FlexFuel and Facts
 

Hi guys,
I'm going to try to be as politically correct as possible in this thread and hope for the best (please don't ban me!). But I really wanted to address some misinformation that is being spread around on this forum. I cannot not say if the misinformation spreading is intentional or just due to a lack of understanding/testing. Either way, it just needs to be addressed.

... so let's talk about flexfuel kits.

First a little background, we are big proponents of flexfuel kits in turbo cars. In fact, we developed and currently sell the first (and currently only) one for the BMW n54 twin turbo engine. It works great. So great that on a stock car running our flexfuel tune/flexfuel kit on 91oct, it makes 340whp (stock is 275). And when running on straight E85 (with no changes to mapping), boost/timing/fuel automatically get adjusted and power climbs to 430whp. This is the beauty of turbo engines and e85. The engine management computer can read actual ethanol content (frequency signal from flexfuel sensor) and boost can be raised, advance can be increased and AFR can be adjusted. And you end up with HUGE 100whp gains. Great! Sign me up.

Now let's talk about a naturally aspirated FA20. The stock engine does not need a lot more octane to make maximum power. This is because effective compression ratio isn't very high compared to that of a turbo engine. So whereas a turbo engine will benefit from say 105oct more than it would 100oct, an NA FA20 will only need perhaps 100oct to make maximum power. Anything above that will not help. Which means that in terms of octane/knock suppression, the FA20 does not need to run E85. It could support maximum power by running something closer to E40.

So, to say that running an E85 tune without a flexfuel sensor to account for seasonal/daily ethanol % variation is dangerous is not true. Running an proper E85 tune and then suddenly filling up with a tank of E60 isn't going to make your engine knock. Simple as that.

But what about fueling? Isn't getting a tank of E60 going to make your car run rich without a flexfuel sensor/flexfuel code to adjust your fuel mapping?
Short answer: No

Whereas some people want you to believe that you need a flexfuel kit to adjust fuel mapping in order to achieve a desirable AFR at WOT, they fail to understand that the function of the factory adaptation fueling system is to adapt to changes of fuel composition. Want proof? OK.. here are two datalogs taken today.

1st Log. Taken this morning running straight E85 (measured at E80). It's nearly 3 minutes long and captures cruise conditions and several WOT runs in single gears and multiple gears:
ENTIRE LOG--http://datazap.me/u/shivvishnu/stage...e-e80-fuel?0-1

The last part of the run shows a 1-2-3-4th gear WOT pull:
http://i85.photobucket.com/albums/k4...506/E85log.jpg
What you see are nice looking logs with AFR in the low to mid 12s and with LTFT of -2.34 at WOT.

2nd Log. And this is the kicker. This log was taken immediately after adding 3.5 gallons of gasoline to 9.7 gasoline to the tank of E80 (as tested in the first log). The datalog is quite long (20 minutes) and begins from the point of starting the engine (at the gas station) and ends 10 miles later when I take my exit off of the highway. There was quite a bit of traffic so most of what was logged was cruise conditions (as you can see in the log):
ENTIRE LOG--http://datazap.me/u/shivvishnu/stage...g-gasoline?0-1
45 seconds after topping off the tank with gasoline and driving a bit, I did a 2-3rd gear WOT pull:
http://i85.photobucket.com/albums/k4...94506/Rich.jpg

What you see is what most of expect to see when you run an E85 and suddently get a tank full of E60. The car runs rich at WOT (mid to high 11s). LTFT during WOT is still the same -2.35% it was in the first log when it was running E80. The engine still feels strong because it is running full timing (no knock retard) with Adv Mult firmly at 1.0. But it's running rich and that will cost us some power.

But then the "magic" happens. And it's not exactly magic if you understand how sustained STFTs migrate over to LTFT. During the next 5-10 minutes of driving, the ECU starts adapting for the changes in fuel composition. It does this by monitoring the change in STFT. And when that change is sustained for more than a few minutes, it transfer it over to LTFT which, unlike STFT, stays there during WOT. So by the end of the drive, LTFT smartly moves from the original -2.34 to -7.81. All by itself. No change of tune. No special ECU resets or change in driving technique. As expected, this change in LTFT makes our AFR at WOT adjust perfectly to where it was before when running the E80 mix (low to mid 12s):
http://i85.photobucket.com/albums/k4...just_right.jpg

So if your concern with running an E85 tune has to do with pump-to-pump ethanol content variance and engine safety, don't believe the hype. Just give your ECU a little time to adjust to the new change in mixture (if you believe there to be a big change). The ECU will do what it was designed to do. And it will do it very well. Just take a look at the links to the complete unedited datalogs on www.datazap.me or try this test out yourself.

Of course, I don't recommend testing an E85 tune on straight 91 gasoline. Not only would it take a good amount of time for the ECU to make that big of a LTFT adjustment, it would also result in knock retard (from the aggressive timing maps) when it finally does. So my suggestion is to keep the fuel mix between E50 and E90 which is well beyond the range you would see at the E85 pump.

Sorry for the long post which is most certainly full of grammar errors. But I was hastily written on a busy day. But frankly, I grew tired of fear mongering and people promoting mapping/hardware options as necessities.

Cheers,
shiv

Kudos to you

Shiv,

Thanks for doing this. Really.

lol thanks guys. I have a couple other pet peeves (ie, using Mustang dyno results to "calculate" Dynojet dyno results) but I think that's enough for today. But serious, is it really that hard to take the car to a Dynojet after you tune it to get actual authentic Dynojet results? :sigh:

💡+😮=😎


Flexfuel without a flexfuel kit, and proof from a data log.

I learn something new everyday.

👍👍

Very informative.. Thank you so much for providing data logs to support.

FlexFuel and Facts
 

Thanks for this post Shiv - our ecu is definitely much smarter than what we had in the 'old days'. That combined with the amazing stability and cooling E85 has over even 93 octane, I believe what you say.

One thing that has been brought to light lately is negative effects of running E85 on systems not designed for flex fuel. Mostly anecdotal, but lately I've read a couple of good articles, particularly about the hydroscopic properties of ethanol and how water content can corrode critical components like injector nozzles. In your experience (with Subaru, BMW, dsm, etc) have you seen evidence of these issues? If so how can it be prevented - additives? Fuel system upgrades?

Thanks


Sent from my iPad using Tapatalk - now Free

I've been tuning cars that exclusively run on E85 for over a decade and haven't seen any reoccurring failures. Our general suggestion is to not park a car for extending time with E85. If you aren't going to drive your car for weeks, probably better to have gasoline in the tank due to the hydroscopic property of ethanol. Another suggestion is to reduce the oil changes interval by 50% or so (every 3000 miles) since the constant use of ethanol will contaminate your fuel at a high rate than gasoline. Additives may also be helpful with regards to the aforementioned caveats but I have not experimented with them myself :)

i've accidentally flashed a pump gas map onto my car when it had e85 in it. i drove it. it didn't explode.

LOL...When did you do this?

In VW R32 world we have flexfuel tune without adding any hard ware ( ethanol analyser) since year mine is from VR6 speciallist in Europe but UM in USA also do it
. it just use the oem O2 sensor and knock sensor.
The main thing that my tunner did was to change the range of fueling adaptation from 25% to 40% and also change the speed at where STFT are implement to be LTFT.

Now if I fill up full tank of 93 after a tank of E85 it take less than 1 minutes where the car is hesitating and then run smoothly with Ltft adapted when loging. I have more than 200000 Km with that tune without any problem.

I wich we have also something like that for my GT86 because if police stop me and see that i have a ethanol analyser I will get trouble in my country. It's not allowed to make a car flexfuel if it didn't come like that from factory.

We have also a big forum of E85 and guy are trying to run their car without any hard ware or tune on many car because in my county it's half price.
And about 50% of the car from market can adapt automaticaly and log's show nothing wrong in fueling.

Our fueling compensation range is 40% by default, more than sufficient to compensate for e85. That said, running huge trims isn't good of you don't have to. It can introduce inconsistency in open loop and at part throttle/tip in when the trims are hunting up and down to find their place in the world, but as long as you drive around easy long enough to let the ltft settle it's not a huge deal. I constantly tweak the map to keep trims down but it's nice to know it's not absolutely necessary. I accept larger trims with e85 on the basis that density is more variable and it has a much wider range of 'good' afr's, so even minor fueling error introduced by the trimming isn't as big a deal as if it were running on dinosaurs.

I am so happy that you are part of this community. :)

not long ago when i was first converting my pump gas tune to e85. now i keep them in separate folders :thumbup:

This is all excellent information. One thing worth noting though, and I could be wrong, but if LTFT gets to +/- 25 don't you throw a lean/rich code? (assuming you haven't disabled it, lol)

Also, I've put a few k miles on Shiv's e85 tune and I've seen some fluctuations in the ethanol content myself. PERSONALLY, I prefer to add a bit of gas when the trims are on the lean side just because it makes me feel better. Plus, when the trims are on the lean side (high ethanol), my car hates to start on cold mornings. It still starts, but I hate trying more than once.

But admittedly, I'm a bit of a perfectionist and I like to see my LTFT as close to zero as possible. :)

Having tuned before I understand the closed loop process for fueling. IE: adjustments based upon STFT's and LTFT's.

I've always understood however that AFR's while running methanol/ethanol fuels should be somewhat richer? Which tuning and commanded AFR's won't account for since tuned to run regular fuels?

So let me get this right I can put E85 in my car with a tune from OFT and not have to buy a $650 flex fuel kit? I'm new to this tuning stuff and don't want to spend money on something that isn't necessary.
Thanks

Correct - and if you want to test the Ethanol content out of curiosity all you need is a turkey baster and a 100ml graduated cylinder - I bought mine off amazon.

Ok great. Can't wait to try it out. Thanks for your help


Sent from my iPhone using Tapatalk

Shiv, can you comment on flex fuel kits and quality of starting in cold weather?

FYI, it was 35 this morning according to the car, and there was ice on the ground. Started great on e85. A quarter second of stutter.

Do you know if there is a digital plug in ethanol content tester or is that just part of the whole flex fuel kit . I know its not needed but would like to get content while I'm in car.instead of going the turkey baster route.
thanks again

you can get the gauge and sensor in a variety of configurations from zeitronix directly. runs about $350-370 for the whole setup iirc.

Can you elaborate how this works? Does the ethanol separate?

Sent from my SGH-T999 using Tapatalk

Ethanol is Hydroscopic meaning it likes to absorb water, if you mix the E85 with Water and shake it to mix it, the gas will now float on top of your Alcohol water mixture...if you did your maths correctly, you can look at the level in the graduated cylinder where the GAS and Alcohol/water separate and deduce your % of alcohol

FlexFuel and Facts
 

You fill the cylinder up with 25ml of water and 75ml fuel. Cover and shake. After it settles, the ethanol will join with the water and what you have on top will be the pure gasoline. You can equate the percentage of ethanol content by taking the the new separation line (call it x), which is should be in the 80's, and plugging it into this equation:

(x-25)/75

Basically you are figuring out how much ethanol was added to the water (x-25) then what percentage of the original fuel (75) that is.

If the separation line is now at 88 (x=88) then the equation would be

88-25=63
63/75=.84 (or 84% ethanol)

At least that is how I understand it :)

Count me in as one of those people who have noticed the car automagically (word use intended) handles variations in the fuel. I've been running a mixture of either e85 or 92 for the past 3.5 weeks. The car handled everything I threw at it, and between the cars computer and shiv's awesome tune on my esc everything is incredible.

Quick update:

Took a datalog today on the way back to the office from Chipotle. After 3 more days (~200 miles) of driving on E60, you can see that no additional LTFT has been done. In other words, all the learning that the ECU did in the last 200 miles of running E60 (instead of E85) was done within the first few miles after leaving the gas station. And at no time (even during that first WOT run before learning) did the car feel "out of tune". It hasn't felt anything less than perfect since adding gasoline to my E85 tank.

Still goes to show that it's not necessary to be concerned about ethanol % variance in E85. The ECU will handle things effectively and quickly. And without the having to add any more hardware (flexfuel sensor kit) or custom code.

Link to log:
http://datazap.me/u/shivvishnu/stage...3-days-driving

Full log:
http://i85.photobucket.com/albums/k4...4daystotal.jpg

Partial log:
http://i85.photobucket.com/albums/k4...after4days.jpg

It's worth noting though, that lowering your ethanol % will improve fuel mileage. So if the car is getting all the knock protection it needs, and running the most timing it can with only around 100 octane requirements, then is there any reason you couldn't regularly run a 65/35 mix of e85/91? Assuming e10 gas, that gives you e58 and an effective octane of 100 even.

In "theory" you'd get a 12.5% improvement in fuel mileage over straight e85.

I thought the whole reason for flex fuel was to make it easy to pull up to any pump and fill the tank with whatever was available without having to switch between a gasoline vs. an E85 map.

That is correct. But the purpose of this thread was in response to those who are now claiming that a flexfuel kit was necessary for those running exclusively on E85 due to the ethanol content variance that is typical from station to station and from season to season. The point of this thread was not to suggest that a static non-flexfuel tune can handle flexfuel duties. But rather that a static non-flexfuel tune can indeed handle even the widest reasonable ethanol variance found in pump E85 :)

The proof is in the logs. I myself really wanted a full flex fuel setup, but the more I have seen the e85 tune being run from various members (with various setups, ethanol content, and temperatures), the more I am convinced a quality tune is all that is needed.

our take it to a shop that has both a mustang and dynojet like us :D

we had a bimmer here for some oulls running your flexfuel set up and tune, i forget the exact numbers somewhere in the mid 500's iirc...very cool

A conservative tune targeted to an 85% ethanol mixture should run the engine pretty well with any mixture between 60% and 95% (give or take) since the lambda changes are well within the authority range of the closed loop system. The only area where it will not function as well as a true flex fuel system is in the cold start domain. The reason for this is that below 50F, the ethanol is basically useless and only the gasoline fraction plays a role in starting. This means that from E60-E95 you are dealing with gasoline content in the 40% to 5% range, which is an 8:1 variation . Essentially, you will need about 8 times as much cranking fuel to start the car cold on E95 as you will on E60. Lambda sensors don't work unless the engine is already running, so on cold cranking without a flex fuel sensor, the ECU is running blind.

A non-flex tune will probably be set up to expect 65-75% ethanol below 50F since that is your average winter mix across most of the nation. With higher ethanol mixtures, the engine will probably start, but take much longer or many tries before it does. If the tune is set up to expect 85-90% ethanol, it may easily flood the engine, again requiring longer cranking times and more retries to successfully start.

Is a flex fuel sensor absolutely required to run E85? No. Is a flex fuel sensor always a waste of money? Not if you have the electronics and tune to properly use it and you value the flexibility of never having to worry about what's in the tank enough to offset their cost. It's a personal choice.

i've never tuned a flex-fuel system, as i'm not a real tuner. i'm just a nerd, and they don't let us nerds play with the cool toys (edit: i guess they do now). to me though it just doesn't seem like a great idea unless you have lots and lots of time to dial it in.

it's like electronic boost control. it's a wonderful idea. solves all of our problems. it's automagical! but then, it isn't. it's a bitch to tune, you have spiking and creep and tailing and all sorts of stuff to deal with that you don't have with an mbc. i'm sure it could be great, but in 99% of the installations i've seen, the user would've had better boost control with a cheap ball and spring. keep it simple...

in the same way, ethanol content analyzers are great. you can adjust boost and timing and fuel by eca, it's automagical! except i'm sure it's not. someone has to tune the thing. and if past experience (and that of the collective internets) is any indication, getting a car tuned right via email is hard enough just getting the basics right.

one perfect example: a buddy of mine has flex-fuel (i won't name names). his tuner accidentally mixed up the boost maps, so he was running 16psi on pump and 10 on e85. Not great for long-term reliability. this can't happen with an mbc. sometimes, manual human intervention is a good thing. he's running a hallman pro and loving it now, fwiw.

the other risk is that people will assume that because they have flex fuel and a 'good tuner', they've got nothing to worry about. that's insanity. of course you do. have you read other people's logs? there are people driving around with very, very bad tunes who either don't know enough to realize it or just have blind faith that their email-buddy will keep everything together for them. there are people driving around in tuned cars that don't even own a cable to log with, and vendors promote this practice! this also is insanity. blind faith is not warranted here. 'trust but verify' as they say.

point is, some view flexfuel as a 'fool-proof' way to run various blends of e85 without having to do boring tuner-y stuff like log and tweak maps. but the truth is nothing is fool-proof, and e-tunes generally suck big donkey balls even without the added complication of flex fuel. by adding it, that's one more thing your tuner has to get right. in my experience, it's unlikely that they will. so in any case, you're back to reviewing logs. or you remain oblivious and just take whatever comes your way. kinda like before you bought the flex fuel setup lol.

I think flex fuel is cool, but seeing how flexible the ECU is makes me think it's not worth tapping into my factory fuel system. We've seen in many different posts how not doing that properly can go HORRIBLY wrong.

C'mon you amateur tuner, logging is for pussies.
I had my car dyno tuned by a master tuner and it looks good.
:laughabove:

speaking of flex fuel...I just swapped back to 91 from e85 for the first time since I went e85. I got my tank down to 45 miles past the fuel light, filled up, drove 1.5 miles slowly and started seeing my trims go rich rich rich...parked and shut car off. Flashed gas map. Started up and saw my trims lean lean lean...let idle for 2 mins and watched trims clean up. Drove slowly for 1/2 mile...got on freeway and watched trims fix themselves over the next 15 miles. Trims look perfecto now.

So yeah, if you don't want to do that you need flex fuel. I don't mind it.

some of them don't drive anymore. at least not their brz/frs.