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Re: Air/fuel ratio monitors

To: "Deikis, John G" <John.Deikis@va.gov>
Subject: Re: Air/fuel ratio monitors
From: Dave Carpenter <d.carpenter7@verizon.net>
Date: Thu, 26 Apr 2007 21:27:40 -0400
I had both an A/F meter and an exhaust gas temp gauge on my turbo car 
that I drag raced. I think  the EGT gauge was probably the better of the 
two. It had a small probe that you drill a hole into the pipe and 
wrapped the hose clamp around the pipe. No leaks. Got it from an 
airplane supply for about $85. It was quick to react to changes in 
throttle setting and load. Richer=cooler, leaner=hotter.
Dave

Deikis, John G wrote:
> A question for you engineering types:
>
> I'm thinking about monitoring my A/F ratio to try to keep my car from
> holing pistons at inopportune moments.  I've read up on the limitations
> of using the cheap 3-wire O2 sensors and the relatively inexpensive
> LED-segment or needle swinging processor gauges (total cost maybe $50)
> vs. using a UEGO sensor and 0-to-1.0 volt digital read out display
> (total cost $250-500). Keeping in mind:  no ECU to control, no turbo, no
> fuel injection...just Mr. Skinner's wildly exotic array of metering
> needle profiles to choose from.  The issue that I've read about
> repeatedly is that the older narrow-band sensor samples a more or less
> binary output and averages the voltage to light up the appropriate
> number of LEDs on the gauge.  This is non-linear and so only tells you
> are you "on the rich side", "on the lean side", or stoichiometric.  It's
> also criticized for being too slow in its response.  The UEGO-volt meter
> set-up is more precise and can give you an actual A/F ratio to look at
> more or less instantaneously.
>
> So...since I don't have to control any electronic engine management
> systems, do I need to know more than "too lean", "too rich," "just
> right" to diagnose high exhaust gas temp issues or to select the best
> needle profile for a modified motor?
>
> I am trusting you guys with my money, so advise me wisely!
>
> -JohnD




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