Do IFR's Have a Effect at WOT?

[RD_Racing]

Do the idle feed restrictors have any effect on delivering any fuel at WOT in the mid to upper RPM range?

[Walter R. Malik]

Do the idle feed restrictors have any effect on delivering any fuel at WOT in the mid to upper RPM range?

YES ... but, not how you probably think.
When there is enough depression within the main well the Idle feed restrictions can become another place to bleed air into that main system.

[Mike Laws]

Do the idle feed restrictors have any effect on delivering any fuel at WOT in the mid to upper RPM range?

YES ... but, not how you probably think.
When there is enough depression within the main well the Idle feed restrictions can become another place to bleed air into that main system.

This...

[MadBill]

Can it have enough of an effect to measurably alter the WOT fuel curve compared to much bigger/smaller IFRs, or is it more a theoretical than a functional effect?

[RD_Racing]

I reduced my IFR's by 5 numbers (that got my idle mixture screws where they needed to be) and then made a test hit and it felt like it didn't pull as hard so I was wondering if I needed to jet up a little to compensate?

[levisnteeshirt]

I reduced my IFR's by 5 numbers (that got my idle mixture screws where they needed to be) and then made a test hit and it felt like it didn't pull as hard so I was wondering if I needed to jet up a little to compensate?

Just a 60ft or full pass

[Walter R. Malik]

I reduced my IFR's by 5 numbers (that got my idle mixture screws where they needed to be) and then made a test hit and it felt like it didn't pull as hard so I was wondering if I needed to jet up a little to compensate?

If you are referring to Wide Open Throttle then increase the HSB a couple thou.
If Part Throttle is the issue, it will require some slot tuning or re-arranging some emulsion bleed locations.

[RD_Racing]

Just a 60ft or full pass

I went through 1st and most of 2nd to about 80mph

[RD_Racing]

I reduced my IFR's by 5 numbers (that got my idle mixture screws where they needed to be) and then made a test hit and it felt like it didn't pull as hard so I was wondering if I needed to jet up a little to compensate?

If you are referring to Wide Open Throttle then increase the HSB a couple thou.
If Part Throttle is the issue, it will require some slot tuning or re-arranging some emulsion bleed locations.

It was full throttle, it just didn't feel like it pulled as hard as it did the day before I reduced the IFR's (same road, same test hit).. I have dual carbs and the IFR's in both were reduced.. Everything else, including part throttle seems perfect.

[jmarkaudio]

Reducing the idle feeds alone would bleed less air in at WOT. Try dropping the jet one, see if that helps.

[RevTheory]

Wow, I had no idea that well depression could pull air through an idle feed restrictor. It doesn't do that with the restrictor at the bottom of the metering block, does it?

[Geoff2]

Do not see how reducing the IFR would reduce/bleed the air into the system at WOT.

[Tuner]

Do not see how reducing the IFR would reduce/bleed the air into the system at WOT.

LOL Among all our various human talents, some have 3-dimensional imagination and some don't.

To visualize this: At WOT, where is the lowest pressure in the carb?

[Geoff2]

At the booster.

From the original Holley book by Holley engineer Mike Urich: "When the throttle is fully open, there is not enough vacuum at the idle port to draw any fuel-air mixture through the idle system".

[Walter R. Malik]

At the booster.

From the original Holley book by Holley engineer Mike Urich: "When the throttle is fully open, there is not enough vacuum at the idle port to draw any fuel-air mixture through the idle system".

EXACTLY ... however, there is sometimes enough depression in the main well to draw air from the idle circuit in the opposite direction.
What is connecting the idle circuit to the main well ...? The Idle Fuel Restriction.

Also, another quote from Mike Urich within that same publication,
"When tuning, it the results differ from your theory ... believe the results and invent a new theory".