|Topic Review (Newest First)|
|Today 05:53 PM|
By the way, the factory 102 engine manual gives a fairly clear picture and description of where the PHH carbs get their vacuum to activate the secondary diaphragms. It’s vía a small tube from the diaphragm capsule over to the primary barrel where the increasing air velocity of an accelerating engine creates enough vacuum to open the secondaries.
I’m convinced that displaced FB port tubes were a bandaid to solve problems caused by the crude emulsion tubes of the day.
Note that your picture is of a 1900 engine described as being from 1952, and using early generation DCO carbs. There is a fellow, Keith Franck, who has spent about ten years deconstructing the emulsion tube theories, and starting over with new concepts. He’s solving the off-idle transition zone slump via internal jet and tube changes. He’s not perfected things yet, but is enough better to declare Alfa’s and Weber’s early struggles as a result of insufficient research rather than the airflow/vacuum conjectures you propose.
Meanwhile, trying to make even a de-siamesed Solex manifold work is about as sound as asking a horse to win a race with two legs tied together.
|Today 05:38 PM|
"Esse ad posse valet illatio"
You are claiming "When something does exist, one can validly argue it possibly does exist." Well, dear friend Don, I will go to the trouble of modifying my intake manifold with the Sportiva type tubes and let you try it. I hope to be at Monterey next August with all three two liters. I am finally retiring as a lawyer at the end of this year after fifty five years. Will finally have time to fiddle or piddle on my cars as I see fit. Jay
|Today 04:18 PM|
I love ya’, but you got so much wrong in your summary I’m going to have to come up there, buy you dinner and some good drinks just to walk you through the concepts.
Meanwhile, my two 102s are working great with Webers, and float vents opening right next to the carb bores.
What is your Latin saying that translates as “that which has been done, can be done”?
|Today 03:05 PM|
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).
|Today 02:41 PM|
|DPeterson3||I'm waaaaaaay overdue for a visit to Provence. I've heard they have good taste in food, wine, and cars over there.|
|Today 02:01 PM|
|Today 01:47 PM|
Today, I work hard with the Sadler in order to finalise the car :
I will provide you more pictures about the tonneau cover that I love so much.
The car is now back at home (...). Tomorrow I'll work on the door panels and, if I have time, on Weber.
|08-09-2019 07:44 AM|
This afternoon I received photos of the laying of the cover Tonneau.
|08-09-2019 05:40 AM|
Originally Posted by PS70 View Post
|08-09-2019 03:56 AM|
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.
The tonneau cover is in progress.
For my part, I take care of the door panels and soft top compartments.
|07-14-2019 04:37 AM|
First seat nearly finalized, second ongoing :
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 ...
|07-07-2019 02:40 AM|
Originally Posted by PS70 View Post
|07-07-2019 12:19 AM|
Originally Posted by DPeterson3 View Post
How was Bogota ?
|07-06-2019 04:07 PM|
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.
|07-06-2019 03:44 PM|
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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