Marc Pedings's injector flow tester is working
great. Thanks again Marc. I notice the MSD and 2nd
gen Nippon Denso injectors work down to about
.8 ms. While the red and yellow RX8 injectors
quit around 1 ms. All of them draw about
.6 to .7 amps at 95% duty cycle.
Next step is plumb them up and measure the flow
as a function of pulse width and RPM. I still need
a few parts like a 50 psi fuel pressure gage which
I will order tomorrow from McMaster Carr.
Paul Lamar
Might I suggest an oil pressure gage. I've had no problems using them,
namely the same one for ~10 years.
Cheap & easy to get from your favorite auto part store.
Marc Pedings
Thanks for the tip Mark.
Paul Lamar
The next day. ---------------------------------
Got the system working. See the attached jpg. Found out a very interesting
fact. The RX8 red injectors quit working at 1 ms and below if you up the
fuel pressure much above 40 psi. I set it up with 1.1 ms and 1800 RPM
for an half hour at 40 psi and I got 75 ml. That is 150 ml per hour or about
4.8 ounces of fuel for both. Lets see that is .01875 per injector
or .0375 gallons for both, Since there are 6 pounds in each gallon
that is .225 pounds. At .55 pounds per HP per hour that is less than
about .4 HP. I doubt the engine will idle at .4 HP. What I saw on
the dyno was about 10 HP at idle so these injectors are rather
amazing. They are probably near useless for our purposes. I'll check
the mid range shortly just to make sure. They have a nice foggy
spray pattern however. Check my arithmetic.
The return line had very few air bubbles in it and they were moving fast in
a 3/8 ID return line so if you are not returning fuel to the tank you are drawing
from, this system will empty that tank lickity split, mostly while you are
taxiing out to take off. ALWAYS return the fuel to the tank you are
sucking from. I don't know what the flow rate was yet but I will test it
shortly. The MSD high pressure pump was drawing 8.75 amps at 12 volts.
I connected my auto parts store vacuum pump to the pressure regulator
and discovered a slow leak. What this means is the regulator will
not lower the pressure at part throttle (15 inches of Hg MAP) and
your engine is likely to run too rich. Hopefully putting Teflon tape on
the 1/8th pipe thread where the intake pressure goes into the regulator
will fix the leak. If you are having problems with Tracy's EFI system
this vacuum pump is a good investment to check for leaks in the
vacuum system feeding Tracy's pressure sensors.
Also I consider a good aircraft manifold pressure gage a must.
BTW McMaster Carr has some cheap 2.2 inch diameter gages with 1% accuracy
and silicone fluid filled for damping at about $15 dollars each. I am using
the 60 psi version for monitoring the fuel pressure. Works great.
Paul Lamar
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