Ethanol questions - converting non-flex fuel to ethanol

[BLK02WS6]

I have a 2006 Tahoe that is a non-flex fuel vehicle (12587811 OS) and I was looking into what it would take to run Ethanol in it... I am looking at everything from 2 seperate tunes (simplest way), to ways to use the flex fuel OS with a dial or something to blend the tables.

My first question is that in the flex fuel 2006 Tahoe OS (12605114), it says that it doesn't have a flex fuel sensor... so, how does it know how much ethanol is in the tank? How does the PCM know how to blend the tables?

Has anyone out there done anything like a dial - I would guess using a pinout on the PCM - to dial in how much ethanol (say you stop and fill up with 1/4 tank of gas still left)...

or is a retrofit possible - not sure what that entails since the Tahoe doesn't have a sensor...

[Chevy366]

Here is a good read; http://forum.efilive.com/showthread.php?13171-E38-Flex-Fuel-On-the-fly-timing-and-fueling-anyone-interested&highlight=ethano
(http://forum.efilive.com/showthread.php?13171-E38-Flex-Fuel-On-the-fly-timing-and-fueling-anyone-interested&highlight=ethanol)

When you say "you want to run ethanol", I assume you know that most gas now has at least 10% ethanol in it.

[the_red_shark]

I have switched my vehicle to e85 in the last week from 98ron. It is an e40 ls2 in an Australian HSV z series senator. I have had some great help from swingtan,Luis @ APS, Dale @ CHE and others in the EFI users fb group.

With the e40 there is a checkbox in fuel to enable flex fuel, this is negligent as it does not run a flex fuel sensor. There are a few changes firstly stoichiometric ratio needs to be set per ethanol content of the fuel used, Wallace racing has a lambda/afr converter for all fuels on their site. You will need RC10 for this as previous versions dont have this in e40 tables.

Next you need to tell the PCM that you are running ethanol as it won't know this. In table b0145 set all % values to 1 as it then forces the PCM to use the ethanol tables.

That's a start and then go from there, I have not finished have too lean cold idle and a couple of little things. Give it heaps of fuel to start with you can always back off and tune to lamda

[BLK02WS6]

Sorry - I'm talking E85 here - should have been more specific...

Does anyone know how a flex fuel OS works without a flex fuel sensor? I understand how all of the tables interact in that OS, but just don't understand how it can work without knowing the blend of ethanol in the tank...

I would really rather not have to run the tank to empty if I have gas in it and then put E85 in it and push a seperate tune...


Edit: I read the link above - good read, and it explains how the Virtual Fuel Sensing works in the E38 - so is that how the older PCMs do it too? Does anyone know if there is a pin for "hard" sensing on the older (2006 Tahoe) too?

[joecar]

A flex fuel OS without the sensor works by looking at the trims over some period of time, I'm not sure of the details.

[GMPX]

The tables behind the ethanol estimation are baffling.
Your best option on an E38, E67 or E37 is to fit a real sensor (even though the price is scary). In EFILive you can tell the ECM that there is a real sensor, but here's the catch, not all GM calibrations had the ethanol tables done. For example, the Northstar engine has blank (or non configured) ethanol tables, so even if you fitted a sensor it still wouldn't work. Most of (if not all) of the GenIV's have the tables all set to go. If you look at the Stoich table and it's not all the same number then chances are GM had the E85 calibrations done ready to roll.
What is interesting is that GM have starting fitting real sensors to the cars again, maybe the estimation just wasn't accurate enough as emissions get tighter.

[ScarabEpic22]

Ross, BLK02WS6 is looking to do this on an 06 LS1B 1MB PCM, not a Gen IV ECM. I have 0 experience with this type of conversion as there is 1 gas station in all of Seattle that sells E85 (Seattle + surrounding areas is ~3-4 million). So doubtful Ill be working on E85 related stuff anytime soon haha.

[BLK02WS6]

So, I wonder if I took the flex fuel OS for an 06 Tahoe (12605114) and full flashed it into my non-flex fuel 06 Tahoe, would it then be a flex fuel Tahoe... Sounds funny, but it seems that is all there is to it.

[the_red_shark]

No it would not be any benefit. With ls1 PCM you theoretically should be able to tune it to e85 similar in way you tune to petrol just as a completely different tune. As it doesn't have the flex fuel tables nor the sensor you tune to the specific fuel and as I said above change Stoich ratio to 9.77 (off top of my head) and then go from there.

Then, use the v2 to store multi tunes then if need be change tunes at the pump.

[GMPX]

Ross, BLK02WS6 is looking to do this on an 06 LS1B 1MB PCM, not a Gen IV ECM.
:doh::doh:Must read a little deeper next time.

[the_red_shark]

A flex fuel OS without the sensor works by looking at the trims over some period of time, I'm not sure of the details.

Without the intank sensor your ecu has no idea the mix of fuel that is actually going into your engine. All it knows is stoich mixture is 1 lamda. So when tuning you see lamda 1 or 14.76 on your wideband gauge, its actually showing you the stoich mixture of whatever fuel you are using.

So by my understanding you really don't tune it any differently than you tune gas. Cruise at 1 (14.7), and WOT say 11.7 (very rough example to show a point), so your thinking doesn't need to change. Which leads me to the point that any ethanol tables are irrelevant to any vehicle without a flex fuel sensor.

[Chevy366]

The thing with E85 is to run it you have supply more fuel. E85 motors have larger injectors, while you can tune a non-flex-fuel to run E85.
Here is some more; http://forum.efilive.com/showthread.php?9158-Want-to-run-E85&highlight=E85
Do a site search "E85" there is a lot of info here on it.

[BLK02WS6]

Without the intank sensor your ecu has no idea the mix of fuel that is actually going into your engine. All it knows is stoich mixture is 1 lamda. So when tuning you see lamda 1 or 14.76 on your wideband gauge, its actually showing you the stoich mixture of whatever fuel you are using.

So by my understanding you really don't tune it any differently than you tune gas. Cruise at 1 (14.7), and WOT say 11.7 (very rough example to show a point), so your thinking doesn't need to change. Which leads me to the point that any ethanol tables are irrelevant to any vehicle without a flex fuel sensor.

I don't think what you are saying about the ethanol tables being irrelevant is true. From the research I have been able to do, it appears that they have the PCM set up so that it drives the tune to the ethanol tables based on O2 feedback or something - but I can't figure out the details - one guy was talking about the sign wave that the O2 sensors makes changes... maybe because of the ethanol burning cooler? I don't know and was hoping one of the experts on here knew how it works...

I agree about lambda being lambda no matter which fuel you run - but the calculation to get AFR is where the difference comes in. 1 lambda is 14.76 with gas, but not with ethanol - it is 9.76... Maybe that is how they get the PCM to force into the ethanol tables... If the PCM sees 1 lambda from the O2 sensors, when ethanol is in the tank, it will take more fuel to maintain 1 lambda - maybe that's how it knows...

I know for sure that some year model flex fuel vehicles don't use a sensor in the tank...

If I end up going to ethanol, I really want to be able to run both fuels from the same tune - not have to flash a different tune in order to switch. And not have to run the tank down to empty either...

[BLK02WS6]

Here is a writeup I found on the Virtual Flex Fuel Sensor - this was for the 2006 Impala, but the theory would be the same for any flex fuel vehicle that doesn't have a sensor...

"In the past, GM had some small trucks and SUVs that could operate on different mixtures of ethanol-based fuels. These vehicles used a fuel sensor in the fuel line that signalled the computer how much ethanol was present in the fuel; the computer would add or subtract the amount of additional fuel required. Now, the Impala flex fuel system can perform this analysis without using any additional sensors. GM has developed a Virtual Flex Fuel Sensor (V-FFS) software program that calculates the ethanol content in the fuel, instead of using a sensor to measure it. When the fuel level in the tank increases as the vehicle is refueled, the computer recalculates the percentage of ethanol in the fuel and automatically changes the air/fuel ratio. To do this, the computer temporarily stops the operation of other emission systems and monitors the oxygen sensors to determine ethanol content. The test is done several times until calculations remain stable. This can take several minutes when the engine is idling, but much less time at higher fuel flow rates."

and another I found:

"For 2006 and 2007 models, E85 compatible vehicles marketed in North America no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle "learns" (calculates) the alcohol content of the fuel, (and subsequent mixture in the fuel tank), through a series of measured adjustments.

Adjustments

After the re-fueling event, the system registers the amount of fuel that was taken on-board, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines the ethanol content of the fuel that was added. Based on that determination, it adjusts itself to the expected alcohol mix in the fuel tank and lets the fuel trim and O2 sensor activity fine tune 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 vice versa, can result in driveability symptoms due to the inability of the system to adjust for fuel composition (by not attaining the parameters necessary to reach closed loop operation). "

[the_red_shark]

I don't think what you are saying about the ethanol tables being irrelevant is true. From the research I have been able to do, it appears that they have the PCM set up so that it drives the tune to the ethanol tables based on O2 feedback or something - but I can't figure out the details - one guy was talking about the sign wave that the O2 sensors makes changes... maybe because of the ethanol burning cooler? I don't know and was hoping one of the experts on here knew how it works...

I agree about lambda being lambda no matter which fuel you run - but the calculation to get AFR is where the difference comes in. 1 lambda is 14.76 with gas, but not with ethanol - it is 9.76... Maybe that is how they get the PCM to force into the ethanol tables... If the PCM sees 1 lambda from the O2 sensors, when ethanol is in the tank, it will take more fuel to maintain 1 lambda - maybe that's how it knows...

I know for sure that some year model flex fuel vehicles don't use a sensor in the tank...

If I end up going to ethanol, I really want to be able to run both fuels from the same tune - not have to flash a different tune in order to switch. And not have to run the tank down to empty either...

If you look in the description of the tables it's explains it better. If the ethanol blending it is commanded to run off the ethanol tables, whereas if it isn't runs off the normal fueling tables and you tune to suit.

Your o2s don't know what fuel is in the car they read the mixture and adjust trims. The ecu based off what you command is no different from ulp to e85, lambda is 1 so let's say your Stoich value on ulp is 1 you will require a richer mixture on e85 so whilst your wb reads lambda 1 your fuelling is up say 30% for example to achieve that.

By my thinking, and I'm very happy to be corrected as I'm always looking for ways to improve, flex fuel cars without the intank sensor would work in a fashion that the o2s would sense the lean mix and assume an ethanol fuel was being used and adjust trims heavily to compensate, how this would be represented in the tune I am not sure.

[Chevy366]

Here is a writeup I found on the Virtual Flex Fuel Sensor - this was for the 2006 Impala, but the theory would be the same for any flex fuel vehicle that doesn't have a sensor...

"In the past, GM had some small trucks and SUVs that could operate on different mixtures of ethanol-based fuels. These vehicles used a fuel sensor in the fuel line that signalled the computer how much ethanol was present in the fuel; the computer would add or subtract the amount of additional fuel required. Now, the Impala flex fuel system can perform this analysis without using any additional sensors. GM has developed a Virtual Flex Fuel Sensor (V-FFS) software program that calculates the ethanol content in the fuel, instead of using a sensor to measure it. When the fuel level in the tank increases as the vehicle is refueled, the computer recalculates the percentage of ethanol in the fuel and automatically changes the air/fuel ratio. To do this, the computer temporarily stops the operation of other emission systems and monitors the oxygen sensors to determine ethanol content. The test is done several times until calculations remain stable. This can take several minutes when the engine is idling, but much less time at higher fuel flow rates."

and another I found:

"For 2006 and 2007 models, E85 compatible vehicles marketed in North America no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle "learns" (calculates) the alcohol content of the fuel, (and subsequent mixture in the fuel tank), through a series of measured adjustments.

Adjustments

After the re-fueling event, the system registers the amount of fuel that was taken on-board, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines the ethanol content of the fuel that was added. Based on that determination, it adjusts itself to the expected alcohol mix in the fuel tank and lets the fuel trim and O2 sensor activity fine tune 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 vice versa, can result in driveability symptoms due to the inability of the system to adjust for fuel composition (by not attaining the parameters necessary to reach closed loop operation). "

Have not tested it, but a non-module flex fuel OS should work as long as it is for the year and body of the vehicle, the only problem would be the injectors they are definitely larger in a Flex Fuel engine. I would assume the refuel event is handled by the ECU.
There are some 20 plus tables that are different in a Flex Fuel tune versus a non FF tune. I have posted on a 5.3L the differences somewhere on the site. It looked as thought the EQ table (EQ table has a sliding scale based on the determined percentage Ethanol content, thus commanding the correct EQ/AFR) was the determining factor ie 14.76 versus 9.76. There was minimal change in the VE, MAF and timing tables.

Something I found;
In 2006 GM changed the way ethanol percentage of fuel was calculated by their trucks. This new system was deemed Virtual Flex Fuel System. Instead of using an additional sensor in order to measure ethanol content, the ECM had a software upgrade which allowed it to make this measurement by utilizing the fuel tank pressure sensor and level sensor signals. At a key on event the ECM looks to see if the fuel tank level sensor signals atleast a 2 gallon change from the last key off. If so, the ECM shuts the tank vent solenoid, monitors the fuel level and fuel tank pressure. These readings are applied to a formula which gives an ethanol percentage. The commanded air/fuel ratio is then changed according to ethanol percentage of the fuel.


In 2006 GM trucks used the same 160 pin ECM with blue and green terminal position assurances as did the 2002-2005 trucks.

[BLK02WS6]

Yeah, it appears the injectors would be my problem - would have thought they would all use the same for cost reasons, but flex fuel are bigger. I would think my stock ones could come close to supporting E85 since the engine is totally stock, but if that were true, they would have done it that way...

The price spread of regular gas over E85 around here has not reached a point where it is worth it yet - but if something crazy happens and gas goes through the roof, I wanted to know if I could do it by simply flashing in a new OS... I would still be tempted to put my injector tables into the flex fuel OS and try it on E85 to see how far it is off... I would put in half a tank only so I would have room to put gas in if the injectors run out early. I'm thinking if you didn't run the crap out of it, the injectors would handle normal driving. Would be nice to have that flexibility if the world goes Mad Max one day and gas is $10 a gallon LOL!


Edit: looked up the fuel pump and it is different for the flex model too... just got even more expensive to do it... oh well, at least I know now and understand a little more how it works!

[driver456]

I didn't read through the whole thread,But here's what I did to my 99 Silverado with a 0411 pcm.I hooked up the ethanol sensor and full flashed a flex fuel tune in,Works pretty good.I tuned the truck 1st on a full tank of pump gas.I hooked up the scanner a few times and you can see the comm.fuel change on what ever % the ethanol was,But my a/f gauge always reads the same no matter what % of ethanol I have in there.Now I don't have to worry about changing tunes:grin:http://i42.tinypic.com/2vmgfet.jpghttp://i44.tinypic.com/2ljokeb.jpg

[driver456]

Towing my car to the track,I used 5 gallons more fuel with 65% ethanol compared to to 10 or 15%

[Chevy366]

Towing my car to the track,I used 5 gallons more fuel with 65% ethanol compared to to 10 or 15%
So you left stock injectors? I have read that the stock injectors will work fine. Did not know about the fuel pump, what is the difference there?
At the beginning of E85 people said they just filled up with it and off they went with no problems. Some did have to change fuel filter (became clogged due to tarnish in the tank and lines turning lose) and that was about it.
The 5.3L tune I showed as a comparison I had to hand change all tables because we can't compare different OS tunes, so I found and copied all tables to a like tune so as to be able to show differences(PITA). :Eyecrazy:

[minytrker]

I didn't read through the whole thread,But here's what I did to my 99 Silverado with a 0411 pcm.I hooked up the ethanol sensor and full flashed a flex fuel tune in,Works pretty good.I tuned the truck 1st on a full tank of pump gas.I hooked up the scanner a few times and you can see the comm.fuel change on what ever % the ethanol was,But my a/f gauge always reads the same no matter what % of ethanol I have in there.Now I don't have to worry about changing tunes:grin:http://i42.tinypic.com/2vmgfet.jpghttp://i44.tinypic.com/2ljokeb.jpg

Thats a pretty cool setup.

[driver456]

I have 55# inj. and my 5.7 motor from the vette in my truck.I'm putting a Fast 102 & 102mm TB on it this weekend.Need a wee bit more HP :hihi:

[engimuneer]

BLK02WS6 has it exactly right on his virtual sensor description.

Here's my take based on using 07+ E37s.
We took an 09 Cobalt E37 ECM (non FFV) & turned on the FFV switch using EFILive. When I put all the appropriate values (~20 ethanol related tables) from an 09 HHR E37 ECM (FFV), it ran flawlessly as an FFV, including learning the fuel. They had the same Operating System & Calibration File.
I'd assume this is also the case for your 06 Tahoe. The programming should already be in there to virtually learn the fuel, just need to have the appropriate values in the ethanol tables. Use SAE.E85R to monitor what the vehicle thinks the E85 content is.

As for the injectors, we verified through WitchHunter Performance the stock 2.2L injectors flow enough to support E85/M60 without going over 80% duty cycle. The 2.2L FFV injectors we tested only flowed 20% more than stock and had enough leeway for modifications & E85 flow. I do not have data for GM V8s yet but have confirmed this is also true of most 05+ Fords.

[BLK02WS6]

Thanks Engimuneer - that's good to know! I'm probably not going to try and switch it unless gas goes up to where it is an advantage, but wanted to know how hard it was to switch...

[engimuneer]

Thanks Engimuneer - that's good to know! I'm probably not going to try and switch it unless gas goes up to where it is an advantage, but wanted to know how hard it was to switch...

I'm fortunate enough to have a 23% price gap in CO, while only losing 5-18% gas mileage. I feel the advantage doesn't necessarily come from my wallet, but from buying domestic fuel. What drives me nuts about the whole price ratio argument, is you have to buy fuel at some time. Next time you buy it, the price of either fuel could easily be another 10% higher. BUT because that price gap exists, people assume they are getting a better deal on gasoline. Both prices are going to fluctuate, but which will keep the money within the economy?

[BLK02WS6]

I somewhat agree with what you are saying (but unfortunately I have to consider money out of my pocket period with my budget), the bigger issue for me is availability - only 2 stations and they aren't exactly up the street... Believe me, I would love to flip the freakin middle east the bird and see our whole country grow it and burn it - back to the way this country used to be - take care of ourself and to hell with all this PC crap and supporting other countries economies! unfortunately, I don't see it happening until things are a lot more painful - if then...

[kbracing96]

I didn't read through the whole thread,But here's what I did to my 99 Silverado with a 0411 pcm.I hooked up the ethanol sensor and full flashed a flex fuel tune in,Works pretty good.I tuned the truck 1st on a full tank of pump gas.I hooked up the scanner a few times and you can see the comm.fuel change on what ever % the ethanol was,But my a/f gauge always reads the same no matter what % of ethanol I have in there.Now I don't have to worry about changing tunes:grin:http://i42.tinypic.com/2vmgfet.jpghttp://i44.tinypic.com/2ljokeb.jpg

What OS did you use? I have a turbo on my 01 and already have one of these sensor. I LOVE running Mixes of E85, usually 25% E85 to 93oct but I always tune for it. I would love to hook up my sensor and put a FF OS in it and then the COS3 version of that OS and be able to run what ever % of E85 I want (cheap race gas!) and have the PCM automatically adjust the fueling and increase the timing for the better fuel. :)

Also, I see that you have the sensor on the feed side of the fuel system. Would you think putting it on the return side would hurt anything? I believe that's how the stock FF setups are and that would let me get the max out of my fuel system since I at the max of line flow and everything with a AM340 fuel pump and 800RWHP! :lol:

[kbracing96]

Anyone have any input on this???

[joecar]

I don't see any problem with having the FF sensor on the return line

(the return line always flows fuel as long as fuel pressure is above some threshold, which if it isn't then there are other problems).

[kbracing96]

I think it would be fine too Joe. Now I just have to find a way to run boosted, 2bar SD and find an OS with FF tables to work with it. Seems none of the 99-02 COS's have the FF tables... :(

I don't know if I could just setup a 1 bar with the MAF tables all scaled to work with boost and use a stock FF OS...

[BLK02WS6]

Is a 2003 drive-by-wire? that's the reason you need 99-02?

[kbracing96]

Is a 2003 drive-by-wire? that's the reason you need 99-02?

Ya, DBW and a 1 meg PCM. Mine is the 512K pcm. There are 1 or 2 FF OS's for the 512's but nothing with a COS. I need to be able to tune for the boost too...

[BLK02WS6]

That blows...

[Tydriver]

Hey guys, I know I am late to the thread but I thought I'd donate my $.02 if ya don't mind reading.. I've seen some people questioning the hardware related to the use of E85.. Just a heads up, as far as I understand the major differences are related to the corrosive-ness of the fuel.. You CAN run e85 just fine in anything that wasn't designed for it, but for prolonged usage keep in mind it would be best to start considering swapping over to alcohol friendly pumps, fittings, senders, fuel lines etc.

The biggest difference that I am aware of is that components that come in contact with e85 are made from stainless vs. regular steel.. (hence the increase in costs that are e85 friendly)

I've also seen a couple of photos of guys that let e85 sit in cars that weren't designed for it and it can do some damage.. If you plan on storing the vehicle for a while consider swapping back to regular fuel a tank or so before you park the car so it doesn't sit with e85 in it for extended periods.

I stole this photo off a GTO site:

14119

[the_red_shark]

Good info, back when e85 talk started a few years back we were told to treat it like methanol. Seems thought it's a bit friendlier to fuel systems as every man and his dog are running it, sit in traffic and get wiffs here and thete

[Boost]

Not only that but it's all the rage in 'big juice' race cars these days. I work during the day at a VW race shop and our 1000 hp Audi S4 runs E85. Also, my friend that tunes 700-900 hp imports has used E85 in just about every single digit (1/4 mile) car that he has tuned lately.

Great thread. I remember during my GM dealer technician days having to reset the alcohol content in the '06+ Impalas with the TechII. The older guys would always ask me how to do it because the cars sometimes wouldn't run right after a fuel pump change.