The E85 Discussion Thread

[45SET]

you wont get get much further then, if you keep not reading what people post!

But this post was in volume, not weight.

The air fuel ratio of the e85 fuel is totaly different to petrol!! This will be hard to explain and harder to understand but if u get it ,it will all come together! i will try my best to explain. i will use n/a air fuel numbers as thats what most of u will see/use.

Petrol's perfect air to fuel ratio is 14.7(air)to 1 (fuel). So 14.7 litre's to 1 litre of fuel. Cars are tuned to around low 13's at full trottle on a dyno(n/a).

E-85's perfect air to fuel ratio is around 8.5(air) to 1 (fuel). Therfore 8.5 litres of air to 1 litre of fuel. This is tuned to around 7.4 at full throttle on a dyno(n/a)

So if an engine uses 100 litres of air and fuel, at the prefect ratios you will use 6.4 litres of petrol or 10.5 litres of e-85. This works out to be 40% more fuel for the same amount of volume(air+fuel) through the engine.

Please note the numbers used might not be 100% correct but are very close and i am not a tuner!This information is to be used as a guide to explain the difference in fuel requirements and air to fuel ratios of the different fuels!

This physics thing is annoying. I'll just stick with my banking numbers.

[tinkerbell]

and it just to ram it home - it is a AIR to FUEL not a FUEL to AIR ratio...

14.7:1 AFR = 14.7 parts of air to 1 part fuel

air is the BIG bit, fuel is the small bit...

you keep posting it BACKWARDS!

[stevan]

why would it create more 'powerful' combustion?

the most heat is created at stoich, and leaner also means slower burning...

(unless you are detonating, but that is not what you should be setting out to achieve)

Because one would assume leaner mixtures will have fully combusted fuel hence a greater energy release, this is obviously reliant on the fuel volume being the same in both cases. I did not consider that highest power output would be by cramming as much fuel into the cylinder as possible in which case the AFR would be rich as Tom mentioned.

[45SET]

14.7:1 AFR = 14.7 parts of air to 1 part fuel

air is the BIG bit, fuel is the small bit...

you keep posting it BACKWARDS!

Wait... what...

Gee's I'm an idiot.

Everything makes sence now.

Thanks Tink.

[tinkerbell]

Because one would assume leaner mixtures will have fully combusted fuel hence a greater energy release, this is obviously reliant on the fuel volume being the same in both cases.

complete combustion (i.e. the available chemicals are used completely) only occurs at stoich, not leaner than stoich (or richer than stoich)...

leaner = more air (oxygen) than can actually be used to combust with the fuel... richer = more fuel than can be completely burned...

I did not consider that highest power output would be by cramming as much fuel into the cylinder as possible in which case the AFR would be rich as Tom mentioned.

the concept that a richer mixture provides the most power is a basic principle and applies to nearly all internal combustion engines...

i have tried to find some sources for you , but hard to provide a distinct 'simple answer' as it is massively complicated...

here is a response to a similar question:

http://www.newton.dep.anl.gov/askasc...9/eng99611.htm

Hi Jesse,

You are correct that in order to produce maximum power, a very small enrichment is helpful, especially when accelerating. But it is completely incorrect that a lean mixture burns hotter. The hottest flame temperature occurs at the stoichiometric ratio of 14.7:1. The old wives tale that a leaner mixture burns hotter, came about because years ago as a result of relatively primitive fuel metering devices like carburetors, most engines had to run a little rich (around 13:1 or so was common) all the time to allow reasonable "driveability". So when the mixture was leaned out to a "perfect" 14.7:1, more heat was produced. But mixtures leaner than 14.7:1 burn progressively cooler, not hotter.

The reason for this is pretty obvious when one thinks about it, and you were right to be suspicious. The amount of air an engine inhales at full throttle is the same, no matter what the mixture is. To get a lean mixture, you must inject less fuel. It makes no sense that injecting less fuel, will result in more heat! With that logic, injecting no fuel at all, will result in an infinite amount of heat! Of course, that would be nonsense.

As a mixture is made more and more lean, more and more air that is not used for combustion, and this air only serves to dilute the charge, and cool the combustion process. As stated above, the combustion chamber temperature is at its highest, when a "perfect" 14.7:1 mixture is used, and the temperature falls when the mixture is either made more rich or made more lean.

a detailed analysis of the chemistry (focused on emissions) is here:

http://www.autoshop101.com/forms/h55.pdf

page two, last para covers the rich/stoich/lean behaviours...

[tinkerbell]

Wait... what...

Gee's I'm an idiot.

Everything makes sence now.

Thanks Tink.

a bit like getting your debt to equity ratio backwards, lol

[45SET]

a bit like getting your debt to equity ratio backwards, lol

Well... yes...

Don't want to mix something like that up.

[k20eg]

Thanks tinks, have learnt something new today.

[wpg81]

Sorry to mis-inform people,mass not volume. I have learnt something new today also.

[stevan]

thanks Dave

[Timmy_B]

Wheres the positive rep button for Tinks? LOL

Great info mate

[45SET]

Wheres the positive rep button for Tinks? LOL

Great info mate

This isnt OzHonda Tim... everyone here is an equal...

unless you're a mod...

Just joking :P

[tinkerbell]

look, it'd be even better if i could relate the info to E85... but i can't...

I only know my engine & how it responds on petrol, would love to try it on E85 (I am 12.5:1 CR) but if i did - it would be a caged track car only...

i assume the different fuel density positively effects power, but to what extent is the question? I just keep on 98 'for the convenience'....

[tinkerbell]

calling all E85 tuners???

I know Toda is one...

EDIT: the output i am gunning for (not reached) with my engine is the one set by Troy with his 2.0L B18C with ITB's @ 165kW on E85

[Pizzo321]

calling all e85 tuners???

byp