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Fueling Around: Better Carburetor Tuning

by Richard Ehrenberg.
Copyright © 2005 Richard Ehrenberg. Reprinted by permission.
First printed in Mopar Action

We're bound and determined to get
our carburetion ills dialed out. Step one is drilling a
hole in the exhaust pipe or collector.
Those who don't recall, our tall-geared, tightconvertered,
hot-cammed engine kinda laid
down about 100 feet out of the starting line,
and didn't really come back to life until a
few hundred feet down the dragstrip. Not a
full-fledged bog, just extreme "laziness."
Tired of shots in the dark, we decided to
avail ourselves of the latest tuning aid: the
UEGO oxygen sensor.

concept is simple: a spark-plug-sized
sensor mounts in the exhaust stream, and
generates an output voltage in proportion to
the air/fuel ratio.
For years, we've been using oxygen
sensors as a tuning aid, hooked up to one
of many aftermarket display gizmos that
convert the sensor's voltage to a
comprehensible reading. However, the
standard O2 sensor has a fatal flaw, at least
when is comes to performance use: While
being extremely accurate and repeatable at
ratios of around 14.7-14.85:1,
and equally accurate at leaner mixes, they
are notoriously inaccurate on anything richer, making them ineffective as a
performance tuning aid. Consider them an
emission and fuel economy device.

The new generation of widerange
(UEGO) sensors overcome that
limit, but have, until recently, been expensive. Recently, the price
of the sensor has dropped dramatically. Most of the devices
on the market are space-age-looking
rectangular, digital-only displays, something
clearly out of place in a '69 Road Runner.
Then we spotted Advance Engine
Management's P/N 30-4211 unit, which
combines the latest technology into a '60s-style
round gauge case, at reasonable price.
The AEM has a further advantage of having
both a 3-digit LED digital display, and a
round LED bar graph of LEDs that are, in
effect, an analog, read-it-at-a-glance
pointer. The one we picked even has white-on-black lettering.

Jaw Font Spoke Circle News

Old school meets new,
and everybody's happy.
Installation was easy, with the only
step requiring more than a minute's work
was drilling and welding the sensor's
mounting bung into the header's collector.
We must add, however, that the
AEM-supplied instruction booklet was one
of the best written, clearest, and most
informative we've seen. Whoever their tech
writer is, he's got us looking over our

Only two caveats here: The exhaust system
should be leak free upstream, and at
least 10˝ downstream, of the sensor, and
the business end of the sensor should
always be at least slightly lower than the
wiring end to prevent condensation
collection at the tip.
Now the sensor simply screws in. While
the guts are super high-tech, the
installation is monkey-wrench simple.
For now, we simply lashed the AEM's
display to the side of our existing gauge
panel with a cable tie. We'll probably
wind up making a second gauge panel to
take the place of the ash tray.
The display, being only simulated analog,
has right-now response and zero lag and
overshoot. It's super visible, day or night.

The AEM deal comes pre-wired, just plug
it in. You only need to hook up one
ground wire and a source of switched
twelve volts. (The AEM does provide data
and raw sensor voltage outputs for use
with PCs and dataloggers.)
We used a die grinder-you could also
use a rat-tail file-to size the hole for the
sensor bung.

Advanced Engine Management,
2205 126th Street, Unit A, Hawthorne
CA 90250; (310) 484-2322

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