Stock WOT AFR 10.5??

[A_W_O_L]

I just bought an NGK AFX w/ NTK and installed it on my 2003 Silverado ECSB. This is a low mileage truck (> 50K ), I'm the 2nd owner and I'm almost 100% positive that the tune has not been messed with (except by me ...see below) I've calibrated the sensor free-air for 15 mins. and adjusted the offset in the scanner (not easily done ... but it's within approx .1 afr of the controller readout from what I can eyeball). I'm trying to determine:

1. is the sensor out to lunch or calibration off?
2. are the stock WOT tunes really that rich?
3. Target AFR for WOT? I've read 12.5 - 13... but that info is mostly found on the cars.... would it be richer on the trucks due to weight (conservative tune to prevent knock?) I rarely tow anything, but It's not like I'm at WOT during towing anyway.

The following is just what I have noticed during a road trip this last weekend...I've made no changes to any of the stock timing or fueling....the only changes to the stock tune are related to tire size and some tweaking to shift ponts/pressure:

I was seeing a commanded AFR of ~11:1, measured of ~10.5 - 11:1 depending @ WOT. The targeted AFR at cruise is 14.68 (naturally), and the measured avg's are 14.3 - 14.4 depending on the cell. Is this typical???

Most of what I read has little info on the stock targeted AFR. I'm trying to figure out if this is a typical reading or if I have a sensor that is out to lunch. My inital reaction was that the stock tune wouldn't be that rich... but looking at the commanded it seems like the sensor is probably fine.

Thanks in advance guys for the feedback!

[BBA]

Stock on regular gas would not be that rich, on ethanol, would be that rich. What are your trims and can you post the tune and a scan log?

[A_W_O_L]

This is on 91 octane Chevron.... it *might* have 10% ethanol...

The fuel trims are between +7 and +15 depending... which doesn't seem too off the wall for a stock tune (K&N CAI and Magnaflow Catback). The two logs below are on different days.
Attached are 4 files:

1. Current Tune
2. 1st Log (the trip back home approx 3hrs...just part throttle)
3. 2nd Log (short WOT at 18:50 ... passing old slow people on 2 lane road)
4. Config file used during logging


Note: WHY is uploading so SLOW? I have a 768K upstream and this is slower than uploading pics using dialup? I'll post the files as fast as the website can take it.

[A_W_O_L]

I don't know if it matters on the scans or not.... but I'm now using the beta verson of HPTuners... changes to the tune (the tire size changes, shift point tweaks, ect.) were made a while ago using the full release...

[Mez]

Test fuel for E10 and if it is, change stoich to ~14.2 and watch the LTFT %. Sounds like that's what you are using. Once I changed mine to 14.2, my LTFT fell in line.

Once you do this, I strongly recommend to convert your analysis to Lambda because thinking in terms of AFR compared to 100% gas will be screwed up.

[madvette08]

Its typical to see a stock tune being that rich. My stock 08 vette ran from 11.0 to 10.7 at WOT and it was commanding 11.5.

Every car is different, some cars are dead on and some are not.

Ian

[A_W_O_L]

Mez:
I'll order a test kit, I've searched and found one that I will probably end up ordering next week..any suggestions on a kit? In the mean time I think I will test changing stoich for E10, see where the fuel trims fall, and report back. I'm working on changing my config file for Lambda... I used AFR for the trip because it was easier for me to relate to at a glance.... Lambda does make the most sense...just not used to it yet.

Mad:
Wow I would have thought that they would be a little more consistent than that... at one point mine is commanding 11.07 and measured is 10.46... I guess after having the software for a while (6 years) it's surprising to finally see how far from the 12.5 AFR that everyone talks about being the "best" target AFR....or should I say .85 lambda . If it turns out that I'm running E10 after all then I guess that would explain the rich reading I'm getting. The AFX controller is setup for AFR of pure gasoline, so what I am reading on the controller (and subsequently trying to offset for...for the scanner to line up with the controller) isn't correct if it is E10. I need to send NGK a nasty email...Lambda on the controller would be a nice option

Again Thanks for the feedback!

[axekick]

I see 14.57 as lambda when I'm looking at mine. I actually tune by EQ since thats what all the table use.

[A_W_O_L]

Before I made any changes to my tune I decided to look things over again. I came back to the scanner and the setup of the wideband in the primary table ect. It seems like for the NGK AFX there are differing opinions on how to set it up. Apparently it's a good sensor as several very well respected people recommend it. Before I go any further, I need to ensure that I have it setup properly.

I will ask here just for reference, but I am going to add a link to a new thread reguarding proper setup of the NGK AFX. Are you suppsed to use an offset, use NGK's documented ranges and linear math HPT, or measure the output ranges with a DMM and then the linear math values in HPT? It doesn't seem like anyone that has one is actually using the pre-configured NGK Wideband setting. I have searched and the only thing I keep seeing is alot of uncertianty.

Axekick:
I think you misstyped something.... I don't follow.

[A_W_O_L]

Here is the link to an existing thread and my conversation with Brian at AFX Tech Support. Basically... the published transfer function in thier manual will scale the scanner to match the controller (Lambda = 14.57 AFR) which they have found to be a more real world AFR for pump gas (no ethanol). Hopefully that will clear things up.

I'm going to re-do the WB in the scanner and set it up to scan for lambda and report back what the measured lambda is (assuming 14.57 = lambda) and go from there.... I may not be as rich as I thought.