How to Tune and Modify Automotive Engine Management Systems - All New Edition: Upgrade Your Engine to Increase Horsepowe

338 Pages·2013·50.07 MB·English

by  Jeff Hartman

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By Jeff Hartman

AUTOMOTIVE ENGINE
MANAGEMENT SYSTEMS

HOW TO TUNE AND MODIFy

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Contents

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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Chapter 1
Understanding Fuel Delivery . . . 14

Chapter 2
Understanding Automotive
Computers and PROMs . . . . . . 25

Chapter 3
Sensors and Sensor Systems . . . 38

Chapter 4
Actuators and
Actuator Systems . . . . . . . . . . . 56

Chapter 5
Hot Rodding EFI Engines . . . . . . 75

Chapter 6
Hot Rodding Electronic
Diesel Engines . . . . . . . . . . . . . . 92

Chapter 7
Recalibrating Factory ECMs . . 102

Chapter 8
Tuning with Piggybacks,
Interceptors, and Auxiliary
Components . . . . . . . . . . . . . . . 115

Chapter 9
Standalone Programmable
Engine Management Systems . 129

Chapter 10
EMS/EFI Engine Swapping . . . . 147

Chapter 11
Roll-Your-Own EFI . . . . . . . . . . . 159

Chapter 12
Installation and
Start-up Issues . . . . . . . . . . . . . . 165

Chapter 13
Designing, Modifying, and
Building Intake Manifolds . . . . . 171

Chapter 14
EMS Tuning . . . . . . . . . . . . . . . . 178

Contents

Chapter 15
EMS Troubleshooting . . . . . . . . 222

Chapter 16
Emissions, OBD-II, and
CAN Bus . . . . . . . . . . . . . . . . . . . 240

Chapter 17
Project: Supercharging the
2010 Camaro SS . . . . . . . . . . . . . 256

Chapter 18
Project: Twin-Turbo
Lexus IS-F . . . . . . . . . . . . . . . . . . 262

Chapter 19
Project: Supercharged
Jag-Rolet . . . . . . . . . . . . . . . . . . 270

Chapter 20
Project: 1970 Dodge
Challenger B-Block . . . . . . . . . . 276

Chapter 21
Project: Real-World
Turbo CRX Si . . . . . . . . . . . . . . . 282

Chapter 22
Project: Honda del Sol
Si Turbo . . . . . . . . . . . . . . . . . . . . 294

Chapter 23
Project: Turbo-EFI
Jaguar XKE 4 .2 . . . . . . . . . . . . . 300

Chapter 24
Project: Two-staged Forced
Induction on the MR6 . . . . . . . . 310

Chapter 25
Project: Overboosted
VW Golf 1 .8T . . . . . . . . . . . . . . . . 321

Chapter 26
Project: Frank-M-Stein:
M3 Turbo Cabriolet . . . . . . . . . . 325

Appendix . . . . . . . . . . . . . . . . . . . . . 328

Index . . . . . . . . . . . . . . . . . . . . . . . . . 331

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Introduction

T
his how-to book is designed to communicate the theory and
practice of designing, modifying, and tuning performance
engine management systems that work. In recent years electronic
engine and vehicle management has been among the most
interesting, dynamic, and influential fields in automotive
engineering. This makes it a moving target for analysis and
discussion. Electronic control systems have evolved at light
speed compared to everything else on road-going vehicles. This
has paved the way for unprecedented levels of reliable, specific
power, efficiency, comfort, and safety that would not otherwise
be possible.
Simply reconfiguring the internal configuration tables of
an electronic engine management system can give the engine
an entirely new personality. Changing a few numbers in the
memory of an original equipment onboard computer can
sometimes unleash 50 or 100 horsepower and release all sorts of
possibilities for power increases with VE-improving speed parts
and power-adders. But you have to do it right, and that can be
a challenge.

The AuTomAkers And elecTronic Fuel injecTion
And engine mAnAgemenT
In the case of the car companies, electronic fuel injection arose
as a tool that allowed engineers to improve drivability and
reliability and to fight the horsepower wars of the 1980s. It
also helped them comply with federal legislation that mandated
increasingly stiff standards for fuel economy and exhaust
emissions. The government forced automakers to warrant for
120,000 miles everything on the engine that could affect exhaust
emissions, which was everything related to combustion. In
other words, nearly everything. Intelligently and reliably
controlling engine air/fuel mixtures within extremely tight
tolerances over many miles and adapting as engines slowly
wore out became a potent tool that enabled car companies to
strike a precarious balance between EPA regulations, the gas-
guzzler tax, and performance-conscious consumers who still
fondly remembered the acceleration capabilities of 1960s- and
1970s-vintage muscle cars.
Going back further, in the 1950s, engine designers had
concentrated on one thing—getting the maximum power,
drivability, and reliability from an engine within specific
cost constraints. This was the era of the first 1-horsepower-
per-cubic-inch motors. By the early 1960s, air pollution in
southern California was getting out of control, and engine
designers had to start worrying about making clean power.
The Clean Air Acts of 1966 and 1971 set increasingly strict
state and federal standards for exhaust and evaporative
emissions. Engine designers gave it their best shot, which
mainly involved add-on emissions-control devices like positive
crankcase ventilation (PCV), exhaust gas recirculation (EGR),
air pumps, inlet air heaters, vacuum retard distributors, and
carburetor modifications.
The resulting cars of the 1970s ran cleaner, but horsepower
was down and drivability sometimes suffered. Fuel economy
worsened just in time for the oil crises of 1973 and 1979. The
government responded to the energy crises by passing laws
mandating better fuel economy. By the late 1970s car companies

had major new challenges, and they sought some new “magic”
that would solve their problems.
The magic—electronic fuel injection—was actually
nothing new. The first electronic fuel injection (EFI) had been
invented not in Europe, but in 1950s America, by Bendix.
The Bendix Electrojector system formed the basis of nearly all
modern electronic fuel injection. The Bendix system, originally
developed by Bendix Aviation for aircraft use, used modern
solenoid-type electronic injectors with an electronic control
unit (ECU) originally based on vacuum-tube technology but
equipped with transistors for automotive use in 1958.
The original Electrojector system took 40 seconds to warm
up before you could start the engine. Sometimes it malfunctioned
if you drove under high-tension power lines. In addition to the
liabilities of vacuum-tube technology, Bendix didn’t have access
to modern engine sensors. Solid-state circuitry was in its infancy,
and although automotive engineers recognized the potential
of electronic fuel injection to do amazing things based on its
extreme precision of fuel delivery, the electronics technology
to make EFI practical just didn’t exist yet. After installing the
Electrojector system in 35 Mopar vehicles, Chrysler eventually
recalled all and converted to carburetion. Bendix eventually gave
up on the Electrojector, secured worldwide patents, and licensed
the technology to Bosch.
In the meantime, mechanical fuel injection had been
around in various forms since before 1900. Mechanical injection
had always been a “toy” used on race cars, foreign cars like
the Mercedes, and a tiny handful of high-performance cars in

Turbo Chevrolet Corvair engine from the early 1960s. Boost and performance were
extremely limited due to mechanical engine management consisting of carburetion
and ignition breaker points, with boost pressure limited by exhaust backpressure.
Later, extremely high-output turbocharged engine output was unleashed with the
marriage of efficient turbocharged and electronic fuel injection with digital electronic
engine management.

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of failures when teamed up with the turbocharger. Carbureted
turbo engines that were manufactured circa 1980—the early
Mustang 2.3 turbo, the early Buick 3.8 turbo, the early Maserati
Biturbo, the Turbo Trans Am V-8—are infamous. If you wanted
a turbocharged hot rod to run efficiently and cleanly—and,
more importantly, to behave and stay alive—car companies
found out the hard way that electronic fuel injection was the
only good solution.
For automakers, the cost disadvantages of fuel injection
were outweighed by the potential penalties resulting from non-
compliance with emissions and Corporate Average Fuel Economy
(CAFE) standards, and the increased sales when offering superior
or at least competitive horsepower and drivability.

hoT rodders And Fuel injecTion
In the 1950s, the performance-racing enthusiast’s choices for
a fuel system were carburetion or constant mechanical fuel
injection. Carbs were inexpensive out of the box, but getting
air and fuel distribution and jetting exactly right with one or
two carbs mounted on a wet manifold took a wizard—a wizard
with a lot of time. By the time you developed a great-performing
carb-manifold setup, it might involve multiple carbs and cost
as much or more than mechanical injection (which achieved
equal air and fuel distribution with identical individual stack-
type runners to every cylinder and identical fuel nozzles in every

America, like the Corvette. Mechanical fuel injection avoided
certain performance disadvantages of the carburetor, but it was
expensive and finicky and not particularly accurate.
In the 1960s, America entered the transistor age. Suddenly
electronic devices came alive instantly with no warm up. Solid-
state circuitry was fast and consumed minuscule amounts of
power compared to the vacuum tube. By the end of the 1960s,
engineers had invented the microprocessor, which combined
dozens, hundreds, then thousands of transistors on a piece of
silicon smaller than a fingernail (each transistor was similar in
functionality to a vacuum tube that could be as big as your fist).
Volkswagen introduced the first Bosch electronic fuel-
injection systems on its cars in 1968. A trickle of other cars used
electronic fuel injection by the mid-1970s. By the 1980s, that
trickle became a torrent.
Meanwhile, in the late 1970s, the turbocharger was reborn
as a powerful tool for automotive engineers attempting to steer a
delicate course between performance, economy, and emissions.
Turbochargers could potentially make small engines feel like big
engines just in time to teach the guy with a V-8 in the next lane
a good lesson about humility both at the gas pump and at the
stoplight drags. Unfortunately, the carburetor met its Waterloo
when it came up against the turbo. Having been tweaked and
modified for nearly a century and a half to reach its modern state
of “perfection,” the carb was implicated in an impressive series

Bosch DI-Motronic Gasoline-Direct Injection EMS crunches data from multiple lambda (O2) sensors, mass airflow (MAF) and manifold absolute pressure (MAP) sensors, the
throttle position sensor, and a standard complement of OBD-II Motronic sensors to control high-pressure injectors spraying directly into the cylinders, in some cases over the
CAN bus. The system also controlled a fly-by-wire throttle actuator, variable cam timing actuator, electronic fuel pressure regulator, and ignition driver stage. The system could
provide homogenous charge mixtures for maximum power at wide-open throttle or a stratified-charge for maximum fuel economy in which a richer mixture in the vicinity of
the spark plug lights off a leaner mixture elsewhere. Bosch

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systems, by their nature carbs inherently require one or more
restrictive venturis to create a low-pressure zone that sucks fuel
into the charge air. By definition, this forces tradeoffs between
top-end and performance at lower speeds. The carburetor’s
inability to automatically correct for changes in altitude and
ambient temperature is not a problem if the goal is simply decent
power at sea level. Distribution and accuracy problems, however,
are unacceptable if you care about emissions, economy, or good,
clean power at any altitude. Or if you want to run power-adders
like turbos, blowers, or nitrous.
Throughout the 1970s, hot rodders and tuners had begun
applying turbochargers to engines to achieve large horsepower
gains and high levels of specific power for racing. Mainly, of
course, ’rodders had to work with carburetors for fueling. They
discovered that carbureted fuel systems are problematic when
applied to forced induction. Yes, it was possible to produce a lot of
power with carbureted turbo systems, but at the cost of drivability,
reliability, cold-running, and so forth. Nonetheless, though carbs
were a problem, they were a well-understood problem, and
besides, what else could you do if you couldn’t afford a mechanical
injection system more expensive than the engine itself?
Around this same time, car manufacturers began switching
to electronic fuel injection. In 1975, GM marketed its first U.S.
electronic injection as an option for the 500-ci Cadillac V-8 used
in the DeVille and El Dorado. In 1982, Cross-Fire dual throttle
body electronic injection arrived on the Corvette. The new EFI
would give tuners who wanted to modify late-model cars a whole
new set of headaches.
The problem for hot rodders was that there was no easy
means to recalibrate or tune the proprietary electronic controllers
that managed car manufacturer’s EFI systems, and it was difficult
to predict whether electronic engine controls would tolerate
various performance modifications without recalibration.

runner). Assuming the nozzles matched, fuel distribution was
guaranteed to be good with constant mechanical injection.
Mechanical fuel injection has been around in various forms
since about 1900, and it has always been expensive. Mechanical
injection could squirt a lot of fuel into an engine without
restricting airflow, and it was not affected by lateral G-forces
or the up-and-down pounding of, say, a high-performance
boat engine in really rough waters, when fuel is bouncing all
over the place in the float chamber of a carb. Racers used
Hilborn mechanical injection on virtually every post-war Indy
car until 1970.
The trouble is, air and gasoline have dissimilar fluid
dynamics, and mechanical injection relied on crude mechanical
means for mixture correction across the range of engine speeds,
loading, and temperatures. Early mechanical injection was also
not accurate enough to provide the precise mixtures required
for a really high-output engine that must also be streetable. GM
tried Constant Flow mechanical injection in the 1950s and early
1960s in a few Corvettes and Chevrolets, but it turned out to be
expensive and finicky. Bosch finally refined a good, streetable,
constant mechanical injection (Bosch K-Jetronic) in the 1970s,
but as emissions requirements toughened, it quickly evolved into
a hybrid system that used add-on electronic controls to fine-tune
the air/fuel mixture at idle.
By the late 1970s carburetors had been engineered to a high
state of refinement over the course of many decades. However,
there were inescapable problems intrinsic to the concept of a self-
regulating mechanical fuel-air mixing system that could only be
solved by adding a microprocessor or analog computer to target
stoichiometric air/fuel mixtures via pulse width-modulated
jetting and closed-loop exhaust gas oxygen feedback.
In addition to the accuracy problems and distribution issues
intrinsic to cost-effective single-carb wet-manifold induction

Fuel injection, 1950s-style, meant Chevrolet constant-flow venturi fuel injection.
Most Americans’ first exposure to Bosch fuel injection on 1970s- and 1980s-vintage
VW, Porsche, Ferrari, Mercedes, and other European engines was this K-Jetronic
constant-injection system (CIS), which varies fuel pressure based on a mechanical
velocity air meter measuring air entering the engine. Although later K-Jetronic
systems had add-on electronic trim, the system is not a true electronic engine
management system, it is not easy to modify for hot rodding, and more than a few
such performance vehicles still on the road have been converted to programmable
EMS. Chrysler

The original Electrojector fuel injection was invented by the American company Bendix
in the 1950s. The package was expensive and finicky, and many were converted
to carburetion in the days before the cars were collector items. Bendix had already
successfully demonstrated pulsed electronic port injection (the Electrojector system),
but the pretransistor vacuum tubes had to warm up like an old radio before the car
could start, and the whole system could wig out if you drove under high-power lines.
A practical system required the solid-state electronics of the 1960s and beyond.
Bosch licensed from Bendix the concept of a constant-pressure, electronically
controlled, solenoid-actuated, individual-port, periodic-timed fuel injection system and
put it into production in some 1960s-vintage VWs. Bosch evolved the original concept,
resulting in the newest Motronic engine management systems.

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reasons behind the superiority of fuel injection and electronic
engine management. In fact, there were plenty of carb-to-
port EFI conversions of vintage vehicles for the following highly
valid reasons:

AdvAnTAges oF individuAl-PorT elecTronic
Fuel injecTion
•
Injection of fuel against the hot intake valve prevents a
situation in which fuel vaporization in a carburetor has the
potential to lower intake air temperature below the dew
point in cold weather, allowing water vapor to condense
and form ice crystals to build up in the carb to the extent
that the engine runs poorly or not at all. This problem
is so serious on carburted aircraft engines that they are
equipped with a “Carb Heat” control that causes hot air to
be injected directly into the carb intake throat.

•
Low pressure and high temperatures in fuel lines can
cause vapor bubbles to form in the fuel supply system that
impede operation; the higher pressures of port EFI systems
(30-70 psi) normally eliminates the problem.

•
Greater flexibility of dry intake manifold design allows
higher inlet airflow rates and consistent cylinder-to-
cylinder air/fuel distribution, resulting in more power and
torque, and better drivability.

•
More efficient higher engine compression ratios possible
without detonation.

•
Extreme accuracy of fuel delivery by electronic injection
at any rpm and load enables the engine to receive air/
fuel mixtures at every cylinder that falls within the
narrow window of accuracy required to produce superior
horsepower and efficiency.

•
Computer-controlled air/fuel ratio accuracy enables all-out
engines to safely operate much closer to the hairy edge
without damage.

•
EFI can easily be recalibrated or adapted to future
engine modifications as a performance/racing vehicle
evolves. When adjustments and changes are required
to match new performance upgrades made to an
engine, it’s often as simple as hitting a few keys on a

Early EFI control logic was not in embodied in software,
but was hardwired into the unalterable discrete circuitry of
an analog controller, and while early digital fuel-injection
controllers were directed by software logic and soft tables
of calibration data parameters, these were locked away in a
programmable read-only memory (PROM) storage device that
was, in many cases, hard-soldered to the main circuit board.
In all analog electronic control units and in a fair number of
the digital ECUs, changing the tuning data effectively required
replacing the ECU. And even when the calibration (tuning)
data was located on a removable PROM chip plugged into a
socket on the motherboard, the documentation, equipment, and
technical expertise needed to create or “blow” new PROMs was
not accessible to most hot rodders. While enthusiasts were able,
in some cases, to buy a quality replacement PROM calibrated
by a professional tuner with tuning parameters customized for
high-octane fuel operation or recalibrated to handle specific
performance modifications, in those days it was rarely practical
for an enthusiast to tune the fuel injection himself. And if you
modified the calibration and then made additional volumetric or
power-adder modifications to the engine, the new performance
PROM was likely to be out of tune—again.
It was only in the late 1980s, as the final factory-carbureted
performance vehicles aged and the first aftermarket user-
programmable EFI systems became available and the first
generation of performance EFI vehicles aged out of warranty and
depreciated to the point that it was practical for more people to
consider acquiring or modifying them, that large numbers of hot
rodders and racers began to take a hard look at the possibilities of
EFI for performance and racing vehicles.
In those days, many hot rodders and enthusiasts objected to
electronic fuel injection for various reasons:
•
Too expensive

•
Difficult or impossible to modify

•
Illegal in some racing classes

•
Too high-tech (that is, complex, finicky, inaccessible,
incomprehensible, mysterious, difficult to install
and debug)

•
Typically required expensive auxiliary electronic
equipment for diagnosis, troubleshooting, and tuning

•
Regarding the carburetor: “It ain’t broke, why fix it?”
Eventually, all these considerations would become much
less of a factor, but for a time they put a brake on the hot
rodding of newer vehicles. For a time, the sport of hot rodding
split into two evolutionary branches centered around 1) familiar,
older low-tech specialty vehicles with pushrod V-8 engines—
often equipped with carbureted fuel systems—and 2) more
efficient newer vehicles with high-tech computer-controlled fuel
injection—often powered by smaller engines with multivalve,
overhead-cam cylinder heads, some with turbochargers. The
advantages of EFI created the critical mass for the 1990s sport-
compact performance craze that revitalized hot rodding, but in
the early days of EFI there were actually a fair number of engines
converted from EFI backward to carburetion.
Knowledgeable racers and hot rodders soon discovered that
well-tuned modern programmable EFI systems almost always
produce significantly higher horsepower and torque than the
same powerplant with carbureted fuel management, especially
when the engine is supercharged or turbocharged. This increased
performance is within the context of improved drivability,
cleaner exhaust emissions, and lower fuel consumption. Early
adopter hot rodders discovered there were solid technical
Big Block 426-type Hemi with twin Whipple twin-screw supercharges and (out of
sight) electronic fuel injection.

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of fuel and air surrounded by mostly pure air, which keeps
the flame away from the cylinder walls for reduced heat
loss and lowered exhaust emissions.

•
No throttling loses on some gasoline direct-injection
engines when engine speed and output are controlled
by ignition timing and injected fuel mass rather than by
throttling engine air intake.

•
G-DI engines achieve improved performance in
Stoichiometric or Performance Mode by combusting a
homogenous mixture achieved by injecting fuel during
the intake stroke as pressures as high as 3,000 psi, which
improves combustion via improved atomization of fuel
molecules and improved air/fuel mixing in the cylinders.

•
G-DI engine performance can be further improved
in some cases by a second injection of additional fuel
late during the power stroke, particularly on turbo-
charged powerplants (though problems with exhaust
valve erosion from some fuel octanes caused some engine
manufacturers to eliminate Fuel Stratified Injection
during normal operation).

•
The extremely high injection pressure of G-DI
systems improves the atomization of injected fuel
enough that improved fuel vaporization actually chills
the intake air enough to improve density and lower
combustion temperatures.

•
Compared to the 40-70-psi pressure of multi-port
EFI systems, the extremely high rail pressure allows
G-DI systems increased flexibility of injection timing
and fuel apply rate, which can be tuned via pressure in
the common rail and the number of injection events.
Combined with twin-cam electronic cam phasing, G-DI

PC to change some numbers in the memory of the
onboard ECU.

•
Electronic engine management with port fuel injection
is fully compatible with forced induction, resisting
detonation with programmable fuel enrichment and spark-
timing retard, enabling huge power increases by providing
the precisely correct air/fuel mixture at every cylinder.

•
EFI powerplants have no susceptibility to failure or
performance degradation in situations of sudden and
shifting gravitational and acceleration forces that might
disturb the normal behavior of fuel in a carbureted fuel
system with float chamber(s).

•
Electronic injection automatically corrects for changes in
altitude and ambient temperature for increased power and
efficiency, and reduced exhaust emissions.

•
Solid-state electronics are not susceptible to the
mechanical wear and failure possible with carburetors.
Tuning parameters stay as you set them, forever,
with no need for readjustment to compensate for
mechanical wear.

AdvAnTAges oF individuAl-cylinder
direcT injecTion
•
Gasoline-DI engines achieve improved fuel economy
when operating in ultra-lean burn mode under very light
loading or deceleration. In this mode fuel is injected not
during the intake stroke but during the latter stage of the
compression stroke. G-DI engines are able to combust
a stratified charge that is richer near the spark plug but,
overall, as lean as 65:1 air/fuel ratio.

•
Stratified charge combustion restricts the burn to an island

Norwood Performance built this gorgeous custom twin-turbo system for a radically hot rodded Gen-1 Toyota Supra. Under Motec EMS control, with 900 horsepower on tap
from 2,954 radically-boosted cubic centimeters, this streetable machine was equally at home as a dragger or a Silver State racer.

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run rich during boosted conditions, or by dynamically altering
injection fuel pressure with artificial means (such as a variable
rate-of-gain fuel pressure regulator) such that the calculated and
commanded injection pulse width would deliver more fuel during
turbo boost.
A few enterprising companies offered performance PROMs
that could easily be swapped into factory engine-management
systems such as GM’s Tuned Port Injection. These provided
alternate tables of rpm and load-based values for fuel-injection
pulse width and spark advance that improved power with
premium fuel calibrations or provided modified internal fuel
and spark tables calibrated specifically for certain packages of
hotter cams and other hot rod engine parts. Several standalone
programmable aftermarket engine management systems were
also available, the most successful of which was the Haltech F3.
The F3 was an EFI-only system with an installed base of maybe
2,000 systems that could not manage ignition tasks at all. This
was all about to change.

elecTronic engine mAnAgemenT in The
oBd-ii erA
In the 1980s, independent repair facilities lobbied hard for
regulations to force automakers to provide open onboard
computer diagnostic interfaces and to document and standardize
interface protocols so independent shops servicing multiple

systems can vary valve overlap, injection timing, and
ignition timing to heat catalysts lightning-fast on cold
start and spool turbochargers much faster by using large
valve overlap and retarded fuel and ignition timing to blow
some turbo boost through the combustion chamber to
supply a combustible mixture in the exhaust.
In the very early 1990s, many new EFI vehicles still utilized
factory EFI conversions of formerly carbureted engines (such as
the 5.0L Mustang, and the TPI 5.0 or 5.7 Camaro and Corvette).
In some cases, such vehicles had separate or quasi-separate
distributor-based ignition systems (along with instrumentation
and chassis electrical systems that were not integrated with the
engine management system). In those days virtually all onboard
computer systems, with the exception of idle and light-cruise
fuel-air mixture trim and idle speed stabilization algorithms,
had no means of detecting if commanded engine management
actions were successful. If the computer ordered the opening of a
solenoid valve, it had to assume the valve had opened. Many early
1990s aftermarket EFI engine tuning strategies for modified hot
rod powerplants worked by inciting the factory computer into
providing (more or less) correct fuel enrichment and ignition
timing on engines with upgraded volumetric efficiency during
high-output operation using mechanical or electrical tricks that
might, say, substitute false engine sensor data (such as artificially
low engine coolant temperature) that would cause the engine to

MegaSquirt V3.0/V3.57 wiring showing connections for all required and optional engine sensors and actuators. Note external wideband controller circuit at lower left. Major
DI-Motronic components. A powerful digital computer with large non-volatile memory space runs multiple OBD-II monitor software agents with the ability to detect problems
such as combustion misfires from minor changes in crankshaft rate of acceleration. New Motronic systems are powerful and complex, but they are table-driven and extremely
flexible, which makes modifications a simple programming change—if you’ve got access for a reflash. In most cases aftermarket hackers have always found a way. Bosch

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required automakers to implement countermeasures that made it
reasonably difficult to tamper with the calibration without having
access to a special password known as the security seed (sometimes
referred to as “security by obscurity.” At the same time, OBD-II
was defining a powerful mechanism that could be used to retune
engines without changing any hardware or even so much as a
PROM chip. Or even more: it potentially enabled recalibration
of an OBD-II computer—or even replacement of the operating
software itself!—to handle an alternate engine or important
additional engine systems, or even to stop doing OBD-II.
The logic of modern digital engine management systems
is highly parameter driven, meaning the software design is
complex, modular, universal, and all-encompassing in design.
It is also highly conditional in behavior based on the status
of a set of internal settings (parameters) stored in tables in
memory. Changing such parameters can drastically transform
functionality, giving the computer a whole new personality—for
example, enabling it to manage an entirely different engine with
fewer or more cylinders or one with additional power-adders and
so forth.
Before OBD-II, such parameters (where they existed)
were stored in read-only memory or programmable read-only
memory and could be changed only by physically opening
the computer and installing a new ROM or PROM, which
sometimes involved soldering and de-soldering and jumpering
or cutting the motherboard. It would not be long before
clever aftermarketers would reverse-engineer the security
seed and sell specialized power-programmer devices designed
to connect to the diagnostic port to change parameters like
top-speed-limiter or rev-limiter, or even to hack the air/fuel
or ignition timing tables on GM OBD-II computers (for off-
road use only, of course). When researchers at the University
of Washington and University of California examined the
security around OBD, they discovered it was possible to
gain control over many vehicle components via the OBD-II

brands did not need expensive and esoteric brand-special scan
tools for every make and model of vehicle.
The Clean Air Act of 1990 finally forced automakers to
get serious about plans they had been developing since the first
serious California air pollution problems in the late 1950s.
Standardized onboard vehicle/engine diagnostic capabilities
designed to keep engines operating in a clean, efficient, peak state
of tune arrived in 1996 (in a few cases as early as 1994). Now
that digital computers had conquered the original-equipment
automotive world, there existed at last both the possibility of
and the necessity for sophisticated electronic self-testing and
diagnostic capabilities.
The result was OBD-II (Onboard Diagnostics, Second
Generation), a blessing for the typical car buyer, potentially
a blessing and a curse for the hot rodder or tuning shop.
OBD-II, which was required on new vehicles no later than
1996, implemented a number of interesting capabilities. It
defined standards for hardware bus connectivity to onboard
computers for scan tools and laptop computers. It defined
a handshake for communication between the ECU and
diagnostic equipment. It defined an extensive set of standardized
malfunctions that the engine management system had to be able
to self-detect, and it defined a standardized set of alphanumeric
trouble codes. These codes had to be stored by the ECU semi-
permanently in nonvolatile memory that would retain its
integrity even if the onboard computer lost battery power. OBD-
II defined protocols for resetting such codes once a problem had
been fixed.
The consequent use of large-scale electrically erasable flash
memory to store calibration information and trouble codes was
revolutionary because it was now feasible to reflash the device
with new calibration or configuration data in the field without
PROM. OBD-II thus defined a system that could be used to
update the entire parameter-driven engine calibration should
a bug be discovered that affected emissions or safety. It also

Lee Sicilio’s 1969 Dodge Daytona Bonneville Racer, powered by a Keith Black 498-cid Hemi with twin Precision 91mm Pro Mod turbochargers. The engine was controlled
by a DIY Autotune Megasquirt MS3X engine management system providing sequential fuel and spark. The MS3 driving was set up to drive eight Pantera IGN-1A coil packs
and the fuel injectors were 225 lb/hr Injector Dynamics units with flow capacity of 2800hp on gasoline, and more at increased fuel pressure. The chassis dynamometer used
for power testing maxed-out at 1500 wheel horsepower at 6-psi boost, but with an estimated 3000 horsepower on available at higher boost, Sicilio race team was hoping
the Charger would eventually smash its way to 310 mph on the salt. In preliminary testing, the car hit 283 mph at the salt running just 8-psi boost. Scott “Dieselgeek” Clark,
Chad Reynolds (Bangshift.com)

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controls, active lateral-instability countermeasures, electronic
shifting, Controller Area Network bus (required on all light U.S.
market vehicles in 2008 for communication between multiple
specialized onboard controllers/computers) , and dozens of other
highly specialized and esoteric eMotion control functions.
One such example is a scary-sounding thing GM called
“Adaptive Garage Fill Pressure Pulse Time and Garage Shift
Pressure Control.” And more: Some of the most advanced
Motronic engine management systems are equipped with
algorithms that deliver directly measured torque-based engine
management. Some of the newest BMWs can fire up the engine
without a starter motor by identifying the exact engine position,
injecting fuel into the appropriately positioned cylinder, and
then firing the plug.
The amount of time invested in carefully developing
flawless engine calibrations for such vehicles is phenomenal,
and can take years, even with complex modeling and simulation
tools. The simplest millennium engine management systems
used to manage economy subcompacts incorporated months or
years of test-and-tune efforts on dynos, test tracks, and highways
under all climatic conditions.
Meanwhile, standalone aftermarket programmable engine
management systems also increased in power and complexity,
with the newest systems from Motec, Electromotive, DFI, and
others offering extremely sophisticated software engine modeling
and highly flexible and configurable hardware with the capability
to control a wide range of complex engines with a wide variety of
sensors and actuators, and to keep up with engine management
capabilities found on new factory vehicles.
The most powerful aftermarket systems target pro racers
and professionals building tunercars for people for whom
money is, shall we say, not a problem. Such systems are not
cheap. All involve substantial configuration, calibration,
and installation efforts to approximate anything close to the
observable functionality of a millennium-vintage factory vehicle
(much less sophisticated little tricks like Adaptive Garage Fill

interface, and they were able to upload new firmware into the
engine-control units without proprietary documentation, and
concluded that vehicle embedded systems were not designed
with security in mind. In fact, there are documented instances
of thieves using specialist OBD reprogramming devices to
steal cars without the use of a key. The primary causes of this
vulnerability lie in the tendency for vehicle manufacturers to
extend the OBD-II interface for purposes beyond the original
specification, and the lack of authentication and authorization
in the OBD specifications, which instead rely largely on
“security through obscurity.”
OBD-II effectively required implementation of a range of
new engine and vehicle sensors to provide additional feedback
to the computer so it would know when there was a problem or
might be a problem. For example, where the computer might
have previously commanded a valve to open to purge the charcoal
canister of fuel vapors (and assumed it had, in fact, opened),
OBD-II might, for example, require a sensor to measure if, in
fact, the valve actually had opened.
OBD-II mandated many new diagnostic capabilities, such
as the ability to detect misfires. This required precise and highly
accurate crankshaft position sensors and new, more powerful,
high-speed microprocessors with the computing power to
measure micro-changes in the rate of change in crankshaft speed
in real time that indicated healthy combustion versus misfire
events. Misfire-detection required the computational ability to
correlate a transient misfire to a particular cylinder. Basically,
OBD-II required the development of completely new engine
management systems.
Since they were developing entirely new engine management
hardware and software with a clean-sheet-of-paper approach,
automakers and their OEM suppliers such as Bosch took the
opportunity to develop powerful new onboard computer
hardware and operating software. They made plans to implement
an architecture able to handle an impressive range of new vehicle-
management capabilities, including fly-by-wire throttle, traction

Motec ADL3 Dash/Logger communicates with the M800 ECM using a 2-wire CAN bus, which also supports a laptop PC with Motec tuning software and various other sensors
and actuators.

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management system that plugs into the stock wiring harness
(typically with a short adapter harness) in place of the stock
ECU, ready to rock ’n’ roll.
Just getting all the engine sensors and actuators wired to
an aftermarket programmable computer can be a formidable
task. It’s more akin to buying a motherboard, power supply, disk
drive, case, bios, and operating software from Fry’s Electronics
and building your own Windows system. But it’s even worse,
because in the case of a programmable engine management
system, you’ll need to locate subsystems, sensors, and actuators;
route wiring; and terminate and crimp wires to connectors that
need to work reliably in an environment rife with heat, cold,
water, oil, vibration, and various G-forces.
AEM plug-and-play systems provided adapter wiring that
was designed to allow a user to remove the stock computer
and plug the stock engine wiring harness into an adapter on
the programmable computer. Plug-and-play system vendors
like AEM, Hondata, Haltech, and most others by now usually
provide a starter calibration that will start and run the engine
and enable the vehicle to drive without any user intervention to
calibrate it. But installation instructions warn users that virtually
any significant modifications to the factory engine’s volumetric
efficiency—that is, performance modifications—would require
recalibration to prevent possible engine damage.
Another response to the increased complexity of OBD-
II-era original-equipment engine management systems, and
the difficulty of reproducing the quality of their factory
calibrations, was aftermarket tuners increasingly turning
to auxiliary computers or mechanical devices rather than
standalone aftermarket engine management systems. Tuners
have used variable-rate-of-gain fuel pressure regulators (some
even computer-controlled!) and electronic interceptor devices to
intercept and modify or augment the actions of fuel injectors
or input-output signals from the factory onboard computer to
change the behavior of the engine under the relatively limited
operating circumstances when power-adders are in action (at
wide-open throttle and higher-load operating conditions).
A number of vendors have specialized in supplying
programmable “piggyback” computers (in some cases very
sophisticated) designed to modify or trim specific designated
sectors of the factory air/fuel or spark timing curves—via laptop
or, in some cases, dial pots on the processor box—during power-
adder operations without affecting the factory tune during
non-boosted conditions when the engine is lightly loaded. A
related alternative to the interceptor or auxiliary computer is the
programmable sensor or actuator that enables tuners to influence
the behavior of the main engine management computer by
selectively lying to it or by being creatively disobedient.
The complex interactions and constraints of ECM logic,
ECM calibration data, ECM anti-tampering or self-protective
countermeasures, fuel pump capacity and fuel pressure, injector
capacity, duty cycle, electrical limitations, pressure, ignition
components, and other such factors have made modifying
engines for increased performance challenging, yet potentially
rewarding. The tuning of electronic engine management systems
has evolved to the point that tuners have managed to achieve
stupefying levels of streetable specific power that had previously
only been seen in the wild turbo era of Formula One racing.

The PurPose oF This Book
This book is designed to communicate the theory and practice
of designing and redesigning performance engine management

Pressure Pulse Time and Garage Shift Pressure Control). Of
course, conversion from OEM to programmable aftermarket
engine management is not strictly legal for highway use unless
the manufacturer or tuner tackles expensive CARB or Federal
Test Procedure (FTP) testing in order to prove that their engine
management system does not degrade exhaust emissions on one
or more specific vehicles in a simulated drive cycle involving a
cold start and 20 minutes or so of rolling road exercise during
which exhaust is captured in a big plastic bag for subsequent
analysis. The FTP procedure was updated in 2008 to include
four tests: city driving (FTP-75), highway driving (HWFET),
aggressive driving (SFTP US06), and optional air conditioning
test (SFTP SC03). In general, the Cold Start CVS-75 Federal
Test procedure has been the regimen required to achieve street
legality for aftermarket power-adder systems, though Cold 505
can be used, and in the case of diesel-powered vehicles, Hot Start
CVS-75 may be applicable.
By the time OBD-II was required on all vehicles sold in the
United States in 1996, it had been six years since a carbureted
engine had been available on a car or truck in America, and the
digital microcomputer was definitely king, both in the onboard
ECU (now referred to as the powertrain control module or
PCM) managing the engine and in the scan tool or laptop
in the hands of the diagnostician or tuner. Powerful laptop
computers with graphical Windows or Mac OS interfaces were
ubiquitous by 1997, and most people who had been in school
since 1982 had at least some degree of training and familiarity
with the personal computer. This new generation arrived on
the automotive-performance scene entirely comfortable with
installing and manipulating user-interface and tuning software
on a laptop to recalibrate engine management systems.
Unfortunately, this was only one piece of the puzzle.
Ignorant jacking with calibration numbers in the computer of
a vehicle with significant engine performance modifications
will make a bad situation worse. Tuning an engine well with
good diagnostic equipment requires patience, experience, and
methodical R&D troubleshooting techniques. Tuning an engine
in a car on the street without diagnostic equipment is a risky
proposition that is difficult or impossible to do well.
Many casual or inexperienced performance enthusiasts
are simply incapable of achieving a good, safe, efficient,
drivable tuning calibration from scratch, particularly on high-
output engines with power-adders. If such a well-meaning but
inexperienced person is lucky, they’ll probably end up with
an engine that fails to realize the potential of its improved
volumetric efficiency. If they’re unlucky, they’ll end up with a
polluting, gas-guzzling slug with marginal drivability or possibly
a damaged engine. Even really experienced pro...