yep, here's the deal.....the compounds are only days from going in, but
I wanted to try chemical intercooling before I went to the extreme of
plumbing in another air to air.
This shows how far the nozzle carrier and feed pipe extend into the inlet tube
here's the two intake horn nozzles....an 865 cc/min and a 520 cc/min (@
200 psi). Because I have the intake nozzles staged later than the
pre-turbo nozzle, I have also placed a solenoid valve in line which is
controlled by a Hobbs switch located in the intake manifold, which is
set at 30 psi to turn on the intake nozzles.
This shows where I mounted the pump...behind the PDC on the fender, and the resevoir.
here's the hobbs pressure switch under the air horn that enables the air horn nozzles.
here's the pre-turbo assembly. Note another pressure switch that brings
the pre-turbo nozzle on at 20 psi, another solenoid valve to keep it
isolated, and cut down on afterbleed
here's the pre-turbo nozzle in action. It is a furnace nozzle rated at
5.5 gph, though at 220 psi closer to 8 gph (500 cc/min). It is a hollow
cone to not flood the compressor wheel nut, and an 45* angle to stay
close to the center of the wheel. The standard spec of the nozzle is a
5.50/45*A. 5.50 being 5.5 gph at 100 psi, 45* being the discharge
angle, and "A" denoting the cone type...hollow in this case
here's a close up of the same picture above. Note the narrow angle of
the spray pattern keeps all the water towards the center of the wheel,
negating any tip erosion. Note as well how the hollow cone of this
nozzle nicely works around the nut, even though it is very close to the
wheel. This nozzle sprays at 6 microns @100 psi, which is below the
size that supposedly starts to cause tip and leading edge erosion. Time
will tell, but wheels are cheap compared to the awesome advantages of
spraying, especially in compounds, as I intend to finish in the next
few weeks, to act as an intercooler.
so there you have it....now for the results. I really wish I had a dual
channel IAC gauge, maybe in the near future, but for now, the seat of
the pants as well as the boost and pyrometer tell enough of the tale to
know the results. In high gear at a sustained 20 psi, and upon
activation of the first stage (pre-turbo), boost increased to 26 psi
without any accelerator change...the compressor section definitely
became more efficient, acting as a larger compressor. As EGT's aren't
high (800*) at this point, the turbo is in it's highest efficiency
state, and the aftercooler is fully capable of cooling the current
intake charge temps, there is no other aspect that can explain the
increase in manifold pressure other than the injection pre-turbo
obviously made a big difference in the compressor section of the turbo.
Now under full acceleration at the 35 psi ceiling I have the turbo set
at, my net manifold pressure climbed to 43 psi with the full system in
operation, and egt's dropped by about 300*. I could never use more than
about 2/3 throttle in 5th, or temps would pin the gauge. With the
injection on, I max out at 1400*....still a bit high, but the compounds
will take care of that.
So there you have it. Come to your own conclusions, but I believe
pre-turbo injection just might be a way to increase a small
compressor's efficiency past any other means available. And the benefit
of pre-turbo injection will be even more invaluable in compounds to
cool the air between stages without having to fabricate an air to air
intercooler. By hitting the secondary with water, the end heat result
will be well within the aftercooler's ability to efficiently casue a
reduction in charge air temp. Follow that up with some post cooler
injection and intake temps can be way down and consequently air mass
very high. This will enable us to keep the compressor(s) in their peak
efficiency range, and not push them into the upper reaches of their
map, especially the secondary. I will know more when I can swing an IAT
gauge as well as incorporate these theories into my compounds. Until
then let the opinions and debate ensue...........
Chris
