I have an upright conversion type 4 in my bug. This is my first time working with IDFs on my own car and would like to get them perfect. The issue I have is my idle speed which when hot is 1050-1100. I'm as low as I can go on the throttle stops for the butterflys. they are barely touching. Here is my current configuration:
44 IDF
32 vents
50 idle
135 main
200 air correct
pump jet is stock forget the size
decent accelerator pump squirt
The engine is a bone stock 1.8 out of a bus. It generally runs well. It has a small amount of popping out of the exhaust (stock bus) which I think is a lean condition on my idle jets. It has a slight stumble off idle that may be related to the distributor which is a chrome 009 with only a single spring on the weights. Crappy choice but I had a MagnaSpark for it which wouldn't fit due to the oil line location. I'd like to raise the idles to 55 and I think it would help the off idle stumble and popping however, I already need to lower the at idle RPMS and figure this won't help. These 44s just may be too big for it? I can't seem to find any smaller venturis for the 44s. If I need to get a set of 40s I will. I have a 2.0 longblock with big valve heads still in the parts gathering stage and will use these carbs on it instead.
Bottom line is this; Is there no way to slow the idle? If I need to go to smaller vents, It looks like a different set of smaller carbs.
carbs too big.......bitch to tune....Dell 36s perfect for this!
or you could build a bigger motor! <3
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I agree, you are using 200hp intakes on 100hp motor, so while it will run it is not a good fit.
You will probably always have tuning challenges...am skeptical a vent size would help idle..maybe for transition
About all I would verify is that the little used idle air bypass circuits are closed (one never knows what previous owners do)
Yeah some may call it overkill, but you can't have too much overkill.
The idle issue may be an air leak , or I have you checked that the air bypass screws are closed all the way on all 4 throats ?
According to a weber Venturi selection chart 32mm vents should be about right . In a bus it wouldn't be ideal with the 44's but in a light bug you may get away with it as long as you don't expect to be able to mash the throttle at low revs .
There is a very long(because people don't read the first 15 pages !) and good thread on the samba on setting up dual throat carbs under the Wideband results thread .
Try and find a original type 4 distributor , hook up the vac advance and throw the chrome 009 in the bin .
As above, If you isolate the linkage from the carbs,back the butterflies off so there closed AND it still runs there's an air leak or someones drilled a hole in each butterfly, I've drilled mine for a tune up reason.
I was also going to say intake air leak, but was beaten to it.
Same with making sure bypass screws are closed..
Still un-mentioned is bent throttle shafts.
This is common, especially on VWs with their odd linkages.
Have to make sure the shafts are straight and not bent or twisted,
Otherwise the butterflies won't seal tight.
IMHO, you should be able to make a set of 44s idle correctly.
With small vents, they should work well all around.
Did just that with a set of 44s on a stock 1600 years ago..
Thanks for all the replies. The carbs are basically brand new so nothing bent and no holes drilled in butterflys. I'm using LinkSync cable operated linkage so no issues with out of wack or tight joints. Air bypasses are all closed. No vacuum leaks as far as I can tell. I do believe they are just too large for this application. I'm going to try and fit a set of ICTs from CB performance. I had them to start with but couldn't make the linkage work. Now I think I may be able to make them work with the new linkage being offered by Vintage Speed Taiwan. I'll update when I get the new setup.
Simple question is there slack on the cable joining the 2 carbs while you try to sort out the idle issue . Maybe try taking the sync link off the throttle shafts and see if you have the same idle speed .
if you take the carbs off , with the butterflies closed ,there should be no daylight getting past the butterflies if you look up the throat . If the butterflies are fully closed the engine shouldn't run . It will not be getting any air .
If they are new, are they Chinese copies?
If yes, they need careful inspection, clean & any issues corrected. For example, the butterfly plate may not be fully seating. If that’s the case, you can loosen the screws, lightly snap the throttle shut to centralise the butterfly and retorque the screws (threadlock if you like). That’s just one example. Spindle leaks are another.
Webers to ICT'S noooooo, stick with it .If you put the palm of your hand over each velocity stack ,it should try and suck your palm in to the throat. A BIT. When it does this you may hear a hiss sound from the air leak. This sound is air being drawn in through the air leak gap.
