|
Tech
| Fuel Injection Tuning Tweaks
CIS injection (such as K-Jetronic or
KE-Jetronic) is one of the simplest and
most elegant fuel delivery systems around.
Once set up, the system requires little
mainte- nance other than keeping the fuel
filter clean. Vehicles from 1976 to 1980
in California and as late as 1981 in other
states have the basic K-Jetronic system
which is easily adjusted. Versions of
these vehicles came with catalytic
converters early in California, and later
elsewhere.
In mid-1980, Volkswagen changed to the
K-Jetronic system with Lambda. This
system, using an oxygen sensor (Lambda
sensor), very effectively aids in reducing
engine emissions while leaning down the
fuel mixture and gaining economy. The
Lambda system maintains an average of 50%
duty cycle which approximates a 14.7:1
air/fuel ratio.
In 1983, Volkswagen introduced the 1.8L
engine. This unit has a larger air flow
sensor, as well as a modified Lambda
circuit. This modification is a
microswitch on the throttle body which, at
full throttle, disengages the oxygen
sensor from the circuit (termed going
"open loop"), changing the duty cycle to
65%, enriching the fuel mixture.
In 1985, Volkswagen and Bosch made an
update to the CIS system. The warm-up
regulator, along with some other
components, were removed. This new
injection system, known as KE-Jetronic or
CIS-E, works on the same principle as a
speaker magnet. As more electrical current
is added to one side of the fuel plate,
extra fuel is drawn into the system. Since
it has a "closed-loop" idle circuit with
fixed parameters for idle running, this
system should not be modified by making
manual changes. If the system is adjusted
incorrectly, the control unit can overheat
and burn-out. Add-on circuit boards which
control the input current for this system
are the only sensible approach to fuel
enrichment.
In 1988, VW introduced the Digifant II
system (a pulsed, non-CIS system) on the
Golf and Jetta models. Digifant II has the
ability to control ignition mapping as
well as fuel system parameters. This
Motorola controller-based system brings
with it new obstacles when injection
modifications become necessary.
In 1990, VW introduced KE-Motronic on
its 2.0L 16V engine. It is a CIS system
utilizing a Motronic-based controller for
both fuel and ignition maps. Here is where
computer chip tuning started with
VW's.
In that same year, The G60 Corrado was
introduced to the US, using Digifant I, a
system more akin to other Bosch systems
than Digifant II. Both fuel and
knock-sensor ignition are controlled with
one ECU, as with Motronic.
In 1992, VW began using full fledged
Bosch Motronic injection on the VR6, and
later, on the US Golf 3 and Jetta 3 cars.
Motronic EFI uses a less restrictive,
"hot-wire" mass air sensor, rather than
the mechanical airflow sensor used on CIS
systems. The advantages of a pulsed
injection with ignition map control are
many. Chip tuning on VW's has entered a
new era. Good horsepower can be derived
from the CIS system, and it is capable of
handling very large horsepower demands. On
CIS cars which do not have the Lambda
system, the system pressure can be
adjusted to optimize the cars perfor-
mance. We recommend adjusting your
injection to 5.4 bar system pressure by
using our shim kit and fuel pressure
gauge. Later model cars with Lambda work
well leaving the Lambda sensor (oxygen
sensor) in the circuit and rarely need to
be adjusted anyway.
|
site
map
| shipping
information
| order
info
