2006 GTO Flexfuel

[JoeMama's GTO]

OK, I just installed a flexfuel sensor on a 2006 GTO and verified that it is working. Now I understand how the flex spark tables work but the fueling has me a little confused. I think what needs to happen is I change the Stoic AFR table under Engine>Fuel>General>Stoich AFR. Then the commanded PE AFR will be the Stoic AFR value for the percent alcohol I am running divided by the EQ ratio. Now, I am confused by the blend factor table in the Open Loop menu. Why would I need to use a blend factor based on fuel composition for Open Loop and PE if I already have stoich dependent on fuel composition? Also, in the PE menu there is only an EQ ratio for gas so I am assuming changing that stoic table will take care of all the fuel addition I need to run E-85.

Also, I plan to leave timing alone to begin with so I have zeroed out the Flex Spark table so nothing gets added or subtracted. Is this a bad idea? Seems like I would want to dial in fueling and then add spark if needed.

Thanks for your feedback.

[GXPLS4]

Your stoich table needs to be a sloped table. The PCM will reference that in relation to how much alcohol content you have. Simple as that. Your p.e can stay the same. And for flex fuel you can start out with adding 1-2 degrees across the board and seeing where you're at.

[JoeMama's GTO]

Excellent, thanks. It just threw me off that there would be two ways to "blend" the fuel tables based on fuel comp.

[JoeMama's GTO]

Hmmm, it seems to be a little lean still. Also I was logging commanded AFR (using a different device than HPT) and it was 14.66 multiplied by my EQ ratio. So the commanded AFR was between 17 and 19.6ish. However, actual AFR was decreasing as boost/RPM increased. I am only running 30% alcohol right now to get a feel for the tuning. Maybe I will change the stoic more aggressively based on alcohol %.

[GXPLS4]

You divide your commanded by eq ratio to see what your final Afr is not the other way around. Do you have a wideband ?

[JoeMama's GTO]

Yeah, that is what is confusing. I have a WB and I am logging low 12's and high 11's when it should be mid to low 11's. I have attached the file. Also of interest is that a Alcohol EQ table does not exist like some files I have seen from FlexFuel equipped vehicles.


Flex Tune DK.hpt

[GXPLS4]

try this under the stoich AFr tab, yours was unlike any ive ever seen, straight jacked up
use these values and see where youre at

Labels 0.00 6.25 12.50 18.75 25.00 31.25 37.50 43.75 50.00 56.25 62.50 68.75 75.00 81.25 87.50 93.75 100.00
Stoich 14.678223 14.322266 13.965820 13.609863 13.252930 12.896973 12.541016 12.184082 11.828125 11.472168 11.115234 10.758789 10.402832 10.046875 9.689941 9.333984 8.978027

[JoeMama's GTO]

Yeah I am going to contact the guy that originally tuned it before making that change. It has ran very well for years on that tune and I am assuming he had a good reason for creating that stoich table (his was actually 17.3 across the board I changed it to slide down for E85).

[GXPLS4]

I don't know why. If you're not using a sensor and he tuned it like that the PCM automatically goes for the 0% value which is 17.3 in this case.

I'm on e85 same PCM and os, but I keep my stoich table flat lined at 9.87 and never have Afr fluctuations. Everything matches up, except my wideband gauge which no matter what reports its default of 14.7 which let's me know I'm on target.

[JoeMama's GTO]

Thanks for your help, I think I figured it out. The AFR was scaled because my injectors are 80lb/hr (vs. 63.5). I did not properly account for the E85 scaling when making that table because I had it in my head that 100% alcohol = 100% E85 which is not true, LOL. So I rescaled based on stoich AFR for alcohol and included the scaling factor for the larger injectors. Now my gas and E30 logs match up although I think my wideband is going south. It reports chunky data and is getting more lean which is how this sensor likes to fail.

[aaronb]

Sorry to some what change the subject but what pin on the E40 is the flex fuel sensor wired to ? Thanks