Weber 32/36DGV verses the Weber 38DGES

yodta
(pooh bah)
Sat Apr 09 2005
05:04 AM
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What the heck, as long as we're on the subject of main jetting and results ...
Emulsion tubes. It had been mentioned before on this long and tired post , but here's some details about my replies.
F50 emulsion tubes are just a baseline installed in DGV's for sale in North America . It is well understood that most of us here are
satisfied with "it starts and moves" . Not so in Europe and if you look at factory E tube types/sizes you will find some surprises.
Not one engine type near the 1.2-2.0L size will use an F50 E tube. Why? Well, several reasons and some are almost startling.
Take Yodta's jetting:
75/60
140/150
185/190
A 75 idle is very high, most Euro cars use 45's at most. His main jets also warrant a close inspection of how the carb is being
metered. A single carb on his type intake is naturally going to exhibit this trait, almost no way around it since the total volume of
the 4 cylinders will overcome the transition too quickly at initial throttle movement. A couple of things can help;
Increase the accelerator pump nozzle size
Lose that F50 Etube!
The size and orientation/height of the holes in the Etubes govern how/when/where/how much air is blended into the fuel stream
for the venturi. Float height is also criitcal as the amount of fuel in the wells also governs how the Etubes work . Upon close
inspection, the F50's have a lot of small holes near the top of the tube but almost none at the bottom . They are also fairly small in
overall diameter as well as the interior hole size and depth. This overall design produces a lean mix at low velocity (read: during
transition to wide open throttle). Consequently, you have to increase the main fuel jet size to correct it . But, in doing so, the air jet
must increase a LOT due to almost no air being mixed during high velocity(wide open throttle/high revs). So, the F50 is really not
a good choice. Remember my comment about the Suzuki's using 75 idles commonly? Same problem, same manifold/engine
design just smaller. In this case, an F6 would be a better choice since it will provide a steeper fuel curve initially and lean out
properly at higher velocities. Now, unless you have a very extensive set of tubes and the time to play with them, the F50's work
fine and can be dealt with. But , the F6's can actually give way better response to jetting as well as better fuel usage.
So, what do you folks think of all that now that my fingers are sore and I'm blind again? BTW, sent Yodta some Etubes to
experiment with, I'm also interested in tube changes in Toy's since I also build carbs for them...
Sarge
Re: Weber 32/36DGV verses the Weber 38DGES
okay, first, as noted, that jetting config was killing me, so made a couple of quick changes tonight before installing the new
RAM-Flo filter.
I'm now at:
idles: 70/65
mains: 140/145
airs: 175/180
seems to run best overall with the timing around 3-4*
seems a little more solid here. it was just too flat in the bottom end the way I had it before. I'm after good solid response
throughout the driving range. this is like a friggin' rubik's cube -- easy to get one side, but hard to get all sides solved.
Sarge, you're right -- the 32/36 on my truck has 3.5/4.5 aux venturis. and you're right about my thinking I needed a larger main jet
in the secondary. I mean, it only makes sense that more air needs more fuel, right? apparently not so. I hadn't considered the
vacuum's effect.
I've been following along in my pierce manifolds Weber Tuning Manual -- they say the same thing about the e-tubes -- holes at
the top are for mixture weakening at low rpm or slight acceleration. tubes with holes at the bottom are for enrichment at low rpm
or slight acceleration. my solution was going to be an huge primary idle jet (80), a 140 main, and a 185 air. that's ridiculous when
I can avoid this situation altogether by changing to an e-tube that will enrich the mix at the lower rpm allowing me to use smaller
jets all around, but that's where I was headed.
and guys, for those of you who've never seen an emulsion tube, here's a quick (and crappy) scan to give you an idea. the
emulsion tube sits in a well right underneath each air corrector jet. looking at the F6 compared to the F50 which is stock (note the
difference in placement of the holes guys), my questions are (1.) how will this affect the response at higher rpm?, and (2.) what
kind of jetting are we looking at now? significantly smaller jets overall? how will this affect fuel economy?
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