[GoinManta]

Could someone answer these? It would be a huge help to everyone.

Emulsion tubes

1A) - Emulsions tubes do what?

1B) - If you only change from F50 to F66 or vice verse what happens?

1C) - What is affected as far as the other jets go?

Main (Fuel) & Air Jets

2A) - I assume increasing main jet size increases fuel to barrels - Thus richer

2B) - I assume reducing main jets limits fuel - Thus leaner

2C) - I assume reverse is true for air jets

2D) - If running lean is it better to increase main jets or reduce air jets?

2E) - If running rich is it better to put smaller main jets in or larger air jets?

2F) - How can you tell if you have to go with air or main jets when your dialing in the carb?

2G) - I assume that if the carb is running rich or lean you dial these jets in and not the idle jets.

Idle Jets

3A) I assume primary purpose is idle

3B) Where do you start with these? Is it best to start with a set of 50s and get the air and main jets dialed in and then deal with them.

3C) What symptoms would one see from improperly sized idle jets? But you have the main and air jets right...

Walk-through..

4A) Could you walk us through the decision making process in which set of jets you start adjusting and when you go to the other parts.

4B) How can you tell if the Primary or Secondary is dialed in, but the other side isn't. I.E. the primary is perfectly set the secondary is out of whack, or vice verse.

Just fill in the following.. :

Emulsion Tubes

1A)

1B)

1C)

Main / Air Jets

2A)

2B)

2C)

2D)

2E)

2F)

2G)

Idle Jets

3A)

3B)

3C)

Walk through

4A)

4B)

Bits and pieces of these questions have been answered before, but not in a concise FAQ manner. Where someone could refer to it in a single post, hopefully with help from the Carb gurus out there we can have one.

 

[bq97]

Not a Weber expert but I have learned a lot about them since i got my GT so I'll show my ignorance. If I'm wrong please somebody correct me.

Emulsion Tubes

1A) They mix fuel and air together before the mixture is drawn thru the auxiliary venturis

1B) You change the air fuel ratio of the pre mixture, also and for lack of a better term, the density of the mixture

1C) I don't think the other jets are affected I believe the fuel/air is mixed better with the change kind of like pancake batter bigger holes in the E tubes lumpier batter smaller holes smoother batter but I could be wrong

I think the change in the E-tubes helps keep the fuel in suspension better as it flows thru the intake manifold.

Main / Air Jets

2A) Yes

2B) Yes

2C) Yes, larger air correctors = more air = leaner the reverse is true

2D) Depends on how big a change you need, main jets for coarse adjustment, airs for fine adjustment.

2E) Same as 2D

2F) Same as 2D

2G) Depends on what RPM range you need to change

Idle Jets

3A) Idle and low speed < 2500 rpm

3B) You have to start somewhere and no two engines will be the same unless they are absolutely identical and at the same place with the same fuel.

3C) Improperly sized idle jets will show up as little to no change when the idle mixture screw is turned or a screw that is too far in or too far out

Walk through

go here >>>>> http://www.carburetion.com/Weber/adjust.htm

4A) I started with the stock jets and dialed in the idle first. Then went for the proper main jetting by looking at the plugs and overall drivability on the primary side did the same for the secondary side.

4B) I could tell when the secondary opened, it stumbled badly when it did. I reduced the secondary mixture with the main and air correctors to get a seamless transition.

Like I said not and expert but this is what I understand from rejetting my Webers.

hth
Brian

 

[GoinManta]

Excellent... anyone else want to make corrections? OR enlighten us a bit on the Emulsion tubes? When would it be best to run F50 over F66, etc.. this one I am really curious about becuase the DFAV had F66s and so does the Double Pump, but the std Weber 32/36 seems to have 50s..

 

[RallyBob]

When would it be best to run F50 over F66, etc..

Trial and error mostly....there is little to no documentation on emulsion tubes. The numbers mean nothing relative to each other. I arrived at the 38DGAS emulsion tube changeover via testing, took about 6 different combos and a lot of stop and go driving.

Basically the tubes need to match the characteristics of the engine. That's why the stock 38 DGAS tubes don't work well on the Opel, the carb was originally fitted to a 2.8 litre V6. More cylinders, more displacement, different airflow characteristics. So the induction pulses will tend to be stronger and closer together. The Opel has a weak induction pulse by virtue of a short stroke design and low compression, so changing the emulsion tubes here strengthens the air/fuel emulsification helping to make up for an otherwise weak mixture signal.

Bob

 

[GoinManta]

What characteristics would you notice from yoru engine if the jets were right but the Emulsion tubes wrong?

 

[RallyBob]

What characteristics would you notice from yoru engine if the jets were right but the Emulsion tubes wrong?

As an example, no matter how you jet a 38 DGAS for an Opel there will be a stumble at low rpms (not far off idle). You can try various combinations of idle and main jets to try to cover the transition from idle circuit to main circuit, and still the stumble persists (not really a bog, just a slight stutter). But changing the emulsion tubes can enhance the transition period emulsion, eliminating the stumble.

It again has to do with the signal strength. Opels are not known to have strong vacuum, and a low compression ratio or 'hot' cam can worsen this aspect. There's not enough 'pull' at that low rpm (out of the engine's efficiency range) to create a strong atomized mixture (ever notice at idle speeds you'll see a constant drip, drip from the auxiliary venturi rather than an atomized mist?

Ironically the bigger the engine, the less of a problem this is. Higher compression really helps too. My old 11:1 compression 2.0 litre Ascona engine not only pulled crisply from 1500 rpms with a 242 degree duration cam, it had bored out venturis (from 27 to 31 mm) and a 3/4" spacer under the 38 DGAS! But it had enough 'pull' to use the bigger modified carburetor and the spacer plate. I tried the same spacer plate and carb on a nearly stock 1.9 with flat-tops and it was a dog at low rpms...not enough signal strength through the carb to pull fuel cleanly and atomize it. Perhaps a change to emulsion tubes with more holes down low on the tube (emulsifies at lower speeds) would have helped the crispness of the response, but it still would not have helped with overall power...just driveability.

 

[GoinManta]

Thanks Bob, that cleared it up for me a good bit.

If no one has anything else to add I will make a Weber tuning guide from this and the link in the second response. Along with some info from the Haynes Weber guide.

Charles.

 

[tekenaar]

Change ratio: mains to airs

2D) Depends on how big a change you need, main jets for coarse adjustment, airs for fine adjustment.

Bob,
A while back, in one of your posts or e-mails to the group, you mentioned an equivalence ratio between main jet change and associated air jet change, i.e. one size main jet ~ equals "X" sizes air jet change (I think it was 3). That's a useful, "general reference" piece of information that should be included here and added to Charles' "Guide".

I tried, but couldn't find it here by "Search". Would you mind restating it here for inclusion in the "Guide"?

 

[GoinManta]

Yes, any simple "Rules of thumb", guides, bits of wisdom, etc..

Trying to make an "Idiots guide to jetting a Weber" article

For those like me..

Also any 32/36 differences, especially those that make a difference in jetting..

I plan on listing the main different versions.. to help clear that matter up too..

I.E.

In our Opels we require the use of the 32/36 DGV series, it is not recommended to use the 32/36 DFV series fitted to some Fords (Pintos, Mustang 2s, etc..

The primary difference is the Primary and Secondary locations are reversed.

DGAV versions include:

32/36 DGV - Manual Cable operated choke

32/36 DGAV - Water Choke
Best for Cold climates where a accurate choke is necessary in the winter months.

32/36 DGEV - Electrically operated choke
Best for mild and temperate climates where choke is only really required at start-up.

Other Variants:

32/36 DGEV w/ ICO
This version has an electrically operated Idle Cut Off circuit seen mainly in California approved carbs.

32/36 DGAV (18A) w/ Secondary Accelerator Pump (The Double Pump)
Rare carb with a vacuum operated secondary circuit, for improved acceleration.

>>>>

As I write the article I will post pieces here like this one to have fact checked, etc..

Charles

 

[RallyBob]

A while back, in one of your posts or e-mails to the group, you mentioned an equivalence ratio between main jet change and associated air jet change, i.e. one size main jet ~ equals "X" sizes air jet change (I think it was 3).

You got it right Otto. To make a comparable change to an air corrector jet (as a main jet), you need to change it in increments three (3) times that of a main jet. And of course, numerically it works in the opposite direction of any fuel jets, since it meters air, not fuel. Bigger number main>>>>more fuel (richer). Bigger number air corrector>>>>more air (leaner).

Worth noting is the main jet feed the engine throughout every part of the rpm band (the idle jet is a branch or capillary from the main jet to fine tune the low rpms). The air corrector primarily affects the mid-upper rpm range, not so much the lower-middle range.

Example: You have a 140 main jet and a 180 air corrector. It is too rich at most speeds. You try reducing the main to 135. It runs better throughout, but it now lean at higher rpms. So you reduce the air corrector to 170, which would be equivalent to 2/3 of a main jet size increase, but affecting primarily the middle/upper rpms range.

Hope this lends some light rather than confuses. Sometimes the best way to learn this stuff is to just play with the carb and make big changes (one at a time) and just observe what happens. It really helps with the understanding.

Bob

 

[GoinManta]

It definitely adds light and is exactly what I was trying to pull out of you and others with this thread

Any more insights like that would be great .. !

Not to mention any additions you have to the Carb list above.

Charles

 

[tekenaar]

Yes, any simple "Rules of thumb", guides, bits of wisdom, etc..

. . .

DGAV versions include:

32/36 DGV - Manual Cable operated choke

32/36 DGAV - Water Choke
Best for Cold climates where a accurate choke is necessary in the winter months.

32/36 DGEV - Electrically operated choke
Best for mild and temperate climates where choke is only really required at start-up.

Other Variants:

32/36 DGEV w/ ICO
This version has an electrically operated Idle Cut Off circuit seen mainly in California approved carbs.
32/36 DGAV (18A) w/ Secondary Accelerator Pump (The Double Pump)
Rare carb with a vacuum operated secondary circuit, for improved acceleration.

>>>>

As I write the article I will post pieces here like this one to have fact checked, etc..

Charles

DGAV is only water choke version, Charles, "type" is DGxV, where "x" is used to indicate choke type used.

DGAV vs. DGEV choke "season" usage comparisons: Seasonal temperature ranges have nothing to do with choke operation as long as chokes are properly adjusted for the season. Reluctance to adjust choke seasonally is the real culprit here . . . YES, that means separate "Winter" and "Summer" adjustment for optimal operation of both types in any climate. Most older repair manuals that deal with carbed engines specifically state this in their tuning sections.

32/36 DGEV w/ ICO
This version has an electrically operated Idle Cut Off circuit seen mainly in California approved carbs. These carbs must also have float bowl vents vented to a "charcoal" evaporation canister for complete compliance with CARB rules.

 

[GoinManta]

DGAV is only water choke version, Charles, "type" is DGxV, where "x" is used to indicate choke type used.

DGAV vs. DGEV choke "season" usage comparisons: Seasonal temperature ranges have nothing to do with choke operation as long as chokes are properly adjusted for the season. Reluctance to adjust choke seasonally is the real culprit here . . . YES, that means separate "Winter" and "Summer" adjustment for optimal operation of both types in any climate. Most older repair manuals that deal with carbed engines specifically state this in their tuning sections.

32/36 DGEV w/ ICO
This version has an electrically operated Idle Cut Off circuit seen mainly in California approved carbs. These carbs must also have float bowl vents vented to a "charcoal" evaporation canister for complete compliance with CARB rules.

I appreciate that.. didn't know about the bowl.. anyone got a picture of this carb? All the others I should have.

As for the double pump, I know you could convert to a E series easy enough. But from all the research I have done on it, it only came in the A variant. As a 32/36 DGAV 18A or 32/36 DGAV 19A.

Similar to the DGEV w/ ICO. I would assume since its a CA carb, and came on the scene later, it can be converted to a A model, but more than likely all were E versions stock.

This matters because novices will compare the model name stamped on the base to this article.

With the A vs E comments. In the case of the E, it doesn't sense engine temperature, in severely cold climates I have heard (since I live in a temperate one and noticed little difference) that the fact the A senses engine temp makes it more friendly in harsh winter conditions.

So I would think that one adjustment is fine for the A no matter the temperatures since it sense engine temperature. It shouldn't need a summer and winter adjustment, Where I can see the need for that on the E which is only time released.

But obviously a comment or two about what the A and E really mean (Water versus Electric) would be good. I probably should also show how they hook up and the fact you can swap the A and E setups on a carb, if you have a preference.

Charles

 

[GoinManta]

Transferring some comments from other posts:

I already have on most counts....just gotta look over three year's worth of posts. It would take a considerable amount of time to re-write all that info on one post. I suspect a few thousand words at least.

Thats why I am doing this So its not on a hundred different posts.

I'll answer your last two questions though.
Always get the main jet correct first. It feeds everything else in the system. If you get the idle jet perfect, and the air corrector perfect, and then change the main jet, you'll have to start tuning all over again since everything feeds from the main the jet. In other words, build the foundation before you put up the first floor!

Get the primary barrel dialed in first. It does all your idling, and all your normal driving duties. The secondary is for power only. Often if I am short on time I'll dial in the primary side, and will 'get to' the secondary tuning later on....often weeks later. Also, if you concentrate on the primary side, then when you get around to the secondary you won't have to worry about the effect the primary side has on the secondary when you're at full throttle.

Bob

Thanks to Travis for pulling this gem out of the mailign list archives:

Here's one of Bob's better posts on carb tuning from 03/01 on the classicopels list

-Travis

-------------
>I need some advice. I had a standard 32/36 Weber on my car running great,
>>smooth idle, smooth take off, running clean, plugs looked great. BUT... I
>>have a "double pumper" 32/36 that I just installed on the car. It
>>has accel. pumps on both barrels
>>instead of just on the primary like the standard Webers. With this carb,
>>the car will tear up the brand new 195-60-14 tires. The difference in
>>power is amazing.



*****Same throttle bores, same venturis. There should be no difference in
power unless one is badly jetted. The throttle response however, is notably
better with the double pumper (IF correctly calibrated, otherwise it may be
worse)


>>The only problem is the car has a bad stumble when you first mash the
>>pedal, the engine stumbles then the revs scream and the car takes off. >>I know it is running
>>way rich, when I rev the car in nuetral it stumbles and emits a puff of
>>black smoke, and the plugs are a bit sooty.


*****The secondary accelerator pump is actuated only when vacuum drops in
the secondary venturi, so at that point more fuel is squirted into the carb.
After confirming the main jets and air correctors are the same as the
regular 32/36, try installing a smaller secondary idle jet, this is what can
cause the stumble you spoke of. Normally, the secondary idle jet does ALL
the fueling when the secondary throttle plate initially opens, but with the
extra pump shot, it will likely be too large.

>>The mixture screw seems to
>>have little effect on the idle quality other than the fact that when it is
>>all of the way in, the idle speeds up a bit.


*****Bingo. If it gets smoother when you screw it in (leaner), then the
primary idle jet or main jet is too big. Remember, the main jet feeds
EVERYTHING. The idle jet is a fine-tune of the main jet for the low rpm
circuit (between idle and 1500 rpm's or so), and the idle mixture screw is a
fine-tune of the idle jet (affects idle and just off-idle only). Changing
the main jet means re-adjusting everything! (i.e., new idle jets and idle
mixture)

>>The idle mixture screw on
>>the carb I had on it before was extremely sensitive. I dont think I have
>>any vacuum leaks, I cant hear the usual hissing indicative of a leak.
>>
>>My question is: does anyone have any tuning advice for this carb? I have
>>a few extra idle jets around that I could swap in. I was running a 45 pri
>>and 55 sec and the car really screams, but it stumbles on throttle tip
>>in (these are the same as I was running on the other carb that ran great).
>>Could it be that the mixture is too rich everywhere? Why does the idle
>>mixture screw seem to have little effect?


*****Check the main jets! Even if the idle jets are the SAME, if the mains
are bigger on one carb, that carb will run richer even in the idle range.
The idle mixture screw is a FINE adjustment. If everything else is out of
whack, it will do virtually nothing.
Wanna know how I baseline my main jet settings? Gotta tune it barrel by
barrel. I'll set the idle speed screw for about 3500 rpm's, and walk away
from the car for 5 minutes. If it's seriously lean, and you're worried abot
doing damage, don't worry, there's no loading on the engine, and a very lean
engine will "pop" and sputter significantly enough to warn you. After the 5
minutes are up, I'll shut the engine off clean. Don't drop the rpm's! Now
check #2 spark plug. Why #2? It runs the leanest, at least on a 1.9 head.
If I'm happy with the color of the plug (light brown to tan porcelain),
then I'll "rough-out" the tuning of barrel #2. Bring the idle speed back to
normal, in fact, close the primary throttle plate down to nothing. The car
won't idle, but while you're dropping the idle speed down via the idle speed
screw, start to open the secondary throttle plate by hand. Back off the idle
speed screw completely so the primary throttle plate is out of the picture.
Now, keep in mind you won't have very good throttle "tip-in" on the
secondary side unless you have a double pumper, but that's not what we're
after right now. Open the secondary throttle plate up enough to maintain the
same 3500 rpm "idle" speed, and retain the linkage so the rpm's hold. A
screwdriver inserted into the linkage should work, or needle-nose vise
grips. Wait 5 minutes until the plug gets colored up, and shut the engine
off clean. This time, I strive for the same color plug as the primary, but I
will immediately go up 2 main jet sizes on the secondary side to get more
fuel for better power. Remember, the primary side is your economy and
cruising barrel, the secondary is for power. Now, time to check idle jets.
Bring everything back to "normal", set the idle speed and turn the idle
mixture screw for smoothest idle, or about 1/4 turn out from the point the
rpm's start to drop. Hit the throttle and feel for the bog. Sputters, pops,
bogs or backfires? Probably a lean miss, you'll need to increase the idle
jet, reset the base idle, and readjust the idle mixture screw. Keep testing
until it's crisp. Black smoke or a SLOW bog on tip-in? Probably rich. Rejet!
Next I try cracking the secondary throttle plate on its own, without
the primary. Yes, it will bog a lot. But keep messing with the secondary
idle jet until a slow tip-in is smooth. Now try to crack the primary and
secondary together, and see if it's boggy or crisp. If you got the secondary
idle jet right, it'll rip! Lastly, there's the air correctors.
Realistically, you can only tune them by taking it out and romping on it,
then checking plugs again. As a baseline though, expect the air correctors
to be about "30" to "45" higher. By this I mean, if you have a 140 main jet,
you'll probably need somewhere between a 170 to 185 air corrector. The
exception is with a hot cam, it'll need about "20" to "30" higher, this will
allow less air to emulsify at higher rpms, making the mixture richer at
those rpms. This is VERY basic, and I always fine-tune on the road or track,
but you can get yourself 90% of the way there in your driveway this way.

Bob Legere

 

[RallyBob]

But obviously a comment or two about what the E and A really mean (Electric versus Water) would be good.

E - elettrico (electric)
A - agua (water)

 

[GoinManta]

E - elettrico (electric)
A - agua (water)
--------------------------------------------------------------------------------
Last edited by tekenaar : 18 Hours Ago at 07:57 PM.

???? Bob and Otto one in the same ?

Come to think of it.... I am not sure i have ever seen them at the same show at the same time...

 

[azopelnut]

Both Professors (Bob and Otto) were in attendance at the 2003 OMC picnic.
2004 neither were in attendance. It would be great to see them both again.

 

[baz]

its little known but otto is a moderator too , i had to remind him once as he had forgotten

 

[tekenaar]

editing

???? Bob and Otto one and the same ?

Come to think of it.... I am not sure I have ever seen them at the same show at the same time...

You noticed that I only edited the quoted part of the post, right?

 

[bear]

"Both Professors (Bob and Otto) were in attendance at the 2003 OMC picnic.
2004 neither were in attendance. It would be great to see them both again."

Not only that Paul, but our one-time "Über Moderator" Keith and his family were there then too, and you're right it would be great to see them again.