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How to select the right carb boosters?

General engine tech -- Drag Racing to Circle Track

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F-BIRD'88
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Re: How to select the right carb boosters?

Post by F-BIRD'88 »

Tuning using a wide band may be part of the problem.
Give it the fuel it wants to go fast VS some text book AFr @wot... Let it eat as required. Use the afr meter as a basic "your getting pretty lean bud" warning device to keep you out of trouble....

IMHO the 750 carbs (any brand/type carb) are generally just more powerfull than any 600-650 cfm carb or any type..
Doesn't matter if its on a 305..... or.... the 750…s just make more Top end WOT power and run at least a bit faster on pretty much everything... I hope that 650 avs2 carb is not really as lame (WOT power) as you are seeing.
I have the benefit of measuring the performance on the car of compare various carbs and stuff. Never yet messed with the 650 avs2 carb yet.. Joe Sherman liked the 800 cfm avs eddy carb. (Previous version before AVS2 series.
plovett
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Re: How to select the right carb boosters?

Post by plovett »

BOOT wrote: Wed Jun 09, 2021 9:58 pm
plovett wrote: Wed Jun 09, 2021 4:28 pm What is the connection between heat and annular boosters?
From my understanding this is how it works

Heat aids atomization but hurts performance, less heat(cooler engine) increases the need for other means to aid atomization. This is why injectors are great at cold start-up and driving w/o warming up first, also why OEM's used the exhaust heat to warm the intake faster for carbs. Heat does causes expansion, cool more dense air and atomized fuel make more power. On a hotter running engine dumping(not really) fuel cools the intake so it doesn't heat up n expand the air(NA it's harder to increase air than fuel) and that causes the fuel to atomize, if the fuel is already atomized then it doesn't cool nearly as well decreasing the density of air.

To be clear a carb does not dump fuel. Opening the throttle allows atmospheric pressure to drain into the engine and that draws fuel from the bowls.
Thanks. Makes sense. Annular boosters make a carb a bit more like fuel injection in that respect.

I wonder if standard boosters would be better in a supercharged non-intercooled blow-through engine? More charge cooling? Seems that all the blow-through carbs have annular boosters though. I assume that is too maintain a decent A/F ratio at very high airflow through the boosters?

paul
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Re: How to select the right carb boosters?

Post by jmarkaudio »

Blow thru I would tend to run annulars. Roots style supercharger is more aggressive and generate a lot of heat, downlegs are fine for those.
Mark Whitener
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