ELECTRONIC FUEL INJECTION BASICS
Electronic fuel injection metering, when properly designed and
programmed, is today's accurate way to introduce fuel to an internal
combustion engine. With it's many sensors and input signals it can be
tuned to meet the demands of an engine operating over an extremely
broad range of conditions. The most commonly sensed inputs are:
1) Engine rpm
2) Throttle position
3) Barometric pressure or manifold absolute pressure (M.A.P.)
4) Air temperature
5) Water and/or oil temperature, and sometimes fuel temperature
6) Rate of throttle opening
When choosing an electronic fuel injection system there are many features and options, it can be confusing. Kinsler offers six manufacturers electronics, each manufacturer has several models. Our staff is here to help you sort through the 'mysteries' and give you the "real" information so that you can make an informed and educated decision. The first decision on EFI is which type of electronic control unit is the best suited for the application and budget. There are two basic types of multi-port EFI : Group and Sequential. Below is some of the basic information on the two types of systems so you will have a better understanding of their operation.
GROUP FIRED :
This injection system generally triggers a group of the injectors
simultaneously. The ignition system or crank trigger provides the
signal to the electronic control unit (ECU) for speed input and thus
The good thing about the group fired system is it's low cost. The
problem is that while some injectors will be close to properly timed,
others will not. If an injector is triggered at the wrong crank angle,
fuel may collect in areas of the intake port or cling to the runner
walls. When the intake valve opens, only a portion of the fuel injected
will be in suspension when the air enters the cylinder, the remainder
may be running down the port wall as liquid. This can cause erratic
mixture conditions to exist in that cylinder, especially during low
speed engine operation, due to the small amount of air movement in
the intake runner.
Since EFI injectors turn on and off, the interrupted flow causes
pressure waves to bounce around in the fuel rails, especially at wide
open throttle where the flows are the highest. In a group fired system
you often trigger two or more injectors at a time in a given fuel rail.
The simultaneous pluses can reinforce each other at some rpm to give
unusually high pressure pulses, sometimes causing poor fuel
distribution. It often helps to run a larger diameter fuel rail. Kinsler
extruded aluminum fuel rails are .680 inch inside diameter. A large
diameter smoothes out the pulses quite well when compared to
smaller sizes. Running higher overall system pressure also helps. We
often run about 72 psi instead of the more normal 36 to 43. The
amplitude of the pressure spikes will remain about the same, but will
be relatively smaller based on the percent change in injector flow. We
also like the better atomization achieved with the higher pressure and
it sometimes gives better power and economy. Be careful about
running the fuel pressure too high, as some ECUs don't have enough
current to lift the disc or pintle in the injector consistently off the seat
against this added pressure, which will result in poor fuel distribution.
Be sure your fuel pump is capable of supplying the engine with the
volume required at a higher fuel pressure.
SEQUENTIAL FIRED :
This system triggers each injector at a precise crank angle on every
cylinder, usually near top dead center overlap (intake valve opening).
This improves idle quality, low speed engine smoothness, and fuel
economy. Some systems can even be programmed for different
injection phasing for each speed site in the fuel map.
Triggering a sequential system is more complicated than a group fired
system, as it requires a separate triggering signal to reference the start
of the injector firing sequence. This signal is typically generated once
every two crankshaft revolutions on a 4 cycle engine and is most
commonly referred to as the " CAM" or "SYNC" signal. The sequential
system also requires a "Crank" signal, generated at a specific crankshaft
angle on each cylinder. This signal is used to calculate engine rpm and
crank angle position for injector firing and ignition triggering from the
ECU. "Crank" and " CAM" signal requirements will vary with each
manufacturers ECU. Most manufacturers required either a sine wave
signal, typically generated by magnetic sensor, or a square wave signal,
typically generated by a Hall effect sensor.
A large selection of high and low resistance injectors are available.
Flows ranging from 15 lb/hr @ 45 psi to 200 lb/hr @ 70 psi.
Flowing and grouping sets of injectors is available.
Pressure relief valves, fixed and adjustable ranges from 20 -160
psi. Vacuum/boost referenced, gas or methanol.
Fuel filters, Billet and stainless steel housings,
disposable /replaceable 10-micron paper or cleanable stainless
steel elements. For gas, alcohol, and nitro. Replaceable fitting,
available from 6AN to 12AN.
Electric fuel pumps Flows from 200 lb/hr to 1000 lb/hr. AN and
Flow testing available.
1,2, or 3 Bar MAP sensors. Large selections of throttle position
sensors. Selection of sensors for air, water, and oil temperature.
Weather-Pack connector-flat, square, round- 1,2,3,4,5,6 pin,
terminals. Mil-spec connectors and pins.
Kits for any number of cylinders and configuration.
Fuel rail material, weld-in bosses, stanchions, machining one-
step cutting tools.
Group and Sequential
Distributor less Ignition control
N2O Control (1,2,3 Stages)
Wide band exhaust sensing