Just installed my wideband. What should my air/fuel ratio be?

Discussion in 'SN95 4.6L Mustang Tech' started by Sonic04GT, Apr 4, 2011.

  1. First of all, what a pain in the ass it was. Hardest part was getting the sensor cable up to my pillar where the gauge was mounted. The thick wire/connector just would not fit between the dash and pillar. Took nearly 30 mins to get it through trying like 3-4 different methods.

    Got the bung welded right downstream from the header collector, at about 2:00-3:00 on the driver side of the H-pipe, facing inward. Then zip-tied the cable off to the tranny and ran it up through the shifter. Fortunately there was enough cable to where the main connection between the sensor harness and the gauge harness is actually inside the car sitting next to the shifter.

    Tomorrow I have to figure out how I'm going to get the wires to fit in the pod and down the pillar because right now it's SUPER tight and the pillar is just sitting on my dashboard with the gauge hanging out of it.

    ANYWAY, THE QUESTION...Where should I be sitting? I couldn't drive the car because I have wires hanging everywhere down by the pedals, and the pillar on the dash as mentioned above but...

    At idle it starts around 15 and within about 20 seconds it gradually drops to about 11.8. Goes up to around 12 something I believe if I rev and hold around 2k RPMs. Only ran the car for a minute. It was pretty much cold. Where do you guys feel it should be sitting around idle? Hopefully tomorrow I can get a WOT reading.

    I calibrated the gauge in clean air using Innovate Motorsport's method in the manual.
  2. The reading will vary depending on a number of factors, including engine temperature, run time, throttle position, rate of throttle opening/closing etc. It may take a few moments after cold start for the PCM to enter closed-loop fuel and so you might see the engine running a little on the rich side (<14.7:1). Just cruising down the road at a steady state I'd expect to see it pretty close to 14.7. If you get off the throttle and coast/overrun expect it to go very lean.

    At WOT, expect <12:1, depending on the tune.

    Did you calibrate the sensor in open air before installing it?
  3. On a cold start, that sounds reasonable. Under warm idle and cruise conditions, you should see a constant 14.7:1. At WOT, it will depend greatly on the tune. A naturally aspirated combination could be fine anywhere between about 12:1 to 13.2:1. You'll probably find the stock tune is lean at WOT in the low to mid range, at around 13.5, then lean out to 12.0 by red line. If you can make it steady between 12.8 and 13.1:1, then you'll probably make a little more power and torque. Just my thoughts.
  4. Thanks for the quick replies. Yes I calibrated the sensor while it was dangling beside the midpipe before I actually screwed it in and secured the wiring, read 22.4.

    Also read 22.4 turning the ignition to on while it was mounted in the pipe, after the display showed "Heater". Started the car after it had sat for 2-3 hours, jumped to around 15 then fell to about a steady 11.8

    I will take some readings tomorrow :) Here is the dyno sheet from the tuning session. Looks fairly steady minus the little spike.


    14.2 in a stock '97? Not bad! Nice driving on street tires.
  5. Nice numbers, what are your mods?
    My bad, I see them.
  6. Thanks!
  7. Thanks, I had an H-pipe and some cool weather, but that's it. I really want to go back now that I have PI cams, intake, underdrives, and a tune.

    Your dyno looks very nice and the AFs are great. If you wanted to take the power to the ragged edge, you could lean it out to 12.9-13.0:1... but it wouldn't be as safe and you would only gain a few hp.

  8. Yeah man you should be able to make 13's. I really need to race my car. My best is 14.2 on a crappy track and it was my 3rd time ever drag racing. That was before the gears, longtubes and pullies. I would hope I could do 13.5.
    Well it's my daily driver so a safe tune is important, especially when we're dealing with minimal gains. At least it looks good on paper :)

    Anyway, and update...I just tucked the wires away so that I could drive the car. After I got up the block and the car warmed up, everything balanced out to 14.5-15.2 at idle and while cruising. I went WOT for a quick burst in 3rd gear and it dropped to about 12.8ish. Another WOT was in the low 12's, I think maybe hit low 13's at some point too. Let off the throttle cruising to a stop and it pegged lean at 22.4.

    Sounds like it's at least reading accurately right?

    Car sat for about 30 mins and cooled back down. When I started it up to leave it was back to the rich readings, even dropped into the 10s for a sec. Once I got a couple blocks away everything balanced back out again to the stoich range.

    Is it just because the car/sensor are cold?

    Internet is out at the house due to crappy weather. I have a video I'll post up later.
  9. do you have any other tips on the install? i've had mine sitting around for months and its about time i put it in. did you have to extend any wires and where did you run the +12V and ground wires?
  10. Well first off is it an Innovate? What kind of wiring/cables do you have?

    The ground and power were already there from my previous narrowband gauge installed by a local shop when I was in TX. However, it looks like 12v power is tapped to the ignition, I can try to get a pic for you. He just used a scotchlock. Alternatively you can look at the fuse diagram and find one that turns on/off with the car and has the proper amperage, I believe minimum 3amps. Then use one of the mini Add-A-Circuits. I did this for my Garmin install. The ground is on a big bolt below the steering collumn. I'll have to look again to be more specific. Like I said the wires were already in the pod so I didn't mess with anything down below. I believe I grounded my cluster overlays using the bolt that holds the ODB-II port on and that has been working well.

    The wires coming out of the back of my Innovate MTX-L certainly wouldn't reach down below. Used some 20-22 gauge wire I believe to reach the ignition wires. I didn't use the dimming wire so I just put the ground and that together into a male bullet connector, then put a female connector on the existing single ground wire so I could remove the gauge fairly easily if needed. The brown and yellow I just isolated with tape and zip tied to the main cable harness.

    Make sure you don't zip tie anything until you calibrate the sensor in clean air because it has to twist while screwing the sensor in. Don't forget to put some anti-seize on the sensor and obviously don't touch the filament on the end. Make sure you zip tie everything tight enough so that it doesn't slip around and chafe, and be sure it clears the hot exhaust pipes. I cut a hole in the rubber shift boot and came up through there, then under my trac control switch area and out by the pedals to get to the pillar. Followed and zip-tied around the tail end of the tranny. It's raining today but I'll try to get some pics under the car tomorrow. I'll also take pics of what I can in the interior. My A-pillar is still sitting on the dashboard with the gauge hanging out of it because the wires are so damn thick I can't manage to get them tucked away to fit the pillar back on satisfactorily. I'll work that maybe tonight.
  11. Yeah mine sits pretty at 14.6-14.7 once it warms up and is at idle. Actually you can see it in my Sig :rlaugh:.
  12. Yeah mine is pretty solid after warming up and idling. I don't see anything in your sig :)

    I'm just really curious why it starts out rich, then goes to stoich, and stays there. It never goes back to rich once it gets past that initial startup, well, startup and drive for a sec. I guess if I let the car sit long enough to idle up to operating temp it may go on its own.

    Edit - Nevermind your sig hadn't loaded yet haha
  13. Mine does the same thing. Goes all the way rich, but after maybe 2-3 seconds it falls to 14.7..unless i open my electric cut outs haha...
  14. It has to do with the warm up time of the stock narrow band O2 sensors and the programing of the computer. The stock sensors are very accurate right at the stoich ratio of 14.65:1 and the computer tries to maintain this ratio for mileage and emissions when possible. The stock O2 sensors take a few moments to warm up and begin functioning, so on a cold start, the engine is in open loop (not using the O2 sensor feedback). In this condition, the computer looks to the cold engine fuel tables to determine what AF to run, then makes it's best estimate of how much fuel to add in. It should be very rich when the engine is cold to keep the engine running happily. Then, soon as the O2 sensors come to temperature, the computer can use the feedback of them to control the AF to a stoich 14.65:1. Again, on a hot start, the O2 sensors are basically ready to go, so you instantly get to closed loop.
    Make sense?
  15. Makes perfect sense. Good to know the gauge and my car are working normally :) Had me worried running that rich. Not as harmful as running really lean but anything out of the ordinary has me paranoid haha
  16. Some improved results plus the boring video.
    YouTube - IMG 1177

    I think the extreme range was about 14.5-15.2. Usually stays between 14.6 and 14.9
    Excuse the not so permanent mounting solution :p Wires are so damn thick it's hard to get the pillar re-mounted. Gotta play around with the wires tomorrow in daylight.