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FUELforTHOUGHT
by Dave Koehler
8/9/04
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I have a hat
injection. What is the proper way
to adjust BV? I have heard to set
butterflies .006 and leave it alone-never
touch after that. Then set idle
at 1500. But for BV if you lean
it out until stumble (of course
rpms go up) would I need to adjust
butterflies to keep idle at 1500
while looking for that stumble and
then richen it 2-3 flats? I am totally
lost on correct procedure. Hope
to hear from you soon.
Thanks,
Bill
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Bill, The "leave it alone" deal is
because those big butterflies create a lot bigger
air leak than a carb does, but you can fudge
it up a little to gain rpm. I would not go less
and risk having them stick. You will have to
richen the barrel valve to bring the rpm back
down to your rpm target. Some call this adjustment
dance the Butterfly Barrel Valve Two Step.
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Simply
put, your final idle rpm is actually controlled
by adjusting the fuel delivery at idle while
leaving the air leaking butterflies pretty much
alone.
As to where it should idle? Wherever it is
comfortable for you, the engine and the converter.
1000 - 2500 rpm is common. With the engine warmed
up, (trying this with a cold engine is useless)
do just what you are saying. Lean it to bring
it up the rpm and richen it to slow it down.
I am assuming it idles now but you might be
trying to make it "crispy". Yes? Crispy
can be construed as using very little fuel at
idle. Wrong idea. You are looking for a "gee
whiz, WOW!" response when you snap the
throttle.
Okay, having said that, let me throw a red herring
in here. If you bring the rpms up at launch,
then the off idle response doesn't mean a whole
lot. You could adjust it so that it uses as
little fuel as possible at idle but you probably
won't be able to snap the throttle from idle
without a backfire. The procedure with a warm
engine and a "crispy" idle would be
to roll into the throttle slowly to get the
pump up to speed when doing a burnout or driving
around.
Are we gaining on it?
Dave Koehler
www.koehlerinjection.com
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Previous
Stories
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Fuel
for Thought
—
7/7/04
Dave Koehler answers your
nitrous & fuel-injection
related questions
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