using 14.047 for desired AFR and not 14.63?

[mr.prick]

The NBO2's look for Stoich regardless of what AFR stoich is.

How Wideband (and narrowband) Sensors Work

[CalEditor]

I have been following this also.

I am wondering, don't the narrow bands only read stoich.

Brad

Correct You are changing Stoich switching AFR

This is figured from Air Mass and Fuel Mass

[CalEditor]

Can some one post the cal file for 1GNEC13Z82J242956 maybe I can later

[TunasTwins]

I have been following this also.

I am wondering, don't the narrow bands only read stoich. EQ1????
Can the computer compensate for the difference in commanded?

When I get a chance I will do some logging to see the difference but it seems that even if you command 14.37 that the narrowbands will still look for 14.63.

Or I may be way off base. Do the switchpoints make that difference in the stoich points?

Any insight?

Brad

This is basically what I'm trying to verify, along with the function of the %alcohol fuel AFR table (I'm using tunercats) on non flex fuel vehicles. I did post over at monodax but it usually takes a while for an answer. TIA

[TunasTwins]

sorry, didnt see the above post from MR. Prick. Guess I'll leave the 14.3 in the % alcohol table and set the 02 to switch around .525 and see what happens. Thanks guys.

[CalEditor]

This is basically what I'm trying to verify, along with the function of the %alcohol fuel AFR table (I'm using tunercats) on non flex fuel vehicles. I did post over at monodax but it usually takes a while for an answer. TIA

JWS6
pm me your email and I will get you more info.

[gmh308]

Please explain. The vehicle is NON flex fuel. Did I effectively change the EQ? Will this change the target AFR in closed loop also? Is changing the 02 switch point mandatory? TIA

The AFR table is simply a reference lookup for the ECM to determine fueling in relation to measured (MAF) or calculated (VE table) air mass flow.

i.e. in in open loop if MAF indicates 14.7 grams per sec of air and the AFR table at 0% alcohol is cal'd to 14.7 the injectors will delivery 1g/s of fuel.

If the table is set at 10:1 fueling will be 1.47 g/s.

It is a variable table to support flex fuel so that when the ECM knows via the fuel composition sensor or virtual fuel sensing system that the ethanol content for example is 50%, it can adjust the fuel flow accordingly to represent 11.8 parts of air to 1 of fuel by mass. In non flex fuel cals it simply sits at 0%. Pre flex fuel PCM's still had this calibration but it was a single number for gas.

NB O2 sensors are simply that: sensors. They measure and "report" oxygen content of the exhaust gas and are designed to be most responsive around stoich in terms of voltage output to oxygen content.

The ECM "drives" them by varying fueling around the crossover point/rich-lean threshold. There are 3 key points being the crossover point, the rich turn-around point and the lean turn-around point.

For example the crossover might be set at 500mv the lean turnaround 250mv and the rich turnaround 750mv. So the ECM adds fuel and the sensors see the voltage get to 750mv and then it pulls fuel until the sensors see 250mv and then it adds full again and graphed it looks similar to a sine wave. In an ideal world the crossover will represent stoich and the lean/rich turnaround points will be an equal distance from the crossover point but generally the calibrations will be adjusted slightly to cater for different O2 sensor response curves, engine characteristics and to achieve emissions targets, and maybe if thats all ok maybe some fuel savings can be fitted in as well by keeping them on the lean side a fraction longer than the rich side without screwing emissions.

[CalEditor]

This is a 2002 5.3L Tahoe Flex Fuel calibration from a 512kb 0411 PCM in bin format

[SS Enforcer]

I tune my car in OLSD as I can do it quite well and car runs fine like that whenever I put any e10 in it i have noticed it run a bit lean. I mainly run the e10 just to keep the fuel system cleared of water, more of a maintainence thing really. I basically have 2 tunes setup for it so I can reflash it once the e10 is gone from the system.

The way I read it is we basically will use 5% more fuel running E10 over 98 ron fuel would that be a fair estimation?
If this is the case E10 needs to be more than 5% cheaper to attain any financial benefit from doing so. Given that E10 is usually only about 2-3 cpl cheaper than 91ron the average punter is getting ripped when they use E10.

cheers

[picnic_george]

Back from the dead... I just read this whole thing. My big question is...
On 91 my tune is really close, but I also run vp100 which has a stoich rating of something like 14.16. I've had 100 in my car for while and my LTFT are positive. I run CL MAF. I do tune in AFR(which I've been reading for years not to but I'm not changing lol).
I know what I want my AFR to be and it seems that is where it is. I set my car to run 12.3-12.5:1 on 91 which equals closer to 12.1-11.8:1 on 100 and that's where it runs.
So here is the big Q..
If I change B3601 to 14.16 what will I see happen? Will my fuel trims correct themselves closer to 0, when I scan WO2AFR(efilive) will it show me 12.5ish(even though my gauge will still show 12.1 unless I configure logworks) or will it do both?
And not that I have any plans in the near future to change over to e85(presumably exactly 85%), what would happen if I left everything the same and set B3601 to 9.85. Would it be in the ballpark?

Thanks
Kris