Introduction
Within
the following pages you will find
information and ideas concerning the use and tuning of a home built
water/
alcohol system. This particular setup is a two stage design. The
reason for more than one stage is to allow a more progressive flow of
injection
fluid as boost rises. There appears to be a small delay in the time
that
fluid is injected and the cooling effect takes place. More cooling is
needed
at higher boost levels than is needed at low boost levels. To inject a
maximum flow at a low boost level in order to be effective a moment
later
as the boost rises will slow the turbo's spoolup due to the excessive
cooling
of the exhaust gases. The two stage design allows the user more
efficient
use of the injection fluid and better part throttle, street drivability.
Much of the information
to follow is the result of street testing the system under a wide range
of temperatures. Conditions have not been favorable for much testing or
tuning. Right out of the box the system performed very well. Much of
the
testing and limited tuning was directed at getting the system to
perform
seamlessly whether at part throttle or wide open throttle. Particular
attention
has been paid to the areas of performance where improvements could be
made.
The basic goal after the initial success of the system has been to
eliminate
ALL knock under both part throttle and WOT conditions, rapid
acceleration,
gradual acceleration, and under all weather conditions. I have tried to
satisfy all of these requirements while running 93 octane, 23-25 lbs
boost
and aggressive timing (108 race chips).
Several types of injection
fluids have been used. Fifty percent distilled water ia assumed to be
mixed
with any of the alcohols tested. Although unscientific, I have come to
the following conclusions. Isopropyl alcohol is economical and works
well.
If injecting too much at medium boost levels it appears to cause a
flutter
effect as if the combustion is beginning to die out. It feels something
like a miss but it is not violent, produces no knock, and is not like
the
surge felt when timing is retarded. Methanol seems to have about the
same
anti knock capabilities as isopropyl alcohol. It seems to add more
power
back into the mix. It feels significantly stronger in acceleration and
pull than isopropyl. It also seems to have less tendency to cause
flutter
at part throttle and high flow rates. Denatured alcohol seems to have a
huge advantage in cooling effect over the other alcohols. At the same
flow
rates as the other alcohols boost will actually drop 2 lbs as the
second
nozzle opens at 12-13 lbs. No flutter is experienced but it seems that
the exhaust gases are cooled so much that the turbo actually slows
down.
This downside only seems to be noticeable at part throttle, medium
boost
when both nozzles are injecting. Denatured alcohol did not seem to add
power as the methanol did. No additional pull was felt as the second
nozzle
opened like it did with methanol. However, the super cooling effect of
denatured might yield an advantage with additional tuning.
At this time I feel
that a mixture of denatured and methanol might be the best of all
world.
Just what proportions of each alcohol to use for best results is a
question
mark. My gut feeling is that a 50/50 mix of denatured and methanol (dry
gas) along with distilled water may be the easiest to tune with.
It may be interesting
to note that at the rate of injection that I am currently using I am
injecting
nearly 1/2 gasoline and 1/2 alcohol/H20. I believe alcohol weighs
something
like 8 1/3 lbs. per gal. At 23 GPH injection that equals 191 lbs/hr. My
car uses 36 lb/hr injectors. At full flow that yields 36 X 6 injectors
= 216 lbs/hr. So 191 divided by 216 = .884 This equates to a
ratio
of .88 lbs alcohol/water for every 1.0 lb of gasoline. These figures
may
not be 100% accurate but they should be reasonably close.
Circuit
Operation
Two hobbs switches control
the set points for the two stage system. The first switch turns on at 4
lbs. boost. This switch activates the pump and injects alcohol through
a 10 GPH nozzle in the uppipe. No solenoid is required for this stage
since
the nozzle is connected directly to the pump. The pump operates in the
80-100 psi range. The pump is controlled by a relay activated by the
hobbs
switch.
At 14 lbs. boost the
second hobbs switch activates another solenoid. This relay turns on a
solenoid
which opens a path to the second nozzle. This nozzle is a 13 GPH nozzle
which is also connected in the uppipe.
A bypass or return
line always returns some fluid back to the tank and is used to control
injection pressure and to halt cycling of the pump on and off between
the
upper and lower pressure settings of the pressure switch that is a part
of this type of pump.
Upon deactivating the
system (no boost), the return line allows some of the fluid to
flow
to the tank. This drains the fluid from the first nozzle and some of
the
lines due to the height and placement of the alcohol lines. Therefore,
there is no siphoning of fluid through the nozzles due to vacuum. The
lines
are not totally drained and it is estimated that fluid remains within 6
inches of the low pressure nozzle due to the placement of the
nozzles
and lines. The same conditions apply to the second stage nozzle.
The fluid reservoir
holds approximately 3 qts of alcohol.mixture. This supply is enough for
roughly 2 minutes injection at full boost. This is probably enough for
8-10 quarter mile passes in the mid 12 sec. range although I'd suggest
refilling the tank more often.
The ball valve in the
return line is adjusted so that when only the first stage is activated
the indicator light attached to this stage will blink. This indicates
that
the pump is reaching the 100 psi setting and is shutting off until 80
psi
is reached and then turning on again. When the second stage is
activated
the light no longer blinks and another light also turns on to indicate
activation of the second stage. When the second nozzle is injecting
(along
with the first nozzle) the flow rate is more than double that of the
first
stage alone. This additional flow from the pump lowers system pressure
slightly and causes the pump to not reach the 100 psi limit. By
adjusting
the first stage just to the point of cycling, the system pressure will
be close to 100 psi when both nozzles are on but not quite high enough
to cause the pump to bounce off the 100 psi limit and start cycling.
System
voltage will cause this setting to vary a little bit at times.
Well, there you have
it. I hope some of this info proves valuable to those interested in
high
performance on pump gas.
Next Page
Back to index and my other alcohol
injection pages
