I only use V-power.

 

Can someone please explain in laymen terms what this 10% ethanol will do to our cars at WOT... I keep seeing leaner, richer, etc. Is this going to make my car slower? I was thinking it would help out a little bit because alcohol can raise effective octane..

 

With the 10% ethanol fuel, the O2 sensor will report a leaner mixture, and the ECU's fuel trims compensate to bring things right back to where they need to be.


Disconnecting the O2 sensor will cause the ECU to revert to open loop, and fuel economy will worsen regardless.

 

Well personally I think there is a different thing going on....

02 sensors do what they sound like... read the 02 NOT the fuel. Therefore, since your wideband is displaying the Lamda for Gas, it should always read 14.7:1 regardless of the fuel. Even if you dump Methanol in there and run it... if the car can compensate enough (It will need to double the amount of fuel it puts in there) your wideband would still read 14.7:1 even though in reality it would be closer to 6:1.

AFR = Stoich * Lamda

O2 sensors read Lamda (1.0 Lamda = 14.7 for gas, 6.x:1 for Methanol, 9.x:1 for Ethanol). I hope this makes sense... to put it simply.... the o2 sensor will always read 14.7 when your at stoich for whatever fuel is unless you calibrate the display to show the AFR for a different type of fuel. AFR is kinda like Ferenheight.... people should never have gotten used to using it to tune Lamda is the correct way.

 

You are correct. My point was that, if 10% of ethanol is suddenly substituted for gasoline, any given injector pulse that previously maintained a specific lambda with 100% gasoline will suddenly result in a slightly lean mixture with the 10% ethanol fuel. The ECU will simply flag the change and make the correction.

 

True, the trims will adjust eventually, and should settle itself.. 14.7 AFR is a human readable number, all of these sensors use Lambda values and will settle on the Stoich in closed loop after a drive or two..

I assumed the same thing as Ted B about how fuel trims bias open loop maps also, But after looking at the ECU, it doesnt appear to do that at all, if it did, our cars and the ECU would be flex fuel compatible and its not.

It just happens to be that our open loop fuel maps are rich enough to compensate for the different fuel formulations (up to about 30%) which is why they are so rich from the factory..

I got my Evo around the time MTBE's were still in Fuel formulations, and noticed a different when I switched between Ethanol blend and MTBE Blend fuels, MTBE got better mileage, and made a bit more power at the same level of boost.. But Ethanol blend got slightly lower gas mileage, but was more resistent to knock when I ran higher boost and the car made slightly more power. I never saw anyone else make this observation so I never talked much about it. But when I first got the car, I was Averaging over 300 miles to the tank with MTBE blends, and currently 275 or so with the current Ethanol Blend..

Just a bit of food for thought..

The only time you may have a problem is if your closed loop operation has fuel trims that are enough out of range that the ECU cannot alter the trims any more.. This is also why you have to be very careful when you tune a car to leave some headroom in your tuning, especially if you live somewhere that there is MTBE gas, since switching to a different blend can suddenly find the car a bit down on power, running leaner, or other problems.

 

Hence the P0171 system too lean and P0172 system too rich.
.

 

10 % ethanol only requires an additional 3.4% fuel and it raises the octane by 2 points.

Also most premium doesnt have Ethanol in it, so why worry?

the long/short term trims can go +/- 25-30 % so there is a bunch of fudge room

 

you need to run a bit richer in the winter time.

you have to understand that 14.7 afr ratio is a perfect 1:1 fuel to air ratio, which is good for the emissions, but not neccessarily something you would want in the colder weather.

you add more fuel for starting/warming up in the morning/ etc., it just makes more sense that colder dense air should effect your afr, and you should try to run a bit richer in the winter time.

that's what I think...