"oldjag" wrote in message
oups.com...
Water injection on a newer non-turbo vehicle really has no benefit. It
does have have plenty of potential problems, and will likely reduce
your mileage. Your E350 if probably has port fuel injection. It uses
an O2 sensor in the exhaust stream for closed loop control of the AFR
to a stoichometric Air/Fuel ratio during cruise, which for gasoline is
around 14.7:1. This is optimal for operation of the 3 way catalytic
convertor, while maintaining best possible economy. Make sure you O2
sensor(s) is fairly fresh, ie less than 50K miles on it for best
operation, and avoid cold starts and short trips for better mpg. New
engines have vastly better cylinder to cylinder AFR distribution than
25 years ago. Adding water vapor has several possible issues; 1.)
Added upstream of the mass air sensor it may damage the sensor,
downstream It adds an unmetered volume to the intake, ie the computer
has no way to account for the volume. 2.) If it condenses it may cause
corrosion damage to the fuel injectors, valves, rings etc., (think
moist shutdown with steel & aluminum parts in a confined space). 3.)
Metering water vapor accuratly is much more difficult than it seems at
first glance, and if not metered correctly, or if it accidentaly drips
into the intake it can hydrolock the engine bending rods, breaking
pistons. 4.) It needs to be mixed with methanol for freeze protection &
atomization. 5.) More water will wind up in your crankcase oil, and
the PCV system will likely get hosed up at a higher rate. 6.) On some
newer vehicles you may trigger the OBDII and set fault codes for a
failed catalyst. 7.) The water, unless it is totally mineral free will
eventually clog or foul the metering device unless it is either very
crude or very expensive. 8.) On a fuel injected intake manifold which
is usually unheated, (unlike most older cars with carbs.), icing may
occur, possibly jamming the throttle or screwing up the metering. And
probably 10 other things I have not thought of...

Right on the money! It would have to be an OEM thing and the costs outweigh
the benefits from a corporate point of view.