> Aribert_Neumann wrote:
> I am considering installing an O2 sensor and an A/F gage to monitor my
40DCOE
> carb set up. Specifically looking at the $35 J C Whitney A/F gage (as
opposed
> to the $120 K&N unit sold thru Pegasus Racing Supplies). I am assuming
that
> the gage is no more that a mili-volt meter. Anyone have experience with
using
> A/F gages in general and the J C Whitney A/F unit in specific?
> Follow up question - how long will an O2 sensor last when the A/F mixture
is too
> rich (hours/miles - exhaust tips are sooty)?
I went the cheap route and built my own O2 sensor monitor. The wiring
diagram is out on the web at
http://www.students.tut.fi/~eppu/dev/EGO-bar.html. There are a number of
designs designed around the LM3914 chip ($2 - $5) so a quick search on the
net will ferret out more data. I incorporated a junkyard Ford Escort sensor
($5) that includes and internal heater. As long as the sensor is near the
engine (mine is at the bottom of the down tube) there is no need to wire up
the heater unless you plan on doing a lot of tuning at idle. Also you might
encounter discussions about how the sensor is subjected to a oscillating or
triangular signal that must be filtered. This only applies to computer
controlled cars and is not applicable for your application.
What you will find is the fact that the biggest variable when tuning carbs
is the underhood temperature. A 50 degree Fahrenheit change in temperature
creates a 10% difference in the air to fuel mixture ratio. With the Zenith
carbs there is no way to compensate for this temperature variation short of
tweaking the mixture constantly.
My exhaust tips are sooty and I've gotten over 12,000 miles on a two used
sensors (one for each exhaust).
I should also mention that the web has information on how to test used
sensors with a propane torch to ensure that you have a good one. Let me know
if you can't find the data and I'll see if I can find it again.
Good luck and contact me if you need more information
Lee Janssen
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