Tech info

[Greg Hermann]

>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