Air/Fuel ratio meters

[1965 Mustang]

Being a tool junkie, I am thinking about buying an air/fuel ratio meter (have not used one in almost 50 years) Are there any reasonably priced ones on the market today that will work with old, carbureted cars? Most of the one's I see online are for permanent installation and seemed to be intended for use with modern cars that already have O2 sensors and computers. Thanks

 

[TomInCologne]

i have had my A out today and got the flue gas analyzer out of the toolbox. It's not a special automotive one, i use it for huge gas burners but the results may give you an idea.


I put the analyzer probe into the exhaust pipe, about 100mm/4" in. That's the maximum length of my probe. Did it pickup any false-air? Maybe.


@400rpm, idling
O2 18,8%
CO 2.100ppm
exhaust gas temperature 70,7°C


@700rpm
O2 14,6%
CO >16.000ppm
exhaust gas temperature 91,2°C


@1.200rpm
O2 13,3%
CO >16.000ppm
exhaust gas temperature 137,6°C


I am pretty sure that the O2 values are way too high, this would mean a pretty lean combustion...

 

[32Ford13]

From what my old memory tells me, the pick up needs to be closer to the head for accurate readings. A bung welded into the down tube hidden on the inside towards the block, then install probe and take readings as needed? Got me thinking now....

 

[TomInCologne]

i thought so but i am not going to take anything apart or drill holes…

 

[Flathead Fever]

I was mechanic for the phone company for 30 years. We had to have smog licensees since we were able to smog our own vehicles. I also worked for the state of CA developing the smog test questions for the new mechanics. I ate and slept all those exhaust readings. I've been retired now for 15 years, and I have just about forgotten what most of them were. I never thought I'd forget that stuff, but I haven't used any of it now for 15 years.

 

[Jim/GA]

The smog test probes used lately in the USA on cars go into the tailpipe about 12 to 16 inches, while running the car on a drum like a dynamometer. They have been mostly replaced with onboard diagnostics where the test station computer talks to the car's computer to confirm all is good.

The advantage of a permanently welded in-bung O2 sensor, up close to the exhaust manifold, is that you can take readings while you drive. You can see the impact of changes to the timing or GAV settings.

 

[ModelA29]

The advantage of a permanently welded in-bung O2 sensor, up close to the exhaust manifold, is that you can take readings while you drive. You can see the impact of changes to the timing or GAV settings.

Tune on the go. I wish we could have done that when I was doing Mobil Economy Runs back in the late 60s.

 

[TomInCologne]

something else i wanted to mention but forgot about it...


See the CO (carbon monoxide) levels? In idle we see 2.100ppm, on higher revs my flue gas analyzer just says '---' because the value is over the max value for my CO sensor. This means that the CO level is over 16.000ppm. Lethal.


So: DO NOT EVER EVER LET YOUR ENGINE RUN IN A CLOSED SPACE. CO IS DEADLY. BEST CASE SCENARIOIS THAT YOU JUST DIE, WORST CASE IS THAT YOUR FAMILY HAS TO SPOON-FEED YOU TILL THE END OF YOUR LIFE.