A/F Ratio Guage Questions

[Andrews-bad-SE]

I have a Zetec, with no tune...

I have a CAI, and flex-back exhaust from Option Racing...

I got an instrument cluster from a friend's zx3, which has the tach and everything...

But, there are two things that I want to monitor. A/F mix and voltage.

I'm going to put in a dual gauge pillar pod.

My concern is the A/F gauge. How do I wire it? I've heard it splices into the black signal wire of my upstream o2 sensor. Will the extra "drag" on the signal current on the wire to the gauge have any adverse effects on the A/F signal going to the computer? Just wondering before I do anything.

I want to avoid a tune to stay smog legal, I'm trying to "go legit." lol...

Any help or insight is greatly appreciated! Rock on, guys and gals.

[Sponsor]

[Magus2727]

I think the best way to do it is to install a new bung and wire up a dedicated O2 sensor. The bungs usually only cost $15 and a weld shop should be able to install one for 20 bucks or so. If you know electronics you can add a buffer stage between the O2 sensor and the A/F gauge do you dont change the impedance of the line.


A Tune does not make it not smog legal as long as you dont disable systems. And the only system I believe that would violate this would be if you disabled the EGR system.

I would get a triple and measure you oil pressure also...

[ratimpulse]

Just curious...
Why the need for an a/f gauge? Without a tune, the gauge will stay at 14.7
Seems like a waste of 200$. Get an Ultragauge and call it a day.

[Andrews-bad-SE]

Originally Posted by ratimpulse

Just curious...
Why the need for an a/f gauge? Without a tune, the gauge will stay at 14.7
Seems like a waste of 200$. Get an Ultragauge and call it a day.

I just thought having one would be cool. I saw a Sunpro one that has LED's that read "lean, ideal, and rich." It'd just be cool to see it work, it's only like 30 bucks. And I get a discount.

[Andrews-bad-SE]

Originally Posted by Magus2727

I think the best way to do it is to install a new bung and wire up a dedicated O2 sensor. The bungs usually only cost $15 and a weld shop should be able to install one for 20 bucks or so. If you know electronics you can add a buffer stage between the O2 sensor and the A/F gauge do you dont change the impedance of the line.


A Tune does not make it not smog legal as long as you dont disable systems. And the only system I believe that would violate this would be if you disabled the EGR system.

I would get a triple and measure you oil pressure also...

That sounds like a better idea. How would I wire up a "buffer stage?" It sounds like a more feasible option.

[Magus2727]

Look up "Unity Gain Op-Amp" and then see if it would be worth the effort. Cost you $4-$5 at radio shack you do need to look at data sheets to make sure you build a stable circuit but is not that hard... but then again I am an electrical engineer....

Personally it seams like you just want some flashy lights. a $30 A/F gauge is going to tell you nothing and most likely is not very accurate to start with. And what has been said above it will stay fixed at basically 14.7.. may drop to 14.6 or 14.5 at the high revs. So it will always stay ideal. I can wire you up a dial with an LED you plug in that will always illuminate lettering that says "Ideal" :-) give you good price....

What other gauges do you get a good discount on? go for oil pressure or oil temp or volt? those 3 you can easily do and will actually provide you with good information and be easy to install. You could also do a water temp, the gauge one is not very accurate. Its use is limited to Nominal temp and better shut the engine off.

[Andrews-bad-SE]

Originally Posted by Magus2727

Look up "Unity Gain Op-Amp" and then see if it would be worth the effort. Cost you $4-$5 at radio shack you do need to look at data sheets to make sure you build a stable circuit but is not that hard... but then again I am an electrical engineer....

Personally it seams like you just want some flashy lights. a $30 A/F gauge is going to tell you nothing and most likely is not very accurate to start with. And what has been said above it will stay fixed at basically 14.7.. may drop to 14.6 or 14.5 at the high revs. So it will always stay ideal. I can wire you up a dial with an LED you plug in that will always illuminate lettering that says "Ideal" :-) give you good price....

What other gauges do you get a good discount on? go for oil pressure or oil temp or volt? those 3 you can easily do and will actually provide you with good information and be easy to install. You could also do a water temp, the gauge one is not very accurate. Its use is limited to Nominal temp and better shut the engine off.

Haha, man you're always a big help. You're pretty spot-on with the "wanting cool flashy lights" thing. I just thought that the cheaper A/F gauges were more accurate... But, now that I know otherwise, I'll steer clear of that! I have just always loved the look of pillar gauges. I'll probably do what you said, just oil pressure, temp and voltage.

[sleepyboy]

narrow band a/f ratio gauges are just flashy lights. You want to get a wide band O2 or nothing at all. There are better gauges that will actually tell you whats going with the motor like oil pressure, oil temp, water temp, or even a trans temp gauge if you have a auto. I highly recommend getting a tune, and if you have a wide band O2 that can even help make the tune that much better by letting the tuner know what's the actually a/f ratio.

[4g63T]

Sleepy has it right, tune before AFR gauge. Narrow band is pointless on the stock tune. Boosted, you will see differences of course. But not N/A. Widebands are always nice to have.

[disciplerocks]

Narrow bands are pointless period.