Tech info

[Gary Derian]

I think E85 is 85% ethanol and 15% gasoline.  The gas lets the engine start
when cold.  The O2 sensor will tell the engine to go rich until it reaches
stochiometric but I would believe that an error code would be set before it
got there, therefore your need to reprogram.  The OEM's have demonstrated
cars that could run on everything from 100% gas to E85.  They included a
fuel sensor to tell the computer what the mixture was without having to wait
for the O2 sensor to feedback.

Gary Derian <gderian at cybergate.net>



>>Hi everyone,
>>
>>I am going to be tearing into a new 1999 Chevy 1500 P/U with the new 5.3L
V-8.
>>I know that it is based on the corvette LS1 motor.  I am seeking info
about
>>how to work around the EEPROM and reprogramming the damn things, I also
need
>>some tech info on the operations of O2 sensors.  The engine will be
converted
>>to E85 and I wonder how the extra Oxygen in the ethanol affects the O2
sensor.
>>It seems that since gas doesn't have Oxygen, and Ethanol does, then there
>>would be an abundance of O in the exhaust.  Since the O2 sensor would
likely
>>read too much O, and 'theoretically', the only supply of O is from the
>>incoming air charge, it would tell the PCM to deliver more "gas".  Thereby
>>causing the engine to run rich all the time when operating on ethanol.
Can
>>anyone support my logic?
>>
>>Thanks,
>>Chris Gano
>>chrisgano at aol.com
>
>No, I cannot.
>
>The O2 sensor voltage switches when the exhaust goes from having no O2
>(below lambda = 1) to having some (above lambda =1), pretty much regardless
>of the fuel involved, so long as the fuel does not foul the sensor.  The
>trick with what you are doing is that lambda =1 (lambda = 1 is defined as a
>stoichiometric fuel mixture) is very different for gasoline vs. ethanol.
>For (typical) gasoline it is 14.7 : 1 , air wieght to fuel weight. For
>alchohol, unless my chemistry is failing, it is more like  8.3 : 1 (air to
>ethanol, by weight). If "E85" is what I think it is, 170 proof ethanol, or
>85% alchohol, 15% water (also by weight) , you will have to multiply the
>8.3 by .85 (giving a lambda = 1 at an air : fuel  ration of more like 7.1 :
>1, so as to allow for the amount of non-combustible water in the fuel.
>
>Regardless of the oxygen in the fuel, there will be excess oxygen in the
>exhaust at a lambda leaner than 1, and none when richer than 1---and the
>sensor will switch at the stoichiometric ratio for whatever fuel you are
>burning. Your real problem is going to be injectors big enough to flow this
>much more fuel, and making sure that EVERYTHING in the fuel system is
>impervious to corrosion by the E85. This would mean that the tank would
>best be stainless (304 would probably be OK, 304L or 316L would be
>excellent), any aluminium parts in contact with the fuel would have to be
>hard anodized, the injectors themselves must be alchohol compatable, the
>fuel pump must flow a much bigger volume and be impervious to alchohol
>corrosion, all the lines would have to be stainless, etc.
>
>The big bonus is that you could probably goose the engine's compression up
>to 14.5 or 15 :1 without any sign of detonation problems if you run an 85%
>ethanol / 15% water mixture for fuel.
>
>Fortunately, the alchohol compatable injectors are out there because Brazil
>requires that at least some cars there burn alchohol.
>
>Regards, Greg
>