I have a 6.2 1500, which is not a flex vehicle, sitting here.
The stock tune has Virtual and Enabled.... the stoich table is 14.1 across.
Will this vehicle act like a Virtual Flex truck (like the 5.3) if I just correct the stoich table for Flex?
I have a 6.2 1500, which is not a flex vehicle, sitting here.
The stock tune has Virtual and Enabled.... the stoich table is 14.1 across.
Will this vehicle act like a Virtual Flex truck (like the 5.3) if I just correct the stoich table for Flex?
Higgs I don't know, but I'd give it a try. Always could put a gallon or so of e85 in it after your correct the stoich table and see what the fuel trims are doing
I don't think its the same 5.3s have the alcohol sensor which will add or take away timing adjust fueling by itself, you can mix it on a 6.2 already did a mix on a c7 works wonderful
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that's not what I asked. I run E85 on my C7 as well.
my 2015 6.2 1500 has ALL of the flex tables calibrated including an enabled virtual sensor in the stock tune, just like my 2015 2500 has except for the stoich table....
I haven't had a chance to test the stoich table yet. I'm wondering if there are calculations that can only be made by flex operating systems or if it's really as simple as one table change.....sort of like lean cruise not working in U.S. cars even though the tables were there and enabled in the older cars.
Post tune. It adjust fuel rate and timing in the virtual tune. Adding a flex fuel sensor would allow you reference stoich table. Here is little info on virtual flex fuel:
E85 Flex Fuel Description
E85 compatible vehicles no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle calculates the alcohol content of the fuel through measured adjustments.
The ethanol calculation occurs with the engine running after a refueling event has been detected via a measured change in the fuel level sender output. The virtual flex fuel sensor (V-FFS) algorithm temporarily closes the canister purge valve for a few seconds and monitors information from the closed loop fuel trim system to calculate the ethanol content. This logic executes several times until the ethanol calculation is deemed to be stable. This may take several minutes under low fuel flow conditions such as idle, or a shorter time during higher fuel flow, off-idle conditions.
Air-fuel ratios and the corresponding ethanol percentage are updated following each purge-off sequence. The fuel alcohol content percentage value can be read on a scan tool.
When an E85 compatible vehicle is built, an ECM or PCM replaced, or if the learned alcohol content has been reset with a scan tool the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content.
A minimum of 11 liters (3 gallons) must be put in the tank in order for the vehicle to recognize a re-fueling event. It is not necessary to turn the ignition OFF in order to have the re-fueling event recognized, however local safety regulations should be followed.
After the re-fueling event, the system registers the amount of fuel that was added, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines if the fuel added was either ASTM Gasoline or ASTM E85. Based on that determination, the system adjusts to the expected alcohol mix in the fuel tank, and then the fuel trim and O2 sensor activity fine tunes the adjustments. The system must remain in closed loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining closed loop operation.
Switching Between Gasoline and E85
No special precautions need to be taken when switching back and forth between gasoline and E85 other than re-fueling events must be 11 liters (3 gallons) or greater, and the vehicle must remain in closed loop long enough, usually by the time the engine has maintained full operating temperature, to calculate the composition of the new blend in the tank.
Last edited by Road; 05-05-2015 at 08:57 AM.
Yes, I believe I had read that somewhere before, thank you for posting it.
The question that remains for me is you say adding a FF sensor will allow the stoich table to be referenced however, with the virtual sensor don't you think the fuel trims that are monitored must also be referencing the stoich table? How else would trims translate to an ethanol %?
I'll change it and try it when I get a chance, just checking to see if anyone been down that road.
I just tuned a 2015 2500 w/6.0 and it is set to virtual flex fuel and has the flex fuel stoich table. We don't have any E85 around here to test it. Don't know what's up but letting you know that they do come from the factory that way.Originally Posted by Higgs Boson
I am talking about the 1500 6.2. The 2500HD 6.0 is advertised as a Flex Fuel vehicle and I just traded a 2015 2500HD for a 2015 1500 6.2 which is not advertised as a Flex Fuel vehicle but has all tables enabled. I ran E85 exclusively in my 2500 as I do in the C7.
Did you tune your c7 to E85. I have not seen a flex fuel C7?
Yes, many people have.
I would think tuning your truck to flex fuel would be no different than tuning your C7. I personally have never seen a 5.3 or 6.2 DI motor that is flex fuel. The stock high pressure fuel pump and the stock DI injectors cannot handle the fuel demand of E85. Hence the reason they not enabled in the tune and the necessity for meth injection on boosted DI motors. Are you using the stock fuel system on your C7 flex fuel conversion? If yes I am curios how well it supplies the demand of E85?
Road, that is incorrect info
What is incorrect (I have been wrong before)? What V8 DI motor is flex fuel? I know the 3.6 is but I personally have not seen a V8 DI flex fuel. Correct me where I am incorrect?
All of it is wrong. The 5.3 DI motor in the 2014/2015 Silverado 1500 is Flex Fuel. The 6.2 tune, as this thread discusses, is completely set up for Flex Fuel except the Stoich table.
There is TONS of headroom in the 6.2 fuel system, the only thing you can't do is E85 with boost. A supercharger will run the injectors close to their limit on 93, E85 will take a stock motor to about 22% DC with a max in the 40% range.
my C7 has a stock fuel system, I changed the stoich table to 10.0 and retuned MAF/VE (along with a couple other tweaks to things like startup airflow, etc) and duty cycle is like 28% at WOT if I remember right.
Most people are installing a Flex Fuel sensor so they don't have to reload a 93 tune vs E85 tune every time they switch. I leave E85 in it 100% of the time so no big deal for me.
Thanks for the replies back and looks like I learn something here. I looked at every DI window sticker on our dealer lot and none of them are flex fuel none of the brochures have flex fuel in them searched SI found nothing there and talked to inventory manager and and its a option but it want let you order a flex fuel yet. I do know they make three different injectors low flow med flow and high flow and the Z06 has the high flow. Sounds like you already knew the answer to your question before you posted this thread. Thank for the education but I still don't think they come flex fuel.
The question I am asking is not the one you are trying to answer.
Last edited by Higgs Boson; 05-08-2015 at 09:45 PM.
After further research I found out I am wrong and here to apologize. Every 2014 5.3 I have read is flex fuel enabled but the 2015 seams to be disabled and all the 2015 on our lot don't appear to be flex fuel I am going to pull the tune on a few of them to see if it's enabled. Again my bad and I apologize for being so hard headed.
It's no big deal, you don't have to apologize for anything. We are all hard headed on car forums.
It looks like they went to a $100 checkbox Flex option in 2015, although it does default to Flex on the build site. The 6.2 trucks are "not Flex vehicles" according to GM they are not available with the option. However, as we have access to make our own tunes, it is just a few clicks away.
Our sales manager said the option is there when he order's the 5.3 but it want let him check the box to order them on 2015 models. Appears that GM has disabled it for now for reasons unknown.
The 6.2 knows when it has 10% in it, I'm sure it would know when it has 85% as well. I'm just saying😒
It would really look bad from a marketing standpoint if my farm truck put down better numbers than the Base C7
Last edited by mm_n_p; 06-13-2015 at 04:29 PM.
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