Ok, I've been doing some thinking about how I can get my a/f ratio a little better.. My idea is that I take an o2 sensor and weld it in to the y-pipe and then connect it to my multimeter to read the output and then go for a spin. Cruise, WOT, idle.. I can tell whether my jets are sufficient or not. I know this isnt a terribly accurate method, but it will get me in the ballpark.

My questions are, will it work? What sensor should I get, and what voltage should I be looking for at WOT and idle?

Anyone done this before?

 

yes its been done before

here is a chart

Volts A/F ratio

.1 17:1
.2 16.5
.3 16:1
.4 15.4
.5 14.9
.6 14.4
.7 13.8
.8 13.2
.9 12.7
.985 12.1

Narrow band o2 sensors are really only accurate when reading a air/fuel ratio at or very near 14.7:1.

Sensor voltage output accuracy varies when on the rich side based on temperture of the sensor. ( it tends to drift)

The ideal chemical air fluel ratio is 14.7:1

Its a good ratio for cruising at part throttle ( lowest Emmisions with good exhaust temps) it is not the best ratio for fuel efficientcy.

A leaner ratio about mid 15:1 is best for fuel efficiency but may random missfire and will have hotter exhaust temps. ( watch for detonation)

You won't likely get a carb car to idle at 14.7:1. Anything around 13- 14.5:1 AFR is good. tune for best idle quality and manifold vacuum.

For WOT operation 14.7:1 is way too lean the engine will not make max power and will overheat. The ideal WOT air/fuel ratio is around 12.5:1 Your engine will want a ratio real close to this for maximum output. 13.3 to 12.2 range.

Trouble with tuning the WOT air/fuel ratio with a narrow band O2 sensor is, the voltage output will drift a little based on how hot the sensor is even thou the actual AFR is the same . But you can use it as a guide along with other indicators of correct WOT AFR.
(correct spark plug coloring, Maximum power ( highest MPH at the dragstrip) A .85 to .9 MV reading tells you you're close. The correct WOT Airfuel ratio will also want less ignition timing a too lean ratio or too rich ratio will want more timing.
A 2 wire o2 sensor may not work well at idle if its located too far away from the exhaust port. (tends to cool off at idle) A 3 or 4 wire sensor is better.

A narrow band O 2 sensor is especially good at telling you your engine is just too lean at WOT which definatly needs to be avoided.

be aware that a engine that is misfireing will make the o2 sensor show a lean(er) air/fuel ratio. The oxygen passes right through a missing engine and is picked up by the sensor in the exhaust.

1988 ford F-150 3 wire o2 sensor CTC $67

You'll need a good Volt/ohm meter with a fresh battery and good wire connections.

This is what you really need.

Wide band AFR meter

 

Aces! Thank you!

Now, if I got a 3 or 4 wire sensor, what do I connect everything to?

 

I would just get a one wire O2 sensor.

The 3/4 wire heated O2 are better and more $$. Heated is nice for EFI vehicles. But its not needed for carbs, since you don't want to read what your AFR is until the engine is warmed up anyway ( the single wire will be warmed up as well).

Hope that makes sense.

 

The heated exhaust sensor maintains a more constant temperature and therefore is more accurate than an unheated one. Still not great for tuning though.

 

True, but it might help a bit. Basically I need to tune out:
-off idle bog
-when I rev it when it's cold, it stalls - dad thinks it's flooding
-When it shifts into second, it loses all power for a sec, basically bogs at like 2500 RPM, then picks up again a second later
-where did my torque go?

 

A narrowband sensor won't respond quickly enough to help diagnosing those problems.

Check the idle mixture and accelerator pump and vacuum advance for off-idle problems. You can also look for blockage in the transfer slots.

Check the choke operation for cold-running problems. Reving it cold isn't a great idea anyway.

Are you having problems with the 2nd gear shift at WOT, or all the time? Is it bogging before it shifts, or after?

 

Install a new ground wire running from the valve cover bolt to the fire wall. Don't ask why, just try it.

My car had these problems and narrowed it to a bad body ground. Not sure why but it fixed the problem.

 

Right after it shifted, at anything over like 20% throttle. But it's fixed now. Sonix helped me out. It turns out the main cause was that screw that limits the downward travel of the power piston. WAY too low...

 

I just got one of those Innovate wide-band kits for my carbed SBC. Although it was a little frustrating at first (they are very sensitive to picking up electrical interference if you get the wires anywhere near any ignition stuff) it is pretty cool now.

I had a Automoter narrow-band (and still have it on) and have found it useless (and it does not really match the wideband at times-eg- wideband will say 14.5 and the narrow will be reading way lean). Also, with a carbed car the afr, even while cruising jumps around alot more than EFI and it can lead to some weird readings....i wouldn't trust a narrow band for anything on a carbed car...even around stoich.

I also never realized how significant the idle screws on a Holley screws were until getting this meter and their effect even on light cruise situations. I was able to lean out my 45MPH cruise from mid 12s to low 14s because my idle screws were 1 3/4 turns out (I turned em a little more than 3/4 in)..cleaned up my overly rich idle as well (mid 11s to high 13s/low 14s). In fact the idle circuit is more involved in cruising than the main jets in my experiences(I have alot of vacuum advance and cruise around 1,900rpms with like hardly any throttle input).

 

The old Sun 920 and 1120 diagnostic machines had an exhaust gas analyzer built in. I grew up on those machines. If used correctly, they could probably be used tune a system as well as any OBD system in use today. The problem is that changing conditions alter the result, so carburetion that isn't under constant mixture control is going to be lean at some point and fat at others. That's why general aviation aircraft have mixture control *****.

 

I'm bringing this post back from the dead, due to the fact it seemed to be the only one on using a stock style O2 sensor. Hence why i'm quoting F-birds response.
I'm having a hell of a time figuring if i'm too lean, or too rich, at certain easy to reproduce parts of the RPM range. I'm thinking I can get an O2 sensor like this, shoe horn it into my y-pipe, then run some wires into the car, hook up to an analog volt meter, for the quicker response. All I need is to know if i'm rich, or lean, that's it basically.
Think this would work for me?
How do I stick this in my y-pipe? Buy a bung with threads that are...? Then drill a hole, weld the bung, and screw it in? Y-pipe a good place for it?

Thanks guys

 

ok, buying the O2 sensor today, and an 18mm nut (bung), to put it in. Probably tommorow night.

Any hints or tips to remember here? Never used an O2 sensor before...