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Old 02-26-2004, 09:38 PM
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air/fuel gauges

Hey guys,
I have done some searching on air/fuel gauges. Some say they are accurate and others say they aren't. For those of you who have had experience with these, what do you think?

Also, all air/fuel gauges measure in the exhaust right? A buddy of mine says they also make the gauges with sensors that go under the carb but I have never heard of that. Is he right or wrong? Thanks for your help guys!

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Old 02-26-2004, 10:02 PM
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I just installed a 1 wire 02 sensor. I cut off a spark plug non fouler and welded it on for the sensor to screw in. I hooked it to the air fuel meter. I'm trying to tune a holley with it. So far I have read nothing but rich. I lowered jet size but haven't got the right accelerator pump cam yet. I'm also planning on throwing a volt meter on the 02 sensor to see what range I'm in there. At cruise I read you should be between 400 to 700 millivolts. Please let us know how it turns out.
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Old 02-26-2004, 10:46 PM
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I recently bought a $20 o2 sensor for a camaro and a $30 air/fuel gauge at auto zone and installed it on my 69 nova. I read an article someone wrote who uses the ~$120 edelbrock o2 sensor/gauge, and they said they use it to completly tune the carburator. I don't like the edelbrock gauge becuase it only has 2 lights, lean and rich.

Anyways, I love my setup. It tells me everything I need to know. Cruising, i mash the gas, it leans out a little, then after about 3000 rpms it richens up. Someone told me that it is perfect that way. I also used it to tune my idle adjustment, air/fuel adjustment.

As far as your buddy telling you they make one that goes under the carb.... i'm no expert but i think he is way off. The gauge reads the temp/volt of burnt gasses/exhaust. I don't see how it can work before the air/fuel explodes/burns.
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Old 02-26-2004, 10:51 PM
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I used the auto meter gauge and put it in one of the old air condition vent holes in the dash on my TA It is a life saver for tuning carbs. Get the 3 wire 02 sensor though. 1 Wire sensors arent as accurate and have to heat up in order to read correctly whereas the 3 wire has a built in heater. Autometer has a kit...
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Old 02-26-2004, 10:57 PM
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hey 79transam....

how inaccurate do you think the 1 wire sensors are? reason i ask is b/c thats what I use. It does take a while to heat up (reads fully rich unti its ready) but after that it seems to work OK.

BTW don't let the o2 sensor wire hit the header... it will burn up and read way rich
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Old 02-26-2004, 10:58 PM
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onecoomofo, I like the how your setup sounds.

79, I was thinking of doing the same thing with my air/fuel gauge with putting it in the A/C vents in my dash. How does it look?
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Old 02-26-2004, 11:19 PM
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Hi,

This may sound ignorant of me to ask, but can you put an O2 sensor and then a guage on the end of that to adjust the carb correctly? I have a hell of a time adjusting my holley by ear! If someone could please educate me on this by pm/post reply, I would appreciate it.

Thanxx!
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Old 02-26-2004, 11:23 PM
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Standard O2 sensors consider stoichiometric mixtures as perfect (i.e. 14.7:1 A/F), this is necessary to ensure proper treatment of the exhaust gases in the converter. Most engines can run much leaner at cruise than that.

Personally I found them to be of no use unless you like watching the flashing lights. A wide band O2 sensor is a better tuning aid since it can read mixtures leaner than 15:1 .

Wide band A/F meter.
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Old 02-26-2004, 11:43 PM
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Quote:
Originally posted by 4 Jaw Chuck
Standard O2 sensors consider stoichiometric mixtures as perfect (i.e. 14.7:1 A/F), this is necessary to ensure proper treatment of the exhaust gases in the converter. Most engines can run much leaner at cruise than that.

Personally I found them to be of no use unless you like watching the flashing lights. A wide band O2 sensor is a better tuning aid since it can read mixtures leaner than 15:1 .

Wide band A/F meter.
Please explain why you find them to be of no use. I mean fire the engine up, at idle see what the gauge says. If it reads on the richer side.... thats bad, it should idle a little lean to preserve fuel economy. Then take it for a drive at WOT and make sure you aren't leaning out the whole time.

IMHO, that is enough information for me to go out and buy one.

So, not argueing with you, just asking you to be more specific since you have more experience than me.

Thanks
Sean
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Old 02-27-2004, 01:34 AM
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I agree with 4 jaw chuck. The meters are set to tell you when you are near the 14.7:1 ratio. Problem is, you need to be leaner than this when cruising at a steady RPM, and much, much richer than this for maximum power output.
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Old 02-27-2004, 04:53 AM
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I have never needed a gauge to set idle mixture, I use my nose and ears for that, usually a quick blip of the throttle to check pump shot timing and listen for the slight over-rich sag on initial opening and I consider that good to go. I also look for a nice quick blast of grey smoke out of the exhaust too. Experience after doing it a hundred thousand times is all I have ever needed, the sensor doesn't help with anything but steady idle readings or cruise anyway, they respond too slowly to be of much use and have too narrow a range. 60 foot times are a much better judge of performance and can be done nearly anywhere there is no traffic, think industrial park.

O2 sensor? We don't need no stinking O2 sensor chico
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Old 02-27-2004, 06:14 AM
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Quote:
Originally posted by 4 Jaw Chuck
Experience after doing it a hundred thousand times is all I have ever needed. 60 foot times are a much better judge of performance and can be done nearly anywhere there is no traffic, think industrial park.

O2 sensor? We don't need no stinking O2 sensor chico
Amen to that! Twenty years ago that was all we needed. No fancy laptops and computer tuning back then. Technology is a good thing but not when it causes people to loose some of the basics of hotrodding. Like learning math on a calculator before ever learning how to do it longhand on paper.


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Old 02-27-2004, 09:22 AM
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Quote:
Originally posted by 4 Jaw Chuck
I have never needed a gauge to set idle mixture, I use my nose and ears for that, usually a quick blip of the throttle to check pump shot timing and listen for the slight over-rich sag on initial opening and I consider that good to go. I also look for a nice quick blast of grey smoke out of the exhaust too.
Thanks for the info.... thats what i was lookin for. I can't wait until i get enough experience to feel comfortable doing it that way.
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Old 02-27-2004, 06:15 PM
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Try this site for info on this topic. They talk about adapting this system to your carb fed motor and the pros' and cons' that arise by not having a computer to trim the mixtures. http://www.carcraft.com/techarticles/116_0402_tune/
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Old 05-20-2005, 12:11 AM
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I wanna bring back this discussion for a second as I want to tune up my edelbrock carburetor. I don't care whether i can tune with a wide band and maybe make it ideal for an extra 10 horsepower, just as long as i am somewhere in the ballpark. Heres the scenerio as I figure it:
-You make a narrowband setup for about $40 as opposed to $350+ (usd)
-Run the carb with the narrow band at full throttle it'll say rich lean or stoic (assuming those are the only 3 measurments we can assume precision on from the narrowband)
-If its rich downjet the carb until you get a lean/stoich indication then just go up a size or two

And for part throttle:
-Go down in jetsize till it displays stoich, then go maybe one size leaner and you're good to go.

For an everyday (non supercharged) stock engine doesnt this seem like a better method then guessing and checking? Especially for us born in 1985 as opposed to 1945? who don't have the knowhow to do it by ear?
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