Ron & netters,
Sequential fuel injection if from an auto configuration requires a high
pressure/high volume pump, very different from the Facet pumps that we are
talking about for carbs. In order for the injection system to work properly the
fuel rail pressure must be maintained between 30-60 psi for most manufacturers.
The early Volvo, & VW/Audi injection systems required as much as 80 psi. This
is because the computer is going to "pulse" open the injector so many times a
minute, and the rail pressure determines how much fuel is delivered with these
pulses, or openings. Unlike an airplane injection system that is set for
constant flow and volume is determined by the flow regulator attached to the
throttle, the ECM makes the decision based on throttle position, manifold
pressure, coolant temp, and oxygen sensor readings. In very late model they
use mass airflow meters. These systems provide for all engine conditions by
changing the pulse width or times of opening, or increasing line pressure or
both. The line pressure is regulated by a pressure regulator which has a
vacuum connection to the intake, and when manifold vacuum is lost during
acceleration, this diaphragm called the pressure regulator, closes to make more
fuel pressure available to the injection system. Since they use a high volume
rotary pump it is essential that recirculation back to the fuel tank is
maintained, or the pump will burn up in a short time. The return line must
also be located in the tank below the fuel pickup in order to prevent foaming
of the fuel, or else you will get air into the fuel system, and cause cutting
out and surging. Some carb pumps can be used for TBI or throttle body
injection systems, since they typically use only about 10-15 psi fuel pressure.
But in any injection system I have seen in autos, re-circulation back to the
fuel tank is critical for proper system operation, and pump life. This systems
when right are some of the smoothest running and power producing, but they tend
to be complicated to set up & maintain. For instance if you decide to try and
help your system stay cool and install a 160 degree thermostat, instead of the
factory 195 degree, your engine will stay cool, but the computer will always
see a cold engine in flight and will constantly have the engine running richer
than it should. This will definitely shorten its life. Better to have more
radiator than you need and run the hotter thermostat. Then your engine runs at
a more constant temp no matter what, and lasts alot longer. Other questions
can be made directly to me if anyone has them.
To the new guy about the A 65, it is my understanding that that engine is a
poor design, too heavy for its output, weak at best in durability, and too
expensive to maintain for what you get. Try a VW, Corvair, or C 85, or O-200
if you must have a certified engine.
Colin & Bev Rainey
KR2(td) N96TA
Sanford, FL
[email protected]
or [email protected]
http://kr-builder.org/Colin/index.html
