[Diy_efi] Is E85 worth it?

[Torbjörn Forsman]

Older FFV cars (like the Ford Taurus from around 1996) have a fuel 
quality sensor which measures the dielectricity constant of the fuel. It 
is sort of a capacitor which uses the fuel as the dielectric, together 
with a capacitance measuring circuit.
Today's FFV vehicles usually don't have any such sensor but uses the 
ordinary lambda control and adaptation functionality of the ECU to adapt 
for different fuel mixtures. In fact, some non-FFV vehicles have a large 
enough adaptation "window" to run well on either gasoline or E85, if 
they only get somewhat higher fuel pressure or larger injectors.

The difference in fuel consumption between gasoline and E85 is often 
smaller than one might believe from the heat values of the fuels. This 
is due to E85's higher hydrogen content and lower carbon content than 
gasoline. The exhaust gases will contain more water steam and less CO2, 
which gives the engine better thermal efficiency as the steam takes more 
room per mole (please refer to any thermodynamics text book for more 
details). Additionally, the higher octane number of E85 permits earlier 
ignition and higher compression ratio than we are used to from gasoline 
engines.
As it is more difficult to evaporate E85 than gasoline, it is very 
important to make sure that everything concerning the fuel vaporization 
is in best possible order. Good intake air preheating helps much, as 
well as using modern types of injectors and a relatively high fuel pressure.

Best regards

Torbj?rn Forsman


Garrett P. Beauregard wrote:
> Yes.  There is a sensor that detects the mix. No clue how it works, but it
> does and it's seamless.
> 
> Garrett
> 
> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
> Behalf Of C. J. Frederick
> Sent: Thursday, August 24, 2006 9:24 PM
> To: diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] Is E85 worth it?
> 
> 
> I often wondered what happens when you have, lets say an 1/8 tank of one or
> the other fuel and have to fill up with the opposite fuel.  Can the ECM
> seamlessly adjust for a mix (E85 and gas) in the tank?
> 
> CJ
> 
> 
> 
>>E85 has about 70% of the energy content of gasoline. So, e85 needs to cost
>>70% of the price of gasoline to break even. The last number I saw was
>>something like 450 stations in the US had E85. With most E85 being supplied
>>by local refiners, prices and availabilty will vary. The NEVC website has
>>some good info, but they play down the disparity in energy and economy:
>>http://www.e85fuel.com/index.php
>>
>>There is also some "value" associated with the reduced pollution when
>>running E85, but that doesn't accrue monetary benefits in your wallet.
>>
>>Remember that you can still run old-fashioned gasoline in a FFV until E85
>>becomes more widespread and cost effective.
> 
> 
> 
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