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How To Tune and Modify Automotive Engine Management Systems by Jeff Hartman | PDF Free Download.
This 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 have 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.
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 the 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. The 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 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.
Solidstate 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 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.
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 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.
The 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.
The early mechanical injection was also not accurate enough to provide the precise mixtures required for a really high-output engine that must also be treatable. 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 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 were 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.
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.
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