I was wondering if anybody had any experience with the air/fuel gauges you can buy from like Autometer? I don't know anything about them and by just looking at the gauge, it doesn't seem like it could be that accurate. Any thoughts?

They're basically just a little light show. You'd need a good wideband O2 sensor for accurate readings. You're betting off getting a EGT gauge if you want to see how your engine is running.

Khiem

[QUOTE]Originally posted by spdracerUT
[B]They're basically just a little light show.

LOL Im just gonna get that volts gauge LOL

From what I have been told they are pretty accurate at full throttle. Correct me if I am wrong!

I have an Autometer ultra lite carbon fiber Air/Fuel gauge on my turbo car, and just like rob said, they're accurate at WOT. This gauge reads very well on my car.

How do you know its accurate?


Terrin
92 SE-R

I hope this helps! Take it for what it's worth. I have an A/F on my car.

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The A/F Ratio Meter is a voltmeter with a range of 0 to 1 Volt. The meter displays the output voltage of the vehicles oxygen sensor through 20 LED's. The first LED will come on at a voltage of .050V, the second at .100V, the third at .150V, etc.

LEAN RANGE: Four red LED's (.050 to .249V)
STOICHIOMETRIC RANGE: Ten yellow LED's (.250 to .749V)
RICH RANGE: Six green LED's (.750 to 1.000V)


The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The on-board computer or Powertrain Control Module (PCM) monitors the voltage from the oxygen sensor. If the PCM sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the on time to the fuel injectors. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the PCM immediately starts to increase the fuel metered to the engine by increasing the on time to the fuel injectors to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The PCM is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further.
Since the oxygen sensor output is non-liner and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the PCM is in closed loop and trying to maintain a stoichiometric A/F ratio.

The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph.
During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time.
During hard deceleration the PCM will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate.

i thought only wideband's monitored from 0-1? I thought most were only 0-.5?

Originally posted by nismo91
I hope this helps! Take it for what it's worth. I have an A/F on my car.

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During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time.


This is exactly why Autometer A/F gauges should never be used as a tuning tool. It's gonna tell you rich no matter what at WOT since at WOT you are in "open loop" and the ECU doesn't even trust it's own O2 sensor's outputs at WOT - why? Because it's not wideband!! The only time the ECU "listens" to the O2 is during "closed loop" or when you're cruising.

Hence, if you're using a cheap $50 A/F gauge then you have a closed loop/open loop indicator.

Well I appreciate the response. "Now I know, and knowing is half the battle."

I've talk to Clark Steppler @ JWT about it awhile back, and he didn't recommend it especially if your using a JWT ECU. According to him the autometer A/F meter "CAN" send wrong signals or noise to the ECU. I used one anyways only when i had the Nitrous Armed, I just wanted to be on the safe side and made sure it was "Rich" when WOT.

I am running a JWT ECU, so when my autometer is telling me i am running rich at open boost i'm leaning out?

Originally posted by SE-Rious B14
I am running a JWT ECU, so when my autometer is telling me i am running rich at open boost i'm leaning out?

Nope. If it says rich, then your running somewhere less than 14.7 A/F. How much less you can't deterimine with a narrow band o2 sensor. Btw, I wouldn't worry about your gauge adding noise to your signal.

Just had to add my .02 cents to this topic. A/F meters are a good low end tuning tool, with a Greddy EGT you are armed with the power to enable you to tune correctly, if you are a guy who likes to tinker with your ride, IE (those not running a JWT ECU). Typically the leaner your engine is the more power it makes, but the hotter things are inside, so it goes with the old saying, your car will never feel as fast as it does right about the time your pistons start to melt. The Greddy EGT is very accurate especially if the probe is placed in the exhaust manifold. It will let you know how hot/lean your engine is running and if it's actually in a safe range, usually 900 - below. The A/F meter is just a guide to let you know the range you are in as far as air fuel is concerned. Personnaly I don't recommend Autometer anything for that matter. Good A/F meters come from Greddy, EFI, or jumptronics. All of these gauges come with their own O2 sensor and are very high quality. Ultimately it is best to use these tools on the dyno even though the dyno comes with its own A/F meter, but the EGT is a good tool to have while making the run. It's more for tinkering on the street or just to keep an eye on things. Again just my two sense. Again just IMHO