L83 5.3L Flex fuel conversion with Dyno sheets. Followed with tune and more dyno sheets.

[Grumpy Bear]

43 minutes ago, truckguy82 said:

I’ve never driven a car with e85, they dont offer it in my area.

 

but I would think the e85 changes ignition and fuel timing. I would think that would give you a boost in the low end too. Maybe it only changes the open loop tables? But that doesn’t make that much sense either.

 

hmm

 

Meh....not that I noticed. Maybe I would have it I was matting it at every stop sign and signal light. But I accelerate at the same pace regardless of the fuel. So I expect that IF there were some life altering feeling of power I'd have just pushed the pedal 2% less and gone about my merry .25 G pull up to speed. People forget than alky has allot less heat content than gasoline and because of that requires allot more of it;  but the number of oxygen atoms in the air is unaffected. A .25 g acceleration rate takes the same amount of power no matter what fuel is loaded. Force is dependent on mass once rate is established. You have to ask of the fuel, given the same mass, a greater rate of acceleration than the base fuel can supply to GET THE DIFFERENCE it may supply. I don't drive like that on city streets. Save that for the track and I haven't been there in years. That's just physics. I can do nothing about people perceptions. 

[KARNUT]

1 hour ago, Alec Kerchner said:

Yeah, the grunt off the line and throttle response is like driving a different vehicle. It's amazing how different it is just by switching fuels. 

My 14 GMC had flex fuel. Did I notice the 25HP yes. The throttle response was better, less input needed. I also had a can tune. Usually I would check the box for the premium tune I didn’t. I did the usual increase shift points and RPM increase and 50 percent TM. What a difference. What I like the best was on trips back to reg gas. Do I burn rubber at every light? No. I like knowing that it’s there if I’m feeling the mood. It’s wasn’t all about  fuel mileage to me. 

[lucas287]

It's really quite simple - @Grumpy Bear doesn't get deep enough into the load range to notice the difference that the extra ignition advance adds. Here's a paste of a stock Flex Fuel timing table. This adds (or subtracts) based on another multiplier which references alcohol content. 

 

 

Something else worth mentioning is knock learn factor. Allow me to explain. If you've been running 87 then your ECM will have certainly "learned" to run less ignition timing because it detects knock at higher loads at various RPMs. Basically, if the ECM detects greater than 3* (on my L86) of knock then it will interpolate between the high and low octane spark table to find a value that doesn't knock. If you randomly fill up with premium then it will slowly realize that there isn't any knock present and start learning back to the high octane table. 

 

Why do I bring that up? If you run ethanol for several consecutive tanks you are allowing the ECM to bring back ALL the ignition timing that it's been removing (assuming 87 octane) PLUS it will be adding more timing in the higher load ranges. This extra timing should make a big difference in the way it feels in top gear lugging around. 

Edited October 27, 2021 by lucas287

[truckguy82]

14 minutes ago, lucas287 said:

It's really quite simple - @Grumpy Bear doesn't get deep enough into the load range to notice the difference that the extra ignition advance adds. Here's a paste of a stock Flex Fuel timing table. This adds (or subtracts) based on another multiplier which references alcohol content. 

 

 

Something else worth mentioning is knock learn factor. Allow me to explain. If you've been running 87 then your ECM will have certainly "learned" to run less ignition timing because it detects knock at higher loads at various RPMs. Basically, if the ECM detects greater than 3* (on my L86) of knock then it will interpolate between the high and low octane spark table to find a value that doesn't knock. If you randomly fill up with premium then it will slowly realize that there isn't any knock present and start learning back to the high octane table. 

 

Why do I bring that up? If you run ethanol for several consecutive tanks you are allowing the ECM to bring back ALL the ignition timing that it's been removing (assuming 87 octane) PLUS it will be adding more timing in the higher load ranges. This extra timing should make a big difference in the way it feels in top gear lugging around. 

i’d assume the maps instantly change when the sensor detects e85.

[lucas287]

8 minutes ago, truckguy82 said:

i’d assume the maps instantly change when the sensor detects e85.

 

For all intents and purposes - yes. The alcohol sensor will immediately report composition changes exceeding 2% to the ECM. Then, there's a delay based on volume (.28 liters for my truck). Basically, it wants to use all the fuel from the sensor to the rail first BEFORE making changes. 

[truckguy82]

7 minutes ago, lucas287 said:

 

For all intents and purposes - yes. The alcohol sensor will immediately report composition changes exceeding 2% to the ECM. Then, there's a delay based on volume (.28 liters for my truck). Basically, it wants to use all the fuel from the sensor to the rail first BEFORE making changes. 

Wouldn’t that negate your post about learning via knock sensor?

 

i mean it’s changing to a different map, I’d assume it’d have to relearn.

 

also I though the learning process was much much faster than a few tanks. i can’t verify this, just what I’ve heard

Edited October 27, 2021 by truckguy82

[lucas287]

10 minutes ago, truckguy82 said:

Wouldn’t that negate your post about learning via knock sensor?

 

i mean it’s changing to a different map, I’d assume it’d have to relearn.

 

also I though the learning process was much much faster than a few tanks. i can’t verify this, just what I’ve heard

 

Nope. The flex fuel table only adds (or subtracts) from the current "learned" amount of timing it's running. While I don't fully understand how "knock learn down" function works the values prepopulated in HPTuners looks like it would take a hot minute.  

Edited October 27, 2021 by lucas287

[Grumpy Bear]

3 hours ago, lucas287 said:

It's really quite simple - @Grumpy Bear doesn't get deep enough into the load range to notice the difference that the extra ignition advance adds.

 

Perfect Lucas. Thank you.

[CamGTP]

Knock learn factor is simple. The KLF starts at 1 or 0 depending on the PCM used and year range and they go to 0 or 1.

 

Say it starts at 1 and goes down to 0. The 1 would be the high octane table current timing number, lets say 25 degrees. It detects some knock and slowly works it way toward 0 on the KLF and lets say it stops at .50. If the low octane timing table had 19 degrees in the same area of the timing curve it would pick 22 degrees of timing.

 

The knock learn factor doesn't even need to wait for a new fuel to work it's way back to "1" on the KLF, it just doesn't have to show knock for a long enough period of time to make it from .50 back to 1. You should be able to watch the KLF in the HP Tuners scanner to see it working. I partly think that once it knows it's been showing a decent amount of knock everytime the go pedal is pushed hard enough, the predictive knock function of the calibration called burst knock starts to play a larger roll in how much timing it quickly yanks away before any actual knock is detected. Then once a better fuel is ran for long enough it slowly weens that off because it's not showing as much or any knock anymore.

Edited October 28, 2021 by CamGTP

[TJay74]

I am glad someone point out, there are more than just the 2 timing tables used when on E85. You have the high/low table for gas, the high/low table for gas when DOD is active, you have the main adder table for E85 and then the modifier table for the composition of E85 that the ECM is seeing from the Ethanol sensor.

 

The E85 main table adds to the main gas table and then based on the E85 percentage composition reported then uses the modifier to determine how much of the E85 main timing added is used. So if the E85 main timing table is calling for an additional 5° of timing and the Ethanol sensor is reporting E70 then the composition modifier table references the percentage of timing adder allowed (say 50% for this example, but it is a sliding scale) and adds 2.5° of additional timing to the main timing table for gas.

You can log all of the timing PID's in the HP Tuners scanner app and see exactly where the ECM is adding or subtracting timing from at any time.

[M1ck3y]

How high can timing actually going at wot if you have the appropriate octane?

 

I ask because my truck usually sits around 26 in the summer months, but I recorded some data this past fall and it hovered around 27, but went as high as 29. I know very little but isn't 30 degrees of timing at wot scary high? I have everything I need to run e85 in the spring. Probably go with a e30-e40 mix, but I'm wondering how much more timing I can get out of my truck? 

[TJay74]

12 hours ago, M1ck3y said:

How high can timing actually going at wot if you have the appropriate octane?

 

I ask because my truck usually sits around 26 in the summer months, but I recorded some data this past fall and it hovered around 27, but went as high as 29. I know very little but isn't 30 degrees of timing at wot scary high? I have everything I need to run e85 in the spring. Probably go with a e30-e40 mix, but I'm wondering how much more timing I can get out of my truck? 

You would need to be using HP Tuners using the scanner app and log all of the timing modifier tables to be able to see what your actual timing is. I have about 8 or so timing channels I log to see what is actually impacting timing.

With that E85 has a octane rating of around 105 octane, E85 also imparts a cooling effect on the combustion process and keeps the combustion chamber cooler which allows more timing to be added. While E85 does require more fuel, it isnt anywhere near the 30% or 40% I see people quote as it depends on the EQ Ratio that is being commanded and if it is part throttle or WOT.

There is no reason to run E30-E40, if you have the ethanol sensor installed and the tune is setup correctly you can run E85 at full strength (what ever your local pumps are, mine in OKC are anywhere from E60-E75 in the winter and E75-E80 in the summer) with zero issues. 

Only running E30-E40 is only going to give you maybe an additional 1° of timing advance.

[Grumpy Bear]

44 minutes ago, TJay74 said:

While E85 does require more fuel, it isnt anywhere near the 30% or 40% I see people quote

 

You are correct in part because even 100% ethanol would only be a 34.1% loss and in part, E-85 is rarely 85% ethanol. I ran  last summer using E-85 and I tapped into the ECU to read the alcohol % and monitored the mpg vs Eth% and found it tracks very well with the mass balance the chemistry shows. 

 

https://www.autoblog.com/2007/02/27/when-is-e85-not-85-percent-ethanol-when-its-e70-with-an-e85-st/

 

 

https://mnbiofuels.org/media-mba/blog/item/1511-octane-and-ethanol-for-beginners

 

[quote] In terms of its octane rating, ethanol has a rating of 113. As mentioned above, fuels with a higher octane rating reduce engine knocking and perform better. Also, almost all gasoline in the US contains 10 percent ethanol. When you mix 10 percent 113 octane ethanol with 85 octane gasoline it increases the octane two points to the normal 87 octane most consumers use. So the higher the ethanol content, the higher the octane. The octane rating for E15 (15% ethanol) is 88 octane and E85 (85% ethanol) is 108 octane. [End quote]

 

The last assumes 84% ethanol concentration in standard 85 octane base. Never happens at a pump. Not even SUNOCO E-85 R reaches 108 (R+M)/2. 

 

https://www.sunocoracefuels.com/fuel/e85-r

 

Torco T98 is only 103 (R+M)/2

 

https://torcoracefuel.net/products/torco-race-ethanol-fuel-e98

 

Edited December 17, 2021 by Grumpy Bear

[M1ck3y]

4 hours ago, TJay74 said:

You would need to be using HP Tuners using the scanner app and log all of the timing modifier tables to be able to see what your actual timing is. I have about 8 or so timing channels I log to see what is actually impacting timing.

With that E85 has a octane rating of around 105 octane, E85 also imparts a cooling effect on the combustion process and keeps the combustion chamber cooler which allows more timing to be added. While E85 does require more fuel, it isnt anywhere near the 30% or 40% I see people quote as it depends on the EQ Ratio that is being commanded and if it is part throttle or WOT.

There is no reason to run E30-E40, if you have the ethanol sensor installed and the tune is setup correctly you can run E85 at full strength (what ever your local pumps are, mine in OKC are anywhere from E60-E75 in the winter and E75-E80 in the summer) with zero issues. 

Only running E30-E40 is only going to give you maybe an additional 1° of timing advance.

 

Thank's TJay74. I don't have hptuners but I do have efilive where I can see where the timing is at any given point. I'm not concerned about what is or isn't changing the timing right now. I know that environmental conditions are what's impacting it for the most part.

 

I guess I should have said..

According to the high octane table what's the maximum allowable advance in timing?

 

I don't know much about tuning, but I have to believe there's more timing to be gained. There's several studies indicating that e40-e50 provides max timing. Anything over e50 and your just benefiting from extra charge cooling not resistance to knock.. 

 

@CamGTP you run e50 don't You?

@lucas287?

Edited December 17, 2021 by M1ck3y

[CamGTP]

On page one I posted a picture of a 2015 5.3 files high octane timing and the flex fuel spark adder. If we go by that picture the timing allowed is only going to be around 18-20ish and then it uses all of it's adders to get it higher. Like a gas spark adder, IAT, ECT and VVT will all add timing. It's hard to give an exact answer on what the max allowed timing is because it can change from cell to cell in the timing tables. You seeing mid to upper 20's surely does seem possible though.

 

And in the summer I run pump E85 which was usually around 60-70% at the pump, I noticed no huge difference once over 50%. Lots of people do say that once you are over that 50-60% mark that it's not doing a whole lot more power. It would make a difference if you were running E85 or E98 racing fuel.