Engine plant model_development for hil system and application to on-board dia...
B11127 mano c ice tuning
1. Internal Combustion Engine Tuning
Mano C. (B11127)
IIT Mandi, Mandi
Email: manoc1993@gmail.com
(Name and email of Reviewer: Mahendra Singh Meena
mahendra_singh@students.iitmandi.ac.in)
Contents Outline
1. Introduction: What is engine tuning?
2. How is engine tuning done?
3. Functioning of the ECU
3.1 Data logging in perspective
4. Engine tuning parameters
4.1 Spark/ignition timing
4.2 Lambda/air-fuel ratio
4.2.1 Throttle body control
4.3 Valvetiming and lift
4.4 Boost pressure
5. The caveats
6. Prospects: What does the future hold?
7. References
2. 1. Introduction:What is engine tuning?
Chip tuning refers to changing or modifying an erasable programmable read only memory
(PROM)chipin an automobile's electronic control unit (ECU) to achieve superior
performance – this could be more power, cleaner emissions, or better fuel efficiency.
Modern engines are equipped with an engine management system (EMS)/Engine Control
Unit (ECU)whichcan be modified to different settings, producing different performance
levels. Manufacturers oftenproduce a few engines whichare used in a wider range of models
and platforms, and this allows them to sell automobiles in various markets with different
regulations without having to spend money developing and designing differentengines to fit
these regulations.
Operationslike settingthe idle speed, fuel/air mixture, fuel flow,spark plug and distributor
point gaps, and ignition timing on modern engines are electronically controlled.
Engine tuning is typically done after adjustments to the car’s stock configuration -
aftermarket camshafts, fuel injectors, supercharger, turbocharger, nitrous, higher
compression pistons, ported cylinder head, intake runner, header, and/or exhaust - have
been made. Withoutre-mapping the fuel tables, some of the performance gains from the
modifications may not be realized.
The larger and more powerful the engine in the first place, then generally the more gains
you'llget fromremapping. The cost of an ECU remap in India starts at around 70,000 INR
and goes up to around 3 lakh INR depending on the capacity of the engine, level of tuning,
and remapping brand.
Figure 1: An ICU chip
Evena car getting a relatively low power gain from a remap will actually be livelier to drive.
The engine's response under acceleration and its torque curveare the primary reasons for
getting into chip tuning.
3. 2. Howis engine tuning done?
The most common way to "upgrade" the electronic controlunit is using either plug-in
modules as mentioned aboveor using a specialist tuner whowill use an On Board
Diagnostics (OBD)Flash tool. These devices generally plug into the diagnostic port although
in some cases the reprogramming is done directly on the circuit board. Maps are supplied by
tuners. Software upgrades will generally be less expensive than either ECU or chip
replacement.
i. ECU Flashing: Most new cars are able to be “flashed” through the factory OBD-IIscan
port. Flash tuning an ECU allows fordirect control overall functions similar to a modified
stockECU, but without the need to remove/modify the ECU.Flash tuning is oftentimes
the best choicefor tuning on newer cars due to being able to retain emissions
functionality and cost, reduce time, and provide a one-size-fits-all standard map.
ii. Modified stockECU: A modified stock ECU is typically one that is EPROM chip based.
Using a real time programmer in place of a chip replacement, a custom tune can be
performed. A modified stock ECU allows fordirect control over all functions of the
factory ECU,so excellent performance, fuel economy,and overallrunning can be
achieved.
Another alternative is to have a custom remap for yourvehicle. The car/van is connectedup to a
laptop just like with a standard map, but instead of a one-size- fits-all map being uploaded, the
parameters foryour individual vehicle can be altered. This is usually combined with runs on a
dynamometer, so your vehicle'sperformance and fuelling all the way through the rev range is
checkedand tweaked.
3. Functioning ofthe ECU:
The ECU, the manager of processor-intensive functions,uses closed-loopcontrol, a control
scheme that monitors outputs of a system to controlthe inputs to a system, managing the
emissions and fuel economy of the engine (as well as a host of other parameters). With the data
it gleans fromsensors, it performs millions of calculations each second, including looking up
values in tables to decide on the best spark timing and determining how long the fuel injector is
open. A modern ECU might contain a 200-MHz processor at its core.
3.1 Data logging in perspective:
Data logging is essentially the ability to accumulate values of parameters - such as engine rpm,
coolant/air temperature, engine load (PSI),air/fuel, injector duty cycle,throttle position, vehicle
speed - related to engine operation. All of these parameters can help you get the maximum
performance for a given application, as well as be vital in troubleshooting issues that arise.
Data logging can show something as simple as boost leak, being too rich/lean, or not being full
throttle. It gives youthe ability to compare runs, and make changes to the tune or other settings
4. based on results. You can achieve much greater results in much shorter time when having as
much information as possible on engine/car performance. Some of the sensors used are:
1) Camshaft position sensor: The camshaft sensor determines which cylinderis
firing to establish injectorsynchronization and coilfiring sequence.
2) Intake Air Temperature (IAT)sensor: The air charge/manifold temperature
sensor is used by the computer to measure air density for fuel mixture control.
3) Lambda (AFR)sensor: It monitors the proportion of oxygen in the exhaust
stream.
4) Crankshaft speed sensor: It monitors the position or rotational speed of the
crankshaft.
5) Coolant temperature sensor: It measures the temperature of the engine coolant.
6) Knock sensor: When a given frequency of knockis detected, it in turn sends a
signal back to the ECU warning of detonation, and the ECU retards timing.
7) Throttle position sensor: Itsends a voltage signal to the computer indicating throttle
angle and speed of movement data.
8) Mass airflow sensor (MAF):It measures the amount of airflow entering the
intake manifold using a heated grid or wire.
9) Manifold absolute pressure sensor (MAP):It converts engine vacuum/
manifold pressure to an electrical signal so the computer knows how much
load the engine is under.
5. 10) Boost pressure sensor: It is a deviceto control the boost level
produced in the intake manifold of a turbocharged or supercharged
engine.
The changes in the readings of these sensors manifests itself withthe aid of actuators (ignition
coils, fuel injectors, cooling fans, etc.) whichrespond to the ECU’s commands.
4. Engine tuning parameters:
4.1 Spark/ignition timing:
Differenttiming may result in differing performance. However,to cope with advanced timing,
one must run high-octane gasoline to avoid pre-ignition detonation. Manufacturers design fora
specific timing and this may limit performance accordingly.
Ideally, a spark map is developed on a chassis-loading dynamometer. The car is run on the
dynamometer and for every RPM and load, the ignition timing is advanced by tweaking the ECU
until torque starts to drop off.The point right before the torque drops off is called MBT or mean
best torque. Most engines, especially high-compression and forced-inductiontypes, will
encounter knockbefore reaching MBT. Typically,the low-loadignition timing that the engine
uses stock is best. It's really only under high load and with higher-compression
pistons, etc. that other areas in the spark map might need to have some ignition advance
removed.
IAT sensor: The higher the intake air temperature, the higher the chances of knock.If intake
temperatures can be lowered, more ignition-timing advance can be added, which adds power.
.
Figure 2: Ignition timing tuning window
6. Electronic Timing Controllers:
The programmable ECU allows us to make changes at any point of the map we encounter knock,
leaving the rest alone. With the lower end types, you may have to retard the timing forthe whole
RPM map, even though it may only knockat 4500 RPM.
4.2 Lambda/air-fuel ratio:
Most manufacturers tune fuelmaps foroptimum emissions (running rich to protect the catalytic
converter)and fuel economy purposes which can limit performance. This will make the power
delivery a lot more linear, which in turn willmake the vehicle feel a lot livelier to drive and the
engine more flexible.
When we remap a vehicle, especially when fuel saving is the priority,we focus on improving the
low-end torque in particular and widening the power-band as far as we can. This increase in low
end torque will mean less throttle pedal input is required to maintain cruising speeds, when fully
laden or when on a gradient. It willalso mean that the vehiclewill be more comfortablein higher
gears at slowerspeeds as wellrequiring fewergear changes overall.
One of the most important and basic engine tuning aspects is dialling in the AFR or air-fuel ratio.
Unfortunately,14.7:1 is no magical AFR that will net maximum power. Ideally, an engine should
be tuned to have different AFRs under different engine loads and RPM. Rich mixtures control
knocking but yield lowerfuel efficiency,whereas lean mixtures increase emissions and lead to
knocking. For naturally-aspirated cars, AFR's should usually range from 14.7:1 at idle and very
light throttle, 14:1 to 13:1 at part throttle, and around 12.5:1 at wide-open throttle. Engines
under boost usually are tuned to run rich, which leaves extra fuel in the chamber forcooling and
reduces the chances of detonation. On pump gas (91 octane), conservativeAFR targets under
boost (around 11:1 to 12:1) are used.
Fuel maps:
This is a grid with engine speed on one side and engine load on the other.
Figure 3: Air-fuel tuning window
7. The MAP (or MAF)sensor signal tells us engine load and, based on this and the engine speed, the
ECU looks up the two coordinates on the fuelmap and injects the correctamount of fuel.
Programmable ECUsallow youto change these values and change the AFRs throughout the
operating range on the engine.
4.2.1 Throttlebodycontrol:
The throttle response, the response of the throttle body to stepping on the accelerator pedal, can
be varied to provide different driving experiences. These different settings coded into the ECU
chip lead to the availability of different driving 'modes',which provide diverse throttle response
setting from whichto choose. The throttle position sensor comes into play here. Some different
modes are:
a) Normal mode: This is the default mode of throttle response that comes with the stock engine.
It ensures a balance between performance and efficiency.
b) Sport/Dynamic mode: In this mode, there is aggressive throttle response (whichtranslates
to quicker acceleration)and the gear shift points are remapped into the ECU at higher RPMs for
a sporty feel. This means that fuel efficiency takes a hit by letting the engine to rev higher.
c) Economy/Ecomode:Here, the gear shift points are moved to lower RPMskeeping in mind
fuel consumption and emissions norms. The accessory load in the form of running the air-
conditioner is kept a minimum.
Eco-friendly carenthusiasts are obsessed with the Economy mode, whereas those crave the
adrenaline rush would swear by the Sport mode.
Figure 4: Different fuel-air ratio modes
The fuel map shown above is equipped with two map sets: a primary and a secondary. These are
the two different 'modes' in whichthe fuel willbe supplied differently,and in accordancewith
8. the engine RPMand load.
4.3 Valve timing and lift:
Variable valvetiming and liftelectronic control is necessary to improve the volumetric efficiency
of an engine.
It provides the engine with multiple cam lobe profiles optimized forboth low and high RPM
operations. In basic form, the single barring shaft-lockof a conventionalengine is replaced with
twoprofiles: one optimized for low-RPMstability and fuel efficiency,and the other designed to
maximize high-RPM power output. The switching operation between the twocam lobes is
controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle
speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch
from the low liftto the high lift cam lobes when the conditions mean that engine output will be
improved. From this point on, the valves open and close according to the high-lift profile, which
opens the valve further and for a longer time. The switch-overpoint is variable, between a
minimum and maximum point, and is determined by engine load. The switch-downbackfrom
high to low RPM cams is set to occur at a lower engine speed than the switch-up (representing a
hysteresis cycle)toavoid a situation in whichthe engine is asked to operate continuously at or
around the switch-overpoint.
4.4 Boost pressure:
Cars with a turbo fitted can have the requested and allowable boost levels raised, these
applications usually have the most effectif the turbo fitted is a low pressure turbo which leaves
the most room for improvement.
The ECU alters the turbo spool up rates to give maximum power gains. Electronic boost control
adds an air control solenoid and/or a stepper motor controlledby an electronic control unit.
Figure 5: Boost tuning window
Wastegate actuators are installed to workin sync with the ECU modifications. The fuel pressure
is ramped up earlier in the RPM range but still peak pressure is kept within the factory defined
maximum limits, giving a good mid-range powerboost and improving the pick-up under
acceleration as long as boost pressure is below a predetermined allowable ceiling, the EMS will
9. open the boost control solenoid to allow the turbocharger to create overboostbeyond what the
wastegate wouldnormally allow. Once desired boost is reached, closed loop based systems react
by allowing more air pressure to reach the wastegate actuator to stop the further increase in air
pressure so desired boost levels are maintained. This reduces turbocharger lag and lowersboost
threshold.
The partial throttle control greatly increases driver control overthe engine and vehicle.As
overboost reaches the programmable maximum, the EMS begins to decrease the bleed rate
through the control solenoid to raise boost pressure as seen at the wastegate actuator
diaphragm so the wastegate opens enough to limit boost to the maximum configured level of
over-boost.
It is also possible to have a small turbo and large turbo set up withthe ECU to use the small
turbo at low revs and kickin the larger one as the revs increase.
Variable-geometry turbochargers (VGTs), (also knownas Variable NozzleTurbines or VNTs), are
a family of turbochargers, usually designed to allow the effectiveaspect ratio (A:R) of the turbo
to be altered as conditions change. This is done because optimum aspect ratio at low engine
speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo
will fail to create boost at low speeds; if the aspect ratio is too small, the turbo willchoke the
engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and
ultimately lower power output.
The vanes are optimally controlled by a membrane vacuum actuator, whichresponds to the
actions of the ECU. Turbolag is also cut down considerably.
Generally speaking, any carwill see a benefit fromengine tuning, but the largest gains are from
turbocharged applications. NA (naturally aspirated) engine power gains are around 10-20%
and turbocharged engines have around 30-40% on average.
5. The caveats:
Life is full of compromises. This statement holds forengine tuning, too.
i. A poorly tuned electronic control unit can result in decreased performance, driveability,
and may even cause engine damage.
ii. It is very important to use only reputable companies for any sort of vehicle modification
in order to prevent serious engine or ECU damage.
iii. Remember that other safety-related items, such as the brakes, suspension and tyres, may
also require upgrading. You must also inform yourinsurance company of any
modifications and it is advisable to check,before investing in any kind of engine tuning,
how much yourpremium could be affected.Finally, youshould checkthat any
modifications are not invalidating any new or used car warranty.
iv. By chip tuning, youare effectively reducingthe safe margin of error the makers build in.
10. v. Sub-standard fuels, extremes in temperature and altitude, differing emission laws and
even the possibility that vehicle may not be serviced on a regular basis and in accordance
with the manufacturers recommended instructions.
vi. If a gasoline-powered car is remapped, then there is a need to run the car on premium,
high octane fuel – which pushes costs - to avoid engine pre-detonation.
vii. Vehicles with a remapped ECU may be more sensitive to fuel quality and service
schedules.
Not all engine makes can be remapped. Some older engines cannot be remapped, whereas
car tuning agencies are increasingly looking at new ways to tune those engines whichwere
thought to be not capable of being remapped.
6. Prospects:What does the future hold?
a) It is possible to do away with the camshaft entirely, and to move the valves by hooking
them up to electromagnetic actuators. Then, you can trigger the valves individually, and
controltheir timing, simply by feeding power to the electromagnet. Since this is done by
controlling electric power,it is quite easy to have the valvesactuated by the ECU. In addition,
it drastically reduces the number of rubbing moving parts, whichincreases engine reliability
and means that the engine is less likely to suffer a catastrophic failure.
b) Fuel ratio also can be used to regulate or controltwofuel types. Forexample, an engine
may have the ability to run on gasoline and ethanol, one being port injected and the other
directly injected. Although the implementation of this may require two separate fuel lines
and separate fuel tanks, the ratio of the two fuels may be of interest to future ECU
programmers.
7. References:
a)http://www.importtuner.com/tech/0612_impp_engine_tuning_basics/viewall.html
b) http://www.evans-tuning.com/tech-articles/tuning-101/
c) http://www.cittech.co.uk/engine_re_mapping.php
d) http://everything2.com/title/Internal+combustion+engine+valve+actuation+method
e) http://iaesjournal.com/online/index.php/IJAAS/article/viewFile/1197/750
f) http://www.powermod.com.au/index-2.html
g) http://www.torquecars.com/tuning/chip-tuning.php
