FlexFuel and Facts

[vignesh]

Originally Posted by 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

Is there any adverse effect if you start the car with 91 octane tune with e85 in the tank, by mistake?

[lucid215]

after reading this i have noticed something about my car. when i was wot i was always in the mid 11's for afr and high ltft. only time i saw mid 12's was when i was on pump gas and pump tune

[brilthor]

Originally Posted by Shiv@Openflash

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.

If I wanted to deliberately dilute what I get from the e85 pump down to the minimum the car needs for safely achieving maximum power would it be possible to dilute it with 87 (I assume the 15% gas already in the mix from the pump isn't premium to start with) and if so does that change the % mix which is safe to run without risk of knock?

[s2d4]

Originally Posted by brilthor

If I wanted to deliberately dilute what I get from the e85 pump down to the minimum the car needs for safely achieving maximum power would it be possible to dilute it with 87 (I assume the 15% gas already in the mix from the pump isn't premium to start with) and if so does that change the % mix which is safe to run without risk of knock?

Don't.

[Koa]

Originally Posted by s2d4

Don't.

thx s2d4 beat me to it haha

on a related note, we need more interest in getting a (hopefully low cost) open source option going for those planning to stay w/ OS tuning platform.. peep this thread anyone who's interested

Opensource Flex-Fuel Ethanol Content Analyzer with BLUETOOTH

[brilthor]

Originally Posted by s2d4

Don't.

Thanks for the quick response, could you please explain the reasoning?

[Koa]

Originally Posted by brilthor

Thanks for the quick response, could you please explain the reasoning?

He's just saying that you're obviously not running a flex fuel setup, therefore your proposed method would be impossible to accurately and consistently achieve.

[brilthor]

Originally Posted by Koa

He's just saying that you're obviously not running a flex fuel setup, therefore your proposed method would be impossible to accurately and consistently achieve.

Thanks again. Testing the % ethanol from the pump can be reliably done in less than 5 minutes, so it would be possible to easily calculate the ratio of regular to put in on a given stop if I know the target percentage.

Since there is only 1 E85 pump in my city and it is not close by I already take jerry cans with me and pick up as much as I can at once. This means that the amount of time required to test ethanol content is worth it for me so that I don't have to make the trip as often.

So, assuming I can reliably target a %E as described above, is there any other reason this would be a bad idea?

[steve99]

Originally Posted by brilthor

Thanks again. Testing the % ethanol from the pump can be reliably done in less than 5 minutes, so it would be possible to easily calculate the ratio of regular to put in on a given stop if I know the target percentage.

Since there is only 1 E85 pump in my city and it is not close by I already take jerry cans with me and pick up as much as I can at once. This means that the amount of time required to test ethanol content is worth it for me so that I don't have to make the trip as often.

So, assuming I can reliably target a %E as described above, is there any other reason this would be a bad idea?

That tune was done expecting about E70-E75. While it may be possible to have enough octane rating to run down to E60 or below your fuel trims are going to be extremely high and I would expect your going to run into knock problems, especially adding 87.

Unless your going to rework the tune significantly to accommodate your altered average E%

[brilthor]

Originally Posted by steve99

That tune was done expecting about E70-E75. While it may be possible to have enough octane rating to run down to E60 or below your fuel trims are going to be extremely high and I would expect your going to run into knock problems, especially adding 87.

Unless your going to rework the tune significantly to accommodate your altered average E%

It was my understanding that the first post in this thread stated that this was not the case, that the tune would remain optimal on lower %E's. I feel like I'm missing a piece of information.

[steve99]

Originally Posted by brilthor

It was my understanding that the first post in this thread stated that this was not the case, that the tune would remain optimal on lower %E's. I feel like I'm missing a piece of information.

The tune will work on lower e% but the fuel trims will be high when you push the boundaries ie 15% plus trims if your e% is down to below 60% . may cause some hesitation and smoothness issues. at low e% you may also get some knock.

it will be optimal in the middle E% range it was designed for

bit like running car on 91 on stoxk petrol tune it will work but its not optimal.

[misooscar]

Shiv, which flex fuel kit can you recommend for a current vortech OFT300 customer, that wants to run 550 cc injectors and a range of 91 to e85?

[Wayno]

Am I missing something or did he totally miss the point lol?

[Simplicity]

This makes me want an oft sooner than later now as I was thinkin about getting the flex fuel kit at first