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Tuning 3 x 45 DCOE 3 Webers


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#1 Brian Pascoe

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Posted 12 November 2017 - 10:03 AM

Attached File  IMG_2045.JPG   333.28K   8 downloadsI'm in the process of tuning my Webers but have a flat spot (bogging down on acceleration ) The carbs have only 2 progression holes as they are old ones.Any help would be really appreciated .



#2 jd lj

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Posted 12 November 2017 - 11:32 AM

Your dcoe's look like 45dcoe13's(which should have only two progression holes as you said).

What are your jetting specifications and fuel levels? 9 port or 12 port, 186 or 202?
Can you measure your manifold vacuum at idle with a one way check valve fitted prior to the vacuum gauge.

I assume that the hesitation is at approximately 2500 rpm.

Can you post a photo of the progression holes with the cover removed, you should be able to see the top edge of the throttle plates directly below the progression holes closest to the manifold. This is for 45dcoe13's, other models will have the progression holes in different positions.

JD

#3 Brian Pascoe

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Posted 13 November 2017 - 07:00 AM

Hi JD.

Yes,they are 45 DCOE 13.Attached is a photo of the progression holes.Yes, you can see the throtle plate covering the first progression hole.Also I have a AFR gauge that reads 13.5  at idle, then on slight acceleration  leans out to between 16 & 22.Engine specs are as follows.

IDLE JETS = 50F9 & ALSO TRIED 50F8, 55F8, 55F9

MAINS = 155

EMULSION TUBES =F2

AIR JET =210

NEEDLE & SEAT =225 ALSO TRIED 175

FLOAT LEVEL = TRIED 8.5 MM, 7 MM & 6 MM

CHOKE TUBE =40 

SEC VENTURI = 5

CYLINDER HEAD = XU1 9 PORT

ROLLER ROCKERS

10: 1 COMP 

PACEMAKER EXHAUST 2 1/2 IN

CROW CAM 33/75

DIZZY = 14 DEG INITIAL TOTAL 32

FUEL PUMP PRESSURE = 3.0 PSI

Attached Files


Edited by Brian Pascoe, 13 November 2017 - 09:52 AM.


#4 jd lj

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Posted 13 November 2017 - 11:33 AM

When you say that it leans out to 16-22afr what rpm's is that at? I found 50f8's to work well with 45dcoe13's,but this will vary slightly depending on your engine. Different models of dcoe's will have different numbers of progression holes and different diameters as well as positions. But keep in mind that the progression holes upstream of the throttle plates also act as air bleeds to the progression circuit by allowing air to enter from the barrels. I normally set my idle mixture in the high 12's to low 13's myself.

On the brass float carbs set the float at 8mm and then check that it's 25mm down from the top of the emulsion tube and idle jet block to the fuel level, this will put the fuel 2mm below the auxiliary venturis passageway.

I'll continue this later, lunch is now over and I have to return to work.

Don't worry we'll easily sort you, there's some obvious changes to be made.

James D

Are you recording rpm's and AFR on your air /fuel meter? What type of meter have you got?

#5 Brian Pascoe

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Posted 13 November 2017 - 04:26 PM

Attached is a photo of my INNOVATE WIDE BAND SENSOR.hesitation is at approximately 2500 rpm.  .I will adjust fuel level  next to your recommendation and see how I go.I am only recording a visual on the AFR.

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  • Attached File  AFR.jpg   68.47K   1 downloads


#6 jd lj

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Posted 13 November 2017 - 06:37 PM

Hi Brian,
So the hesitation is at 2500rpm at light acceleration as I expected and this will be when you're seeing the 16-22 afr reading but I suspect that below those rpm's it's possibly a touch too rich and 50f8's could be a better choice but you'll know what the readings are yourself.

I'm going to give you this information in instalments as there's a lot to take in and for me to write. I could just tell you what jets to use but then you wouldn't understand why.

The 1.75 needle and seat are adequate for a 186 or 202, they're even enough for a 265 hemi, but if you currently have 2.00 needle and seats fitted they will be fine on a street car. If you were going circuit racing the needle and seat size is more important because if you were on a long sweeping bend with enough G force the fuel level can vary and the wrong size n and s may let in too much or too little fuel and then as you straighten out and accelerate this can effect the mixture and cause spluttering. However keep in mind that the fuel bowl is quite symmetrical and has half of the float in each end and the jets are positioned right in the middle.

Your fuel level is critical in dcoe's. People will talk about it impacting on the mixture of the main circuit (which it will), but more importantly it impacts on the timing of the tip in of the main circuit. The fuel level has to rise up to the level of the auxiliary venturis (AV) passageway coming off the emulsion tube wells so that it can start flowing, this is the tip in timing. There is no atomisation or emulsion going on, it's just liquid fuel flowing to the AV. So as the rpm's rise the vacuum signal that the AV is subjected to rises and this creates a vacuum in the emulsion tube wells. These wells have two orifices to feed this vacuum, the fuel from the main jets and air from the air correctors. To an extent the more air is flowing the less fuel has to. If you look at an emulsion tube there's a ring of holes about a third of the way down (on a f2)and a few above that. The idea of the ring of holes is to blow bubbles into the fuel in the well to raise the fuel level faster and send it flowing down the AV passageway to the AV and into the carb barrels and then into your engine. The problem with f2 tubes in a dcoe is that those holes are located at the same level as the AV passageway, they're high and dry so they can't physically create any bubbles to raise the fuel level, therefore the main circuit starts to late and you get a flat spot at 2500 rpm. Different models of webers (not dcoe's) have different depth emulsion tube wells and f2's may be more suitable in those.

The f2 tubes can be improved by getting them in a lathe and cutting 2mm off the bottom (you'll also need to shorten the part of the main jets that pushes inside the e-tube) and this will put the bubbling holes at the same level as the top of the fuel if it's set at 25mm, ideally it needs to be a further 2mm below this though. Imagine blowing bubbles in a glass of water, the water level rises doesn't it. Now imagine using more straws or straws of a bigger diameter and therefore having more or bigger bubbles, the water level rises even more. The same time happens with correctly designed e tubes with the holes below the fuel level and this means more fuel flowing which gives you a stronger mixture. Once the fuel level has risen enough due to the vacuum from the AV the bubbles are not longer needed and the mixture is controlled by the main jets size and the diameter of the e tube. A narrower diameter tube has less surface area and a larger area for fuel to flow past and therefore will be richer once the bubbles are no longer required and the opposite is true for a fatter diameter tube such as a F16. The WOT mixture is controlled by the main jets but if too many bubbles are being used at the start of the main circuit then these will now lean out the WOT mixture. All the factory e tubes suffer from leaning out as the rpm's rise.

Your fuel level needs to be checked not just by the float gap but individually by removing the E tubes, parking on a level surface and then with a vernier calliper and a torch pushing the probe of the calliper down the well until you see the reflection of the torch on the fuel change when the probe touches it. The bottom of the calliper sits on top of the e tube and idle jet tower. This has to be done immediately after turning the engine off. E tubes are not needed to be fitted to run the engine to do this test.

You have two choices of tubes to use and both out perform std weber tubes, they are both made by Keith Franck in the US. The first is his O6 tubes which work as described above and a few weeks ago he released a totally new design called Venturi Fountain Tubes which work as a venturi vacuum pump. These can be found on "WWW.Webstore.com" under the user "dcoe tuner" he'll normally offer a money back guarantee of satisfaction minus postage and PayPal costs. See my post in a recent thread called "help with triples" for the link.

I'd like to thank Keith Franck for many years of his persistent work reverse engineering dcoe's and everything that I have learnt from him.

To be continued.

James D

#7 jd lj

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Posted 13 November 2017 - 06:40 PM

I'd also change to 4.5auxiliary venturis (AV's) and 34mm chokes.

As I said this is to be continued, I'll elaborate later.

James

#8 jd lj

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Posted 13 November 2017 - 07:12 PM

What pump jets, valves, rods and springs are you using?

I assume that this is a street driven car and not raced??

Remove and plug up the holes for the balance tubes between your manifolds to prevent cross talking between them and then you can synchronise them properly.

James

#9 LC-GTR-1969

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Posted 13 November 2017 - 09:19 PM

Sorry- im in a bit of a rush so I haven't read all of JDs info, so he may have mentioned what I am about to say- JD will get you out of trouble, he will have some great advice...

 

From my quick read of your posts... 

 

I think you have several issues... am I right that you are running 40mm chokes? These are too big unless dedicated track car... Ive run them before myself but 36mm will be better. You could go smaller like 34 but it all depends on your full engine specs and peak HP of your cam as to what chokes your engine will want... 

 

With your current setup, It might help to try smaller air correctors to help kick start the main jet during transition... Your 210 you specified it pretty big, I would try 185s or 190s and this will help bring on the main jet earlier to help it with transition. The big chokes will probably need more than 155 as well as when the carb is over choked, it wants more jet as the slow airspeed can hinder good fuel draw through the jet. I ran 165 MJ with 200 airs when I ran 40mm chokes. You will honestly find smaller chokes will make life easier for you as well as you will find it will probably perform better anyway.

 

But I also think you need to look at your pump circuit as you may have an issue here as well- I would test engine by driving at various throttles and watch your wideband to see how it responds with some quick but light stabs of throttle- if you see lean spikes across various rpm ranges you need to address the pump circuit...


Edited by LC-GTR-1969, 13 November 2017 - 09:19 PM.


#10 jd lj

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Posted 14 November 2017 - 11:23 AM

As stated above your 40mm chokes and 5.0 auxiliary venturis (AV's) are making the situation worse for you. 40mm chokes are too big for a street driven 202 let alone a 186, the air speed through the carbs is simply too low, this is giving you poor low end power and also reducing the strength of the vacuum signal that the e tube well feels. 40mm chokes are great for a race track where your doing high rpm's more often than not but on the street smaller chokes will make the car much more pleasurable and fun to drive.

Using 4.5AV’s instead of your 5.0's will give you a stronger vacuum signal to the e tube well also and they are more than capable of flowing enough fuel for your needs.

When you get some new AV's you'll notice that there's still some flashing and ridges left from where the two halves of the mold come together. If you use a very fine and small file and tidy that up then you'll have less turbulent air flow through the carbs, enough that you can feel the difference.

Once you make any changes to the e tubes, or chokes etc then you'll need to adjust your main jets and air correctors to suit.

Ram tubes that slide into the throat off the carbs will be beneficial also. The problem is that then getting filtered air to the ram tubes can be a challenge if you don't have much clearance around the tubes. I don't recommend the sponge ram tube socks or the stainless steel gauze filters that fit onto the end of the ram tubes because they do a poor job at filtering, restrict the air flow and stop the ram tube from working how they are designed to.

James D

#11 lawn bowls

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Posted 14 November 2017 - 10:40 PM

i know that webers like a fair bit of timing around 36 total.just a suggestion.



#12 Brian Pascoe

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Posted 15 November 2017 - 09:19 AM

Thanks Fella's,I am taking it all on board and will let you know how I go.



#13 LC-GTR-1969

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Posted 15 November 2017 - 11:07 AM

i know that webers like a fair bit of timing around 36 total.just a suggestion.

 

Webers do like some extra STATIC timing but never heard of observed that they like any extra total timing. They should be between 30-32 maybe nudging to 34 in some combos but I would not be running 36' unless it was confirmed on a dyno that the engine needed it. 

 

My setup with triple webers only wanted 27 degrees total- confirmed by dyno... 28 degrees is the max I ran. 



#14 jd lj

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Posted 15 November 2017 - 11:27 AM

Prior to starting any tuning ensure that the engine is fully warmed up and heat soaked, the temperature gauge showing 80degrees or so isn't sufficient, it needs to be running for around ten minutes or so. If it's not up to full operating temperature you'll have incomplete combustion of the mixture and you'll have to set it up richer than what's really necessary.

As a test for you go somewhere quiet like an industrial area on a Sunday or some back streets and remove the emulsion tubes, main jets and air correctors and go for a drive. But be careful, you won't be able to use much power or rev very high, but what you will notice is that the engine begins to die at close to 2500rpm's when the main circuit should normally be kicking in. This will illustrate how the emulsion tubes are starting the main circuit too late and giving you you're hesitation. However the progression circuit still needs to marry into the main circuit as seamlessly as possible to get the best tractability possible.

James

#15 jd lj

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Posted 15 November 2017 - 06:54 PM

There can also be a rare situation where doing the above test with the e tubes removed will not cause the engine to die as the rpm's rise towards 3000rpm's. But considering that you're having a hesitation at 2500rpm's this is very unlikely to be the case in your situation.

James

#16 Brian Pascoe

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Posted 16 November 2017 - 10:30 AM

I raised the float level slightly as the measurement was 26 mm. ( haven't checked it yet ,but looking for  the 25 mm mark)Also increased  full advance to 36 degs at 3000 rpm. Took it for a run and it has improved quite a lot, still a very small lull.



#17 LC-GTR-1969

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Posted 16 November 2017 - 02:41 PM

Also increased  full advance to 36 degs at 3000 rpm. 

be very careful... you shouldn't need that much timing. The timing also has nothing to do with your problem... the extra few degrees will help with mid and bottom and response but 36 is high for most holden 6s. Most find 32 is about right, some want 34.

 

If you want to run 36 degrees get it dynoed as you may do damage if your engine doesn't want nor need that level of advance. It may actually want 36 degrees but as its on the high side, you should check it on a dyno for some insurance. You really should regraph your dizzy so you can run more advance down low and less up top, like 18 at idle and 32 total.



#18 jd lj

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Posted 16 November 2017 - 03:28 PM

For every 1mm you adjust your floats that will equate to 1mm change on your fuel level.

James

#19 Brian Pascoe

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Posted Yesterday, 08:09 AM

With the DCOE13 carbs and the 2 progression holes, wouldn't it be possible to drill another hole or 2 like the more modern carbs.



#20 LC-GTR-1969

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Posted Yesterday, 11:11 AM

With the DCOE13 carbs and the 2 progression holes, wouldn't it be possible to drill another hole or 2 like the more modern carbs.

Possible, yes... good idea, no..

You would need to be very accurate and use a jig to ensure replicability of location to other holes. You would also need size and location but at the end of the day.. the progression holes are not the sole problem you have.

Work in fixing the aforementioned things and you should be in the ball park.

Edited by LC-GTR-1969, Yesterday, 11:12 AM.


#21 RallyRed

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Posted Yesterday, 11:36 AM

Brief Thread steal..apologies -  

Can the missing Webber part here be sourced as a spare? Thanks  . End of thread steal. 

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#22 jd lj

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Posted Yesterday, 12:13 PM

Col,
Your missing jet inspection cover is available as a spare part for approximately $20. Daniel at Weber Performance or Phil at BOI PERFORMANCE and various sellers on ebay will have those.
Just about every weber part is available as spare parts.

James

#23 jd lj

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Posted Yesterday, 12:23 PM

With the DCOE13 carbs and the 2 progression holes, wouldn't it be possible to drill another hole or 2 like the more modern carbs.


Brian,
Drilling additional progression holes can be done but should only be done as a last resort,which you are far from. Change your chokes to smaller ones, fit 4.5 AV’s and most importantly get rid of your f2 emulsion tubes and then use the appropriate main jets and air correctors. I have emulsion tubes that I can adjust the main circuit tip in mixture enough to easily get rid of your hesitation, they can be adjusted enough to flood your engine at those rpm's (not that you'd want to), you just need to understand the physics involved as I described above.

James

#24 jd lj

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Posted Yesterday, 12:25 PM

https://www.webstore..._id,other_items

Here's where to get the tubes that you need.

James

#25 RallyRed

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Posted Yesterday, 12:39 PM

Col,
Your missing jet inspection cover is available as a spare part for approximately $20. Daniel at Weber Performance or Phil at BOI PERFORMANCE and various sellers on ebay will have those.
Just about every weber part is available as spare parts.

James

Luv your work James...thanks   Col






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