How to adjust for Gas/Ethanol

[sascha]

Hi,

Thirst - OBdrive is really a great thing! Thanks a lot to the team.
At the moment I am testing with a gas-ethanol mix (60:40)
What is the best way to set up HOBDrive for that to get reliable consumption gauge?
Adjust the air-to fuel ratio (in this case to 13 something)?
or rely on the lambda and LTFT fuel consumption correction? or all together?
I am afraid that there could then be some double-accounting.
To be honest, I still have a lack of understanding how the measurement actually works and what happens if the engine is not running on standard gas. At least density is very similar for gas and alcohol so that the conversion from consumed mass flow to liters should be similar anyway.

Thanks in advance,

Best regards,
Sascha

[cail]

Sascha,

You should check your LTFT1 and Lambda values when running on ethanol mix.

I know from other users experience (prius on ethanol mix) that there LTFT1 value gave a huge correction (like 30%). Think that depend on vehicle's ECU imternals how it applies the correction.

If you see big LTFT on your vehicle as well, then its just a matter of setting "LTFT consumption correction" in vehicle's settings. Probably you should also track whats happening with your Lambda value. May be its better to use it, than LTFT.

Please share you findings, it really interesting.

[sascha]

At the moment with the 30% ethanol blend LTFT says 10% what is pretty much the theroetical value for the over-consumption. STFT is still OK ..max 15-18%. I don´t need to go with top speed on the highway - just driving 22km with part load throttle to work. - I think 25% is the limit of the injectors. Hence I think a 60% blend is the maximum I can drive without changes at the hardware. But I will post my "lessons learnt".
What about the change of the stoich ratio? Should this be altered or rely on LTFT. Lambda correction I would use anyway.

[cail]

LTFT says 10% what is pretty much the theroetical value for the over-consumption. STFT is still OK ..max 15-18%.

I presume the values are positive? Meaning 10% less fuel in reality comes into the engine?
Another good question should it be correct just to use LTFT, or also add STFT to that correction.
In theory, after a period of driving, your engine should correct LTFT so that STFT comes to zero. But thats a theory. Probably there is a reason in adding STFT into that correction as well.

What about the change of the stoich ratio?

As far as I see this process - your vehicle doesn't know that it should change stoich AFR. It just learns that it should adjust lambda. Therefor I would rely on LTFT or Lambda corrections only.

Lambda correction I would use anyway.

I would be careful on that. Turning on both lambda and LTFT corrections could lead to double correction.
Were you successfull with that new Lambda PID I've sent you? What Lambda values do you see on ethanol?

[sascha]

I presume the values are positive? Meaning 10% less fuel in reality comes into the engine?

I was pretty sure that LTFT +10% means more than predetermined by the characteristics.
Now I am confused? Or was that a question?

In theory, after a period of driving, your engine should correct LTFT so that STFT comes to zero. But thats a theory. Probably there is a reason in adding STFT into that correction as well

I think the ECU will not adapt to the LTFT. It will just try to come along with the "normal" injection timings everytime I restart the engine. As long as I refuel with sth. different than pure gas there will be a deviation - just the LTFT? But I have read that different ECUs of cause can work differently. I found this interesting thread where I found my actual understanding confirmed and broadened - at least it sounded all plausible to me.:
http://forums.turbobricks.com/showthread.php?t=73061

I would be careful on that. Turning on both lambda and LTFT corrections could lead to double correction.
Were you successfull with that new Lambda PID I've sent you? What Lambda values do you see on ethanol?

At the moment with about 30% ethanol lambda (yes It works with the second user.*xml-file version thanks again! ) behaves pretty normal - just around for almost all loads - beginning with 95% throttle down to 0.9 - as it was with gas (10% as we have that "E10" in Germany).
When I go completely from the throttle pedal with a selected gear lambda goes up to 2 - showing that there is actually no injection /combustion as it should be.
So the ECU still manages to control to lambda=1 - what at the end of the day means getting the oxygen fraction in the exhaust gas down below 2% or so - hence it runs on stoich ration with my mixture. That means that the more-consumption must be accounted for by the stoich ratio OR the LTFT. Lambda should not lead to a double accounting or does it?
I will test if for high speed and full-throttle it gets near to the imits of the injectors. If not I will increase ethanol fraction in the blend at next refill.

[sascha]

Hi,

ne update - now, with 50% ethanol LFT is about 20% and I get a "low fuel effeciency warning" . But that is not yet an error code message? The warning say something with LTFT higer than 11.0. Is that a hobdrive value or is it just a warning generated from the ECU? Even I expected this to happen beyond 25% why dous it tell me that 11.0 is the limit. I could not find a parameter in the hobdrive files.
Engine is still running fine - cold start at -5°C without any problem. Consumption is increased by about 10-15% at the moment.

[cail]

Sasha,

This is purely hobdrive's warning. You may change the threshold value in vehicle settings dialog (to disable it).