A/F Ratios Ethanol vs Non OXY gas

"Lambda is a scale that relates the air to fuel ratio of ANY fuel. 1.0 is stoic for every fuel. (the chemically perfect ratio of air to fuel for a complete burn). However, stoic is different for every fuel. Some fuels may need 14.7 lbs of air some may need 6 lbs of air for a complete burn. Lambda 1.0 is always the perfect ratio for the fuel in use.

Some tuners argue that it is better to read air to fuel ratio’s in lambda since it will be accurate with any fuel. To be fair though, most aftermarket gauges will read lambda and convert that number to an a/f ratio for gasoline. If the user then knows the stoic, lean, and rich ratio’s for gasoline, he can apply those numbers to any fuel used and it won’t matter.

What I mean is that if you are running 14.7 (stoic) on a gasoline A/F gauge and you then convert to alcohol ( or E85 ), 14.7 will still be stoic on the gasoline gauge. This is because the gauge is going to read a stoic lambda reading of 1.0 for any fuel, and the gauge is going to output that number as 14.7 on you’re A/F gauge even though we know the true ratio for alcohol is 7.1-9.1.

Many times I have then seen people try and richen the cars tuning map to get down to that A/F value, not realizing that they are already at a stoic burn if the gauge is set up for gasoline reads 14.7."

So between 13.0:1 to 14.1:1 assuming your 5 gas analyzer is lambda probe based. And I am just guessing and have no clue really.

 

ethanol blended fuel runs richer, not leaner. gas mileage goes down with ethanol blended fuels and your engine will run cooler because you are burning more fuel.

 

Where's your car happy running these days? 12.7:1 area? Or higher?

 

When are you going to run the test?

 

i am runing pure gas, no alcohol. there is a station in colorado that sells non-ethynol - yeehaw! my lamba A/F guage shows way rich when running ethanol blended fuel - around 12 - 13:1.
pure gas, i am up to around stoich, 14.2:1.
according to my pyrometer, ethanol blended fuel gives around 800 degrees, while pure gas gives around 1000 degrees.

 

At what point would you conisider too rich for a catalytic converter to start overheating and the unsuspecting 3X8 owner's car to burst into flame? or at what point is it too lean for said result?

 

At what point would you conisider too rich for a catalytic converter to start overheating and the unsuspecting 3X8 owner's car to burst into flame? or at what point is it too lean for said result?

good question. i am not smart enough to answer this with any certainty. i would think that the stock feedback loop between the ego and ecu would adjust the mixture accordingly. when i had carbs and cats, i ran with non ethynol and passed emissions - but then again, my jets were sized accordingly to run ethynol blended fuel back then (feedback from the sniffer on the dyno).

on my 78 308 with TWM and electromotive, i have saved several programs that can deal with different types of fuel. my software setup for non ethynol gas is a bit leaner than the program with ethynol.

 

Cool, this car has air pump? cats?

 

you are right, looks like blended fuel runs leaner. i stand corrected and confused.
hopefullly someone can explain to me (us) why this is so. maybe i will go look it up on google. all i know, is my 308 runs so much stronger on non blended fuel.

 

Less gas=same air=leaner

say you have 1lb of real gas, that needs ~14lbs of air to burn at lambda = 1.
if you only have 85% of that lb of gas with the same ~14lbs of air then you burn leaner then lambda =1
However the ethanol does require some of the air to burn just not as much as the gas so it's influence is less but it is using some of that 14lbs also so it's not as lean as you might think based on 85%. But the net is a leaner burn. Does that make sense?

I need to qualify this by saying I am no expert in fuels. I am using deductive reasoning only here but it sure sounds good.

 

thanks Robert, good deductive reasoning and i understand.

i am equating fuel burnt to power, and thats whats tripping me up.
ethanol has less energy - so you need to burn more to make the same power as you would with non blended gas.??

 

here is what i am talking about: some stuff i puled of the internet..

Ethanol fuel also does not burn as well (which is why they use it to improve octane rating to begin with), it does not burn as hot, and has less volatility. It has about 30% less potential energy than gasoline alone. This results in reduced power, reduced fuel mileage.

Adding ethanol to gasoline displaces some of the hydrogen and carbon with oxygen. Oxygen has no fuel value. You normally get oxygen free from air. But with less hydrogen and carbon to burn, you have less energy. So adding ethanol to gasoline means you must burn more fuel to get the same energy. I.e. fewer miles per gallon.

the last sentence led me to believe this would yeild a rich mixture....but, this (power output and energy) is different than A/F mixtures we were talking about.

 

Agreed. Most interesting thread. I learn more and more. Thanks