water injection

[Darrell Norquay]

At 08:26 AM 9/6/96 -0600, Steve Cicoria wrote:

>>O.K., My daily driver (w/ 160k miles) is starting to knock unless I use
>>premium.  I think I'll put in a water injection system, but have a few
>>questions.  Can you dump in too much water?  I plan on a winshield washer
>>pump, and to have it vaccum operated.  I will monitor the map signal and
>>start pumping water when the engine gets below a certian vaccum.  What
>>I could do with another op-amp and a 555 is have the water pump come in
>>at 50% duty cycle at one vaccum, and full on when it drops below another
>>vaccum.  I don't think I'll get carried away with using a pic chip,
>>because I really don't know the relationship between engine load and
>>knock.

Yep, you can dump in too much water.  This may result (although unlikely) in
hydraulic lock, which bends rods.  More likely you'll just lose power
instead, and/or have to fill the tank every 10 miles....

The Edelbrock Varajection system used 2 inputs, RPM (from the distributor)
and manifold pressure (internal sensor).  It uses a standard OEM type
windshield washer tank with built in pump, and a couple of different nozzles
that you can install in the top of the aircleaner.  It has a small check
valve in the water hose to prevent water from draining back to the tank. It
has 3 pots for setting it up:

RPM threshold - keeps water off until RPM setting is exceeded.  This keeps
water injection off at lower RPM's.
MAP threshold - keeps water off until manifold pressure drops below
setpoint.  This keeps water off at part throttle + cruise.
Volume - this controls the maximum pump speed, and thus the max volume of
water injected.

This was all done with a single LM324 quad opamp chip, a Motorola pressure
sensor, and a handfull of r's, c's + t's.  No PIC's.  BTW, I have a complete
one sitting in my garage collecting dust, if anyone's interested...

And At 01:57 AM 9/7/96 EDT, Jim Steck wrote:

>A good treatise on water injection can be found in Sir Henry Ricardo's fourth
>edition of "The High Speed Internal Combustion Engine" pages 165-171.  His

>He also suggested that mixing up to 50% methanol with the water helped improved
>its volatility.  

I used to use stright windshield washer antifreeze in mine.  The Varajection
is basically all plastic, so corrosion was not a problem.  I read somewhere
that using Acetone/methanol/water mix worked even better, the acetone acts
as an octane boost.  Of course, with this, you may have problems with the
plastic parts.  As far as using Ethanol, who wants to dump in a bottle of
vodka with every fillup?  D'rather park the car, drink the vodka, and dream
about going fast...



regards
dn
dnorquay at awinc.com