance frequency -- similar to a pipe organ -- but the length of the tube probably affects resonance frequency more than its diameter. Matters get more complicated when taking into consideration that we have to constrained volumes (the float bowl and the air intake plenum) connected by a pipe, and we could go on waxing about Venturi and Bernoulli effects.

One way or the other, I think theory and conjecture will not solve this problem -- only observation of experiments will (the diagonally cut pipe is probably no accident, either). So, go and try the tubes you have in mind and see if the results are acceptable.

-Ruedi
[SIZE="1"]'63 2600 Touring Spider (AR 191437, the car that started the 2000/2600 International Register, reassembly in progress)
ex-'65 2600 SZ (AR 856043, the car in my avatar, sold as resto project to Austria)
Maintainer of a private 2600 SZ register (not the one in the Netherlands).[/SIZE]

Last edited by tubut; 07-06-2019 at 09:05 AM.
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post #962 of 1034 (permalink) Old 07-06-2019, 10:35 AM Thread Starter
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So, go and try the tubes you have in mind and see if the results are acceptable.
I'll do so. One month may be.
The saddler is doing a very good job, that help me to wait.
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post #963 of 1034 (permalink) Old 07-06-2019, 03:25 PM
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The FBV does flow air, not just compensate for pressure. The upper end of the emulsion tube carries an "air corrector" jet that accepts the air that is used to emulsify the fuel. Not a lot of air compared to the main flow into the engine, but some.

Keith Franck and a few others are spending a lot of dyno time, and using AFR meters while driving around to perfect their concepts. As I understand them (and I may not) there are two main goals: remove all dips and peaks in the mixture as the RPM/throttle changes trigger transitions from one circuit to the next, AND to eliminate the need for a small primary Venturi to amplify the signal to the secondary Venturi.

It might jar everyone loose from "that's the way Alfa always did it" to tell you that Keith has abandoned the concept of emulsifying the fuel. This is a fundamental change from Weber's core concept.

In spite of it being such a major change, installing his VF tube using my existing main and air correction jets improved the mid range immediately, with no other change to the jetting. Keith has told me he sent his VF5 tube, which he was sure would be too rich. From here, I'll stick an Innovate AFR sensor up the exhaust and start swapping VF tubes until my mid range mixture flattens out. Once I've gotten the driving AFR looking good I'll go back to the dyno.

Keith's extensive sampling of Weber equipped cars is that the transition from the idle circuit to main goes tragically rich, causing the common big slump in that range. Note that he has quite sophisticated and adjustable idle jets to participate in seeking perfection.

A common cause of retrofitted Weber applications falling over is due to using large venturis. This is apparently caused by creating an insufficient boost in the signal to the secondary Venturi. I'm trying to imagine what my 2300 is going to produce if I can switch from my 35mm venturis to 40s with no loss of low RPM torque.

Don P
Carson City, NV

Past Alfas...
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas

Current Alfas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Oops. Add to the "present" list, 10204 01488, 2000 Touring Roadster project

And past...
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)

And present...
64 Mooney M20E ("Rambo". My faithful steed for over 40 years) Over 55 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird


You can snap roll an Alfa only one time...
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post #964 of 1034 (permalink) Old 07-06-2019, 03:44 PM
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As for Sprint falling over.....

At this point, I suspect that Alfa used their odd, dislocated FBV tubes to cause the mixture to lean when the throttle was fairly open, but the revs were in the transition zone. This was probably needed because Weber never really perfected either their carbs or emulsion tubes. The DCOMs that I previously had installed did a much better job than my current early 45DCOE9s.

So, Weber continued to chase a flatter transition curve until carbs were no longer a profitable product. All of the Alfa installations I've seen used DCOE carbs, not DCOM.

So, I don't believe the remote FBVs were because of localized pressure perturbations, I think they were seeking a higher pressure source to compensate for emulsion tube/progression hole inadequacies.

My Sprint fell over because my simple change to ram tubes from plenum took away the "fix" Alfa used to partially weaken the mixture during transition.
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Don P
Carson City, NV

Past Alfas...
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas

Current Alfas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Oops. Add to the "present" list, 10204 01488, 2000 Touring Roadster project

And past...
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)

And present...
64 Mooney M20E ("Rambo". My faithful steed for over 40 years) Over 55 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird


You can snap roll an Alfa only one time...
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post #965 of 1034 (permalink) Old 07-06-2019, 04:07 PM
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Sorry for long notes. I'm
Sitting on the floor of the Bogota airport with nothing better to do until the check-in desk opens in two hours.

Don P
Carson City, NV

Past Alfas...
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas

Current Alfas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Oops. Add to the "present" list, 10204 01488, 2000 Touring Roadster project

And past...
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)

And present...
64 Mooney M20E ("Rambo". My faithful steed for over 40 years) Over 55 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird


You can snap roll an Alfa only one time...
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post #966 of 1034 (permalink) Old 07-07-2019, 12:19 AM Thread Starter
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Quote:
Originally Posted by DPeterson3 View Post
From here, I'll stick an Innovate AFR sensor up the exhaust and start swapping VF tubes until my mid range mixture flattens out. Once I've gotten the driving AFR looking good I'll go back to the dyno.
It is exactly what I plan to do.

How was Bogota ?
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post #967 of 1034 (permalink) Old 07-07-2019, 02:40 AM
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It is exactly what I plan to do.

How was Bogota ?
A gentleman should not comment upon such matters.....

Don P
Carson City, NV

Past Alfas...
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas

Current Alfas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Oops. Add to the "present" list, 10204 01488, 2000 Touring Roadster project

And past...
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)

And present...
64 Mooney M20E ("Rambo". My faithful steed for over 40 years) Over 55 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird


You can snap roll an Alfa only one time...
DPeterson3 is offline  
post #968 of 1034 (permalink) Old 07-14-2019, 04:37 AM Thread Starter
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First seat nearly finalized, second ongoing :

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Quality is still at the level I expect.
Confort seams to be very good :
The springs of the seat have been reinforced.
On the back, lateral reinforcements stop at the deltoids and seem to block the back well in roll.
We'll see when driving ...

Last edited by PS70; 07-14-2019 at 05:06 AM.
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post #969 of 1034 (permalink) Old 08-09-2019, 03:56 AM Thread Starter
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Hello !

The saddler had moved on something else and nothing was moving on my car.
Two days ago, I raised my voice.
Things are moving forward again.

The soft top cover is finished.

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The tonneau cover is in progress.

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For my part, I take care of the door panels and soft top compartments.
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post #970 of 1034 (permalink) Old 08-09-2019, 05:40 AM
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Hello !

The saddler had moved on something else and nothing was moving on my car.
Two days ago, I raised my voice.
Things are moving forward again.
The 'squeaky wheel gets the grease'. Very nice work too!

Mark
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post #971 of 1034 (permalink) Old 08-09-2019, 07:44 AM Thread Starter
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Funny expression!

This afternoon I received photos of the laying of the cover Tonneau.

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post #972 of 1034 (permalink) Old 08-23-2019, 01:47 PM Thread Starter
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Today, I work hard with the Sadler in order to finalise the car :

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I will provide you more pictures about the tonneau cover that I love so much.

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The car is now back at home (...). Tomorrow I'll work on the door panels and, if I have time, on Weber.
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post #973 of 1034 (permalink) Old 08-23-2019, 02:01 PM
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Outstanding!
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post #974 of 1034 (permalink) Old 08-23-2019, 02:41 PM
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I'm waaaaaaay overdue for a visit to Provence. I've heard they have good taste in food, wine, and cars over there.

Don P
Carson City, NV

Past Alfas...
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas

Current Alfas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Oops. Add to the "present" list, 10204 01488, 2000 Touring Roadster project

And past...
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)

And present...
64 Mooney M20E ("Rambo". My faithful steed for over 40 years) Over 55 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird


You can snap roll an Alfa only one time...
DPeterson3 is offline  
post #975 of 1034 (permalink) Old 08-23-2019, 03:05 PM
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Bernoulli jet system

Haven't all of us had some physics enough to realize that air passing ACROSS the front of an open tube (i.e. sideways across the end of a tube) causes the atmospheric pressure inside that tube to be lowered, and the faster the air, the greater the lowering of the pressure.

So, if the weber DCOE carburetor has all three outside holes (i.e. including the one to the top of the float chamber) attached to a cold air box such as on the two liter iron block 102 two liter engine or the 2600 engine there will be a DROP in atmospheric pressure when the air starts rushing across the open hole as more air is sucked into the engine on acceleration. With less atmospheric pressure on top of the float bowl less fuel is sucked into the flow past the needle valves and there is the slight hesitation.

In the 1600 and earlier veloce engine with weber carburetors the air comes directly towards the end of the tube plumbed from both the holes over the float bowls and the air DOES NOT PASS across the end of the tube. That is why those webers work well without the extra tubing that was special for 2600 carburetors to plumb the ends of the three tubes from the carburetors to point directly into the air path being sucked into the crossover pipe.

But on the sportive engine with webers the ends of lines from the carburetors small holes from the top of the float bowl were plumbed to point directly into the air flow instead of allowing the air to pass sideways over the ends. That, in fact, gave a small bit of extra atmospheric pressure called "ram" air to provide a bit more gasoline to be sucked into the air stream coming through the intakes of the carburetor.

Go find a physics book or look at the internet to get some understanding of the rule that air passing over the open end of a tube reduces the pressure in the tube. Simple as that. Solex PHH44's need the water jacket on intake manifold, but it actually uses its vacuum piping to the cold air box pull open the secondary. But webers work on the puff of air theory, and if the puff passes first across the ends of the hole going to the float bowls that causes a momentary drop in the atmospheric pressure pushing down on the top of the fuel and there is a momentary flat spot.

The sporftiva engine had the same 1900 block that the 2000 has, but it had weber carburetors (LOOK AT THE TUBES FROM THE FLOAT HOLES PLUMBED INTO THE AIR FLOW).
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