Water spray injector system
My spray injection system is built from a
windshield washer kit from
JC Whitney.
The nozzle is a modified spray paint can nozzle, attached
to a cut-down washer nozzle. This is mounted in the air intake tube
just downstream of the mass airflow sensor (MAFs don't like getting
wet). I wanted to get as much mixing of the air and water as possible
before it got to the intake manifold.
The plan is to activate the pump from a switch triggered at wide open
throttle, but for testing I've just run the wires into the passenger
compartment, where they're hooked to a push-button switch and a
cigarette lighter plug for power.
On Feb 5, 2006, I was able to do some testing with the system.
The suction cup on my G-Tech Pro failed, so I was forced to do
some less-precise 0-55 mph timings with a stopwatch. The testing
was done on a dry asphalt road, calm winds, and an outside temp
of 12F. The injected runs were done by pressing the injection button,
waiting about 1/2 second for any air to be purged from the line and
the water to start flowing into the intake, then floor the throttle
while simultaneously starting the watch. When 55 was reached, the watch
was stopped, then the throttle and button were released. All runs
were done from a complete stop, no wheel slippage was noticed.
| Injection On |
| 13.51 |
| 13.53 |
| 13.60 |
| Injection Off |
| 13.95 |
| 13.86 |
| 13.98 |
So, injection on averaged 13.55 seconds, while injection off
was 13.93. This works out to a difference of about 2.8%. For a
stock engine running an assumed 210 horsepower, that would be
a gain of just shy of 6 horsepower. Not too shabby for a system
that cost me less than $40 to put together, at least in test
mode.
Update: July, 2006. I added a microswitch to trigger the system
automatically at about 75% throttle. I then ran more tests:
| Injection On |
| 17.30 |
| 17.13 |
| 17.35 |
| Injection Off |
| 17.42 |
| 17.20 |
| 17.46 |
These runs were made on a day with the temperature at 85F, relative
humidity at 37%, and a 13 mph wind. All runs in the same direction.
The power increase works out to either 0.6% or 0.7%, depending on how
you calculate it (about a 1.26 horsepoewr increase). This,
while measurable, is much less significant compared
to the February test. I suspect this mostly has to do with the
makeup of the injection fluid: the winter test used a mix of distilled
water and rubbing alcohol, so it wouldn't freeze. The summer test
used pure distilled water only. I'm guessing that the alcohol acted as
additional fuel, giving a power boost over water-only.