Some interesting tuning stuff regarding E85 good read

B5 S4/ RS4
#1

Since i have not seen any real concrete info on E85 Air/Fuel ratios on this forum, i figured i would throw up what i know so that some of you can make more educated decisions on what AFR you should tune for on E85. I will only discuss E85 AFRs in this thread and will start a thread regarding ignition timing in the near future, as i don’t have the time to do it currently.

I have been tuning many years and have a lot of experience tuning all of the exotic race fuels, along with pump gas. This was actually my first attempt at tuning E85(due to just getting it in my area), but before i attempted to tune the “Corn Juice” i did a TON of research on this amazing alternative fuel. Some things about E85 i already knew, but i found there was a lot i didn’t. I want to share what i have learned while tuning my own car on E85.

Despite E85 having been around for a several years now, there is still a vacuum of info on the fuel and some of the info i found was completely incorrect. Most of your pro tuners out there know that E85 is probably one of the best fuels on the market at any price, but they aren’t so quick to give up what they know on the subject.

First we’re gonna start off with Air/Fuel Ratios and what they mean with reference to E85.

E85 has a stoichiometric fuel mixture of roughly 9.78-9.8:1 in E85’s purest form (Class 1 85% Ethanol summer blend). As the fuel’s Ethanol content goes up the stoich range goes down. For instance, 100% Ethanol’s stoich is about 9.0:1.

E85 will maintain max brake torque much richer than stoich than gasoline will. But, because of it’s excellent detonation threshold(due to lower combustion temps, lower peak cylinder pressures…etc), it can be run much closer to stoich than gasoline safer. E85 reaches max thermal efficiency at about 13% richer than stoich, whereas gasoline is about 16% richer than stoich(with pump gas being even richer). But again, E85 can maintain Max Brake Torque well into the 30% richer than stoich range, unlike gasoline which is limited to about 18% rich of stoich. DISCLAIMER: Just because E85 itself will still make power at super rich AFRs, doesn’t mean it’s a good idea or even recommened. A whole host of issues come with running super rich AFRs, that you need to be aware of, but i will cover later.

Therefore Max Rich Torque of E85 is 7.1:1- 8.5:1

With that being said, here is what i would consider a very safe and conservative fuel tune on E85. *AFR’s listed in bold are for widebands o2s that are calibrated for gasoline, AFR’s in ( ) are actual E85 AFR:

Part Throttle lean (max eco) AFR of 16.5:1(11.0:1) 12.4% leaner than STOICH
Part Throttle rich AFR of 14.7:1(9.8:1)
Spool up… AFR of 13.5:1(9.00:1)
WOT… AFR of 12.1:1(8.06:1) 17.7% richer than STOICH

*If you’re using a wideband that is calibrated for gasoline(14.7:1) and cannot change the calibration of the wideband, take your gasoline AFR and divide it by 1.5 to get actual e85 AFR or use the wideband in lambda mode. 1 lambda is 9.8:1

Here are some common AFR conversions(Gas AFR on left, e85 on right):

18.0:1=12.000
17.5:1=11.666
17.0:1=11.333
16.5:1=11.000
16.0:1=10.666
15.5:1=10.333
15.0:1=10.000
14.5:1=9.666
14.0:1=9.333
13.5:1=9.000
13.0:1=8.666
12.5:1=8.333
12.0:1=8.000
11.5:1=7.666
11.0:1=7.333

Of course, all engines are different and there is still a lot of trial and error when tuning any setup. Having the ability to measure torque output is a must for tuning both fuel and ignition timing with E85. We are only talking about E85’s fuel properties in this thread and not taking into consideration ignition timing, boost pressures, different E85 fuel mixtures…etc. Care must be taken when combining all the aspects of the tune and setup, to assure proper limits and safety.

I will start a thread in the near future to discuss ignition timing as well as go into much further detail on E85’s inert qualities here in this thread.

Now that we have that out of the way, let’s compare E85 with pump 93 octane.

As you can see, the lean side of max rich torque for E85 is 8.5:1, which is 13% rich of stoich. We know gasoline’s max rich torque is about 12.5-13.0:1, but because of pump gas’ low detonation threshold, we must run AFR’s much richer with forced induction. Therefore, AFR’s of 22+% rich of stoich must be used to combat detonation, while running E85 13-15% rich of stoich results in no detonation. Why is this, you ask?

Here are the reasons why:

  1. Lower EGT’s. E85 will typically see EGT’s 200c below pump gas at the same relative AFR (for instance 12.5:1 pump, 8.33:1 E85)
  2. Octane rating of 105 with class 1 e85(raises detonation threshold)
  3. Very high vaporization cooling, much more than gasoline, which lowers mixture temps, thus increasing detonation threshold, along with increasing VE
  4. Peak cylinder pressure are lower while maintaining a higher and longer overall cylinder pressure, thus raising detonation threshold and making more power due to increase in crank angle
  5. E85 burns much more efficiently than gasoline, 27% more efficient
  6. despite lower EGT’s, E85 creates more exhaust gas volume, which helps with spool without added EGTs

So, we know that E85 has a very high detonation resistance, one thing E85 does not have much tolerance for, is pre-ignition. This is where E85 starts to wander from exotic race fuels. E85 cannot withstand pre-ignition as well as it can detonation. I believe this is due to the fact that it actually burns much faster than gasoline(pump or race fuels), among other things. While it’s very tolerant to lean mixtures(detonation), over-advanced ignition timing takes a toll quickly on E85. While E85 will take more ignition timing than pump gas overall, it will not allow a lot of ignition advance at peak VE, but will want more and more advance as RPMs rise, this ending up with much higher peak timing numbers. We’ll get into that in the timing thread i will start.

#2

Any tune I convert from 93 to E85 i start by multiplying the required fuel by 1.3. Basically adding 30% fuel gets you smack in the ballpark.
I also tune with the wideband set on Gasoline still.
Because the wideband is measuring lambda still it’s a lot easier to look at and tune via “gasoline” AFR’s.
For instance, 14.7:1 is lambda 1 for either fuel. Makes tuning a lot easier.

#3

Nice article covering the basics. Where’s the attribution of the article?

#4

Unless this his Evo screenname…I read the thread title, but I still looks like he is trying to pass this off as his own research…especially when he never gave a link to the write-up. Also, phrases like “I have been tuning for many years” threw me off.

http://forums.evolutionm.net/alternative-fuel/print-498732-itunes-e85-tuning-notes-afr.html

8URV8…does this mean your going to self-tune now?

#5

I also assumed it was his words… It’s best to always point out when it’s just copied from the internet…

#6

really? Adam couldn’t go that long without a spelling error if his life depended on it lol

however the title said ‘good read’ which to me meant he posted something he read somewhere

#7

Well it was like 2am when i read it so I guess I didn’t pay attention to the good read part haha

#8

good read implying an article i read online!

#9

So this means you are self-tuning?

#10

Thanks for posting that Adam, it contains a bunch of great info. Sorry for those that can’t read and jumped to conclusions that you were making self tuning claims

#11

Am I simply pissing in the wind by going e85 without building the bottom end? I believe from what I have read and been told that e85 has the potential to reach and exceed the limits of stock rods.

BUT, with a few convenient stations popping up nearby, the allure of ditching crap91 octane “premium” pump gas is calling me.

I would think in the capable hands of Kurt and jhm my car would potentially be better off from a performance standpoint than where I am today handcuffed by terrible life blood. Thoughts?

Has to be a way to get the car to walk the fine line of stock block mechanical limit and safety with a properly tuned e85 and extracting more performance than ever possible when running CA91. New injectors (ev14 72 or 95 lbs), proper fuel pump (currently running 044), tune, and good to go, no? What am I missing?

#12

The article was well written, but that was in 2010 and that was only covering a few aspects of the fuel. Being that I have been a big part of the flex fuel program at SVT you tend to see many things that don’t quite add up as “E85 the greatest fuel ever”. While E85 is billed up as being a magic fuel, it has it’s dark sides. The issue is many people don’t’ talk about the down turns. Many people don’t get enough time using the fuel or even looking into the motor to see the issues that come with it.

E85 Vs California emissions 91.

E85 wins all day long, I doubt many people understand just how bad California fuel is. You don’t need to build your motor to take advantage of the E85, but you do need to have an overhaul of your fuel system. To make this further an issue adding more fuel is helpful but there needs to be major changes to injector delivery time, in onset, duration and clock crank start spray location. Adding more fuel alone isn’t enough, over time you will see small signs of damage.

Remember though, your getting worse fuel mileage with E85 not better. Sure there is more power to be had, but you will only see that a small fraction of the time and it comes at the cost of using 40% more fuel then standard fuel. If you want to use E85 as more then just a standard tune (standard tune= one that limits the power still) then you’re going to have to think about getting a much better suited motor, including supporting components to better withstand the issues that come with running E85.

Being that your currently JHM tuned, there is the switcher option so, you can have more then one tune. This is helpful, if you run into an area that isn’t a E85 friendly area.

#13

another good read

http://honda-tech.com/showthread.php?t=1812349

#14

Thank you for weighing in! So at a minimum, what all is needed for fueling system upgrade in order to see the beiinefficientficientit (albeit limited by stock motor constraints) from switching to e85? Much better motor? Meaning built bottom end? Or better than the 2.7? Sorry if silly questions. I guess looking at this short sided maybe, but again, I am willing to take the chance and make necessary changes in order to be less limited by the “best” fuel I am currently stuck with…

In comparison, will my jhm tune adapt and see similar advantages from adding w/m to the CA91 tune? Without the inherent risk and cumulative damage of e85?

And with switching between tunes from e85 to CA91, having overhauled the fueling system, how does CA91 tune react/adapt or compensate for the change in fueling components? How is such a major change possible with very different fueling needed for e85?

#15

The thing that scares me about e85 is a lack of control over its quality and mixture. There is a big difference between the summer and winter blends of e85. Most winter blends are around 70% ethanol where a lot of the time summer blend is only 80%. Some people on SVTp report seeing e90 setimes, then they fill up next week and its e80. That could spell disaster if you are tuned with true e85 in the tank and the next tank is e70. Knock knock. If you run it, always test what is going in the tank so you know. Another thing, a few companies make e85 specific widebands

VP racing just came out with a product called C85. It’s a true, pure 85% ethanol blend.

To expand on the dark sides of it, it also takes a toll on lines and filters. It gums up paper filters and eats rubber lines.

#16

Ya, educated myself on the different blends. Not too sure how much my area is effected by that? Will need to confirm with local station. We don’t really have a winter in the shithole where I currently reside. Barely see freezing temps overnight in the winter, but not uncommon to have 20 days 100+ with October temps still reaching upper 80’s and lower 90’s.

Also with regard to lines, I would be more than willing to upgrade/replace where necessary and able.

We have two other reliable vehicles and this car is more for fun and weekend warrior so I really like the idea of wheening itself off of CA91!

The stations near me are Propel Fuels. Seems many of them are in California.

#17

Does JHM currently offer an E85 tune? Is the JHM switcher an independent device (like the GIAC flashloader), or is it a software trigger to switch maps in the ECU?

#18

I don’t think a N/A S4 is going to gain much with E85. Just a guess though, we have never seen one run on it and there’s no logs. But traditionally, NA cars don’t like the corn

#19

(this is the B5 section)

#20

N/A Honda K24 2.4L 4 cylinder cars that where making 300whp n/a are picking up 20-30whp and equal tq from switching to e85 from pump gas