OK, but O2 sensors produce voltage in the sub-millivolt range.
How are you going to correlate, say, 0.16 millivolts with power?
At most, the sensor will--with a suitable table of voltage/O2 content
mixture values--tell you whether your mixture is relatively lean or rich
at any given throttle position, but not whether that is the best setting for
power.
Regardless of the needle profile, Healeys (and most older cars) run best
with a richer than stoichiometric mixture. Rich mixtures foul O2 sensors in
a matter of minutes (or less). Last time I bought an O2 sensor it was over
$80, with one for each cylinder that's almost $500 worth of sensors to
be replaced fairly regularly.
Like I wrote, if you want to rig the car this way, and correlate sensor
readings with power output using a dyno you might get some improvement.
But there's other things you can do to get more benefit with less work.
Unlike typical (American) fixed-choke carburettors, when you set the
mixture at idle of an SU you ARE changing the mixture at all throttle settings
... this
is one of the benefits of its elegant design. If you're really into fine-tuning
SUs, you put the car on a dyno and alter the needle profile to produce the
best power at given throttle positions.
bs
********************************************
Bob Spidell San Jose, CA bspidell@pacbell.net
'67 Austin-Healey 3000 '56 Austin-Healey 100M
********************************************
----- Original Message -----
From: "Blue One Hundred" <international_investor@yahoo.com>
To: "Bob Spidell" <bspidell@pacbell.net>; "Healey List" <healeys@autox.team.net>
Sent: Sunday, June 20, 2004 7:24 PM
Subject: Re: Oxygen Sensors
> Bob -
>
> Although I agree with you in principle... the truth is
> that with a sensor, you can do a much better job of
> tuning the car under load - the piston lifting method
> is really only good for setting mixture at idle.
>
> With the SUs the needles rarely, if ever, have the
> right diameter profile for each car... this is where
> the sensor really helps... it helps you adjust the
> needle profile for optimal performance when you are
> under power or at high speed.
>
> All this means is after installing the sensors, the
> car owner would probably run through about three or
> four different needle profiles until they set on one
> that gives the best combination of performance and
> mileage... might even save enough gas over time where
> it'll pay for the effort in a couple years. This is
> especially true for anyone that has modified their
> motor with a rally spec cam, high profile rockers or
> non-standard pistons.
>
> Regards,
>
> Alan
>
> '53 BN1 '64 BJ8
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