Seeking E85 Clarity for 6.2 L86

[SkiDooNick700]

Hey all. Thinking about doing E85 conversion and tune for my 2015 Sierra.

 

Questions:

Is something like the DSX kit enough? I thought early on I seen posts here saying you gotta replace some fuel lines, but these kits I see nowadays seem like just a sensor, wiring harness, and a little bit of flex hose.

 

Secondly, who can do remote tuning to take advantage of the Flex capability? I was emailing with BlackBear, sounds like they can certainly enable the E85 tables, however it seems they don't necessarily tune on the flex fuel side of things - just for pump gas ex 93 octane.

 

 

Any advice??

[CamGTP]

I just added the sensor right at the fuel tank instead of buying the fuel lines for the truck. It's easy enough to tie into the plastic line at the fuel pump and with a couple connectors into the flex fuel sensor. Then I just kinda tie it up on top of the tank so it doesn't move around. Been like that for years honestly lol.

 

The harness is already on the frame rail, I just extended the wire back to the fuel pump so it could plug in. Maybe you already checked by 2014's had the sensors installed at the factory, I think some 2015's did too.

 

Probably cost me $80 to add the sensor and I do my own tuning. If you owned HP Tuners it would be very easy for me to use Team viewer to enable the sensor and adjust the commanded fueling for E85 using your HP Tuners device.

 

I don't really have a suggestion on email tuners or who else to use.

[scrapen]

As cam said much cheaper to just buy sensor/adapter harness/small hose.

 

once installed blackbear updated the tune file for me to turn the e85 tables on

 

 

 

Edited March 5, 2025 by scrapen

[newdude]

I bought this extension harness - LS LT Gen IV V 4 5 Flex Fuel Sensor Harness Extension – ICT Billet

 

Which allows you to use the factory plug where the flex fuel sensor would already have been.  I then bought the sensor and this pipe, p/n 23171534.  With that I did the heat it in water and straighten it method that someone either here or on another forum did which allowed me to put the sensor right in line off the fuel feed line from the tank. 

 

You have to pop that tank line out of the bracket it sits in and let it twist a bit.  

 

Kinda haggard a bit but it worked for 3 years no issues for me.  Came out like this:

 

 

 

[SkiDooNick700]

11 hours ago, scrapen said:

As cam said much cheaper to just buy sensor/adapter harness/small hose.

 

once installed blackbear updated the tune file for me to turn the e85 tables on

 

 

Do you have a 5.3 or 6.2? Do you notice any difference in power on e85?

So,  GM properly configured the E85 tables even tho they're turned off ?

 

 

10 hours ago, newdude said:

I bought this extension harness - LS LT Gen IV V 4 5 Flex Fuel Sensor Harness Extension – ICT Billet

 

Which allows you to use the factory plug where the flex fuel sensor would already have been.  I then bought the sensor and this pipe, p/n 23171534.  With that I did the heat it in water and straighten it method that someone either here or on another forum did which allowed me to put the sensor right in line off the fuel feed line from the tank. 

 

You have to pop that tank line out of the bracket it sits in and let it twist a bit.  

 

Kinda haggard a bit but it worked for 3 years no issues for me.  Came out like this:

 

 

 

 

Thanks for the details! Is that a 5.3 or 6.2 truck and did you have someone do a tune or you handle that yourself?

[CamGTP]

Gm rated the 5.3 at like 380hp over the stock 355hp. Hard to say what the 6.2 would be at but a guess would be about that 20hp bump over 87 octane.

 

On the non flex fuel trucks the Stoich table for the tuning is set to 14.10 for E10 fuels, that table would need to be changed to a a flex fuel version that starts at 14.68 and drops down to 9.0ish at 100% alcohol content. With HP Tuners it's a copy and paste with a flex fuel truck or car.

 

The other tables are usually already populated with data. The alcohol power enrichment that changes the commaned air fuel ratio for wide open throttle is already populated, just not used because it doesn't have a working sensor. E85 mixtures run leaner fuel mixtures at full throttle. The flex fuel spark tables should be populated too, they normally add spark based on the rpm, cylinder airmass and the alcohol content in the tank.

 

It's hard to say how much of a change you'll notice in the butt dyno but in the data logs it will be a lot different for most trucks. Any truck running 87 octane will show some knock ******, which pulls timing out. My truck on any alcohol content over like 30% shows zero knock even with a few extra degrees of timing thrown at it. That is where the power increase is. I run it all summer here, it's super cheap around $2.30 a gallon.

[SkiDooNick700]

10 hours ago, CamGTP said:

Gm rated the 5.3 at like 380hp over the stock 355hp. Hard to say what the 6.2 would be at but a guess would be about that 20hp bump over 87 octane.

 

On the non flex fuel trucks the Stoich table for the tuning is set to 14.10 for E10 fuels, that table would need to be changed to a a flex fuel version that starts at 14.68 and drops down to 9.0ish at 100% alcohol content. With HP Tuners it's a copy and paste with a flex fuel truck or car.

 

The other tables are usually already populated with data. The alcohol power enrichment that changes the commaned air fuel ratio for wide open throttle is already populated, just not used because it doesn't have a working sensor. E85 mixtures run leaner fuel mixtures at full throttle. The flex fuel spark tables should be populated too, they normally add spark based on the rpm, cylinder airmass and the alcohol content in the tank.

 

It's hard to say how much of a change you'll notice in the butt dyno but in the data logs it will be a lot different for most trucks. Any truck running 87 octane will show some knock ******, which pulls timing out. My truck on any alcohol content over like 30% shows zero knock even with a few extra degrees of timing thrown at it. That is where the power increase is. I run it all summer here, it's super cheap around $2.30 a gallon.

 

Man you make me want just go out and buy HP Tuners lol but I really don't want to spend the money plus I would still need to pay someone for a tune anyway. 

 

I wonder if Black Bear guys already know to do the changes to the Stoich table you described or not

[newdude]

10 hours ago, SkiDooNick700 said:

 

Do you have a 5.3 or 6.2? Do you notice any difference in power on e85?

So,  GM properly configured the E85 tables even tho they're turned off ?

 

Thanks for the details! Is that a 5.3 or 6.2 truck and did you have someone do a tune or you handle that yourself?

 

 

Don't have the truck anymore, but it was a 5.3.  Just running it just turning the E85 flex fuel on in the ECM and not doing any tuning beyond that, I can't say you'll notice the 20-25hp gain on it.  A 6.2 might see it?  

 

I had more to notice though as I also had the truck tuned for 93 and E85.  

 

As for the ECM, I had it custom tuned.  The tuner went in to the flex fuel sensor settings and simply turned on the flex fuel.  The ECM has the ability, its just simply turned off.

[Grumpy Bear]

12 hours ago, SkiDooNick700 said:

 

 Do you notice any difference in power on e85?

So,  GM properly configured the E85 tables even though they're turned off ?

 

 

I have a 2015 Flex Fuel 4.3 that I've been running E-85 in for a few years now. Gains are more modest in the absolute but percentage wise the same. So my backside didn't notice any OMG moments but it is friskier on the on ramps. 

 

1.) Motor runs cooler oil temps.

2.) KR is never triggered on any hill in any weather as long a ethanol percentage is over 50%.

     Didn't do that even on Shell V Power Nitro + 93.

3.) Oil stays cleaner much longer. 

4.) Tail pipe is soot free. 

5.) In cold weather I found mixes over 70% would have the motor spin a few more times before it caught fire. Backing the ethanol content down to 40-50% cures that. At least to -20 F. 

6.) Cost me about 28-30% of my mpg which makes it a bust compared to regular but a winner compared to Premium.

7.) My truck runs okay on regular but i use it anyway for the first four on this list.  

 

[KARNUT]

I loved the E-85 option on my truck. I could run it around town then back to regular on trips. With my Texas Edition I had the 345 gear and limited slip rear. I had a hand held tuner to tune shifts etc. One of our sales people had a 6.2. Whoever had the jump led at the 60 MPH mark. For a person who likes a little performance the E-85 option, even it was in mind only was fun. The E-85 option was the reason I didn’t buy a leftover Denali. I wanted that 6.2 in my retirement truck. I saved thousands and got a year newer truck. 

[scrapen]

I really wanted e85 just for the added flexibility since I was putting a 91 octane tune on the truck…and most stations these days rake you over the coals for 93. Can’t say I noticed any added power on the few full e85 tanks I ran.

When I do come across an e85 station I fill 6-7 gallons of e85 and the rest e88 or 87.  Goal is e30 and mileage is actually sometimes better than running 93 which really benefits the wallet.

[CamGTP]

Not likely that you'd notice a lot of gains through the butt dyno or without a data log that shows times and engine estimated horsepower/torque figures.

 

An E30 blend will pretty much run knock free on timing in the mid 20's, going past 50% lets you do 27-29 degrees of timing at WOT with ease but there just isn't a lot to be gained with more timing on a stock engine. A engine with a camshaft, headers and that sort of stuff would see a good improvement in power with more alcohol in the fuel.

 

My truck feels a little stronger on E60-E70 that I run in the summer times, it's making that factory rated 380ish to 390ish horsepower no problem. But even with that it's really not making the truck that much faster, it needs 50-100hp added to make the truck "fast". Different story if it was a single cab and didn't weight much because mines 5,500lbs.