Author Topic: Weber DGEV  (Read 3567 times)

stenis

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Weber DGEV
« on: October 31, 2006, 06:18:00 AM »
Hi,

I have a 1303 Automatic and are trying to use my Weber DGEV on it. I found some earlier posts on this list explaining some details (thanks 68AutoBug). My problems are related to the vacuum feed from the carb. The distributor vacuum feed is not strong enough to use, so shifting takes a looong time.

Did anyone do this successfully?

/Sten

volkenstein

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Not on a DCD that I know of
« Reply #1 on: October 31, 2006, 09:25:35 AM »
Stenis,
         Are you sure the carby is at fault? Are your vacuum connections all absolutely OK? Is the control valve adjusted?
What distributor is on the motor?

Did it get progressively worse or has it been like this for as long as you have had the car?

One other test, pull the small vacuum line off the CV and put your finger over it and rev the motor. You should feel suction.

Lastly, can you post a picture of your setup?

Regards
Volkenstein
1 Super RHD Semi-Auto "Klaus"

stenis

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Re: Not on a DCD that I know of
« Reply #2 on: October 31, 2006, 09:49:22 AM »
Hello volkenstein

Quote from: "volkenstein"
Stenis,
         Are you sure the carby is at fault? Are your vacuum connections all absolutely OK? Is the control valve adjusted?

There is nothing wrong with the Weber (I think). I just don't manage to get it to work with the control valve. I also have the original carb and gearshifting is smooth and promptly with this carb on the engine. The only reason I would like to use the Weber is the fact that it gives me quite a different and much nicer engine compared to the standard setup.
Quote from: "volkenstein"
What distributor is on the motor?

It's a Bosch 009
Quote from: "volkenstein"
Did it get progressively worse or has it been like this for as long as you have had the car?

See above

Quote from: "volkenstein"
One other test, pull the small vacuum line off the CV and put your finger over it and rev the motor. You should feel suction.

Ok
Quote from: "volkenstein"

Lastly, can you post a picture of your setup?
Right now I am using the Solex, but will take some pictures when the Weber is back on.

I think I will have to drill a new vacuum port in the carb, but I'm not sure where the best spot for this would be.

Regards
Sten

volkenstein

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where to start
« Reply #3 on: October 31, 2006, 05:57:22 PM »
Stenis,
          Did some checking and the Weber progressive (of various flavours) does indeed have a weak (for a VW) vacuum signal and people drill the ports larger.
Progressives have a bad reputation for being very hard to get right.
What DCD are you running? A 28/36 or 36/36?

Since you are running a 009, let's forget about the ported vacuum as it is generally timed incorrectly for the CV.

On your Solex, whip off the CV feed and if you have a vacuum gauge connect it to the carb port. You should measure the vacuum at say, idle, 1/4, 1/2, 3/4 and fully open. This will give you a baseline for your mods.

If you are going to drill, drill into the venturi of the primary bore. This is the throttle plate that opens first (the smaller one on a 28/36).

Have a look here and click on the "exploded view" :

http://www.piercemanifolds.com/carbdetails/html/28_36_dcd.htm

There is also a diagram of the 36/36 DCD but their construction is similar.

Where to drill? On your 34 Pict 3 the port enters just below the narrowest part of the venturi. A 2mm hole in the venturi, but the hole in the brass spigot is 1.5 mm. You can pull your carb off and check this yourself.

In the exploded view, the venturi is a removable part and you can see where the narrowest point is. Find a place or unused boss on your DCD and this is where you'll have to place the fitting. What I have tested (on a manual 34 Pict 3 carb) is drill all the way through the blank boss(carefully!!) with a 2mm bit. Then drill a 4 mm hole by 10mm deep into the boss. Make up a brass or whatever fitting from a solid rod and make it 4mm OD and then drill this 3mm but not all the way through. Finish off the hole with a 1.5mm drill. You could start at say 1.0mm and work your way up after checking the vacuum signal against the ones from the Solex.

And I'd think hard whether you want to get into all this. DCD's are an old carb and getting few and far between.

Volkenstein
1 Super RHD Semi-Auto "Klaus"

stenis

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Re: where to start
« Reply #4 on: November 04, 2006, 05:44:20 PM »
Hello, comments inline...

Quote from: "volkenstein"
On your Solex, whip off the CV feed and if you have a vacuum gauge connect it to the carb port. You should measure the vacuum at say, idle, 1/4, 1/2, 3/4 and fully open. This will give you a baseline for your mods.
I took my mac, a labjack and an MPX10DP and created some graphics showing the vacuum on the CV feed and the distributor feed on the Solex.

This is the vacuum signal produced when the accelerator is depressed from idle.
Quote from: "volkenstein"
Where to drill? On your 34 Pict 3 the port enters just below the narrowest part of the venturi. A 2mm hole in the venturi, but the hole in the brass spigot is 1.5 mm. You can pull your carb off and check this yourself.

Volkenstein

Thanks for great info, I'll give it a try.

/Sten

volkenstein

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Your graphs
« Reply #5 on: November 04, 2006, 06:38:34 PM »
Stenis,
         Do you reckon you could put some "real" figures against those graphs. Sorry, but I am a recidivist despite Australia having gone Metric in the early 70's.

Could you plot RPM vs In/Hg (or whatever the hell units vacuum is measured)?


Regards
Volkenstein
1 Super RHD Semi-Auto "Klaus"

stenis

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Re:Your graphs
« Reply #6 on: November 05, 2006, 07:28:08 AM »
Hello,

Y in the graphs is voltage (V). 10mV = 0.3 psi vacuum
X is just time. The full graph is about 1 sec.

I realize that time is not a very useful X-scale, but I don't have an rpm sensor to connect to the labjack. Something I could do is to show the butterfly valve opening angle on the X-scale, but I'm not sure it would add any value.

At least I can modify the Weber until I get about the same graph as I have taken from the Solex.

Regards,
Sten

stenis

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DGEV, no DCD
« Reply #7 on: November 07, 2006, 02:18:32 PM »
Found out I screwed up type designations, my Weber is a DGEV not a DCD as I originally stated in my post.

Sorry for that

Sten

volkenstein

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Bummer..
« Reply #8 on: November 07, 2006, 04:15:03 PM »
Stenis,
         That's bad luck! A DCD would have been better to work on! Re the DGEV.
All anecdotal evidence says they are difficult to tune, have a choke connection which can short out on the shroud, have a weak signal for spark port (distributor) advance, manifold heating (via heat risers) is bad unless you get a really good brand manifold and lucky last is that they don't have a CV vacuum port as well.

Where to drill and sizing remains the same.

A bit of an uphill battle you have on your hands!


Volkenstein
1 Super RHD Semi-Auto "Klaus"

stenis

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Ok
« Reply #9 on: November 15, 2006, 12:20:38 PM »
The modification was in fact quite simple to do and I didn't even have to take the carb apart. I have put some images at http://www.greenray.se:8000/VW1300


Thanks for all good info, without it I wouldn't have done this!

/Sten

volkenstein

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Getting timeouts on your server
« Reply #10 on: November 15, 2006, 04:28:21 PM »
Stenis,
         Having real problems getting to that link. Could you email the pictures to me at ctefehinoz@hotmail.com and I'll put them up on this topic via photobucket links.

Glad to hear it works OK. That makes three types of carb this mod works on!

Did the shifting behave exactly the same or did you do some adjustment on your CV?

Regards
Volkenstein
1 Super RHD Semi-Auto "Klaus"

stenis

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Weber DGEV mod
« Reply #11 on: November 16, 2006, 01:45:51 AM »
Volkenstein,

Shifting behaviour with the modified DGEV is very close to shifting with the original Solex. I will create a vacuum diagram to compare the two.

Please try the URL link again. Port 8000 was closed in my web server firewall. It's now open and you should be able to grab the pictures from there.

Regards,
Stenis

volkenstein

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That's interesting!!
« Reply #12 on: November 16, 2006, 04:37:44 AM »
Stenis,
         I never thought about just going through the spark port vacuum point!! :shock:  With a 009 I guess it doesn't matter anyway!

Oh, the link is all good now!

By all means whip up a measurement graph of the vacuum!! I'm dying of curiosity now :lol:

Being an electronics numbskull, what's the transistor circuits function from your site? The last time I saw something like that was on a '70's Chrysler.
Have you got a Hall effect in the 009?


Regards
Volkenstein
1 Super RHD Semi-Auto "Klaus"

stenis

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Weber graph
« Reply #13 on: November 17, 2006, 09:07:37 AM »
The new Weber cv vacuum graph is uploaded to the URL link above.

The electronic ignition (on the same site) is despite it's simple construction quite effective. It is using the standard breaker points but could possibly be modified to use a Hall sensor.


/Stenis