Wideband O2 readings

[dodj]

I have and Innovate wideband O2 sensor. When I first got it I adjusted the idle to read 14.5-14.7 because that's what I heard you were supposed to be at, at idle.
With the jetting of the 850 QF carb out of the box, Im running about12.5-13.2 at speed. Seems to run fine. Except when I let off the gas quickly. The A/F jumps up to about 18-20 and sometimes stalls the engine. To eliminate the lean out condition I adjusted the idle AF to 12.5-13.0.
Runs great, doesn't stall, but I would like to reduce the 'aroma' while idling. Any ideas on what I need to do?

[GoodysGotaCuda]

Every engine is going to be different at idle. Some like 13.5, some like 14.7, I'd tune for what pulls the best vacuum at idle.

The lean spike when jumping on the throttle is going to be an accelerator pump shot issue, it's not squirting enough extra fuel to compensate for the air rushing in.

Adjusting the idle afr to account for jumping on the throttle and running lean is not the best way to go about doing that. I'm surprised it made much of a noticeable difference.

Cruise afr should be around 15, 12.5-13.0 at cruise is far too rich.

Around 13.0 is pretty safe for wide open throttle.


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[Cudakiller70]

I have the same AFR. I set the idle mixture by highest vacuum method, runs in mid to low 13, 340 motor with cam. At cruise it's in the mid to upper 14's. Still learning about tuning, next will be plug reading.

[dodj]

Goody, I think you misread my post. It's when I let off the throttle it would stall , not getting on the throttle. If I let off the throttle gently, it would be ok. That's why the idle adjustment made a difference.

And both are saying I'm too rich at cruise so I guess I need to find out what jets are in there and order up a few sets. Thanks

[GoodysGotaCuda]

Goody, I think you misread my post. It's when I let off the throttle it would stall , not getting on the throttle. If I let off the throttle gently, it would be ok. That's why the idle adjustment made a difference.

And both are saying I'm too rich at cruise so I guess I need to find out what jets are in there and order up a few sets. Thanks

Gotcha, yes, I misread it!

[dodj]

Well it has an 80 as the pri jet now. So for 6 bucks each order a 78, 76, and a 74? Ive never changed a jet before, don't know how much of a difference to expect with each step?
Or they sell a kit of all the jets between 70 and 80 for 50 bucks.

[bcudachris]

Go on Jegs and order one of their jet kits.  Like $15 for a box with 10 pairs in it for 60-69, 70-79, etc.  They kill you on those little parts piece meal like that.

[Johnny Mac]

Your idle circuit screws are whats going to lean it out at idle....changing jets for WOT or Cruise isn't going to effect your idle mixture nearly as much as the bowl screws will... are you familiar with how to set those?
gotta watch getting too lean at idle however...you can run hotter chasing "stoich"  These are muscle cars with 4 bbls...they stink...  so just make sure you're not going tooo lean at idle and causing it to burn plugs or run hot.

i started tuning my drag car with a wideband and i love it.

[Cudakiller70]

Your idle circuit screws are whats going to lean it out at idle....changing jets for WOT or Cruise isn't going to effect your idle mixture nearly as much as the bowl screws will... are you familiar with how to set those?
gotta watch getting too lean at idle however...you can run hotter chasing "stoich"  These are muscle cars with 4 bbls...they stink...  so just make sure you're not going tooo lean at idle and causing it to burn plugs or run hot.

i started tuning my drag car with a wideband and i love it.

Do your shoot for a AFR number or best vacuum or both and read plugs? Or? Curious to what your looking for at idle and cruise. I'm just starting to tune myself. Thanks

[Johnny Mac]

Your idle circuit screws are whats going to lean it out at idle....changing jets for WOT or Cruise isn't going to effect your idle mixture nearly as much as the bowl screws will... are you familiar with how to set those?
gotta watch getting too lean at idle however...you can run hotter chasing "stoich"  These are muscle cars with 4 bbls...they stink...  so just make sure you're not going tooo lean at idle and causing it to burn plugs or run hot.

i started tuning my drag car with a wideband and i love it.

Do your shoot for a AFR number or best vacuum or both and read plugs? Or? Curious to what your looking for at idle and cruise. I'm just starting to tune myself. Thanks

Since you have a full exhaust, and i'm assuming the O2 sensor is mounted past the header collector, or at least in the merge pipe,  I would say you're in pretty good shape to verify your idle mixture after doing the old school idle screw adjustment.  Vacuum gauge would help, but with a wideband, i would say the quick and dirty method will get you the same results, especially if verified with your wideband gauge.

Here's what i sent a customer a few weeks ago.  forgive the novice of it if you've done this a bunch of times, but I'm thinking it'll help you. since your goal is to correct an idle rich condition, and idle screws havent been mentioned yet....i think this will help.


--------------
This is how i would correct a rich idle, in a running car.


Turn in the mixture screws one at a time.  You want to count the number of turns inward, so you know where you were.
Example (2 full turns)  or 1.5 turns.    Before you lightly bottom out.

The screws will lightly bottom out.  This doesn't take much grunt with a straight screwdriver. Be easy.

The common "starting point"  is 1.5 turns outward from the bottom out point.

I like to compare this 1.5  to what you originally had.   So you know if you started with 2.5 turns...you're already leaner than you were.

You then start the car with the screws in the 1.5 position, and let it idle.  You may have to adjust your idle screw to seek out your 850 RPM.  Unless both your starting turns, and the new 1.5....are about the same.

You then slowly turn the screws (one side at a time) further outward (this is going richer).  Somewhere in the next .5 to 1.5 turns (ballpark)  the engine will start to stutter a little bit.  You'll be able to tell it didn't "like it"   that's why we go slow...

You will then turn that screw back inward, 1 full turn.  This is a happy spot for the engine, and it should idle great there, and not be overly rich.

Do the same on the other side.

If you're not familiar with doing this, its very handy to write all the turn positions down, so you know if you end up richer or leaner than you started.


If plugs continue to get charred black after a few nice long heat cycles, you can bump the idle screws in maybe another ¼ turn, but not much from your "happy spot".  May help that some.


Here is an example. 
I bottomed out the screw from the as-delivered setting, and I went in 2 full turns.
I brought them back out to 1.5 turns  (so I'm .5 turns leaner than I was)
I then stated the car, and turned the screws out another .5 before the engine hesitated (back to where I stared at 2 full turns)
BUT...I then went in 1 full turn as johnny described, so I'm now at 1 full turn outward, opposed to 2 where I stated, so I now have a leaner idle mixture. than i started with.

Pair that with your wideband...and i dont think you can mess it up.  if you do the ear method, and its still reading FAT. take all the screws in another 1/8 a turn..see what happens.  i personally wouldn't go chasing some 17:1 mixture at idle. if it idles good at 14.0...and isn't burning your eye's... so be it.

[Johnny Mac]

I'm assuming this is a vac secondary carb. i see its a QF, so holley based.
i'm not sure of your engine? BB or SB? maybe i missed it,  but its not uncommon to be off 10 jet sizes out of the box if that carb is on the "big" side.
i realize that has nothing to do with the idle screw post i just made,  but i have a 600+ horsepower engine, and jumped literally 10 jets to get into the mid 12 AFR's WOT. my Car runs 10.50's on the footbrake @ 125mph.
just pointing out "box" settings can be close...but they are just a ballpark setting...

[Cudakiller70]

Thanks  @Johnny Mac  for sharing that. Definitely going to give it a try. I'll be curious how it compared to high vacuum method. Also good to learn other ways of tuning. 

[dodj]

Thanks JMac 
Appreciate the post. Will put it to use.

[dodj]

So I progressively went from an 80 main jet to a 74. The cruise afr is about 14+ but when accelerating, the afr goes up to 17 - 18 at first then down to 13.
Accel pump cam? Adjustment of the arm seems fine.

[DeathProofCuda]

So I progressively went from an 80 main jet to a 74. The cruise afr is about 14+ but when accelerating, the afr goes up to 17 - 18 at first then down to 13.
Accel pump cam? Adjustment of the arm seems fine.

@dodj, have you made any more progress on your tuning?  I just finished hooking up an AEM wideband meter in my car, so was reading your post with interest.