FUEL INJECTION BASICS
Typical Enderle Fuel system
Enderle fuel system operation - Fuel pump driven from cam pumps through
the shut off valve to the barrel valve. The main bypass pill/jet is located in
the barrel valve. The pill limits the amount of fuel being RETURNED to the tank.
The remaining fuel is sent directly to the nozzles. The nozzle pressure is
regulated by the spring in the barrel valve popit. Because the fuel pump speed
is dictated by cam speed, there becomes a point in which the engine cannot
utilize all the fuel being sent to the engine at high rpm. The High-speed bypass
is utilized to bypass additional fuel at high rpm.
Hilborn fuel system operation - same as Enderle except the Hilborn barrel valve
does not have provisions for the pill, but rather utilizes a separate pill can
and poppet.
Idle Control
The idle mixture is controlled by the turnbuckle on the side of the
injector. To richen the idle, rotate the turnbuckle towards the rear of the
injector, (shortening the linkage leans the mixture, lengthening richens the
mixture). This adjustment is for idle and throttle response only and has no
effect on full throttle. The idle speed is controlled by the butterfly shaft
stops on each side of the injector.
Main Bypass Jet
Each
fuel injector is furnished with a set of bypass pills. This bypass controls the
fuel mixture at full throttle and has little or no effect on the idle. The
bypass pill is located under the 9/16 hex plug on the metering valve. Use a
smaller bypass to richen the fuel mixture and a larger bypass to lean it. When
installing the bypass, make sure that it is seated at the bottom of the threads.
High Speed Bypass System
Certain applications require the use of a hi-speed lean out. This
consists of a bypass pill controlled by a high pressure check valve which leans
the fuel mixture at high RPM. The check valve pressure is adjusted with shims to
tailor the fuel curve to the engine's requirements. The check valve opens when
the fuel pressure is able to overcome the spring tension. The bypass pill
controls the volume of fuel returned. Adding shims will make the check valve
open at a higher RPM. Removing shims will make the check valve open at a lower
RPM. The hi-speed should be thought of as a fine-tuning device. The main bypass
pill is the primary control of the overall fuel mixture.
Maintenance
The fuel system should be drained between races. It is important to
lubricate the entire fuel system, particularly the fuel pump and blower rotors,
with WD-40, light oil or some other type of lubricant. Remove the inlet line
from the metering valve and lubricate the metering piston to prevent stickiness
and drying out.
WARNING
You must use a 3-way fuel shutoff with a return to the fuel tank. A
2-way style shutoff will damage the fuel pump.
Baseline - Set butterflies at .010-.012 open. Set leak on
barrel valve at 65-70%. Nozzles should be sized large enough that the main
bypass is between .120 and .150. main spring about 5 psi when checked with air
pressure. High-speed bypass spring about 28-30 psi and a pill half size of main
pill.
