Yes, that's all true for a typical auto fuel injected engine. The pressure
control problem is still the same, i.e. maintaining the correct pressure to
the engine-fuel system. A recirc system controls pressure better at part
loads than a stop and go control a carb system without it if the proper flow
control elements are used.
My sequential fuel injection is a custom Autronic system tuned for the
operating parameters of a air-cooled turbo charged engine.
Ron
----- Original Message -----
From: "Colin & Bev Rainey" <crain...@cfl.rr.com>
To: "KRnet" <kr...@mylist.net>
Sent: Sunday, February 08, 2004 5:40 PM
Subject: KR>Sequential fuel injection
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
crain...@cfl.rr.com
or crbrn9...@hotmail.com
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