Question for Weber downdraft gurus

[sreams]

So, I've been doing quite a bit of reading, and I've found a few really good resources that describe the roles the various air and fuel jets play in Weber carbs. My favorite so far is this one:

http://www.datsun2000.com/tech/weber_tuning_methodology.htm

It incudes a chart which shows how much of a role each jet plays at various levels of air flow.

My problem is this: Pretty much every one of these websites describes how various jets are important at various rpms. For instance... the idle jet supposedly has nearly full control over mixture at 2500rpm. But none of these sites seem to consider the impact of load and throttle position. I can see how the idle jet would directly affect mixture while cruising at 2500rpm, but would it also fully control mixture at full throttle at 2500rpm? My guess would be no. Yet this and every other site only ever describe the role jets play at particular rpms. What say you all?

 

[Stevehose]

My experience so far with tuning my triple weber side drafts is that load reduces those numbers by around 1k rpm, so if the idle jets crap out at 2.5k rpm in your garage, on the road they will crap out at 1.5k so the mains need to come in at that point for a smooth transition. Road testing is the only way to accurately dial this in - along with an AF meter.

 

[Mike Goble]

The idle system is progressive. At 2500 rpm in your driveway, the throttle opening will be much different than at 2500 rpm on the road. Moving the throttle butterfly above the idle fuel port introduces a second source of fuel, and as the vacuum in the venturi develops, more fuel is introduced through the main jets.
As the intake vacuum fluctuates, the amount of fuel attracted through the idle circuit will vary. Your accelerator pump should cover this until the mains take over.

 

[61porsche]

The idle circuit is primary up to about 1100 rpm. ( Yeah , yeah, the choke too.)

Above that both the idle and primary are working to say 3500-4000.( At cruise or part throttle)

At 2500 rpm or so, mashing the pedal opens all three plus the pump circuit. Rich mixture needed for max hp.

If what you're asking is how do I get more seat of the pants feel at 2500? Downshift. Get into the torque band.

Now you also didn't say what webers? The neat trick now on 32/36s is to modify the linkage to work like a 38.(both barrels open simultaneously) Pierce manifolds, I believe is the ticket.

But if you're really saying you have a bog or stumble then try to describe the symtom in detail.

 

[sreams]

I'm not trying to address any problem in particular. I mainly want to become more familiar with the roles the various jets play so that I can become more self sufficient when tuning Webers (on any car) in the future.

My car's engine has no discernible flat spots. It runs very well. But I wouldn't mind being able to fine-tune mixture at full throttle (for power) and at cruise (for mileage). I'll be hooking up a wide-band O2 sensor to help, and I'd like to be able to change jets with confidence, knowing what will be changed.