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I dun learned sumthin
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Discussion Starter #1
Does anybody here have any experience with auto meters Air/fuel ratio meters. The kind with the O2 sensor that goes in the header. I want to use one to try and better tune my carb. Just wondering if these are truly worth the money or are they not usefull.
 

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Nordskogs setup with the wide-band sensor is easier and more accurate. It's more expensive. Autometers and others like it that ise the narrow band oem style sensors are difficult to use. It's hard to get an accurate reading because they are so sensitive to changes. One jet size or an 1/16 turn on the idle mixture will send it way off to one side.

Larry
 

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I dun learned sumthin
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Discussion Starter #3
Is the nordskogs unit hand held or does it thread into the exhaust like the others. It seems to me that it is necessary to drive the car while taking readings because you need to measure the ratio all through the power band. Right?
 

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A fuel/air O2 sensor style meter will sense voltage from 0 to about 1.5V the lower the voltage the leaner.

Normally in "general' 12.5:1 is around 800MV. You dont need a rich/lean auto meter, all you need is a multi meter with the positive attached to the postive wire on the O2 sensor and the ground attached as close to the O2 sensor as possible(or where ever you get the lowest resistance) After all is hooked up you will have to wait a good 10-15 min. (maybe less) for everything to get properly warmed up if you DONT wait and just test it at start up it will only messure something like .180 MV. You need to let it warm up.
 

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I dun learned sumthin
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Discussion Starter #5
Nordskogs setup with the wide-band sensor is easier and more accurate.
I looked at Summit and found nordskogs gauges but could not find sending units for them. What sensor do they use?
 

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All the cheap Narrow band stuff is junk. Using a meter with a NB sensor is also usless. Narrow band sensors are designed to sense stoich and show below and above stoich. That is it. It is not designed to show AFR over the entire range and it is a hack to try to do so with it. The only way to measure AFR accurately is with a WB sensor and controller. WB sensors are much more complicated to control and will cost you alot more money, but they are the only way to accurately measure AFR. Even the WB stuff must be calibrated to be 100% accurate.

I am using the WB control circuit on my Genboard and it is awesome. WB sensor makes it so much easier to tune the engine. Put a good EGT sensor on the engine and you can really get something done.

Chris
 

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Technical Support Barry Grant
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As inexpensive as good units are now, it’s silly not to have. A system like the innovate unit which can be downloaded to a laptop or pc. Letting you test in a controlled manor, and see what you’re doing.
 

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I dun learned sumthin
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Discussion Starter #9
Where do you get these good units and how much are we talking about money wise. The carb Im trying to tune is a Speed demon 750 DP. Also is it overkill to try and tune by air/fuel ratio. This is a street application but of course I want all the power I can get.
 

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Technical Support Barry Grant
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Rich/Lean Indicator

I bought one of these devices ten years ago from a company called Camden Superchargers. The company is still in business but has a different owner now and I don't know if they still offer the part.

http://www.camdensuperchargers.com/

They used some standard O2 sensor that screwed into a bung that was welded into my exhaust collector. The readout was a little black panel with a series of LEDs that went from dead lean to dead rich. Half way between was 12.7 (I think that is the right number) for ideal stoichimetric. The LED at 12.7 and each one on either side are green, then the next three or four on either side are orange, and the last two or three are red. These LEDs are lit any time the engine is running.

The idea is that the engine should be in the green range. I found this to be of great value. When I first dynoed my engine (on an engine dyno) the carbs I was using delivered the proper mixture under full throttle according to the dyno readings. However when I put it in the car, I took it out for a drive on the freeway and at cruise I was shocked to see that the rich/lean indicator was showing that it was running extremely lean. All the way into the red zone. While the carb jetting was fine for full throttle, it was way off at cruise. At first I thought my rich/lean indicator was off but a quick look at my pure white exhaust pipes convinced me that further tuning was required.

I have the readout inside the glove box and from time to time I open the door and look at it just to make sure everything is still ok.

I think these things are quite good for giving you a quick and easy display of whether you are in the ballpark or not.
 

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Stoich is 14.7. What is important to understand is that an engine only needs to run at stoich while cruising or possibly idling depending on the combination. While under full power the engine should be much lower like around 12.5. A NB sensor can not accurately sense this mixture and no amount of tuning will make it there. The voltage curve is a steap and it is affected by exhaust temperature. A NB gauge can show full rich at 13.1 which is way too lean for WOT. Since WOT where mixture is most important for power and engine protection.........I say NB is useless. Unless you like the pretty display.

Chris
 

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Not to sure. You would need to know what the sensor is that it uses. I would bet it is NB judging from the price and the number of wires. Most of your WB stuff is $250 up for the controller and then you have to get a gauge or use some kind of software interface.

Chris
 

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brainsboy said:
Just build your own meter. I have a schematic for the design I can send to you.
I like that idea. How'd you do it, how much did it cost? How accurate is it?:)
 

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I dun learned sumthin
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Discussion Starter #16
I am not going to spend that much money on a wide band unit. Im a poor college student. My question is is it worth it to even buy a narrow band unit for tuning purposes or are they worthless. I want to fine tune this carb. but is it better to go with a seat of the pants tune or would a narrow band unit get me close to stoch. but I don't want to buy one if there not any good.
 

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The NB unit can only get you close to stoich. If you read my previous post you will know that is why they are worthless unless you want to tune the cruise mixture for mileage.

Chris
 

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Technical Support Barry Grant
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I would never use a NB sensor to tune a performance engine.
 
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