Turns out it's because there's more oxygen in ethanol fuel! I know someone here touched on oxygenation of fuel but I didn't look into what they really meant.

"Another effect of the oxygen from ethanol is that ethanol blends tend to run "leaner" than pure gasoline because there is more oxygen available in the fuel-air mixture.

My car wouldn't change the airflow through the AFM because without the 02 sensor in the system, it has no idea it's getting more oxygen from the ethanol fuel. Since I'm not talking big swings in the AFR, I was never concerned. I just always wondered why I saw that difference when going from pure gas to ethanol.

That's huge! My F250 only drops about 2 mpg but it's a pig. I'd feel happy if it ever got 17 mpg.

I don't see how that at all adds up.

the Airflow through the AFM or MAF is a function of the throttle
the throttle is done by your foot, or the cruise control


Engine Management happens as a result of air flow through the AFM/MAF , not with airflow.

Throttle determines airflow
TPM + AFM/MAF + RPM determines Main injection output
O2/lambda sensors in the exhaust adjust secondary injection control

None of that controls airflow on the inlet.

if at all the engine gets more or less O2 in it's mixture will be picked up by the O2/Lambda measurements.
and then more fuel gets injected.. Obviously if that fuel itself contains O2, it will do more injection to overcome that
Since it's only a small percentage of the fuel that is Bio and contains extra O2.. it will overcome that surplus quite quickly.

To my knowledge no engine management system adjusts the throttle position on the E-throttle systems as a function of closed loop. Mixture Trimming happens on the injection. Ignition timing is secondary and for performance/knock.

If anybody were to try trimming both injection and throttle, it would be way to complicated to map. to many variables.
No ROI

Only throttle control I can imagine is basic idle control...

I don't think it's as simple as "throttle controls the AFM". And again, my car gets no measurements. There is no 02 sensor in the system so the engine has no idea what's going on.

Something to keep in mind, I don't pay attention so much to throttle under load. When I'm saying my AFR is leaner, I'm talking under idle or cruise conditions. At WOT I'm in the 12.9 range

I'm not saying Throttle controls the AFM.. it controls the airflow

AFM simply detects that airflow.. in a way the AFM is a result of the throttle+temp+pressure. and Technically the throttle does control the result of that AFM, but it's indirect.

If you have no 02/lambda, then you have no closed loop
so whatever your engine does, is preprogrammed based on the inputs.

AFM
TPS
RPM
Knock
other

You said "my engine doesn't know it has extra O2 iun the ethanol, so it doesn't adjust the airflow"

I don't see how your statement can be true, eg that your engine mgmt somehow controls the airflow... That would be unique and groundbreaking.

I probably should have been more clear about where I see the leaner AFR. If I take the car out and get it fully warmed up, my idle with pure gas will be in the 13.6 to 13.8 range. At cruising speed my AFR will typically be in the 13.8 to maybe 14 range with pure gas. When I fill up with a blended fuel I can see the difference in idle AFR as well as my AFR at cruise. I initially set my base idle mixture (running ethanol fuel) so it would be at 14 to 14.2.

I follow what you're saying and I miswrote my first comment. The throttle butterfly controls air flow. I should have said it doesn't adjust the mixture rather than the airflow.

ok, but it's still just what you do with your foot.
at idle, all you can do is control the Idle bypass + idle rpm injection
And perhaps temp sensor so the darn thing understands it needs a bit more fuel in cold state.

AFM really doesn't do much at that point...it only becomes relevant when you move out of idle.
and what fuel you use, it's really not something you can control much , the rpm and airflow is too low and anything you measure becomes a statistical variation you can't even measure or fine tune the idle mixture by hand..

only thing it has to do at idle.. is run smooth enough and not stall
That's all that matters And I'm pretty sure if it runs smooth on bio ethanol, it will run smooth on regular fuel with high or low octane... or vice versa

Like I said, the mention of the AFM and air flow was a mistake on my part. I should have said "mixture".

Not sure what you mean by I can't fine tune the idle mixture. (Forgive me if I'm misreading that. I'm only working on 4 hours of sleep) I can make the idle mixture rich or lean by adjusting the screw on the AFM.

That an engine in idle running state takes in very little air and takes very little fuel
And its very hard to control that idle running smooth by looking at an AFR output in the exhaust.

wether or not it runs smooth for the most part has to do wit h the character of the engine
at that point idle bypass sets the RPM with the air, and smoothness with a idle injection setting.

Sure you can look at AFR at that point.. but your ear is going to be the final judge if you like how it runs at idle or not. It's not a fine tune that anybody can measure with sensors.. either it runs smooth, or it doesn't.. no sensor needed to hear it surges or barks in the exhaust.

Where did we get into smooth running or not? I didn't say the engine doesn't run smooth. I said it burns slightly leaner. You have to be ridiculously off on the mixture to hear a difference.

I'm saying, WHO CARES if it runs a smidgeon leaner at idle
the variation/error of measurement is to big in that operating state of the engine.
None of it matters

unless you are in some kind of lab.. that measurement can go one way or another based on any of the other variables of the day.. barometric pressure, ambient air temp, engine temp state, fuel temp

the fuel you put in
unless you can switch fuels at the flick of a switch and compare the AFR variation each time, on the fly, your measurement and comparison is pointless. It's within the tolerance of your measurement variation.

Okay... you're flying off the rails now. Have a good day.

IF you want to get a decent comparison, you'de be better off with a car that has actual Lambda and trim.

then it's just a matter of driving 2 tanks of fuel worth.. let the ECU figure out what the engine does..
And connecting ODB2 reader, to check short and long term trim
if it's leaner or richer with a certain fuel, you'll see a change in trim state.


spot readings of AFR do nothing . especially not at Idle. Anybody who ever tuned MFI can tell you that.

I'm not flying off the rails, i'm explaining something but you don't care to listen because you made up your mind about it because you have a measurements that backs up your made up mind.

it's not scientific.

It was an observation that I've made on several occasions. I'm sorry for triggering you. Calm down and move along.

Why do you think i'm not calm??

We need to get Sammy to help here...

It had 2 functions

1. Oxygenator for non-attainment counties in the USA. edit - (To reduce CO "carbon-monoxide" in the exhaust)
2. Octane booster

MTBE had the same function and it was "closer" to gasoline in heating value and only required a 5% mix to do the same thing as ethanol.

Refiners could put in either, but MTBE was cheaper. California banned MTBE (in the 1990's?). Since it was mandated at the federal level, MTBE users were "protected" against lawsuits. The EPA pulled that exemption and everyone switched to ethanol.

Then 2005 occurred with the RFS. And the corn farmers rejoiced.- Edit - The RFS mandated the 10% ethanol blend everywhere. And the refiners rejoiced, since they didn't need to make summer/winter and attainment/non-attainment versions of the fuel. Just ONE version.

edit - At the price, E85 seems silly. If it were 30% cheaper than gasoline, sure. But E85 does have a very high octane rating. For flexfuel vehicles that can make use of high octane fuel with advanced timing changes, it can be a good thing for power, etc.

An Air fuel ratio valve is used to adjust the ratio of fuel to air based on the change in the heating value of the fuel. Use a lower BTU content fuel and you want more fuel to air. All of our engines running on Landfill Gas use air fuel ratio valves because the BTU content of the landfill gas is not consistent.

Samny went AWOL along with a whole bunch of long timers in the past year or so ... hope he and the rest of them are doing OK and just avoiding PPOT.

I think he moved out of California and is swimming in a vault of gold, like Scrooge McDuck.