FlexFuel and Facts

[Shiv@Openflash]

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:

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:


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):


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

[OmarGC]

Kudos to you

[Asphalt~86]

Shiv,

Thanks for doing this. Really.

[Shiv@Openflash]

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?

[RC51ed]

💡+😮=😎


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

I learn something new everyday.

👍👍

[rhythmM]

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

[bfrank1972]

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


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[Shiv@Openflash]

Originally Posted by bfrank1972

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


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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

[jamesm]

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

[tg_1981]

LOL...When did you do this?

Originally Posted by jamesm

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

[Mars2]

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.

[Mars2]

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.

[jamesm]

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.

[Superhatch]

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