Weber 32/36DGV verses the Weber 38DGES

yodta
(pooh bah)
Tue Apr 19 2005
01:10 AM
Sarge
(carpal tunnel)
Tue Apr 19 2005
03:24 AM
yodta
(pooh bah)
Tue Apr 19 2005
01:39 PM
Re: Weber 32/36DGV verses the Weber 38DGES
I went back out a little while ago to mess around some more. I couldn't get it to idle at all with the throttle plates closed all the
way. had me scratchin' my head.
anyway, now here's what's really puzzling me.
if I set the mixture screw with the throttle plates closed, and then I reset the idle to something usable, it runs like crap unless I
open the mixture screw more to stabilize it. what good is that?
anyway, with the idle speed screw in just to keep the engine running at 400rpm, ever so slightly engaged throttle, I decided to try
changing the main jet to see if I could get rid of the stumble as I increased the throttle to 2000rpm. with the screw set at 400rpm, I
went to a 150/180 main/air combo, and it still ran crappy up to 1200rpm before clearing up. thinking I went the wrong way with it, I
went to a 130/155 main/air combo, and it still did it and seemed to be worse.
at this point I was thinking I missed something and started thinking about the mixture screw and noticed that when I opened it up
a little more, the bottom end was much smoother.
anyway, I took it for a ride. it's nice, but pretty much the same as it ever was so I don't think I did this right, though I do notice that
the A/F meter is more responsive now. it goes lean on cruise, and responds to slightly richer than stoich on throttle off of cruise.
anyway, I'm surprised at the way it runs with this jetting:
60/65
130/140
155/180
Re: Weber 32/36DGV verses the Weber 38DGES
Ok, let's do some analysis here . The jetting and idling tests show two things. One, main jet sizes are very, very close. Not sure
which F tubes you have installed at this point but for now we'll ignore that and explain what you are arriving at.
Main jets do two things: provide just enough for reasonable power at cruise without a large enough load to activate the power
valve. Two, the size should show just at the lean edge to provide fuel economy without sacrificing driveability. You seem to be
right on the edge of it here. At this point, you adjust the air jet size to bring response and proper mix to the upper end of that
throat. If you have to constantly readjust the idle mix screw to keep the idle running correctly AND have a flat area during the
speed test then the size must be increased. Under a load that test will verify the idle jet is too small for sure. Throttle response
just off idle is probably slow a bit or may even show a flat area . It should take very little throttle to get the truck moving and
actually be a bit touchy to pedal input. One thing to be cautious about is the cruise, if you are driving with very little throttle input
and the meter is showing lean there is a chance you are low enough on the throttle to be running partly on the transition. This is
why the primary idle jet is so important , it is to keep from overcompensating the main to make up for a lack of fuel when the main
is not FULLY operational. Throttle position determines which circuits are active, the overlap between them is the spot that has to
be tuned the most.
This is the whole balancing act here. Too small an idle jet results in too large a main jet, and vice-versa. You also have to take
into consideration how the air jet is affecting the main at lower throttle openings. With certain emulsion tubes like the F50 the low
end of the main circuit is affected quite a bit . F6's and such are not and will exhibit totally different low end properties. Throttle
position must always be considered when trying to tune out problem areas , the farther the opening the less the transition is
active, even at low rpm's. Feathering the throttle lightly will show the problem areas, fast throttle will verify correct tuning overall
but not give good driveability . Also, when you get this close you almost need to move only one step and one jet at a time. Drive it
to work and back home, then do your changes and note results the next day. Constant jet changes confuses the mind and after
awhile you really get lost easily. I do it myself when I'm in a hurry. Also, all vacuum connections and timing advance have to be
hooked up when tuning otherwise settings will be wrong.
The final post's jetting is close , I'd try this :
60 idle
135 main
160 air
Watch out for that spot where the main leans out too much at cruise. You not only risk burning valves but lose power and fuel
mileage running it too lean . It should be just about dead center on the meter so the power valve can do it's job when the engine
feels a load. Slight inclines shouldn't need more throttle input or very little to easily overcome the load.
Don't worry about the secondary for now, just make sure it's not leaning out when you do have to use it . The primary has to be
tuned first and seperately since the secondary is an ADDITION , even with that dual runner manifold. Driveability is the whole key
here , response should be smooth and crisp at almost all times, even when loading the motor below it's pull ranges. Got a
migraine yet? LOL>..
Sarge
Re: Weber 32/36DGV verses the Weber 38DGES
okay. I need to order a few more jets. my airs go from 155 to 165.
I have the F6 in the primary & the F50 in the secondary.
43 of 88