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Information concerning the
tuning of your Alfa Romeo |
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Ever since
the early days of combustion engines it was a necessity
to adjust the air-fuel mixture as well as the ignition
timing to the current operating conditions.
The drivers of Henry Ford's ,"Model A", had
adjustment devices for ignition timing and fuel supply
mounted to the steering column, to manually influence
the engines performance.
Nowadays all modern automobiles are equipped with electronic
engine management. |
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This
applies to the , "Central Port Injection" (Monojetronic),
which functions similar to a carburettor, just like to
the far more efficient "Multi Port Injection",
as well as to modern diesel direct injection systems,
such as common rail systems in conjunction with boost
control. |
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Click on the links below to
take you to the relevant section. |
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The Electronic Control
Unit (ECU) |
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The
ECU is responsible for the entire engine management.
It measures, checks and controls all important functions
of the engine under consideration of the current
load condition and in dependence of all environmental
parameters, such as ambient, engine coolant and
oil temperature, intake air density etc.
This vital information concerning the current operating
conditions, are gained by sensors, that very accurately
pick up pressure, temperature, revolutions, speed,
and air mass (density) signals. In accordance to
this information, the ECU processes the ignition-,
injection-, boost-, and lambda patterns, that are
programmed on to a chip (EEPROM) inside the ECU
and i.e. determines, in dependence to the load condition
and other environmental parameters the ideal ignition
timing, the necessary fuel amount in respect of
the optimal injection timing and the corresponding
boost.
During the process of chip tuning, this database,
programmed on to the EEPOM(Chip) inside the ECU,
is optimized. All relevant patterns and identifiers
for, i.e. injection and ignition timing, boost control,
load limitation and exhaust emissions, are being
monitored over the entire rpm range of the engine
and then changed within certain limits, in dependence
to load and engine-rpm, so that the maximum horsepower
and torque output, in consideration of the durability
of the engine, as well as the least fuel consumption
stand in an optimal relation to each other. Hereby
we gain horsepower as well as a significantly higher
torque output.
Generally one can say, that for turbocharged engines
an increase of horsepower and torque of 20% to 40%
and for normally aspirated engines 8% to 12% is
realistic. In both cases acceleration, top end speed
and elasticity improve significantly.
Moderate tuning will not have any effect on the
durability of the engine as well as drivability
of the car, as long as correct maintenance is provided
and the engine is operated in a responsible manner.
This can be applied to both, stock and tuned engines.
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Tasks of the ECU |
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A)
Retarding and advancing ignition timing
For an economic and efficient fuel combustion, it
is important, to, under all possible driving conditions,
compute the correct ignition timing in dependence
of engine-rpm, load and other relevant parameters
for diesel engines the right injection timing (pump
timing).
B) Dwell control
In dependence of the engine-rpm the time between
ignition trigger signals varies. To ensure a constant
ignition energy it requires a certain ,,Primary
Current" to flow through the windings of the
ignition coil. To sufficiently build up a magnetic
field inside the coil, it requires time. |
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The time delay from switching to interrupting the
primary circuit has great influence on the voltage
induction into the secondary circuit of the ignition
coil the higher the engine-rpm, the shorter the
delay from switching to interrupting the primary
circuit, the less energy is inducted into the secondary
circuit. This may lead to engine misfire at high
rpm.
C) Detonation detection
On all modern automobile engines the compression
ratio is rather high in order to achieve higher
torque output and better fuel economy. Due to high
compression ratios the risk of an uncontrolled inflammation
of the air-fuel mixture is, especially under high
loads running at high rpm, potential is higher.
Detonation causes severe engine damages. Whenever
detonation is detected, the ECU will retard the
ignition timing for the particular cylinder.
D) Fuel injection
In accordance to the signals air-mass (air-flow),
rpm, load and correctional factors such as ambient
as well as coolant temperature etc., the ECU determines
the momentarily needed fuel amount and injection
timing. This increases fuel economy and reduces
exhaust emissions and in the mean time is responsible
for a higher specific engine output.
E) Lambda control
One of the previously mentioned correctional factors,
is the lambda-signal. The lambda sensor located
in the exhaust system, in front of the catalytic
converter constantly measures the remaining oxygen
in the exhaust gases. This signal is used by the
ECU, too, under all driving conditions except ,,
Full Load", adjust the air to fuel ratio to
,,Lambda 1" (14,8 kg of air to 1kg of fuel)
and ensures the highest degree of effectiveness
of the catalytic converter and at the same time
lowest exhaust emissions. Under full load condition
i.e. top end speed, the Lambda system, in order
to gain higher engine output and prevent severe
engine damage due to leanliness of the fuel-mixture,
is deactivated.
F) Idle-speed control
In- and decreasing of internal friction related
to varying engine temperatures and engine wear as
well as operating conditions such as i.e. engagement
of the air-conditioning compressor, will lead to
a strongly fluctuating idle-speed. The engine rpm
signal and current operating information, such as,
idle contact, a/c engagement, gear detection (Park,
Neutral- or Drive mode of the automatic transmission)
etc., are used by the ECU to calculate the appropriate
idle speed. Parameters for hot and cold start, in
dependence of environmental conditions, are implemented
i.e. High Idle during engine-warm-up.
G) Boost control
On cars with turbocharged engines the ECU calculates,
in reference to the load indication, the pressure
and the currently needed air charge- volume and
adjusts, in dependence of the corresponding sensor
signal, the appropriate boost.
H) EGR - Exhaust Gas Recirculation
In order to improve the " Exhaust Gas Quality"
(reduction of NOx), exhaust gasses, by a certain
volume, are inducted into the intake manifold under
partial engine load.
I) Service, security and surveillance
functions
- Monitoring of currently adjusted values, to avoid
malfunction.
- Strict surveillance of "Drive by Wire"
systems, meanwhile installed into all modern automobiles
as "E- Gas" (Electronic Gas Pedal).
- Recognition and memorization of system malfunctions.
J) Top end speed governor and
rpm limitation
One very important function of the ECU is rpm limitation.
Due to enormous mass and centrifugal forces, applied
to all rotating and oscillating parts of the engine
at high rpm, the maximum rpm range of a particular
engine must be constructionally determined and programmed
on to the EEProm. Excessively exceeding this max.
value i.e. 6500rpm, will eventually result in severe
engine damage. The rpm signal is constantly monitored
and in case the programmed value of i.e. 6500 rpm
is reached, the ECU, either by reduction or interruption
of fuel supply or on modern E-gas systems, reduction
of throttle position, or by ignition switch-off,
prevents exceeding of the max. rpm value. The same
parameters apply to the top end speed governor.
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Why is it not originally equipped
this way from the factory? |
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During
the development of an automobile the manufacturers have
to, in many respects, find compromises in terms of fuel
efficiency, horsepower output, drivability and these days,
the most important issue, exhaust emissions. Factors like
fuel quality, maintenance, operational circumstances etc.
as well as financial aspects i.e., insurance classifications,
have to be taken under consideration. The manufacturers
have to assure operational reliability for the final product
worldwide, which means, that in most cases the actual
engine potential is not reached.
Therefore the ignition, injection, boost, - etc. patterns
programmed, are on the "save side".
Furthermore almost all manufacturers offer mechanically
identical or almost identical engines with varying horsepower
output. The gain in output is mainly achieved by software
changes. The stronger and more expensive version of a
particular model car, is often brought out on to the market
1-2 years later after the initial presentation. This is
done to repeatedly draw the attention of customers, who
already bought the previous model and might be willing
to trade in and purchase the new release.
If you are willing to regularly perform car maintenance
and loose some economic efficiency under full load, then
a enormous output potential will be available to you.
Our aim is, to significantly increase torque and horsepower
output over the entire rpm range of the engine, especially
on turbo charged engines. Here you will have the impression,
after the optimization is done, to own a entirely different
car or to have changed into the next higher vehicle class.
Now you are an expert on ECU management! how about taking
some easier steps, but unfortunately not usually as instantaneously
effective.
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Performance and Air Flow |
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Components
that influence airflow into the engine are the:
Air filter
Intake air piping
Mass air sensor (if applicable)
Throttle body or carburettor
Intake manifold
Camshaft
Intake port and valve of cylinder heads
Turbo's compression, section, and supercharger (if applicable)
Components that influence airflow out
of the engine are the:
Exhaust valve and exhaust ports of the cylinder heads
Camshafts
Exhaust manifolds
Turbo's turbine (if applicable)
Exhaust tubing
Catalytic converters
Muffler
When these components are modified to increase flow out
of the engine, pumping losses are reduced. Pumping losses
refer to the amount of HP used to push the exhaust gases
out of the cylinders on the engine's exhaust stroke. Since
less HP is used to get the exhaust out of the engine,
more horsepower is available at the flywheel. An added
benefit of reducing pumping losses is that fuel mileage
will also increase.
No matter how much additional air is forced into the engine,
no additional HP will be made unless additional fuel is
also added. The energy that makes HP in an engine comes
from the fuel, not the air. In general, every two HP produced
requires one pound of fuel per hour. When mods are performed
that increase airflow into the engine, more air is available
for the combustion of fuel. The combustion of the additional
fuel is what translates into additional HP.
Air flow is not just influenced by the size (area) of
the paths it takes into and out of the engine. It is also
influenced by the speed at which it moves.
Specific Port Flow (cfm) = Flow Velocity (ft/min) x Average
Path Area (ft^2)
Whenever an engine mod increases the average area
of the airflow paths into and out of an engine, there
is a chance the velocity of the flow will decrease. Most
of the time the velocity decrease is very small compared
to the area increased, so flow is increased (example -
most aftermarket exhaust systems). If things are taken
too far, the velocity will decrease more than the area
increases, so flow is adversely affected (example - four
inch exhaust system on a 1.6 litre engine)
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