[arrowem]

Hi, I have an autometer digital wideband A/F guage in my car so I can tune it and it also looks cool
But recently I am questioning the accuracy of it. I am always between 14.4 and 14.9 from idle to WOT. I have an Edel 1406 and have the tuning kit for it and have the richest combo from the kit and I cannot get the A/F ratio below 14.
One thing I will try when I fix an electrical Gremlin is to manually press the NOS microswitch (NOS turned off of course) and have someone push the button on the shifter handle that should spray some fuel out the bar and that should bring the number down....in theory anyway.
Any other ideas?

[grandville455]

Did u calibrate it to free air first?

[arrowem]

Um.....no, never heard of that.

[Cliff R]

It is a good tool, but it is a measuring device, and electrical. The mounting point of the 02 sensor can have quite an impact on the results read on the gauge.

In any and all cases, tune you carburetor with a piece of tape over the gauge. Set the idle mixture screws for the best idle quality in and out of gear. Part throttle fuel for the best throttle response/power at part throttle and best fuel economy. Tune the full throttle jetting for best track numbers.

THEN take the tape off the gauge, and observe the readings. These are your "base" numbers. In almost all cases, they will be at or close to your final settings anyhow, and you can use the A/F meter to see how efficient you engine is, and if it falls with "normal" range(s).

Using the meter to tune, can be a real adventure. I have several very good friends that use these devices, one of them in particular splits hairs, then splits them again, and again. In addition to tuning the carb settings, he also changes the timing curve around, back and forth from ported to manifold vacuum, how much is added by the adj advance, how quickly the mechanical curve comes in, total timing settings at WOT and cruise, in conjuctioin with tuning the carb all over the place at each particular setting. He even move the camshaft once during this "adventure".

In each and every case, when the dust settles and smoke clears, he's right back to the very first set-up he came up with BEFORE buying the wideban meter!......LOL.....Cliff

[70 bird]

Pull your your manual choke or put your hand over the carb top to choke it, it should go pig rich. That at least should tell you if its working.

[Socrates]

As we don't all live life just 1320ft at a time, and convertibles are not drag strip friendly, I'm guessing advice to track test may be off base here. A dyno tune with an additional O2 sensor/gauge for comparison to your existing gauge might be more appropriate, if not just trying a different gauge/sensor to compare. If the guys here can't help I'd check out chevelles.com and pro-touring.com for advice. There are lots of guys there who are not afraid of technology like they overwhelmingly are here.

[ericwy]

Originally Posted by Cliff R

<snip>
In each and every case, when the dust settles and smoke clears, he's right back to the very first set-up he came up with BEFORE buying the wideban meter!......LOL.....Cliff

Thanks for reminding us the best tuning device is the one between the ears!

Funny, I installed an O2 Meter but have never got around to installing the O2
sensors. Guess I'll get around to it some day. LOL!

[Cliff R]

"Thanks for reminding us the best tuning device is the one between the ears!"

You are welcome. A/F meters are excellent tools, like many other modern components available too us to keep track of what's going on with our engines.

What gets folks into trouble(s) with them, is that they want to "chase" the gauge rather than the best performance of the engine/vehicle at all levels.

I'm not busting on using these tools, or degrading them in any way as someone seems to suggest above.

Folks must simply keep in mind that some engine combinations are a LOT more efficient than others, for a variety of reasons that would take many pages to cover. My suggestions when using these A/F meters to tune, is to back up the data with actual test results. The actual test results being what really matter, vs what "range" a gauge tells you they should be in.

My very good friend mentioned above ended up caving in a ring land with his hair splitting tuning adventures. It occurred because he kept thinking that "lean" settings would improve power production, mileage, etc. He advanced the cam during the pursuit to effectively run leaner settings, heard some very light spark knock at both light and heavy throttle. After two years of no issues anyplace, he "lunched" the engine in less than a weak with his expiriments.

The terms "lean" and "rich" are widely used in association with this hobby. Folks still continue to associate "lean" with efficiency and improved fuel economy. It takes heat and compression to get an air/fuel mixture to the LEL so that it can burn. The leaner we make the mixture, the more difficult it is to burn. So we must either add more pressure/heat, or give it a longer burn time.

The typical hobbyist is so focused on running his engine cooler that they were designed to run, and making more HP, that they block off heat crossovers, install large camshafts, and often LOWER compression for pump fuel use. What makes one think that cooler combuston temperatures, cooler intake charge, not squeezing it as hard, etc, is going to allow them to run effectively with a relatively "lean" A/F ratio?

My advice for tuning carburetors. Start out with the DISTRIBUTOR. Make sure it is in PERFECT working order. Give it known "base" settings that have been shown to work for your particular combination of parts. Then go after the carburetor, er a bit "rich" in all areas, and sneak up on the best engine and vehicle performance with very slight changes. It often takes several tankfuls of fuel to find the very best settings for cruise A/F ratio(s), and a couple of full throttle runs over a measured/timed distance for WOT A/F ratio(s).

Keep in mind when drag strip of full throttle tuning. On dozens of occassions I've jetting carburetors from "pig" rich to so lean the engine surged slightly, and barely see a tenth or so difference in ET across the entire range. For a street vehicle, chasing a possible tenth or so improvement at the risk of potential engine damage......I'd throw plenty of fuel at it provided it still pulls like a freight train at full throttle and be happy with it!....FWIW....Cliff

[arrowem]

The MAIN reason I get concerned about the lean side of the spectrum is that I have a stock '75 shortblock 557 cast 400ci and stock #62 heads and a Summit 2802 cam. I have not gotten any pinging (that I can hear) yet, just want to be safe.

[myckee]

I have an autometer wide band and last summer the sensor died. It basically behaved as yours did giving near constant readings. Once I plugged the new one in, I was back in business.

[arrowem]

Is an o2 sensor used for the A/F gauge?

[70 bird]

Originally Posted by arrowem

Is an o2 sensor used for the A/F gauge?

Yes

[chiphead]

Wideband Air-Fuel Ratio gauges require the Bosch LSU wideband O2 sensor. The sensor must be free-air calibrated and then mounted as close as possible to the collector. Any exhaust leaks will cause false readings. Leaded gas and excessive idling and rich mixtures will foul the sensor and require replacement.

Recalibrate the sensor first.