Energy of E85

[bretcon]

Many people claim that a change to E85 increases engine output.
Lets look at the numbers and see why.
The CFM of a engine is calculated by
(RPM X Displacement)/3456.
(8000 X 414)/3456 = 958.33 CFM

1 CFM of air weighs .075 lbs. so
953.33 X .075 = 71.88 lbs

The best avg. air/fuel ratio for power
A) gas 11.6:1
B) methanol 5.2:1
C) E85 7.84:1

To find the pounds of fuel/minute we simply multiply the lb/min of air by the inverse of the A/F ratio ie 1/11.6, 1/5.2, 1/7.84
A) gas 6.09 lbs/min
B) methanol 13.82 lbs/min
C) E85 9.17 lbs/min

The Energy content of fuel (BTU/lb)
A) gas 18,500
B) methanol 9,500
C) ethanol 11,500
D) E85 13,460

Now, let's put this all together.

Fuel ---- Engine CFM -- lbs/air--- A/F ratio-- lbs/fuel-- thermal energy
gas ------ 958.33 ------71.88----11:8 ------- 6.09-----112,693 BTU
meth----- 958.33 ------71.88-----5.2:1-------13.82----131,290 BTU
E85 ------ 958.33------71.88---- 7.84---------9.17 ----123,428 BTU

As you can see E85 has 9.5% more btu's than gas @ .8 Lambda
Not taking into account the evaporative qualities of E85 over gas
we generate more cylinder energy. E85 that is sold commercially will have a ethanol content between 70-83 %. Here in North Carolina I have tested ethanol content as low as 72%.

[Heath Daniel]

That's some good stuff bretcon. The fact that E85 can be backed up with math just makes it all that much better. I never thought about all of this but never doubted it's power over gas by the way our own car responded after we converted it some four years ago. Thanks for showing us the reason.

[David7355]

My brain hurts now.

[hobbesnmina2001]

Bretcom,
E85 makes a great race fuel. Due to latent heat of vaporization and oxygen bearing attributes alcohols do increase the volumetric efficiency of an engine vs gas. What always impressed me about methanol or ethanol is that you use the same fuel whether its a 450 hp motor, or 1200 hp. I do appreciate gasolines attributes but for racing the same cannot be said for it.
You all may find some interesting reading on ethanol fuel theory here:

www.journeytoforever.org/biofuel_library/ethanol_manual/manual1-2.html#ch2

We are lucky these days because there is a lot more info available. Jeff Hartman's Book on High Performance Fuels has a wealth of info as well not just on ethanol, but other fuels as well.

Carlos

[Heath Daniel]

I told you guys Carlos was the MAN. ;D

[adamsvega]

read that in words to live by! the richer the fuel mixture percentage to air to reach ideal the less susceptible it is to weather change and h/p change from ideal .= consistent /easy to tune
the higher the btu the more power ........ so for all the guys that dont get into this stuff
E85 IS THE CHEAPEST, MOST CONSISTENT, MOST POWERFUL FUEL FOR THE MONEY