Air fuel code for scangauge

JB1

Well, for what it's worth, until 3 weeks ago I had Berk HFC + Berk CBE and stock intake with Cobb post MAF hoses. As far as I know I never saw the A/F ratio go over 14.7. Since then I swapped the Berk HFC's for the stock cats and the A/F ratio remained the same. But I'll pay more attention tomorrow during my drive to work to see what the A/F ratio does during WOT. I'll report back later!

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Black Fangs // Black rear Valance // Berk CBE // COBB post MAF tubes // K&N drop in filters // Setrab Oil Cooler // Stillen Sway bars // Z1 SS brake lines // Stillen brake cooling kit // Harness bar //

Jordo!

Is that a transformed value derived from the narrowband O2 voltage? In closed loop, all the ECU cares about is seeing the O2 hover around .5 volts (i.e., ~14.68 AFR / lambda = 1.0).

There's pretty much no way it can run too rich or too lean in closed loop (fuel trims will correct) unless something is really fvcked up, in which case you'll get a CEL.

In open loop the AFR will be whatever was tuned from the factory without the narrowband commanding any adjustments (except probably for a long term trim that carries over that is).

Say what? Is that a sustained AFR or only an occasional blip (e.g., going lean on tip-in)?

If you are seeing stable AFR's that lean under heavy load (i.e., WOT, high RPM's) GET OFF THE THROTTLE! You may very well get massive detonation and kill a piston or spin a bearing in short order.

Assuming that value is accurate -- best to confirm with a good wideband O2 either on a dyno or one you can buy (e.g., AEM UEGO)

You do not want to see anything leaner than ~13.5 under heavy load, N/A and a bit richer would be preferred for best power.

Especially if you are using 91 AKI instead of 93... with 93 anything south of stoich is probably okay (N/A), though not best for safety or power.

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JvKintheUSA

Prolly going to get an UpRev tune here at Forged within the next few weeks - that should fix it. Just curious if JB1 runs lean at WOT as well. The car must have been factory tuned pretty lean to begin with and with any bolt-ons will run too lean at WOT. I recommend that anyone with bolt-ons should get their WOT A/F ratio checked.

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JB1

I couldn't play around too much this morning, construction and busy traffic doesn't mix well with WOT driving... But I did get to try it out a couple of times and the A/F ratio was steady at 17.5 during WOT. I mostly tried it in high gear/low speed situations, as this offered me the chance of having a WOT without accelerating into the car in front of me to quickly.

I feel like the 17.5 is some sort of a default value, as it didn't seem to change at all as long as I had the accelerator floored. Also, as soon as I lifted just a little, the reading went back below 14.7

But I'm not sure yet, so I will try it out some more tonight and this weekend to see if that 17.5 is indeed a default value during WOT or if it changes.

Too bad I didn't look at the A/F ratio during WOT driving when I still had the Takeda intakes and HFC's. But then again, I normally have my eyes on the road during WOT driving

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Black Fangs // Black rear Valance // Berk CBE // COBB post MAF tubes // K&N drop in filters // Setrab Oil Cooler // Stillen Sway bars // Z1 SS brake lines // Stillen brake cooling kit // Harness bar //

JvKintheUSA

I did some WOT driving this morning and got the same results. It is not just a blimp up to 17.5, but 17.5 steady at WOT.

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JvKintheUSA

Modshack - to clarify: were you able to get an A/F ratio measurement on Sensor 1, Bank 1 on the Scangauge? Or on the Alternate A/F Ration (general)" setting for CANSF? Or are you referring to the Long Term Trim on Sensor 1, Bank 1?

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Modshack

I am measuring the regular A/F ratio...Bank 1 sensor 1....The first Code line in that CANSF category. On trims, the Programming I am using is left over from when I had this on my corvette: Fuel trims for CANXX vehicles, long term trim bank 1 on page 1

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JvKintheUSA

Another question: How long does it take for the long term fuel trim to be accurate? I just coded my Scangauge to measure the LTF on bank 1 and it says 34 at idle. Is that number derived from a few days of driving, or just since I coded the Scangauge? Did hose check - looks fine.

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JvKintheUSA

Thanks Mod - gonna try right now. Maybe that is the issue.

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Modshack

Sounds like it could be...Let us know!

And you should get instant reading on long term trims...That data is built up in eproms and retained. a few Percentage points + or - 0% is where it needs to be..

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JvKintheUSA

Thanks Mod! Did a quick highway run and it seems that the coding on the Scangauge was incorrect. On the setting that you provided, I now read an A/F ration at WOT of 12.8 to 12, depending on RPM. Long term fuel trim stuck at 34 though..another issue I guess?!

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Modshack

OK...Good! JB1 needs to fix his too..

On the LTF's, I just checked the coding on mine and it is on page 1, CANXX, TXD 07E00107 Yada yada. Double check your entries..

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JB1

Done! Thanks a lot Modshack!

I switched to the Bank 1 / Sensor 1 setting and It now shows a "proper" rich ratio of around 12~13:1 on open loop Opperation. So I guess the "general" setting is not the right one for our cars and that 17.5:1 reading in the "general" setting is indeed some kind of default. BTW, my long term fuel trim shows -8

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Black Fangs // Black rear Valance // Berk CBE // COBB post MAF tubes // K&N drop in filters // Setrab Oil Cooler // Stillen Sway bars // Z1 SS brake lines // Stillen brake cooling kit // Harness bar //

Jordo!

That's a relief! That's perfectly safe and not too far off from the likely best torque AFR (varies from motor to motor, but something around 13.2 is generally ideal N/A).

Congrats!

If you want to learn more about this stuff, I highly recommend you pick up the following text:

Amazon.com: Engine Management: Advanced Tuning (9781932494426): Greg Banish:…

It really spells out all of the basics with some clear information on more advanced topics. It will help clarify what the scanguage is telling you.

Also, regarding fuel trims, note that there are most likely multiple trims --one associated with each cell in the fueling map (which you probably can't access) or at least a block of adjacent cells; cells are graphed by load (based on MAF value and known engine displacement) and RPM.

Short term trims (based on vacilations around 14.68 AFR / narrow band .5 volts) are averaged to create long term trims. One of those is probably carried into open loop (can Modshack confirm or refute that?)

The LTFT of +34 may or may not be a cause for concern. So long as driveability is fine, AFR's in WOT are fine, and the CEL light is off, it's not ideal, but acceptable (ideally, you'd want to have th ecar tuned so that these are all in the single digits and driveability is excellent).

Man, I can't wait to start playing with uprev on this car

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JvKintheUSA

+1 for that info! Thanks!! I might do an UpRev tune or get a Cobb Accessport one of these days.

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