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Is this accurate? 

 

 

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.

 

 

https://forum.hptuners.com/showthread.php?51424-Flex-Fuel-6-2-Silverado

 

This forum post is claiming the 6.2 doesn't need to have a flexfuel sensor to operate on e85?

Edited by M1ck3y
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Is this accurate? 
 
 
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.
 
 
https://forum.hptuners.com/showthread.php?51424-Flex-Fuel-6-2-Silverado
 
This forum post is claiming the 6.2 doesn't need to have a flexfuel sensor to operate on e85?

In my 18 6.2, I run 7 gallons of E85 in every other tank, zero issues


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The stock calibration on a 2016-2018 truck will not have anything flex fuel enabled. There is no virtual sensor enabled on non flex fuel vehicles. The stoich fuel table is setup for 10% alcohol content at all times. The virtual sensor is not that accurate either and lags behind a lot when different fuels are introduced.

 

The only way for the computer to know exactly what is in the tank is to install a sensor and have it enabled in the calibration.

 

People run mix blends of fuels if they want but they are relying on the fuel trims to make adjustments for them and those adjustments only work in closed loop fuel control. If a real sensor was installed the computer could take advantage of that and lean out the fuel mixture under heavy throttle resulting in slightly more power and a more accurate airflow/fueling model.

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Thanks, was hoping to avoid cutting fuel lines, probably for the best though as I'm thinking about doing an e30-40 mix. Ive read that it may be the best balance between the fuels. Potentially improving fuel economy and not missing out on that much power compared to e85?  

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I didn't cut any lines. I just made a couple adapters to plumb the sensor in right by the fuel tank. It stays out of the way and doesn't move around much. I extended the harness that is already under the truck so it would reach to the tank and that was it.

 

Enabled it in the tune and setup all the flex fuel tables to how I wanted them. I don't know if the 6.2 ever had a rated E85 horsepower like the 2014-2015 5.3's did but that was good for like 25+ hp and torque just on E85.

 

Having the sensor would surely let it optimize the commanded fueling at all times and should net the best economy and performance at that given time. Just know that running any mix of fuel will probably reduce mileage by a little bit. Getting 20-21 on the freeway was still do-able on E70 in my truck but city mileage dropped to about 10-12mpg. Mileage isn't something I worried about with my short commutes anyway because even on regular 89 octane I got 14-15mpg in town.

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^ I second all the above. Do the actual sensor. Super easy install. It took me about 20 minutes. 

 

And I do agree that E30-40 is a good sweet spot. The gas mileage is nearly the same but it runs smoother and pulls harder and has virtually zero knock.

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I ran a 50/50 mix of E85 and premium in my 2002.  It wasn't a FF vehicle. This mix seemed to work the best for me.  I ran it for a good 5 or so years.  The performance was noticeable to me at least. Crisper throttle response and my fuel economy didn't take a hit.  If I ran E85 100%  then I would get two codes.  Bank 1 lean and Bank 2 lean.  So I didn't run it at 100% for that reason. 

 

Our 2016 Suburban I added the sensor and had Black Bear Performance turn the table on in the ECM and tune for it as well as what ever else he does for a tune.  Made a really nice difference in that heavy beast.

 

Sad that GM went away from it in the new T1's.  I was hoping they didn't.  I like running it for the performance as well as the cleaner burn in the cylinders.  Not to mention the exhaust smells better.  :)

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Do the sensor.  More accurate readings on the alcohol content of the fuel.  I watched the tuner who did my truck on HP Tuners, you can enable the "virtual" sensor function or the sensor function.  I installed the sensor without cutting any lines and then took it to him with a couple gallons of 93 in the tank and then we added 10 gallons of E85.  Tuning was done on about E70 and I've been running E85 since.  Going back to 93 here for the winter though.  

 

 

Edited by newdude
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1 hour ago, Black02Silverado said:

ISad that GM went away from it in the new T1's.  I was hoping they didn't.  I like running it for the performance as well as the cleaner burn in the cylinders.  Not to mention the exhaust smells better.  :)

Any thoughts as to why they stopped?  I know money is the overall reason but there must be an underlying reason for it not to be a profitable feature. I've owned flex fuel vehicles for over a decade and used e85 for the first time a month ago.  My local gas bar now offers it and the price is substantially less than regular gas.  I know the mpg's are worse but if its better for the air we breath and gives me more horsepower then it's a no-brainer, imo! 

Edited by Donstar
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In my opinion there aren't enough flex fuel vehicles on the road to justify this venture. It was to help farmers. Ethanol fuel is 30 miles away from me. Another turd from the gov. 

Edited by diyer2
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The only vehicle I had that was E-85 was my 14 GMC. My truck love it and the seat of the pants feel was definitely noticeable. The horsepower gains was more than what my performance tune was requiring 93 gas. It was the first time that I didn’t tune the engine, just the transmission. I was able to use regular gas on trips. So at least in that case E-85 was much cheaper than 93 gas for performance use. In my case I got it much cheaper than regular gas at my local Kroger’s store with my Kroger’s card. Paying less for gas that gave me 25HP was a no brainer. So naturally GM would kill the program.


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I've found a number of different threads on e85 and they've been helpful. However, I'm not sure if you have to replace the entire fuel line when going with the oem route; or if it's just a matter of a couple quick disconnects and your done. Will the 5.3cc flexfuel sensor swap over to a 6.2cc?

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4 minutes ago, M1ck3y said:

I've found a number of different threads on e85 and they've been helpful. However, I'm not sure if you have to replace the entire fuel line when going with the oem route; or if it's just a matter of a couple quick disconnects and your done. Will the 5.3cc flexfuel sensor swap over to a 6.2cc?

Read through this one (all the way through lol) the solution on page 3 is what I ended up doing. It doesn't fit perfectly. But it has no kinks, no links, and is working fine. 

 

Ordered the hard parts from Rockauto:

 

ACDELCO 13577429  
ACDELCO

23171534

 

And the harness from here:

 

https://burgertuning.com/products/48-extension-for-fuel-it-flex-fuel-analyzer

 

 

 

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3 hours ago, Donstar said:

Any thoughts as to why they stopped?  I know money is the overall reason but there must be an underlying reason for it not to be a profitable feature. I've owned flex fuel vehicles for over a decade and used e85 for the first time a month ago.  My local gas bar now offers it and the price is substantially less than regular gas.  I know the mpg's are worse but if its better for the air we breath and gives me more horsepower then it's a no-brainer, imo! 

I'm sure it is all about the money.  As for why it would be is beyond me because the trucks and vehicles coming down the line already can handle it. The only difference it a sensor and the alcohol table in the ECM.  Which is there on vehicles that didn't come with it like our Suburban.  It had the table, just needed to be turned on.  So why not just continue and give the public the option?  There are so many out there that have the yellow cap and don't have a clue why and probably never will.  I have talked to several while fueling up at our E85 source,  Sheetz, and told them they can run it and they told me they didn't realize it.  Yellow handle pump and yellow cap.  At least here the E85 is a yellow handle pump.

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Does anyone have a parts diagram for the flex fuel crew cab?

 

I found a another thread where it appears he bought all oe parts for a factory finish. 

 

ACDELCO 13577429

GM GENUINE 23171538

GM GENUINE 20967834 

GM GENUINE 23158923

 

There was also part# 23171537 listed but I couldn't find it. I'm trying to figure out what he did exactly...

Edited by M1ck3y
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