Tuned Port Injection Essay, Research Paper
The first production Tuned Port Injection ( TPI ) systems appeared on General Motors’vehicles in 1985. The GM vehicles built with these systems were the Corvette, Pontiac Firebird, Pontiac Trans AM, and the Chevrolet Camaro. Upon their debut, these systems achieved a 35% betterment over carbureted systems and a 20% betterment over available signifiers of fuel injection in HP, torsion and economic system.
The 1985-1988 TPI system utilized the undermentioned detectors and devices to command the engine: Mass Air Flow Sensor and Module, Manifold Air Temperature Sensor, Coolant Temperature Sensor, Oxygen Sensor, Throttle Position Sensor, Cold Start Switch, Cold Start Injector, Fuel Injectors, Idle Air Control Valve, Vehicle Speed Sensor, Electronic Spark Timing Sensor and Module, and Knock Sensor.
When the key is in the “on” place the Electronic Control Module ( ECM ) , the chief computing machine that controls all detectors and engine maps, powers up and readies the engine for start-up. When the starting motor is engaged and the coolant temperature is less than 100 grades Fahrenheit, determined by the Coolant Temperature Sensor ( CTS ) , the Cold Start Injector provides a spray of fuel to each cylinder via an air distribution system built into the consumption manifold. If the engine temperature is greater than 100 grades Fahrenheit, the Cold Start Injector is disabled by the cold start switch. Upon startup the ECM utilizes information in the Erasable Programmable Read Merely Memory ( EPROM ) to set up the initial pulsation rate for the fuel injectors. The ECM pulsations, or clears and stopping points, the staying 8 fuel injectors in sequence and the engine starts. During this, the Idle Air Control ( IAC ) valve is wholly unfastened to let every bit much air as possible to come in the engine to forestall it from deceasing out. At this point, the engine is runing in unfastened cringle manner and will go on to make so until the engine warms up. After the warm up period the ECM scans the detectors, if all detectors are runing and within their proper scope, the engine so goes into closed cringle operation. This means that the detectors are dynamically commanding the engine. The IAC valve so begins to shut, cut downing the sum of air come ining the engine and therefore decelerating idle to the value specified in the EPROM. In the event that the information received from a detector is higher or lower than the normal scope, a codification will put in the ECM, and the Service Engine Soon visible radiation will turn on.
The ECM receives information on air flow, from the Mass Air Flow Sensor ( MAFS ) or from the Manifold Absolute Pressure Sensor ( MAPS ) , engine temperature, from the Coolant Temperature Sensor ( CTS ) , air temperature, from the Manifold Air Temperature Sensor ( MATS ) , exhaust gas O content, from the Oxygen Sensor, throttle place, from the Throttle Position Sensor ( TPS ) , and vehicle velocity, from the Vehicle Speed Sensor ( VSS ) .
The Mass Air Flow Sensor is located in-line with the accelerator organic structure and air filter box. It is a hollow cylinder with a 4-wire connection. The blue wire carries a mention electromotive force of 8-volts, the grey wire returns the variable opposition to the ECM, the black wire grounds the detector, and the ruddy wire is for the burn-off or cleansing phase. At any RPM above idle, such as during driving or revving, the MAFS begins to map. It straight measures the sum of air come ining the engine at any velocity. The MAFS accomplishes this with a thin wire strung across a graduated tubing. This wire is fed a mention electromotive force that causes it to heat up. When the wire has reached runing temperature, the ECM begins to mensurate the return electromotive force. As air flows through the MAFS and into the engine, the wire begins to chill and therefore changes its opposition. More airflow causes a ice chest wire, which consequences in a lower the opposition, and vise-versa. The ECM so cross-references the return electromotive force to a tabular array stored in the EPROM to find the exact sum of air come ining the engine. When the engine is shut down, the thin wire is so reheated to “burn-off” any dust that is still on the wire. This detector was used on the earlier TPI systems from 1985-89.
The Manifold Absolute Pressure Sensor ( MAPS ) reads engine multiplex force per unit area and translates this reading into a voltage signal that the computing machine uses to supervise airflow into the engine. These reading are used chiefly to cipher flicker progress and fuel enrichment by utilizing complex computations and “fuel maps” to interpret multiplex force per unit area into airflow values. “Absolute” refers to the fact that the detector reads multiplex force per unit area in absolute footings; that is, get downing from 0 as opposed to get downing at low-lying atmospheric force per unit area ( 14.7psi ) . The MAP detector has 3 wires, mention, land, and return. In GM engines, the ECM feeds a 5-volt mention signal to the detector through one wire. As engine manifold force per unit area varies, the opposition of the detector to the 5-volt mention signal varies with it, and the new value is carried by the return wire to the ECM. The higher the multiplex force per unit area becomes, the larger the addition in return electromotive force, and vise-versa. The cardinal constituent in a MAP detector is the strain gage. A thin square Si wafer is attached and sealed to a home base. The infinite between the two is a vacuity and four stretch sensitive resistances are attached to the home base’s borders. As the fluctuating multiplex force per unit area Acts of the Apostless against the perfect vacuity inside the home base, the resistances vary the return opposition. This detector was used on the ulterior TPI systems from 1990-92.
The Coolant Temperature Sensor ( CTS ) is one of the most of import detectors under the goon. About every engine direction map is dependent upon proper information sing engine temperature, and the most convenient index of this is the temperature of the engine coolant. The detector is threaded into either the thermoregulator lodging or the consumption manifold, and has an ellipse shaped connection with two wires, one yellow, and a black land wire. The CTS is known as a negative temperature coefficient thermostatic resistance. This means that as the outside temperature additions, the internal opposition of the CTS decreases. At 0? F, the opposition across the CTS terminuss is about 25,000 ohms; at operating temperature of about 210? F, the opposition drops to under 200 ohms. The ECM determines engine coolant temperature by directing a 5-volt mention signal through the xanthous wire, and so supervising the electromotive force. When the detector is cold, opposition is high, so the xanthous wire electromotive force is around 3-4 Vs; as the detector heats up, the electromotive force will drop, “pulled low” by the diminishing opposition of the CTS. To understand the construct of “drawing low””, think of a H2O pipe with precisely 5psi of force per unit area or electromotive force in it when the terminal of the pipe us closed away. As the terminal of the pipe is opened or opposition lessenings, the force per unit area in the pipe beads; if the terminal of the pipe is wholly opened or no opposition is present, the force per unit area or electromotive force will drop to really near nothing. If you were to unplug the CTS connection and land the xanthous wire, the ECM would see about 0 Vs on the xanthous wire. While the CTS is simple in footings of operation, its truth is perfectly critical to the proper operation of the engine. Everything from air/fuel mixture to torque convertor lockup is controlled to some extent by the CTS. In fact, many engines will non even get down if the CTS is disconnected. While the ECM will expose a cheque engine visible radiation if the detector readings are out of scope, the CTS is the ECM’s merely beginning for coolant temperature information. In many instances, the CTS can be wildly inaccurate while still remaining within scope because the ECM has no other mention to make up one’s mind if the CTS is wrong.
The Manifold Air Temperature Sensor ( MATS ) is really similar in both visual aspect and operation to the coolant temperature detector ( CTS ) , the major difference being that air, non coolant, is the medium that is being measured. The ECM sends a 5-volt mention signal through the sunburn wire to the MATS and so proctors the electromotive force. Hotter temperatures will increase RESs
istance and hence lower the ECM’s electromotive force reading, colder temperatures will hold the opposite consequence. This detector is used by the ECM to find the proper air/fuel mixture. While the detector location varies depending on the engine and theoretical account, on TPI equipped autos the detector is threaded into the bottom of the consumption plenum.
The O detector is one of the most critical constituents in the engine direction system. Its primary map is to supervise the O content of the fumes in order for the ECM to constantly calculate and update the air/fuel mixture for optimal economic system and public presentation. The detector itself looks approximately like a flicker stopper, with anyplace from 1 to 4 wires connected to it. It is ever threaded into a adjustment located between the fumes manifold and the catalytic convertor. Most detectors have a individual wire that carries the signal to the ECM; sometimes this type will hold a 2nd wire that acts as a detector land. Some are heated detectors that have either three or four wires. In three wire detectors the excess wires are for the detector warming component, and the warmer land wire. Four wire detectors have an extra wire to anchor the detector.
The tip of the detector normally contains a ceramic/zirconia component that is coated with Pt at the open terminal, and is covered by a fluted metal sheath. The other terminal of the detector normally has either a little metal case shot or a fictile sheath that contains ambient air. The tip of the detector protrudes into the exhaust watercourse and the difference in the sum of O in the fumes compared to the sum of O in the ambient air “trapped” in the terminal of the detector causes a little ( 0.10 to 0.90 Vs ) sum of electromotive force to be generated. The smaller the O content difference between the fumes and the ambient air, the lower the electromotive force generated and vise-versa. Therefore, leaner mixtures generate lower electromotive forces and richer mixtures generate higher electromotive forces. Actually, the detector acts as a little chemical battery. In operation, the detector electromotive force will “swing” from rich to tilt and back, as the ECM invariably monitors the exhaust O content and alters the air/fuel mixture to counterbalance. The threshold between rich and thin in 0.45 Vs; each clip the detector electromotive force crosses this figure a “crosscount” occurs. Crosscounts are an of import figure for advanced engine direction troubleshooting.
The Throttle Position Sensor ( TPS ) is a rotary 3-wire potentiometer. It produces a variable electromotive force that is used by the ECM to find the place or angle of the accelerator blades. The ECM requires this information to find a figure of engine runing parametric quantities, including air/fuel ratio, torsion convertor lockup, and ignition timing. The TPS is ever located on the accelerator organic structure assembly, mounted on the accelerator shaft antonym of the throttle linkage. The detector is grounded through the ECM, which sends a 5-volt mention signal to the TPS. The 3rd wire supplies the variable electromotive force to the ECM that indicates throttle place.
The Vehicle Speed Sensor ( VSS ) is an frequently misunderstood and neglected constituent of the engine direction system, but it is decidedly an of import 1. Depending on the application, the VSS can command any one or more of the followers: torque convertor clasp lockup, cruise control operation, Idle Air Control ( IAC ) valve place, ignition timing, and switch light activation. There are two primary types of VSS: theoretical accounts with a speed indicator overseas telegram, and theoretical accounts with an electronic speed indicator.
On theoretical accounts that use a speed indicator overseas telegram the VSS is mounted behind the speed indicator caput in the instrument bunch. The smaller black terminal is the pickup, which consists of an infrared Light Emitting Diode ( LED ) and a photodiode mounted confronting each other. In operation a trigger wheel rotates and alternately exposes the LED to the photodiode and hides it. As the photodiode reacts to the visible radiation and dark phases, it sends a signal to a buffer unit at the other terminal of the VSS assembly. The buffer converts the signal into a square moving ridge for the ECM to treat. The higher the frequence of the square moving ridge, the faster the velocity interpreted by the ECM.
On theoretical accounts with an electronic speed indicator, the VSS is mounted straight to the transmittal, where the speed indicator overseas telegram connexion would usually be. This type of detector end products straight to the ECM, which uses the signal both to execute the assorted computations listed above every bit good as to direct the end product to the speed indicator. Unlike the speed indicator mounted VSS the transmittal mounted VSS delivers a magnetic pulsation similar to a distributer pickup detector.
The information from these detectors is used to cipher the proper pulsation breadth for the injectors and the ECM so fires the injectors for the deliberate period. This process is repeated continuously in really rapid sequence to keep the optimal air/fuel ratio. The electronic flicker timing detector and faculty provide maximal timing progress to better engine idle and public presentation. If engine Ping is detected by the knock detector, the timing is automatically retarded to forestall harm from happening. This is besides a uninterrupted procedure.
The Erasable Programmable Read Merely Memory ( EPROM ) bit that is installed in the ECM provides specific information on the engine in the vehicle. EPROM french friess are programmed with different clocking features and injector pulse breadths for different engines. To let for the assorted engine, transmittal, and gear ratio combinations and to run into criterions for emanations, a broad assortment of these EPROM’s were manufactured. The 1985 TPI standardization information is contained in a 32K EPROM. The 1986-89 ECM contained a 128K EPROM, 90-92 ECM’s use a 256K EPROM. The mill ECM has a acquisition capableness that allows it to do corrections for minor fluctuations in the fuel system to better public presentation and drivability. There are two larning characteristics, the Integrator and Block Learn ( IBL ) and Block Learn Memory ( BLM ) . The IBL characteristic has a normal value of around 128. If this value is higher than 128, it indicates that the ECM is adding fuel to the base fuel computation because the system is running thin, a value lower than 128 indicates that the ECM is taking out fuel because the system is running rich. The IBL is a short-run disciplinary action while the BLM is a long-run rectification. The BLM value will alter if the IBL has seen a status that lasts for a longer period of clip. There are from two to sixteen different cell locations that the ECM modifies depending on engine RPM, air flow, manifold air force per unit area, and other conditions such as air conditioning position, etc. The ECM learns how much accommodation is required in each cell, retains it in memory, and applies these accommodations when the engine operates in that RPM or burden scope. These characteristics of the ECM let the system to set itself automatically to your engine and assure peak public presentation. If the vehicle power is disconnected for fix or to clear diagnostic codifications, the acquisition procedure has to get down all over once more.
Several alterations were made to the TPI system throughout its execution. The 1985 system used a Mass Air Flow Sensor ( MAFS ) and a MAFS faculty to command the power and cleansing maps for the MAFS. In 1986 two relays replaced the MAFS faculty and the ECM was changed. In 1989 the cold start injector was deleted. The EPROM provided a wider pulsation breadth on startup to supply a richer mixture for a cold engine. For those old ages, all other characteristics are the same. In 1990 the MAF was replaced with the MAP detector. The1990-92 TPI system still operated the same except that manifold air force per unit area is used to cipher injector pulse breadth as opposed to airflow.
Tuned Port Injection saw continued usage on General Motors’public presentation autos from 1992 through 1994. During that period, the TPI system changed greatly but the basic construct behind its operation remained the same. In 1994, GM killed the TPI system and made the switch to a more modern and efficient Sequential Port Fuel Injection ( SEFI ) system, which is now used all their public presentation autos.
