Methods for flexifuel compatibility

[KW1252]

It seems E85 will be a major player in the future, and why not; it can give a whole lot of more power than gasoline and if the production methods evolve into actually carbon-neutral processes, so much the better. I don't think the issue has been touched before.

The problem here is the ECU needs to know what's inside the tank. And it needs to know it pretty exactly too, a "gas/E85" -switch is no good unless you flush the fuel tank first.

There are few options to detect which fuel is in use. They have drawbacks and benefits.

First, using Lambda sensor. The use of E85 or a blend will cause the engine to go lean. The fuel composition could be calculated from the difference between base map and the needed compensation amount. Then ignition and boost control maps could be applied for maximum performance. It's the way industry seems to be heading, although the industry isn't always about the best solution but the most economical one. The benefits would be the simplified setup and electronics, but the compensation might take some time and be susceptible to errors caused by blockages in air filter, EGR anomalies and such. A broadband O2 would be required. (narrowband could do it too but only during cruising)

The direct method uses a flexifuel sensor. It's a detector that gives out a PCM signal (variable frequency) to indicate ethanol content and PWM for fuel temperature. It should provide immediate data on fuel composition and be oblivious to the error inducing factors in the O2 method. However, it seems the sensors themselves are of limited life span, and they're somewhat expensive too, so they probably can't be scavenged from wrecks with too great success. I think the signal should be decoded in hardware to one or two AD signals so it'll require a board redesign or an add-on board.

Thoughts, ideas, anyone? Anyone? Bueller?

[Fred]

As far as I'm concerned the only option is the flex fuel sensor, doing it by guess work is risky and error prone at best.

Alcohol fuels are only prevalent (note that word) in SOME parts of North America, though, not even all of them. Even in those places, not every gas station carries the stuff. So real world usage isn't likely to be significant any time soon. There is an additional stigma reason for not using it, fuel mileage. It's actually about the same per dollar, but the perceived value is less due to having to fill up so often and mpg going way down. On top of that, range is significantly reduced when running the stuff.

Support pretty much consists of two tunes and some code to blend them based on the sensor input. Not overly complex at all.

Fred.

[KW1252]

I don't think E85 has reached true popularity anywhere, and I actually hope the production methods improve quite a bit before it does. The pioneer nation of ethanol fuel use, Brazil, used to run almost exclusively with ethanol based fuels in the eighties, though the popularity of gasoline have grown since. Yet I do believe it is useful to prepare for the E85 use. The distribution network is steadily growing, and in Europe it's available in most countries already, even if the fuel stations carrying it are few and far apart.

Mileage with E85 does suck, but on the other hand where the real benefits of the stuff comes into play, fuel consumption is somewhat less of a concern

[ehb]

Not sure if this fits this thread, but I'd say this counts as flex fuel
LPG is pretty popular over here in europe (very popular in Holland, a little less in Germany). LPG is readily available every couple miles.
These cars always have a second set of injectors and third party electronics. They start on gasoline and switch to LPG once the engine is warmed up, by intercepting the gasoline injectors and modifying the signals to compensate for energy content differences.

So, it would also be really nice if FreeEMS could drive two independant sets of injectors for this kind of setup, switching between the one or the other would suffice. I'm don't know, but maybe there might be synergies if the fuels are mixed in certain ratios, fuel efficiency wise. Just something to think about. I guess the software architecture for the latter would lend itself to mapped water/meth injection - or vice versa...?

[Fred]

Karri, if all you give a stuff about is power, you can use it exclusively and run a fixed tune that is on the conservative side to allow for variations in the fuel.

I wonder if we have any Brazilians on this forum. I doubt it, but there may be one or two :-)

Also, you have to wonder about it ever reaching true popularity if it was peaking in the 80's and is lower now.

It's heavily subsidised here in the US too.

Fred.

[KW1252]

The entire point of flexifuel is about having a choice. If it indeed was a prevalent option everywhere, it would be very simple, just tune for E85 and that's all there is to it. However, from where I'm typing this the nearest station carrying it is 160 km away. If there is only one fuel to tune for, it'll be petrol with meth/water injection.

[Fred]

Sure, I totally understand. I was just pointing out another option.

[preludelinux]

I plan to run E85 in my setup so support for it is nice, also support for any other fuels like natural gas might be nice too. its also possible to make your own E85/E100 for some people it can get pretty cheap. it also offers some nice advantages for turbo setups.

an ability to tune for pure gas ( which contains at least 10% ethanol and suppose to go up in a couple years ) and tune for pure E85 and work between the 2 with different percentages would be nice. ( winter blends seem to mess up everything )

[Jammi]

This is something I plan to do too. In fact, in my current carburettor car it's roughly usable by keeping the (manual) choke open at all times. Even if there was no easy way to auto-detect the fuel, even a rough estimate by user input, like a potentiometer to set "ethanol content %" utilizing a general analog input could be a start.

[Fred]

an ability to tune for pure gas ( which contains at least 10% ethanol and suppose to go up in a couple years )

It only has ethanol in it in some places. In NZ for example one company sells fuel with ethanol in it, the rest do not. Around different parts of the USA the deal is the same, between zero alc and lots, but it's certainly not stable, which is the issue.

( winter blends seem to mess up everything )

Yep, E85 can be E50 in winter!

If there was code for the flex fuel proper sensor, you could read a pot with it instead and adjust it that way, I guess.

Fred.