Ferrari Mailing List: Re: checking air/fuel ratio

[Hans E. Hansen (FList]

James:

I've used the LM-1 and you will go thru piles of O2 sensors
on a typical carb car.  They apparently were not designed
to withstand the occasional rich conditions that even a well
tuned carb will exhibit once in a while (like cold start).  If your
carbs are way out, you'll use several sensors just getting them back
in line.  They seem to fair better with properly set up Webers,
but a trip around the block in a Holley equipped car will
clog the sensor.

Easiest way to set up Webers:  1. Get it idling well, using your
ear and a decent shop tach.  2. Change out idle jets going
lean as possible until driveability issues crop up at low speeds.
3.  And for WOT, take it to a dyno and measure the
actual A/F.  It's a good idea to set up the carbs in this low-to-high
speed order as the fuel systems tend to be additive.  If you do
the dyno run first to set up mains and air correctors, and then
later find you want to change the idle jets (a bit of a misnomer...),
you could screw up what you learned on the dyno.

Lean at cruise is OK, won't burn pistons, etc. and will keep
engine clean.  Lean at WOT = bad.  Find a dyno.  It's cheaper
than the LM-1.

Hans.

On 1/30/08, Jeff Greenfield <coyote [at] acme-ltd.com> wrote:
> Other than looking at the plugs (best done immediately after doing a
> plug cut, where you drive at high revs, kill the engine without
> backing off the throttle, coast to a stop and pull the plugs) there
> really isn't a good way without instumentation.
>
> The best is to install a bung in the exhaust for an oxygen sensor and
> use one of the many available mixture indicators.
>
> I like the LM-1 and other wide band products from these guys, but
> there are many that will do.
>
> www.tuneyourengine.com
>
> Jeff
>
> Sent from my iPhone
>
> On Jan 30, 2008, at 3:32 PM, "James V. Cunningham"
> <vikelj [at] comcast.net> wrote:
>
> > Does anyone know how to check the air/fuel ration (running lean or
> > rich) on a car without a catalytic converter or an O2 sensor?  Thanks.
> > Jim
> >
> > James V. Cunningham, Esq.
> > 410-625-7400
> > http://home.comcast.net/~vikelj/page3.html
> >
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