Post Weber Jet 32/36 & 38 Sizes + Venturi Sizes for DCOE

[A20A1]

All info contained herein was gathered from this or other sites and compiled here, nothing written should be taken without some sense of scrutiny.





First off it's good to have your Filter and Fuel Flowing to Spec
- Non-Pulsing Fuel Pump
- Fuel Pressure set to 3psi to 2.5psi, May require the use of an adjuastable fuel regulator.
- Vertical Flow Air Filter (The 32/36, 34, and 38 are designed to breathe straight in, not from the sides, up and over the choke housing.)
- Low plenum intake manifolds will try to draw the A/F mixture out of the carb at an angle and creates turbulence under the carb. A 1/2" thick spacer can remedy this, but it only applies if you are mounting the carb to a modified manifold and are not using the adapter plates.

Avoid Vacuum Leaks
Mill Manifold, Adapter Plates in Sequence, & Use Thin Gaskets to Avoid Warping The Carb.
Old Carbs May leak from the throttle shafts.
Synchronous Carbs may be out of sync causing an erratic idle.
Adjustment of the Sync between the throttle plates must be done with the carb off and is difficult but not impossible.

In neutral
Carb warmed up
Choke verified to be off
Drop idle as low as possible (about 400 rpm or less if possible), Now calibrate idle jet size
The lean best idle must be set with the throttle plates seated so you are adjusting only the idle circuit without getting into the transition circuit.

Some intake manifold designs don’t pull or distribute the air fuel mix nicely in the plenum requiring a large idle jet to get good drivability. It’s possible to need a 65-75 idle jets due to this problem. Another way to check idle jet size is to very slowly increase the idle speed screw up into the transition stage and see if there are any flat spots. A flat spot will indicate a lack of fuel in the transition or bad spot in the timing curve.

WEBER TUNING LINK (http://www.racetep.com/webjettune.html)

38 DGES. If you have to open the mixture screw more than 2 turns on a 32/36 DGV or 38 DGES your idle jets are too small...If you have to shut them below 1/2 turn they are too big....Also the 38 DGES can be a little tricky because you are idling on both barrels at the same time. You have 2 mixture screws and they will not be set the same on most cars. This is because the plenum type manifold that they are on distributes fuel unevenly. By having 2 mixture screws you are delivering fuel from 2 places in the intake manifold. The Mixture screw closest to the engine will no doubt need to be in much farther than the outer mixture screw. This is Okay. I do not recommend Stagger jetting the idle circuit on a 38 DGES (In other words, do not use 2 different size idle jets even though you need to adjust the screws differently. This can cause part throttle dirveability issues.) These carbs have fixed venturis so the choke size is not an issue. The pump jets are also not a problem. Do not mess with them. If you have a flat spot or hesitation when you firts take off then it is likely that the idle circuit is too lean. If you know you have the idle circuit right then the main jet is too small....Increase the main jet size 2 steps at a time. (150 main is a 1.5mm hole...Main jets are in steps of 5. eg: 150, 155,160,etc.) Keep checking the plugs after driving it for a few minutes "...shut the car off and roll to a stop" (Do not let it idle when checking the spark plug color for the main jets!) Another good option is to install a Halmeter AF30 Air Fuel Ratio Gauge to help you with tuning. It is fast and accurate and will take alot of the guesswork out of it. This is a particularly valuable tool for cars that get track use so that you make sure you do not lean out and put a hole in a piston...





Idle jets/mix screw settings. Best overall throttle response is important; the idle jets take care of much more than just off-idle response. The main jets really only set the cruise mix, idle jets are responsible for any real acceleration up to almost 3000revs.

Any mixture screw setting over 1.5 turns out indicates the need for a larger idle jet. I've set some up with as few as .5 turns out to get the throttle response where it should be. Float settings and fuel height in the bowl also affects the mains and the Emulsion tubes and how they work in timing with the transition circuit. Too low a fuel level will result in the mains reacting slowly. Idle jets can compensate this a bit and lower fuel settings can be used for off-road applications.

Progressive carbs use the secondary idle jet to blend in the second throat, any blip or hesitation needs the jet size changed. A well tuned Weber will literally howl at high revs when the secondary opens much like the older Quadrajets. The 38DGAS makes the same sound when tuned right in the midrange, it should sound like it's gonna suck the asphalt out from under it. Lack of throttle response is not acceptable to me, I expect an expensive carb to respond and spend the time to tune it accordingly. Main jetting on a 38DGAS can be set for some surprisingly high fuel mileage since the engine only requires light throttle input to hold highway speeds. Mains that are too rich or lean will only increase throttle input and waste fuel.

The air jets in Webers act as a brake of sorts, the higher the velocity in the throat the more fuel the mains can pull. The blend of air into the main circuit becomes more important at high revs and the air jets allow this part of the range to be adjusted. The biggest reason for jetting is to allow the carb to work properly with the engine, no two are alike.






32/36
Idle Mix Screw: 1.0-1.5 turns out.
More then 1.5 turns and you need a larger idle jet.
The starting point when turning the idle mix screw out is first slowly screw the idle mix screw in till it seats inside the carb, usually it will be hard to turn, do not force it or you could damage the seat which could lead to improper fuel mixing.

32/36
Main Jet Size can be the same for both primary and secondary, the secondary however should use a smaller air correction jet to avoid lean conditions.

32/36 WEBER ( 1955cc ) *Standard Jet size that comes in kit.
PRIMARY (32) JET SIZE / SECONDARY (36) JET SIZE

- Main: 140/140
- Emulsion: F50/F6
- Air Correction: 165/160
- Idle: 60/50
- Accel: 50 ( May want 55 or 60 )


32/36 WEBER ( 1324cc )
PRIMARY (32) JET SIZE / SECONDARY (36) JET SIZE

- Main: 135 / Main: 135
- Air: 170 / Air: 160
- Idle: 65 / Idle: 55
- Accel: 50 ( May want 55 or 60 )


You may want to make a collection of jets, remember this is a progressive carb.
There are two easy ways to richen the main mixture
Air Correction Jets ( Smaller # = Richer Mixture )
Main Jets ( Larger # = Richer Mixture )
A lot of the times I see the Air Correction dropped VS increasing the mains to get a richer mixture.
In some cases the mains are the restriction and must be increased, the air correction may be left unchanged or increased.





ACCEL PUMP JETS
| 50 | 55 | 60 |

MAIN JETS ( x2 EACH )
| 140 | 145 | 150 |

IDLE JETS ( x1 or x2 EACH )
| 50 | 45 | 50 | 55 | 65 |

AIR CORRECTION JETS ( x1 or x2 EACH )
| 160 | 165 | 170 | 175 | 180 |

EMULSION TUBES
| F50 | F6 |




34 WEBER



38 WEBER

38 DGAS
Idle Mix Screw: 0.75-1.0 turns out.
Both screws should be as equally balanced as possible.
More then 1.0 turns and you need a larger idle jet.
Synchronous carbs must use the same size idle jets.

38 DGAS
Bogging problem in the upper rpm?
Try F6 emulsion tubes and slightly smaller idle jets to change the fuel curve.
The emulsion tubes will bring the main fuel curve down a bit lower and allow the engine to use it when vacuum is at a decent level.
The upper rpm will lean out just a bit, if needed smaller air correction jets can richen the mixture.

* The 38 weber came with these jets on a different car of ( 2994 cc ) ours is ( 1955 cc ).
(38) JET SIZE x2 , except for Pump Jet

- 1.45 Mains
- 1.85 Air Correction
- 0.50 Idle jet
- 0.65 Pump Jet
- F50 Emulsion Tubes

You may want to make a collection of jets, remember this is a synchronous carb.
There are two easy ways to richen the main mixture
Air Correction Jets ( Smaller # = Richer Mixture )
Main Jets ( Larger # = Richer Mixture )
A lot of the times I see the Air Correction dropped VS increasing the mains to get a richer mixture.
In some cases the mains are the restriction and must be increased, the air correction may be left unchanged or increased.


ACCEL PUMP JETS
| 60 | 65 | 70 |

MAIN JETS ( x2 EACH )
| 140 | 145 |

IDLE JETS ( x2 EACH )
| 45 | 50 | 55 |

AIR CORRECTION JETS ( x2 EACH )
| 160 | 165 | 170 | 175 | 180 | 185 |

EMULSION TUBES ( x2 EACH )
| F50 | F6 |




Try and use the template below when listing the jets and venturi's.
Note: "*" means this part cannot be modified on every carb.

Weber Carb type
--Primary Main Jet =
--Secondary Main Jet =
--Primary Air-Correction Jet =
--Secondary Air-Correction Jet =
--Primary Idle Jet =
--Secondary Idle Jet =
--Accelerator Pump Jet =
--Primary Emulsion Tube =
--Secondary Emulsion Tube =
*--Main Venturi =
--Booster/Secondary Venturi =



SINGLE CFM RATING
CARB

32/36 --- 300 cfm
38 DGAS --- 380 cfm
38 DCNF --- 400 cfm
40 DFAV --- 425 cfm


WEBER 32/36 DGV
255 CFM

WEBER 45 DCOE
400 CFM (32mm choke)
420 CFM (34mm choke)
440 CFM (36mm choke)

MIKUNI 44 PHH
309 CFM @ 12" HG (30mm choke)
393 CFM @ 18" HG (30mm choke)
422 CFM @ 20" HG (30mm choke)

*Remember that we must divide the CFM* flow rate figures by 2, for each venturi, in practicality that supplies only two cylinders.

[Mike's89AccordLX]

I think my car is fine except for the idle jet that's in the mail. My jets are on the accel jet install thread. Hey A20A1 I have a question about a problem with the car stuttering when I floor it. It happend right after I installed my custom throttle return spring bracket and when I removed the vacuum lines. It only stutters when I floor it. Like it will hesitate then take off like 2 or 3 seconds later. The bracket is made of alluminum and bends a lot but would the bracket be the problem? My car is so loud I tried listening for vac. leaks and that's a lost cause.

NEW

Primary Main Jet (1.50) just upgraded to a 1.60
Secondary Main Jet (1.60) just upgraded to a 2.00

Primary Air-correction Jet (1.80)
Primary Idle Jet (0.60)

Secondary Air-correction Jet (1.75)
Secondary Idle jet (0.55)

Accel Pump Jet (0.60)

Primary Emulsion Tube (F-50)
Secondary Emulsion Tube (F-6)

Primary Booster Venturi (3.5)
Secondary Booster Venturi (3.5)

Primary Venturi (26)
Secondary Venturi (27)

STOCK

Primary Main Jet (1.40)
Secondary Main Jet (1.40)

Primary Air-correction Jet (1.70)
Primary Idle Jet (0.60)

Secondary Air-correction Jet (1.60)
Secondary Idle jet (0.50)

Accel Pump Jet (0.50)

Primary Emulsion Tube (F-50)
Secondary Emulsion Tube (F-6)

Primary Booster Venturi (3.5)
Secondary Booster Venturi (3.5)

Primary Venturi (26)
Secondary Venturi (27)

[79EK1]

My 38DGS is on a 1.8L 1G Accord, but the jet sizes should be in the ballpark for a 3G.

1.40 Mains
0.55 Idle
1.85 Air Correction
0.70 Pump Jet
F50 Emulsion Tubes

The engine was running a little rich at idle with 0.60 idle jets, so I dropped it to the 0.55s. It leans out slightly at a steady 4000 rpm so I'll have to bump up the mains and fool around with the air correctors and emulsion tubes. The pump jet might be too large, but that's probably the last thing I'll adjust. I'll have to wait until I get my head back from the shop before I can get started again.

[ET2]

OK ALL THE INFO UP TO THIS PONT HAS BEEN MAINLY FOCUSED ON THE 32/36 DGV WEBER CARB.
I would like to see DCOE owners add there info in as well.

Thank You


Main Jet = 145
Secondary Main Jet = n/a
Air-Correction Jet =190
Secondary Air-Correction Jet =n/a
Idle Jet =45 f9
Secondary Idle Jet =n/a
Accelerator Pump Jet =50
Primary Emulsion Tube =f16
Secondary Emulsion Tube =n/a
Main Venturi =36mm
Booster/Secondary Venturi =n/a

This setup is on a A18 with dual weber 45 dcoe's, delta 272, header & 2 1/4 exhaust system, getting the idle jet's right is pita

[A20A1]

I have a had my weber carb for a couple months and have constantly been trying new jets. Right now i have a:
Primary Main Jet (145)
Primary Air-correction Jet (170)
Secondary Main (170)
Secondary Air-correction (190)
Primary Idle Jet (60)
Accel Pump Jet (55)
I have a couple questions.
- If I start to open the secondaries there is a huge bog
- If I just dump on it the car sounds like it dies then takes off
- If I ease on it is better but there is a big flat spot
- If I don't let it warm up long enough(about 10-15 min), it will die if I bring it off the high idle
thanks very much,
zeph



32/36 hat should fit the 34 weber as well.

JAM Engineering
http://www.jameng.com/products/index.phtml?section=14
Scroll down to see the pics on their site.

K&N
http://www.knfilter.com/Racing/plenum.htm

PIERCE
http://www.piercemanifolds.com/airfilters.htm

Those cold air intake adapters are great, they help in the low end, but in the upper rpm's the plenum can get in the way if it is too large.
You might consider the cheaper route and ditch the air filter plenum and get a foam filter
http://www.racetep.com/ramflolynx.html
These foam style filters are great, they have great reviews in the weber community, I've used simmilar foam style filters from eddlebrock. The 600 CFM unit is the most perfered. You might be able to find them for cheaper... I'm thinking $45.

Here is a spacer, spacers help mixture distribution.
Problem is there isn't any room to use one.
http://www.redlineweber.com/html/gaskets/99005.120.htm
It should help keep the carb cooler, this can be a good or bad thing if you run an electric choke.

- - - - - - - - - - - - - - - - - - - - - - - - - - - -
http://www.webcon.co.uk/
http://www.webercarbsdirect.com/carburetors

http://www.autoquip.co.nz/


-------------

something interesting I found on the interner.
People have been swapping out the;
Auxiliary / Booster Venturies in theie 32/36
They take a 4.0mm Aux. Venturi from the 38 weber or 4.5mm Aux. Venturi from the 40 DFAV Weber and put it in
the Primary 32 Barrel of the 32/36, or they replace both Primary and Secondary Aux. Venturies.
As you may know both Aux. Venturies in the 32/36 are 3.5mm
This extra choke strengthens the carb signal and helps the carb become more responsive. It may not work in every situation.

Slight modification to the venturi may need to be done... the venturi must be installed tight to prevent any air leaks, shims may need to be used to secure the venturi and push it toward the fuel inlet side to prevent air leaks.

The Aux. Venturi is #98
38 Weber
http://i23.photobucket.com/albums/b351/Wendy_girl/38.gif
32/36 Weber
http://i23.photobucket.com/albums/b351/Wendy_girl/32_36.gif

Interesting Chart on Main Venturi Diameter with single 2bbl carb on 4cylinder engine
The Blue line represents a single cylinder cc.
http://i23.photobucket.com/albums/b351/Wendy_girl/venturi-selection.gif

I think the graph was ment for synchronous carbs but I just stuck in the 32/36 progressive in there

http://i23.photobucket.com/albums/b351/Wendy_girl/venturi-selection2.gif

Have you seen these carbs? They are replacements for the DCOE
http://www.webcon.co.uk/
.
.
.
.

[PhydeauX]

The basics can be found here. http://members.aol.com/dvandrews/webers.htm (I have nothing to do with that site, just found it on google long ago and booked marked it). Its not an exact science, you have to play around with the jettings and find out what works.

andy

[A20A1]

THE THREE CIRCUITS

For the sake of simplicity, let's look at the Weber carburetor as having three basic circuits- the idle circuit, the accelerator pump circuit and the main circuit.

The idle circuit is comprised of two components, the idle jet and the idle jet carrier. With these two pieces, the tuner can select exactly how much fuel and how much air he wants to provide the engine at idle and during the low rpm operation, while making very fine adjustments to either, if necessary. The idle mixture is delivered as a proportioned mixture whose total volume can be further regulated with the idle mixture screw, which is located on the lower part of each carburetor barrel. On a correctly-jetted idle circuit, the mixture screw on a 48 IDA is never more than 3/4 of a turn out. This will hold true 100% of the time, no matter what anyone else tells you. If you have to go more than that, you'd better heavy-up the idle jet. Even if you get it to idle, going more than 3/4 turn tells you the jet is lean and you're going to have other drivability problems, which brings us to the next part of the idle jet's function.

The idle circuit in the Weber isn't just an idle circuit - it does more than that. It is actually the circuit which must carry the engine all the way up to about 2,800-3,000 rpm, where the transition to the main circuit take place. That means if you don't drive over 3,000 rpm, you're only running on the idle jets. After 3,000 rpm or so, the idle circuit is entirely bypassed and no longer has anything to announce. So, if you have a tuning problem that "goes away" after about 3,000 rpm, that tells you to play with the idle circuit. Or maybe the opposite is true. Either way, it's very cut and dried as far as the two circuits are concerned - so isolating the problem is a breeze.

One the most frequently experienced "gremlins" with Weber carburetors is a seemingly incurable and very annoying flat spot which rears its ugly head at about 2,200-2,800 rpm. This condition is generally caused by one of two things - you either have the wrong emulsion tube in the carburetor, which is causing a rich stumble due to an under-emulsified mixture at that particular rpm range or the idle circuit is falling off too early to carry the engine up to the point where the main circuit can take over, leaving a "lean hole". In simple terms, the idle circuit is going lean too early. Either condition is easily rectified. In the case of the emulsion tube, there are really only a few which work really well for V8 applications; and if you aren't using one of them it is certainly a big part of the problem. If the flat spot is still there even with the correct emulsion tube, then you'll need to richen up the idle circuit. This is sometimes a tricky area, because the first thing you want to do is throw in a bigger idle jet, but sometimes playing with air bleeds, mixture screws, or choke sizes can accomplish the same thing while sticking with the original jet size. Seeking a little bit of sound advice here can save a lot of time and hassle. The point here is that these carburetors are designed to come off idle and run smoothly all the way up. Your problems can be solved with a little tuning on your own or by relating the symptoms to someone who is knowledgeable enough to help you. Remember, these carburetors will do just about anything you want them to, except maybe wash your socks.

The accelerator pump circuit, just like on any carburetor, is responsible for eliminating "bog" and making a passing maneuver without a hesitation or stumble. The circuit also has two basic elements. These are the pump exhaust valve and the pump jet. The pump exhaust is nothing more than a bypass valve and this is located in the bottom of the float bowl. This is the piece that regulates how much fuel you want to make available when you need that pump shot. Putting a bigger bypass hole in the valve allows more fuel to bleed back into the float bowl instead of out of the shooters. The smaller the hole, the more fuel you're making available. You can even put in a "closed" bypass for drag racing, when you need all the juice you can get in order to get those slicks turning. Obviously, there is nothing complicated about a simple bypass system. The duration of the pump shot is varied by installing a larger or smaller pump jet (shooter). Larger pump jets give a heavy blast over a short period, while the smaller ones will give a finer, longer-duration shot. As long as you leave the bypass valve alone, you're still getting the same overall volume. In most cases, the stock pump jets can be left alone.

The main circuit is the easy one. This is where you make your power. This circuit has three primary elements you should concern yourself with - the main jet itself, the emulsion tube and the air corrector. You're thinking that's a lot of pairs - usually, it's just a main jet. You know how to "read" what your Webers can tell you on a road test, you wouldn't have it any other way. The capability for fine adjustment is what you pay for. Let's take a look at this main circuit......

The main jet is stuck into the bottom of the emulsion tube and sits in fuel. As the carburetor begins to work, the main jet meters the amount of fuel allowed to pass through it and up into the "main well" around the emulsion tube. Air enters the top of the emulsion tube through the air corrector which meters the amount of air to be mixed with the fuel. The air blows out of the emulsion tube through a series of holes along its length and aerates the fuel that is rising up the well around the tube. This emulsified mixture is then sucked out of the main delivery nozzle as the "depression" in the carburetor increases to the point where it's strong enough to pull it out. This occurs by 3,000 rpm or so, and you're down the road like a shot.

Tuning the main circuit for maximum power is something that can be done by a series of road tests and a handful of jets. The simple rule of thumb for jetting Weber carburetors is, if you want to implement a change over the entire rpm range, you play with the main jet. If you want to change the way the car feels at the high end, that's where the air corrector comes in. Also, you should keep in mind that the air corrector is a finer adjustment that the main jet. Example: One step upward in the main jet (richer) equals about the same as three steps down on the air (less air: richer). A change of air corrector would be appropriate; for instance, if the engine pulls strong to 5,000 rpm and then goes flat. This would mean she's going lean on you up top; drop the air corrector three sizes or so, and you'll probably be able to buzz that engine right up to 7,000 rpm. If the motor feels sour all the way up, go one or two sizes heavier on the mains only. No magic! So, tell me, what's so hard about jetting these Webers?

TUNING AND MAINTENANCE

A Weber carburetion system will not be right, unless it's synchronized to ensure that each carburetor is doing exactly the same as the next - the name of the game is perfect cylinder tuning. The synchronization procedure can either be a breeze or a nightmare, depending on whether you have a well-designed linkage system or not. The secret to a good linkage setup is that it must allow independent adjustment of each carburetor without affecting all the rest as you go through the procedure. Here again, if someone tells you they're absolutely impossible to synchronize, you might study his linkage. Chances are, it's incorrect and he's fighting himself. The right components are now available to take this out of the dark ages.

The final idle mixture adjustment on each barrel is a simple adjustment which is performed by ear, but because there are four carburetors, a lot of guys feel intimidated. It's done the same way you do a single four barrel, except in this case, you can listen to each cylinder separately. It may take you four times longer, but it's no more difficult at all. Each mixture screw, as it is turned, will have a noticeable effect on engine rpm, as the wrong setting will cause the cylinder to "go away" - it's just like pulling a plug wire. No matter how hard you try, you can't mess this up if you remember one thing: always start from scratch at 3/4 turn out. From there, you go 1/8 of a turn either way and it's usually in, not out. This will get you out of the woods if you ever get lost.

Once the unit is synchronized and the idle mixtures are dialed in to give you the smoothest possible idle, you can hang up your Unisyn and screwdriver til' next spring, because now it's set! And when it's set, it's set!! They will not suddenly "go out" on you and ruin your day at the picnic.

[PhydeauX]

Better solution...get the front hubs/knuckles/splines from an 85 Se-i and a pair of rebuilt 85 Se-i cv axels. That's what I did, then you get the best of both worlds...2G fitment with 3G size splines at both ends. Andy its good to see you up an active on the board...BTW the pic you have of your 85 Hatch scares me it looks just like mine with the Gen1 Teg rims on it. Give me back my car, LOL!!! :tongue:

This thread is so old I think no one had figured that one out yet. I've only got 2 of the teg rims on the car now. I burned all the rubber of the front two and haven't bothered to replace them yet. Right now its got a pair of steelies from my jetta that I was saving for winter tires. Those tires suck, its like driving on butter. I'm eventually going to save up for some drag radials.

L3G10N, did you read anything on that link I posted? It has all the formulas to figure out the base line jetting for your carbs. If you really need me to do the math for you I will.

I don't know your goals since you didn't post them, but I will assume that you want to make max HP at 7000RPM.

To do this you'd need a 40mm choke. Unfortunately you have DCOM 40 carbs so the biggets you can go is 36mm. My guess is they problaby have 32mm chokes in there now as this is what most 40s come with stock and is the optimum size for a 40mm barrel as far as generating a good idle is concerned. Any way I will assume you'll use a 36mm choke.

To get a base line main jet you take the venturi size * 4
36 * 4 = 144
They only sell jets in incriments of 5 so you'll have to settle for 145

To get the air corrector you take the main jet size + 50
145 + 50 = 195

Emulsion tubes should be either F16 or F2. Most come with F16 already. You might have F9 tubes since 40s are usually used on 1.6L engines, if so buy F2s, its not worth the cash if you already have F16 though.

The idle jet is going to be 50 or 55. The a20 likes it rich so I run 55F9 idle jets. But idle depends alot motor to motor so you have to figure it out for yourself.

For some reason my motor wants alot of fuel when I stomp the gas so I run a 55 pump jet which for a 2L motor is rather large. Something more like a 40 or 45 is normal, but as with the idle jets there is no way to tell until you drive the car.

Anyway to recap you might want to start with:

Ventrui: 36mm
Main Jets: 145
Air Jets: 195
Emulsion tubes: F16 or F2
Idle Jets: 50F9

Try the motor first befor messing with the pump jets. But if they are tiny like a 30 or 35 you might want to just get bigger ones from the get go.

This is all just a base line to get you started. You will most likely have to do more tuning once you get it running, and 40mm carbs are really to small to maximize the full potential of your motor. You really want a set of 45s.

andy

[rjudgey]

40's can have the chokes machined out larger, so although 36mm might be the largest you can buy you can have them machined to 38-40mm.
On mine i run 150-155 main jet with F16 emulsion tube with 165-170 air corrector depending on how hot or cold the weather is.
I find that bigger than 155 engine bogs down with too much fuel, too small not enough fuel, also witht he F16 tube runs best tried F2 just cannot get it right?? The air corrector seem to like it on the low side witht he engine running rich, idle jets is the same and also the pump jets although i have used 50's which work near enough as well. This setting is what i'm currently running on a ET1 head with a ET1 block bored to 2.0litre spec with Felpro Blue Head Gasket, and A20A1 Patent OEM cast pistons so compression is really low only 9:1 probably less as i've flowed the combustion chambers in the head. The ET1 head has custom inlet manifold with 2 inch long runners to the webers with a 15 degree angle. The valves are also stock size but reprofiled to a better shape as well as radiused valve seats and throats. Power is around 200bhp with powerband of 3-7K but engine turns to 7.5K in first three gears which is quite impressive for 272 degree camshaft.

[A20A1]

...One telltale sign of a Weber not in tune at full throttle is a lack of noise. It should be deafening, sometimes actually louder than the exhaust. I get a lot of complaints about the carb being so loud, some folks hate it but after a few weird looks from other drivers the "grin factor" solves that problem. Your last sentence says it all, at full punch you get a huge boost, it should be more like a good and steady surge for the most actual power...

[cygnus x-1]

Hi,
I just wanted to add my experience to the thread.

I built an A20 with a stage 1 triflow (Colt) cam and a mildly ported head. Comp ratio I estimate at 9.0:1
The carb is a Weber 38/38 with the following jet sizes:

1.42 Mains
0.55 Idle
1.85 Air Correction
0.70 Pump Jet
F50 Emulsion Tubes

Idle mixture screws are at 3/4 and 1.5 turns out. Need to try and equalize these. It runs pretty good but the O2 sensor indicates lean under light throttle. Going to try 0.60 idle jets next.

1/6/2007:
Equalized the idle screws to 1-1/8 turns out. No change. Put in 0.60 idle jets and adjusted idle screws to 1 turn out. The light throttle stumble got worse and the lean spot is bigger; strange. Going to try larger mains tomorrow.

1/7/2006:
Put the idles back to 0.55 today. Then switched the mains to 1.50. The light throttle stumble is gone and there is no lean spot. The O2 sensor says rich all across the board but overall it feels pretty good. Exhaust sounds a bit chunky so maybe 1.45 would be better for the mains. Will have to order them though. Could maybe try some smaller idles too.

2/18/2007:
Installed a wideband O2 sensor to get real AFR readings. Changed the mains to 1.47. Feels about the same. Cruise mix is about 14:1. Part throttle mix is around 13:1. Light throttle under load is lean but not too bad, maybe 15.5:1. WOT is still way rich, sometimes 11:1. Going to try larger air correctors next.

2/20/2007:
Bumped the air correctors up to 200 today. WOT is better but still rich if you jump on it. Going to try 210s next.

2/23/2007:
Went to 210 air correctors a couple days ago. According to the AFR gauge it looks like it leaned out across the board. Medium and heavy throttle are pretty good. Light throttle seems a little erratic, sometimes it's rich, sometimes it's lean. Throttle response is still good though so maybe it's ok.

4/20/2007:
Bumped the air correctors up to 215. Medium and heavy throttle are good, WOT is almost dead on 14.7:1. But now I'm starting to see the problem with light throttle. The AFR at just off idle is ok but as throttle is increased it gets leaner and leaner until about 1/3 throttle, when it jumps back down to 14:1. I'm pretty sure this is the main circuit all of a sudden coming in. This tells me that the mains are coming in too late and the idles are at max capacity. Bumping up the idle jets makes light throttle too rich, so the next step is to try different emulsion tubes to bring in the mains earlier. This makes sense with the F50 E-tubes since they have all their holes at the top half of the tube. The farther up the tube they are, the later the mains will come in.

5/4/2007:
The warmer weather is throwing a wrench into things. I tried some F6 e-tubes and they completely turned everything upside down so I went back to the F50s. So to fix the lean hole I raised the float level 2mm to bring in the mains a little earlier, and it definitely helped. But then the cruise mix was getting rather rich so I decided to try smaller idles (0.50) for once. And at the same time I dropped the air jets back to 210. And holy cow, it's nearly perfect! It's very lean on startup and needs some throttle feathering for the first couple minutes, but when it warms up it's almost dead on. Next I'm going to mess with the choke and maybe the idle screws some more to try and make it behave better on cold startup.

6/28/2007:
Made some more adjustments to compensate for the warm weather. Light throttle is a little too lean so it stumbles a bit, but I'm not going to mess with it anymore since I'm switching to fuel injection. So my current setup is:
1.45 Mains
0.55 Idle
2.10 Air Correction
0.60 Pump Jet
F50 Emulsion Tubes

This is a pretty good setup for warmer weather. For colder temps bump up the mains to 1.47 or 1.50.

C|

[2ndGenGuy]

Been reading and reading and reading. Theres so much crazy information on jetting carbs, emulsion tubes, and a/f ratios, that I'm a touch overloaded. I've just been playing with my jetting on my carb over the last couple days and wanted to post my results so far.

I figured after I have the carb completely tuned to how I like it to be running, I'll post my final jet sizes for stock ES2 with Weber 32/36 then in the sticky Weber Jet thread.

So it looks so far like the carb came stock with the following jets:

Primary barrel air correction jet: 170
Primary barrel main jet: 140
Secondary barrel air correction jet: 160
Secondary barrel main jet: 140

Haven't had a chance to see what the idle jets are or which emulsion tubes are installed.

Running like this, my car was great so long as I didn't open the secondary. As soon as I opened the secondary, the car would suddenly stumble and hesitate through the whole RPM range.

I figured that the secondary barrel was running too rich. My exhaust smelled like gas, and the dyno showed a rich A/F ratio. Below 3500rpm, it was at around 11.5. Above that, it was about 13. Never did check my spark plugs though. I've read in my Weber books that the ideal A/F for most cars is 14.7.

So... that is my experience with the carb, out of the box, running on an otherwise stock 1.8 liter ES2 engine.

__________________________________________________ __________

Now I've tried doing some tuning. Once I got past the fear of taking apart the carb, and realized it was only 6 screws and a tiny tiny clip, I realized it is super easy.

As I said before, as long as I was less than 3/4 of the way through the throttle (secondary closed), my car was fine. I decided to leave the jets alone on the primary barrel. However, since I thought that the carb was running rich as WOT, I upped the air corrector jet size on the secondary to 180.

The instant stumble was gone all through the RPM range, but hesitation would kick in about 3000RPM. The hesitation wasn't nearly as bad as stock, but still wasn't smooth.

Just for the heck of it, I went up on the main jet size to see what would happen. I guess richening the mixture back out. I popped in a 152 on the secondary barrel main jet. The power gain at WOT was pretty damn good, it smoothed out a ton, and the car felt like it had more guts through the RPM range. Still there is minor hesitation in there. I'm thinking maybe upping the main jet on the primary barrel just to see what happens... I know thats richening it out again, and doesn't make sense, but it can't hurt to try.

So here's what my car has as of today, I am going to drive it a couple of days and see how things go and mark any notes here. My current jetting is as follows:

Primary air corrector jet: 170
Primary main jet: 140
Secondary air corrector jet: 180
Secondary main jet: 152

Again, idle jets and emulsion tubes were left alone.

__________________________________________________ ______________

Sorry for the long post, but I just wanted to share my experience, as I think I might be the first person on the forum to put any info about this on the ES2. I'm going to keep adjusting jets and post updates on here as I go over the next few days. Any comments or suggestions are appreciated.

[2ndGenGuy]

Oh here's the dyno chart with A/F ratios on it in case anybody is interested. This is the car with the stock jettings.

http://i66.photobucket.com/albums/h256/jgturk/StockDynoChart.jpg

[A20A1]

Thanks for the update :)

[A20A1]

I thought your float might need some adjustment. Glad things are working out so far. I'm getting excited to see what will happen when you throw on your header.

Have you made more room for your air filter to breathe from the top yet?

Oh those rubber vacuum caps on the intake manifold, every now and then the cam I got or something would cause major reversion and those caps would pop right off and I'd end up with a vacuum leak, so I had to add some hose clamps to them but as they got old a dried out over the years the caps just cracked around the clamps... cheap to replace the caps though.

I plan to weld all the holes up on my intake manifold and also add one large brass barbed fitting to the rear to be sure hoses stay on and seal good. I dunno whats the big delay though. I ordered my welding supplies like in december or January and they still haven't come in. :(
.


I see you're using the Fram clear filter, I thought it was a good investment, much better then the clear glass ones from jegs/summit/specrte and no chance of unscrewing and causing a leak.



One more thing, you keep talking about the weather and your mixture adjustments...

I just read something that makes me wonder if I should just keep and manifold heater hooked up to try to maintain a constant temp for the manifold and carb.
http://www.popularhotrodding.com/tech/0511phr_carburetor_boosters_tech/
I seem to be posting that link a lot but the fact that they change booster types based on what cooling is available is an interesting aspect of tuning the carb. Now I don't really see many different styles to the weber booster venturies but it is possible to mod them and even swap venturies from other webers... might be worth a look as well.

.
.
.

[cygnus x-1]

I just the other day was thinking about the carb and air cleaner, and how the hood is right up against it. I think it might be causing some restriction in the air flow. I picked up a datalogging box to measure acceleration force (among other things) so now I can get graphs of HP and torque under actual driving conditions. I started a thread here:

http://preludepower.com/forums/showthread.php?t=266145

The Weber seems to be fairly sensitive to air temperature. I do have the hot water running to the manifold so it is being heated. I should mention though that I'm near Chicago and the temp has gone from below freezing to +70F since I started tuning, so I'm talking about a pretty large temp change. The choke also seems a little sticky sometimes, even though I've greased it a couple times. I only plan to drive the car when it's warm though so it's not a big deal.

Here is a link to my huge rebuild thread:

http://www.preludepower.com/forums/showthread.php?t=238337

C|

[A20A1]

Even if you don't make huge gains it'll pave the way for future tuners.

You know I was reading about E85? carbs tuned for use with ethanol/gas vs pure gas and they make more power than regular carbs using the gas ethanol mixture.

I'm not sure what we will have to do, but if we really need to adjust the air fuel ratio to better meet the change in fuel mixed with even the lower portions of ethanol in gas then it should be taken into consideration when tuning the carb... maybe we'll have to throw out the old book on A/F ratios with regular gas.

They say the octane rating is effected as well, so possibly something we could take advantage of, but only if we ran E85 carbs.

Anyways they said it's corrosive over time and our stock pump if you're using one is immersed inside the tank... so I hope it'll be okay sitting there.

[2oodoor]

Ok refering to the Weber carb I recently picked up at the JY Feb 2008
Weber Carb type= DGV 5A found on a Mazda PU, carb is not from a kit though, looks like OEM Mercury Capri possibly
--Primary Main Jet = 140
--Secondary Main Jet = 135
--Primary Air-Correction Jet = 165
--Secondary Air-Correction Jet = 160
--Primary Idle Jet = 55
--Secondary Idle Jet = 50
--Accelerator Pump Jet = 50
--Primary Emulsion Tube = F50
--Secondary Emulsion Tube = F6
--Main Venturi = 3.5 /26
--Booster/Secondary Venturi = 3.5/27

I have concerns about the secondary main jet size and air correction size on the primary. I have not run the carb yet.. still need to order a accel pump, power valve, and gaskets.
This thing needs to growl!!:cheers:

[Doward]

Ok, I'll be editing this as I tune. Currently:

(4/11/08)
--Primary Main Jet = 160
--Secondary Main Jet = 170
--Primary Air-Correction Jet = 175
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Can't remember - will find out tomorrow
--Secondary Emulsion Tube = Can't remember - will find out tomorrow
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Steady @ 750rpm, slight stumble off idle.
Cruise: Has good power all around, minor throttle input needed to change speed
WOT: Smells rich. Doesn't seem to pull very clean (starts stumbling around 5200rpm in 3rd gear - think I'm running out of fuel in the bowl) - further, I think the current throttle connection is preventing me from completely opening the secondary.

(4/12/08)
--Primary Main Jet = 155
--Secondary Main Jet = 160
--Primary Air-Correction Jet = 185
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 65
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Can't remember - will find out tomorrow
--Secondary Emulsion Tube = Can't remember - will find out tomorrow
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Still good, adjusted timing back to 26º @ 750rpm
Cruise: Better - more power with less throttle
WOT: Still seems to be running out of fuel at the top end. Need to post about Weber Fuel Pump in a few

(4/12/08 - UPDATE)
--Primary Main Jet = 155
--Secondary Main Jet = 160
--Primary Air-Correction Jet = 185
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 65
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Can't remember - will find out tomorrow
--Secondary Emulsion Tube = Can't remember - will find out tomorrow
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Still good, adjusted timing back to 26º @ 750rpm
Cruise: Better - more power with less throttle
WOT: Still seems to be running out of fuel at the top end. Need to post about Weber Fuel Pump in a few
NOTE: Car still relatively cold, WOT in neutral = bogging, and then the engine dies if I hold it WOT. I dropped from 70 to 65 (as there is a noticeable bog down when the secondaries open ip) and the problem seems to have worsened. Will try again tomorrow, after the car is completely warmed up, to see if this remains when warmed up. I currently have no idle jets larger than 70 (I have 50,55,60,65, and the carb came with 70s in primary and secondary)

NOTE 2: When warmed up, it has a noticeable hesitation before revving, if you got WOT in neutral from idle. I'm fairly convinced I'm looking at a lack of AE problem. Searching for a larger AE jet now.

(4/13/08)
--Primary Main Jet = 150
--Secondary Main Jet = 160
--Primary Air-Correction Jet = 185
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 65
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Can't remember - will find out tomorrow
--Secondary Emulsion Tube = Can't remember - will find out tomorrow
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Still nice and steady!
Cruise: Seems to be a little down on power - plugs look very good though.
WOT: Doesn't seem to have as much power. I'm thinking I'll drop the 185 primary air correction to 180 tomorrow.

All of this tuning so far - finally burned a full tank of gas. 302.2 miles. Took 12.1 gallons to fill it. ~24.98 mpg averaged over this tuning period. Very curious to see what happens next (as over 1/2 that tank was burned with me running pig rich)

(4/14/08)
--Primary Main Jet = 150
--Secondary Main Jet = 160
--Primary Air-Correction Jet = 185
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 65
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Can't remember - will find out tomorrow
--Secondary Emulsion Tube = Can't remember - will find out tomorrow
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

NOTE: Had the timing set wrong. Old setting was 26º with #25 port on distributor receiving full time vacuum. Current setting is 24º with no vacuum port hooked up, and vacuum hooked up on port #2 of the distributor.

Idle: Decent, but not as smooth as before. I think with my timing all out of whack, I need to re-tune the idle circuit now.
Cruise: Feels the same as 4/13 - I'm thinking of swapping the air correction jets around, to lean out the secondaries a little, and richen the primary a tad.
WOT: Feels better - the little A20 actually sounds kind of mean under WOT - still get a stumbling when held WOT for too long, though.

(4/18/08)
--Primary Main Jet = 140
--Secondary Main Jet = 179
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Still steady
Cruise: Feels good
WOT: Feels good

(4/20/08)
No change to jetting. Did fill up again though (246.4 miles on 9.5 gallons of gas = 25.93 mpg) Tomorrow I will change the 179 secondary main jet to a 160 and record the results.

(4/25/08)
--Primary Main Jet = 140
--Secondary Main Jet = 160
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Still steady
Cruise: Gotta test
WOT: Gotta test

Note: The Holley 179 jet is fucking TINY. Like, smaller than my weber true 140 jet! Also, had been hitting the fuel level mid-mark around 200 miles. 226 miles before I hit it this time ;)

(4/25/08)
--Primary Main Jet = 140
--Secondary Main Jet = 150
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Idle: Still steady
Cruise: Gotta test
WOT: Gotta test

Note: Later Holley 5200 jets are rated in flow, not the diameter of the hole. This Holley 179 is like a 115 Weber jet. I don't have any 135 main jets, but I think I'm going to order a 130 and 135 to see if I can go a little leaner on the cruise.

I really need to get the signal harness for my WB02 so I can tune this better. 28.28mpg though today (236.2 miles on 8.35 gallons)

(5/10/08)
--Primary Main Jet = 140
--Secondary Main Jet = 150
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0

Got the Wideband O2 finally hooked up! Idle AFRs ~12:1, cruise ~13.2:1, and WOT is PIG rich @ 10.5:1 Going to put the Primary @ 135, and Secondary @ 140, see what happens.

(5/10/08)
--Primary Main Jet = 135
--Secondary Main Jet = 140
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 75
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0
--AE shot - went from hole #2 to hole #3

Idle: ~13.2:1, smooth
Cruise: ~14.0:1, smooth running
WOT: ~11.5:1, which is rich.

I'm thinking I'm going to run a 130 pri, 135 secondary next. If the secondary still needs more leaning, I'll through a 185 air corrector at it ;) BTW, in all of this, I have a lean AE shot. :( I need a bigger AE jet!

(5/10/08)
--Primary Main Jet = 130
--Secondary Main Jet = 135
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 75
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0
--AE shot - #3 still

Idle: ~13.6:1, smooth
Cruise: ~15.0:1, smooth running, but maybe a little lean - we'll see how the engine likes it.
WOT: ~12.5:1, which is richer still than I need to be.

Still have a lean spell when I blip the throttle though :(


(5/25/08)
--Primary Main Jet = 130
--Secondary Main Jet = 135
--Primary Air-Correction Jet = 175
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 70
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0
--AE shot - #3 still

Idle: ~12.6:1, - I'm noticing the weirdest thing. When I set the idle (with the idle screw all the way out) I'm pig rich - like 11:1 AFR, but it seems to run smooth. When I bump the idle screw to bring the RPMs back up, it leans back out.
Cruise: ~14.7:1, smooth running - she seems to like this.
WOT: ~11.5:1, which is richer still. 185 air correctors going into the secondaries later today.

[2oodoor]

excellant Doward, hey exactly what carb do you have?

[cygnus x-1]

Ok, I'll be editing this as I tune. Currently:
(5/10/08)
--Primary Main Jet = 130
--Secondary Main Jet = 135
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 180
--Primary Idle Jet = 75
--Secondary Idle Jet = 70
--Accelerator Pump Jet = 80
--Primary Emulsion Tube = Won't come out!
--Secondary Emulsion Tube = I6
--Main Venturi = 4.0
--Booster/Secondary Venturi = 4.0
--AE shot - #3 still

Idle: ~13.6:1, smooth
Cruise: ~15.0:1, smooth running, but maybe a little lean - we'll see how the engine likes it.
WOT: ~12.5:1, which is richer still than I need to be.

Still have a lean spell when I blip the throttle though :(


The lean lean spot when you hit the throttle can be tricky. Probably you need a bigger pump jet but it could also be the transition from idle to main circuit. Those idle and cruise number look pretty good. WOT could go a bit leaner but it's not bad. One other thing to keep in mind is that air temperature affects the results you get. So if it suddenly gets colder outside your readings will all be leaner than before. And I probably mentioned it before, but don't mess with the emulsion tubes until you get everything else dialed in. Different e-tubes can drastically change the character of the carb, so if you change them you may have to start all over again. If you run into a wall though, changing e-tubes might be just the thing.

C|

[Doward]

Considering I can't get the primary emulsion tube out, that may not be a problem ;) I'd really like to get it out, though, just so I can compare to the stock F50/F6 ones.

[A20A1]

I used a allen wrench to get mine out, I stuck the long part in and just jiggled around inside the tube to loosen it.

[garfunkle55]

What is an AE shot?

[2oodoor]

On Doward's I think he is refering to the Holley version and the accelerator pump lever outside the carb. Those have a few different slots you can use to adjust the stroke depth of the accel pump rod.

[garfunkle55]

ohhh, I've been looking all over weber sites trying to find some kind of jet or something. Thanks for clearing that up.

[enache]

Hi

I might be a bit off topic but I was wondering if anyone has any suggestions on the jet sizes for a 38 DGMS considering it will be on a Cologne 2.8l V6.

Thx

[2oodoor]

Hi

I might be a bit off topic but I was wondering if anyone has any suggestions on the jet sizes for a 38 DGMS considering it will be on a Cologne 2.8l V6.

Thx

I believe that motor came with a 38 (one I had did anyway) and oem jet sizes are published in the weber book, which I don't have handy at the moment but will post them here in a bit since that would be beneficial to us too if someone lucked up and found one in the junk yard.
Capri 2.8 early models...search MK3 performance maybe ..Mains 142, airs 185, idles 45, em.tubes F50, pump 55 is going to be close.

[2oodoor]

Ok this set up is not tested with a wideband but it REALLY woke up this DGV-5a 32/36 on an otherwise stock A20A1. This thing has a hellova relentless grunt now..no bog and pulls hard from a dead stop to full thottle through redline.
This is on a 5 speed car and I dont know how well this would work on an auto, not the pump jet anyway. There is some secondary enrichening there that may not always be needed but certainly has an exciting effect.

--Primary Main Jet = 150
--Secondary Main Jet = 140
--Primary Air-Correction Jet = 180
--Secondary Air-Correction Jet = 165
--Primary Idle Jet = 60
--Secondary Idle Jet = 50
--Accelerator Pump Jet = 70 dual outlet
--Primary Emulsion Tube = F50
--Secondary Emulsion Tube = F-50

[itzdave]

anybody got an recommendations on jet sizes for dual Weber 40 DCOE's? with a few other bolt-ons as well, if that changes anything...

[hondalude86]

He is the jet settings i was running without a wideband... def something to start at if you have basic mods.

Here is what I had mod wise... Delta 285 cam regrind. Bored out to 81mm S&S headers...

Accel pump jets, 45
Accel Discharge, 45 (took out my soldered closed discharge)
main jets, 140
air correctors, 200
emulsion tubes f7
idle jets 50f9

Ran like a bad out of hell with even super low compression in one of the cylinders. It even pulled my b16a prelude with these jets, and it didn't have any problems revving up... you know like when you initially get on it, no dead spots...

and that was with 40mm chokes

[Fixedit]

The Weber seems to be fairly sensitive to air temperature. I do have the hot water running to the manifold so it is being heated. I should mention though that I'm near Chicago and the temp has gone from below freezing to +70F since I started tuning, so I'm talking about a pretty large temp change. The choke also seems a little sticky sometimes, even though I've greased it a couple times. I only plan to drive the car when it's warm though so it's not a big deal.

C|


When I first ran my 38 I had no coolant hooked up to the manifold, and cold start warm-ups took ages. The carb really does not like to be cold, and just the temp changes from noon to evenings really affect the tune. Life’s a bit easier now with the coolant running through the manifold.

Regardless, tuning this thing has been a roller coaster. I finally actually understand the carb though, and I’m sitting at a good spot. Engine is an A20A1, modified intake manifold, 88-89 LXi exhaust manifold, 272 duration camshaft, Weber 38 carb.

--Main Jets = 127
--Air-Correction Jets = 200
--Idle Jets = 0.57
--Emulsion Tubes = F66

My mains may seem lean, but according to the AFR gauge it’s what the car wants. I might be able to run larger ones with a larger air corrector, but it’s the perfect mixture at WOT right now. It actually gets a little rich in the high RPMs wide open. But that’s the least of my concern. My biggest problem has always been partial-throttle lean out. Took me forever to figure out it’s because of the progression circuit, and even then it’s still been difficult to nail a good tune.

To get the perfect idle mixture AND proper cruise mixture (which by the way, Cygnus mentions the cruise mixture is controlled by the mains, I disagree. Changing my mains did nothing for cruise mixture, but idle jets changes it every time. That’s because they also control the progression/transition circuit) has been the biggest challenge. For a while I had 0.60 idle jets, as that’s the only way I could eradicate the lean spot, but cruise mixture was way too rich and mileage was bad (11.0 cruise, 200 miles from full tank). So I tried 0.55’s down to 0.45’s. 0.55 and 0.50, I could idle a healthy 13.8-14.2 with the idle screws 1 to 1.25 turns out, but the progression circuit (at cruise) would lean out from 15.0 through 17.0. So between the 0.55 and 0.60, it was either lean out at cruise or too rich at cruise. I’ve been pulling my hair out about it, and as a last ditch effort I ordered the 0.57 idle jets. Best I can say is it’s “better,” but not perfect. I think about 3/4 turn out on both idle screws. Cruise is closer to 13.5-14.2, progression circuit still leans out but only if RPMs climb (like if I leave it in 2nd with partial throttle at 30MPH) so if I just drive it right I can avoid it. WOT is perfect (14.5-13.5) until about 4200 RPM it hits 12.5. Which I don’t understand with the mains being as small as they are and the engine using a longer duration cam…but I do have a set of 125’s so maybe I’ll try those but I feel like I’m going to run into a different kind of lean spot if I keep going smaller. I don’t understand how other people are able to run such large jets even on a stock A20, like I know no engine is exactly the same but what the hell lol.

[ShiRen]

I dont know the inner workings of the webers too well, but it sounds like to me that you immediately pointed out a problem

Changing my mains did nothing for cruise mixture, but idle jets changes it every time.
Pilot jets should not have a significant difference on cruise operation because once the throttles are open, it creates low pressure in the barrels, pulling fuel from the venturi. It needs to do that because the pilot jet is not a variable flow, it just shoots fuel through the hole with the fuel pressure. So, dont compensate with the pilot jet, set your idle afr according to the Redline manual and dont touch it after that.
It would help to know: Is your carb new? What other jets have you tried? Are you in high altitude?
I would suggest getting this carb ultrasonically cleaned if it is not new. Reset the main jet to something normal like a 140. Set the idle.
Maybe this has something to do with the air correction jets, not familiar with them, but knowing that fuel flow out of the venturi is based on a pressure differential around it, maybe there is something up there, so there is very little flow at low throttle percent. Maybe the air correction jets are too large or the emulsion tubes need to be larger. As far as the lean out on accel, that might help, but the accel pump might need retuned after cruise afr is somewhere reasonable. Also, if you are in high altitude, try to tune it somewhere a few hundred feet lower if that isnt too far from home, it will be easier to find a baseline.

[ShiRen]

38 WEBER

38 DGAS
Idle Mix Screw: 0.75-1.0 turns out.
Both screws should be as equally balanced as possible.
More then 1.0 turns and you need a larger idle jet.
Synchronous carbs must use the same size idle jets.

38 DGAS
Bogging problem in the upper rpm?
Try F6 emulsion tubes and slightly smaller idle jets to change the fuel curve.
The emulsion tubes will bring the main fuel curve down a bit lower and allow the engine to use it when vacuum is at a decent level.
The upper rpm will lean out just a bit, if needed smaller air correction jets can richen the mixture.

* The 38 weber came with these jets on a different car of ( 2994 cc ) ours is ( 1955 cc ).
(38) JET SIZE x2 , except for Pump Jet

- 1.45 Mains
- 1.85 Air Correction
- 0.50 Idle jet
- 0.65 Pump Jet
- F50 Emulsion Tubes

You may want to make a collection of jets, remember this is a synchronous carb.
There are two easy ways to richen the main mixture
Air Correction Jets ( Smaller # = Richer Mixture )
Main Jets ( Larger # = Richer Mixture )
A lot of the times I see the Air Correction dropped VS increasing the mains to get a richer mixture.
In some cases the mains are the restriction and must be increased, the air correction may be left unchanged or increased.

Hi,
I just wanted to add my experience to the thread.

I built an A20 with a stage 1 triflow (Colt) cam and a mildly ported head. Comp ratio I estimate at 9.0:1
The carb is a Weber 38/38 with the following jet sizes:

1.42 Mains
0.55 Idle
1.85 Air Correction
0.70 Pump Jet
F50 Emulsion Tubes

Idle mixture screws are at 3/4 and 1.5 turns out. Need to try and equalize these. It runs pretty good but the O2 sensor indicates lean under light throttle. Going to try 0.60 idle jets next.

1/6/2007:
Equalized the idle screws to 1-1/8 turns out. No change. Put in 0.60 idle jets and adjusted idle screws to 1 turn out. The light throttle stumble got worse and the lean spot is bigger; strange. Going to try larger mains tomorrow.

1/7/2006:
Put the idles back to 0.55 today. Then switched the mains to 1.50. The light throttle stumble is gone and there is no lean spot. The O2 sensor says rich all across the board but overall it feels pretty good. Exhaust sounds a bit chunky so maybe 1.45 would be better for the mains. Will have to order them though. Could maybe try some smaller idles too.

2/18/2007:
Installed a wideband O2 sensor to get real AFR readings. Changed the mains to 1.47. Feels about the same. Cruise mix is about 14:1. Part throttle mix is around 13:1. Light throttle under load is lean but not too bad, maybe 15.5:1. WOT is still way rich, sometimes 11:1. Going to try larger air correctors next.

2/20/2007:
Bumped the air correctors up to 200 today. WOT is better but still rich if you jump on it. Going to try 210s next.

2/23/2007:
Went to 210 air correctors a couple days ago. According to the AFR gauge it looks like it leaned out across the board. Medium and heavy throttle are pretty good. Light throttle seems a little erratic, sometimes it's rich, sometimes it's lean. Throttle response is still good though so maybe it's ok.

4/20/2007:
Bumped the air correctors up to 215. Medium and heavy throttle are good, WOT is almost dead on 14.7:1. But now I'm starting to see the problem with light throttle. The AFR at just off idle is ok but as throttle is increased it gets leaner and leaner until about 1/3 throttle, when it jumps back down to 14:1. I'm pretty sure this is the main circuit all of a sudden coming in. This tells me that the mains are coming in too late and the idles are at max capacity. Bumping up the idle jets makes light throttle too rich, so the next step is to try different emulsion tubes to bring in the mains earlier. This makes sense with the F50 E-tubes since they have all their holes at the top half of the tube. The farther up the tube they are, the later the mains will come in.

5/4/2007:
The warmer weather is throwing a wrench into things. I tried some F6 e-tubes and they completely turned everything upside down so I went back to the F50s. So to fix the lean hole I raised the float level 2mm to bring in the mains a little earlier, and it definitely helped. But then the cruise mix was getting rather rich so I decided to try smaller idles (0.50) for once. And at the same time I dropped the air jets back to 210. And holy cow, it's nearly perfect! It's very lean on startup and needs some throttle feathering for the first couple minutes, but when it warms up it's almost dead on. Next I'm going to mess with the choke and maybe the idle screws some more to try and make it behave better on cold startup.

6/28/2007:
Made some more adjustments to compensate for the warm weather. Light throttle is a little too lean so it stumbles a bit, but I'm not going to mess with it anymore since I'm switching to fuel injection. So my current setup is:
1.45 Mains
0.55 Idle
2.10 Air Correction
0.60 Pump Jet
F50 Emulsion Tubes

This is a pretty good setup for warmer weather. For colder temps bump up the mains to 1.47 or 1.50.

C|
You arent anywhere near either of these setups... have you tried anything similar?

[Fixedit]

The idle jets meter fuel flow for the idle circuit as well as the progressive circuit. The progressive circuit consists of multiple passages right above the idle passage, which are activated with minute opening of the throttle plates (cruise position).

The carb is new, non-ethanol gas only. I have tried similar setups with rich results (which is what trips me up lol, since I don’t have a stock cam).. Since my last post I bumped up my mains to 135. WOT is too rich again but the lean flat spot is gone and cruise is about perfect. Despite all of that, this is the best tune I’ve had so far and I plan to leave it alone until necessary. At the point I want to try larger air correctors. Oh, and I’m right at sea level. I’m no carb expert but this is just what I’m experiencing. Having fun learning the 38 though