Does fuel movement in bowls during acceleration impact AFR?

[BradH]

When a carb is installed in the traditional primaries forward / secondaries rearward configuration:
a) Does fuel being pushed away from the secondary metering block during acceleration affect the AFR, assuming that the jets remain immersed in fuel?
b) And, conversely, does fuel being pushed toward the primary metering block during acceleration affect the AFR?

I think the answer to both is "no", and that the fuel level is the influencing factor. However, I still wanted to ask. Thanks - Brad

[dannobee]

Holley and Moroso make jet extensions to help with secondary fuel starvation under hard acceleration.

[BradH]

Holley and Moroso make jet extensions to help with secondary fuel starvation under hard acceleration.

That's what my qualifier "... assuming that the jets remain immersed in fuel" was intended to cover.

[David Redszus]

Simply plot in- line G forces against lambda values.

The a/f shift due to G forces may be obscured by variations (jitter) in Lambda readings.

[BradH]

Simply plot in- line G forces against lambda values.

The a/f shift due to G forces may be obscured by variations (jitter) in Lambda readings.

And I thought it was a pretty obscure question, only to have found this thread from years ago: viewtopic.php?t=26474

I must apologize in advance: I didn't realize it turned into a Schmidt vs Patterson pissin' contest for most of the thread until I read all of it.

[BlitzA64]

I would say if the fuel stacks away from or up to the metering block opening or covering an emulsion hole that usually the opposite would be normal my assumption would be yes it does. From data on my roundy round stuff it seems that way in corners. Interested to see what the carb guys may say

[BigBlockMopar]

Perhaps unrelated because Carter/Edelbrock carb aren't considered 'racing' carbs, but the long rammed engine in my '60 Chrysler loses power and occassionaly starts to run very rough during 'sporty' cornering. It's my believe one side of the engine goes rich while the other side goes lean.
The carbs are placed sideways on the long ram intakes, so different from their normal orientation.

[smeg]

I know that it does in the plenum at the drags.

[Jeff Lee]

If the float level can effect the rich / lean conditions due to the weight of the fuel on the jets, then I would surmise different amount of “slosh” can have some effects also. I am a firm believer in isolating vibrations to the carb as I have seen for myself that vibration isolations on my AMX Stocker were not only good for 1.2 average / 1.7 HP peak on dyno (I know, “big deal”), but it straightened out the BSFC which made for easier tuning in other departments. I also believe there is a lot of power to be had in controlling aeration which is typically from to much fuel pressure. Air and fuel travel through a jet just fine but your not getting the true amount of fuel you have jetted for. Have some new tricks up my sleeve to alleviate this on my small bowl, small CFM Autolite carb. Many challenges with this carb!

[Lizardracing]

Is this not the same idea as the Willis Super Bowl?

[SchmidtMotorWorks]

If your car only pulls 1G then it is similar to an engine on a dyno with a 45-degree incline.

[SchmidtMotorWorks]

Simply plot in- line G forces against lambda values.

The a/f shift due to G forces may be obscured by variations (jitter) in Lambda readings.

And I thought it was a pretty obscure question, only to have found this thread from years ago: viewtopic.php?t=26474

I must apologize in advance: I didn't realize it turned into a Schmidt vs Patterson pissin' contest for most of the thread until I read all of it.

Having worked at Edelbrock since this thread, I can confirm that everything I posted there is understated.

[MadBill]

I'm not up for revisiting the SMW/TP thread so this may be a repeat, but: although extensions keep the rear jets from sucking air under hard launch conditions (There's a great video of a see-through bowl during a fast 1/4 pass somewhere on S/T, perhaps by Ryan Brown Racing) , there still is an instantaneous lean out due to the changing depth of the fuel affecting the Delta P and thus the flow, just like lowering the float level.

Longer term (say several seconds plus), depending on the fore/aft location of the center of buoyancy, the float could be lifted or lowered by the sloshed fuel, producing a potentially long-term lean out.

[dannobee]

Bill brings up a good point about a more sustained rather than instantaneous lean condition.

I know some guys used to angle cut the nitrophyl floats to combat the fuel slosh (and the corresponding lean condition) in high G circle track cars. It's not a stretch to think that it would work on a drag car. Just cut an angle on the bottom of the long part of the float instead of the side.

Obviously if the fuel stacks up in the bowl, no matter which way, it'll cause the float to rise up and shut off the needle valve.

[Mikej26]

Even if the jets remain covered and regardless of what is happening with the float and needle and seats, wouldn’t the relative increase in fuel level at the front metering block and the decrease in the fuel level at the rear metering block directly affect the emulsion circuit. As well as provide a increase in fuel pressure on the primary jets and a decrease on the secondary jets due to inertia?