mn_vette

I'm looking for something to just tell me if I'm running rich or lean and how badly, I'm not looking for a tuning device, I just want to know if my a/f ratio is in the ball park. I don't really want to buy a wideband o2 setup. Do you think a little $90 meter will do ok for this and if so what would I have to do to hook it up.

vettmech

Why not use a scan tool and read it off your o2 sensors? :seeya

mn_vette

ummmmm, scan tool??? what's that?

mn_vette

Actually now that I think about it would there be something I could get to hook my diagnostic port up to my laptop computer and record data???

MarkBychowski

Check out the scan/tune section -- lots of references for tools you can hook up to your laptop. I use Autotap, but that's only for 96 and newer OBD2 cars.

Also, the stock O2 sensors (or one of the AF meters for that matter) will only tell you that you're rich / lean within a very close range of 14.7/1 (the 'correct' A/F ratio for max efficiency). Once you get out of that tight range, you won't really be able to tell how bad it is.


[Modified by MarkBychowski, 11:37 AM 9/24/2002]

SPD DMN

My Air Fuel meter always shows in the rich. I do know where in the range it should be though. It sits right at the rich/stoich line. The meter itself is not accurate whatsoever though.

Knight Ryder

At the rich/stoich line during normal cruise is where it should be. Within the "stoich" values, voltage on the 02 sensors is very sensitive, i.e. maybe only .1 V over the entire range, so fluctuations within this area are OK. It should go to rich during hard acceleration...

Nathan Plemons

The meters are crap. But, they can give you a ballpark idea. Not a bad thing to have, but like you said, nothing to tune from.

SPD DMN

Actually at cruise, the meter jumps from lean to rich constantly just like the O2 sensors voltage does and really gives no meaingful data. It is only a constant value when the Power Enrichment mode is activated. This is dependent on your programming. Mine goes into PE mode at 5% throttle above 2500 rpms. I think stock is somewhere around 13-15% at the same values.

Also, the fact that it goes to rich during hard excelleration is all dependent on programming as well. Stock, yes it dumps a lot of fuel into the system and makes it run pig rich at WOT. Add a Hypertech or other aftermarket chip programming and they add timing and reduce fuel. I program my own so I know mine sits right at 12:1 Air/Fuel on the dyno which is rich and right around 13:1 on the street. I have run 13.3:1 on the dyno at WOT which is right at 14.7:1 (stoich) on the street and the gauge still reads rich.

At any rate, I know I am close enough to stoich when the constant value of the gauge hits the Stoich Rich line or just a few bars to the rich side. This is using an Autometer Phantom gauge tied into my drivers side O2 only.

fullboogie

I've got an auto meter a/f gauge. It's helpful in the sense that it does tell me how my mixture is affected by changes I make. I also use it to tune at the track, where I've been able to pull a few tenths off my times by playing with the a/f ratio. Is it going to tell me exactly what my ratio is? No, but that's not what I bought it for. Even if it can't tell me that I'm at exactly 13.3 to 1, it IS sensitive enough to pick up small changes in the ratio, which is what I want.

dlmeyers

The 14.7 ratio represents the AVERAGE fuel to air ratio. A good 02 sensor will show voltage jumping up and down. Guess if you are fast enough to write down all the numbers (ha) they should come out to an average voltage representing 14.7. A scanner reading showing little voltage "jump" would suggest a malfunctioning or lazy sensor. This assumes you are in closed loop- cruise. As stated above, the other computer modes vary. Tuners I know work hard at the WOT AF ratio. As expected, they are in constant search for that last 1/2 horsepower. They know it's in there somewhere. One may be surprised by how many times he has to lean one out for more horsepower. Love those guys.

dlmeyers 90 coupe zf6 3 speed shocks