3S-GTE Engine Management Primer

Every generation of the 3S-GTE came from the factory with an engine management system. This system, known as the Engine Control Unit (ECU) in Toyota-speak, is a computer that controls the fuel system, the ignition system, the boost control system, the variable induction system (TVIS) and performs several other important emissions and safety functions. This computer was programmed at the factory to run the particular variant of the 3S-GTE it was mated with for the environmental conditions (boost ranges, temperature ranges, base fuel pressure ranges and type of fuel available) best fitted to the geographic area it was sold. Then, the program was sealed into an integrated microprocessor chip and soldered onto a board with appropriate supporting electronics. No provisions were made for allowing post-fabrication tweaking and tuning of the system to handle different sensors, control components, boost ranges and fuels.

Because the engine management system has complete control of fueling, ignition timing and various other important parameters, it has a big impact on performance. For this reason, engine management is a topic that is of much interest to those wishing to increase the power produced by their 3S-GTE. Modern engine management belongs to the realm of computers and electronics rather than mechanics, and because of that it is often little understood by folks that are primarily electrically and mechanically minded. Nonetheless, with a little help and desire, most power aficionados can quickly learn enough about engine management systems to work with them.

3S-GTE Engine Management Basics

The 3S-GTE is a four stoke, four cylinder, dual overhead cam engine that uses a timing belt to keep the valves in synchrony with the pistons and crankshaft. It has a distributor directly connected to the end of the intake camshaft to provide the ECU with a pair of sensor that allow it to determine camshaft (and, therefore, crankshaft) position. The distributor also plays the traditional role of distributing a high-voltage single-coil discharge to the appropriate cylinder. A solid-state igniter is controlled directly by the ECU to play the role that points used to in earlier engines.

The Yamaha designed 3S-GTE head has appropriate fuel injection ports that allow fuel to be injected via electrically-activated low-impedance fuel injectors from a high pressure fuel rail into the intake runners just prior to the intake valves. A single auxiliary cold start injector is present on some generations of the engine to inject additional starting fuel directly into the intake manifold during cold start conditions. A coolant temperature sensor is located on the coolant outlet pipe to allow the ECU to adjust fueling to meet the increased fuel demands of a cold engine. On some generations of the 3S-GTE an air flow meter (AFM) was placed between the air intake and the turbo to determine the amount and the temperature of the air entering the engine so that an appropriate amount of fuel can be injected. Some later generations of the 3S-GTE use a manifold air pressure (MAP) and manifold air temperature (MAT) sensor to estimate how much air is flowing through the engine.

Some generations of the engine are fitted with a variable induction system (TVIS) which uses vacuum pressure to activate a set of butterfly valves that close one of the two intake runners between the intake manifold and the two intake valves on each cylinder. At low engine speeds, these valves can be closed to take advantage of inertial supercharging effects provided by having the intake air move more rapidly down the runners. These valves are electrically controlled by a single Vacuum Switching Valve (VSV) which is a electrical solenoid that opens and closes a vacuum valve and thus allows the ECU to control the opening and closing of the butterfly valves.

The throttle is fitted with a Throttle Position Sensor (TPS) that senses the position of the throttle. This allows the ECU to determine when the driver's foot is off the accelerator so that it will take over control of the engine's idle speed. It also allows the ECU to more properly enrich and lean the air fuel mixture to handle quick engine speed changes as it can anticipate these by sensing the quick opening and closing of the throttle. The throttle body is fitted with an Idle Speed Control (ISC) valve can be electronically controlled to feed more or less air into the manifold when the engine is idling. This allows the ECU to maintain a constant idle speed under various different load and temperature conditions.

The turbocharging control system uses a basic pressure activated diaphragm to open an internal wastegate and thus limit maximum boost pressure to approximately its 7psi opening force. A simple bleeder type-system controlled by the ECU through a metered orifice and another VSV (the Turbo VSV, or TVSV) is present to bleed air from the wastegate actuator back to the air intake thus increasing the effective opening pressure of the diaphragm to 10-11psi. This permits the ECU to provide two boost pressure levels with the opening of a single valve.

Some variants of the 3S-GTE come with an Exhaust Gas Re-circulation (EGR) system that allows some of the exhaust gas to be circulated back to the intake manifold under certain operating conditions to reduce the temperature of the combustion chamber and reduce NOx emissions. Another VSV (the EGR VSV) allows the ECU to activate the EGR system when the engine reaches proper operating temperature. An oxygen sensor located on the turbo elbow just after the exit from the turbine provides a low voltage signal that the ECU reads when it is in closed-loop operation. In closed-loop operating, the ECU will adjust the amount of fuel injected into the engine based on the content of oxygen still present in the exhaust gases. This allows the engine to be kept at or very near optimal stoichiometry, which is the air-fuel ratio providing the best tradeoff in the emission gas composition. This is essential to meeting state-mandated emissions standards.

To protect the engine from overboosting in the case of a turbocharging control system failure, a manifold air pressure sensor is used to determine whether the boost pressure rises above a predetermined limit. The ECU can then react quickly to prevent potential engine damage by eliminating the flow of fuel into the engine. Likewise, a knock sensor is attached to the engine block and tuned to listen for the presence of knock. When knock is present, the ECU can take corrective measures such as switching the turbocharging control system into the lower boost level and retarding ignition timing to lower cylinder temperatures and begin a safe combustion sequence earlier in the cycle.

A dual speed fuel pump circuit is provided to run the fuel pump at a lower voltage when the load on the engine is low or moderate. A relay provides the ECU the ability to switch the fuel pump to a higher voltage when the load on the engine is high. Another relay allows the ECU to switch the fuel pump off when the engine is not running. On MR2s that came with electric power steering, a control line allows the ECU to switch the power steering unit off when the engine is not running.

In addition to the various sensors already discussed, the ECU is fed a vehicle speed signal. This signal can be used to limit maximum vehicle speed in certain configurations. Also, the electric power steering unit, the air conditioner, the brakes and the rear window defroster units all send signals to the ECU to inform it that they are putting a load on the engine. This allows the ECU to raise idle speed as necessary to ensure that the charging system can continue to deliver sufficient power to charge the battery even under increased idle load. Internal to the ECU is a battery voltage sensing circuit that allows it to increase injector cycles when the battery voltage is low. This is required because fuel injectors take longer to open at lower voltages than they do at higher voltages and that could cause the engine to run too rich or too lean if not properly compensated for.

The Stock ECU

Although frequently badmouthed and demeaned by many wanting to get more power from a 3S-GTE, the stock ECU is a very capable and I would even say flexible engine management system. It is definitely not what I would term a "true" engine management system because it has no provisions for end user adjustments. When you think of all the different conditions and environmental factors the stock ECU can encounter while still smoothly and safely operating the 3S-GTE you begin to appreciate how monumental a task building and programming the stock ECU must have been. When you try to duplicate the programming on an aftermarket engine management system to handle all these different situations, you truly take your hat off to the developers.

The stock ECU was redundantly programmed to protect the engine at all costs and overcoming this programming is essential to increasing the power produced by the 3S-GTE. Even when first level protective layers such as fuel cut are defeated, the ECU still has a second level ignition retard and AFR richening protective response. It is behavior such as this that often requires multiple levels of attack to get the ECU to cease its protective responses so that you can push the limits of what the engine is capable of.

The most common engine management system modification is to use an FCD to prevent the ECU from initialing a fuel cut response when the boost pressure rises above 12psi. The next most common modification is to defeat the TVSV to prevent the ECU from switching between high and low boost modes when an aftermarket electronic boost control system such as the EVC IV is installed on the car. Another widely used modification is to use an air-fuel computer such as the S-AFC to lean out the overly rich AFR programmed into the ECU so that the engine will produce more power during boost. I do not recommend the use of an S-AFC by itself without either an adjustable fuel pressure regulator or an ignition controller because the S-AFC works by modifying the AFM signal such that it appears to the ECU as if the engine is more lightly loaded than it actually is. This not only results in a leaning of the AFR, but it also has the effect of advancing ignition timing and increasing the potential for detonation and subsequent engine damage.

Another area in which the stock ECU does not always behave as desired is in controlling the TVIS. As the 3S-GTE is modified to increase performance, the volumetric efficiency of the engine is changed and the optimal point to open the TVIS is affected. The ECU is ignorant of these changes and thus cannot change its behavior. Also, it has been reported that the ECU does not always operate the TVIS to extract the best performance from the engine but sometimes will use the TVIS as one of its protective layers to reduce engine performance when conditions do not appear to be optimal.

The biggest shortcoming of the stock ECU is its inability to control an upgraded fuel system. Upgrading the stock fuel system becomes an imperative to move beyond the 270-300rwhp level. Because the ECU is factory programmed with the stock injector size, it will heavily over fuel the engine if larger injectors are installed. The tricks used to lean out the AFR are far too dangerous to play when you try to make an adjustment of 25-30% or more.

The Techtom ECU

The Techtom system, which was used by G-Force when they were still in business, and is still available from several other companies, uses a special board to insert a Read Only Memory (ROM) chip with a slightly modified stock ECU program right onto the stock ECU board. There are serious limits to how much the stock ECU program can be changed and the most common modifications are raising the fuel cut limit and unlocking the 14psi and 16psi fuel and ignition maps that are present  in the stock ECU but locked out. This allows the boost to be raised to 16psi without the need of an FCD and provides better accuracy and, consequently, more power in the 12-16psi range.

Like the stock ECU, the Techtom system offers no provisions for end user adjustment. Its biggest advantage is that it is absolutely plug-and-play. It uses the stock engine sensors and harness. Installation is a three minute process, requiring only that the trunk liner be peeled back and that the stock ECU be unbolted and unplugged and the Techtom ECU be plugged in and bolted on. If you do not have a spare ECU, however, "installation" requires sending the ECU away for a week or more to be upgraded. Because the ECU can only be programmed with a special Techtom programmer, very few cars have actually been individually tuned using a Techtom.

Greddy eManage

The Greddy eManage is not a stand-along engine management system, but a sophisticated "piggyback" system which intercepts many of the most critical input and output signals running between the stock ECU and the engine. eManage is, in effect, several separate "piggybacks" rolled into one. The eManage allows the fuel and ignition timing parameters of the stock ECU to be varied by some amount across different speed ranges and can, when properly used, allow even a modestly upgraded fuel system to be safely used with the stock ECU.

Stand-Alone Engine Management Systems

A stand-alone engine management system (known as an EMS or a stand-alone computer) allows the complete removal of the stock ECU from the car. In order to do this, the engine management system needs to provide complete fueling and ignition control. Additionally, a full stand-alone engine management system must allow a wide range of adjustments to these functions to provide proper control even on a significantly modified engine.

There are many good EMSs that fit this description. Most of them have some form of support for the 3S-GTE and can be made to work reliably with it. In many cases, one or more new sensors will need to be fitted onto the 3S-GTE. This is actually desirable, especially in the case of the AFM, which has a limit on the maximum amount of air flow that it can measure and quickly becomes a performance bottleneck after reaching that limit.

Most EMSs can be used to replace the AFM with a MAP and MAT sensor pair. This alternate method of determining airflow, known as speed density, requires that the EMS keep an internal fuel map (a fuel map is a table of values with RPM along one axis and MAP along the other). When this map is properly tuned with injection opening time values that are then adjusted by MAT, battery voltage, quick TSP changes, exhaust oxygen content and coolant temperature to provide a very safe, well performing fueling system that does not physically restrict the intake system and can handle as much air flow the sensors are capable of measuring. One disadvantage of this method is that the map has to be properly retuned whenever any significant change in the engine's Volumetric Efficiency (VE) is made, but those changes always present opportunities for making more power with proper tuning, so retuning presents no real problem for a high power engine builder.

Most EMSs also contain an ignition timing map similar to the fuel map. The ignition timing map, when properly tuned and the resultant timing advance values properly adjusted by MAT, coolant temperature, desired RPM (to help idle speed control) and knock detection signals yields an ignition system that provides the right amount of timing advance under any given situation. While the timing map is not affected by VE as much as the fueling map, it is often readjusted to properly utilize different fuel octane levels and enhanced intercooling such as that provided by larger intercoolers and water injection systems.

In addition to fuel and ignition control, many EMSs also provide capabilities for controlling many other aspects of the engine including idle speed, TVIS opening, turbocharging boost control, EGR control, cooling system control, staged fuel injector controls, water injection control and nitrous control. In many EMSs, these controls are well integrated with fueling and ignition controls so that, for example, fuel can be increased and timing retarded when nitrous is injected.

Several EMSs also provide datalogging capabilities. Datalogging is the ability to save some or all sensor parameters so that they can be viewed and replayed at a later time. If coupled with the ability to accept sensor values from sensors other than just those required to run the engine, this datalogging feature can become a very useful tuning tool.

There are many EMSs available on the market and more introduced every year. It would be impossible to list them all and their features. I will mention some of the ones that are most commonly used to control 3S-GTEs and I will then focus on giving an in-depth description of the Electromotive TEC3 system, software and how it was set up to control a 3S-GTE.

Electromotive makes the TEC3, an improved version of their TEC2 which has also been successfully used to control 3S-GTE engines. The TEC3 and TEC2 incorporate direct fire ignition system using GM-style coils that can be used to produce reliable spark power even under high boost. They require the installation of a crank position sensor (for which an MR2 kit is available). This crank sensor uses a 60-2 tooth wheel and a magnetic sensor to provide a highly accurate picture of the position of the crankshaft at all times, thus permitting a very aggressive setting of the timing map under all conditions. The TEC3 incorporates a knock detection circuit and an oxygen sensor circuit for closed-loop operation, provides four general purpose digital/analog inputs, general purpose digital/analog output circuits and can perform datalogging.

Autronic makes the SMC and SM2 systems. These systems can read the stock distributor cam position sensors to provide the fuel and ignition timing signals. They require the use of a Bosch or aftermarket igniter to operate. They incorporate an oxygen sensor for closed loop operation and support datalogging. They provide limited use of the unused fuel injector circuits and an extra auxiliary output to control additional engine functions such as the TVIS and a boost control solenoid.

Haltech makes the E6K and several other EMSs. The E6K can read the stock distributor cam position sensors and it can operate the stock idle speed control valve (at least with the newer firmware). It incorporates an oxygen sensor for closed loop operation and provides datalogging capabilities. It has a general purpose analog and one digital input and a digital output circuit.

Motec makes the M4, M48 and several other EMSs. The M4 and M48 can be set up to read almost any engine sensor, including the stock sensors on the 3S-GTE and can control the stock or any aftermarket ignition system. It incorporates an oxygen sensor for closed loop operation, can perform traction control and datalogging.

Accel makes the DFI EMS. The DFI Gen VII can read the stock distributor but requires that all but four teeth be clipped from the cam position sensor. It can be connected to a wideband oxygen sensor for closed loop operation.

A'pexi makes the Power FC. The Power FC is only able to plug into Gen III 3S-GTE engines but MR Controls offers a harness that that allows the Power FC to operate a Gen II 3S-GTE with the addition of the appropriate MAP and MAT sensors. The Power FC, unlike most EMSs, can be connected to a special programming device, the FC Commander, which allows adjustment of all system parameters without the need for a laptop computer. For standard laptop programming, which is almost essential for doing a map from scratch, the Datalogit kit which allows the Power FC to be accessed via a laptop is. An optional boost kit can be added to the Power FC to provide full electronic boost control capabilities.

AEM makes a plug and play engine management system for Gen II 3S-GTE engines. It uses all of the stock sensors including the air intake sensor in the AFM. To eliminate the AFM, the engine harness must be modified to wire in a MAT sensor. Also, since the stock MAP sensor is only capable of measuring up to 18 psi, the engine harness is often modified to also use a 3-bar sensor. The AEM engine management system uses the stock distributor sensors and can operate the stock igniter as well as direct fire ignition systems. It incorporates the stock oxygen sensor and performs datalogging. A wideband system that allows the AEM to autotune is also available seperately.

The Hydra Nemesis 2 engine management system is also a plug and play system for GenII and GenIII 3S-GTE engines. It does not use the AFM and comes with a built-in 3-bar MAP sensor. The Hydra Nemesis 2 uses the stock distributor and can operate the stock igniter as well as direct fire ignition systems. It has the ability to select between three different fuel and ignition maps on the fly, making it a very versatile system for racing with nitrous and different octane fuels. The system is capable of using either the stock oxygen sensor or directly plugging into a wideband L1H1 5-wire sensor to use for autotuning. Datalogging features are also available.

In-Depth Setup

Setting up and tuning an EMS after it is properly installed should be done conservatively by a qualified individual and then tuned carefully for maximum torque and power using appropriate measurement equipment such as a dyno, a wideband O2 meter, a knock detector and EGT gauges. Here is a detailed sample of what an Electromotive TEC3 setup on a 3S-GTE looks like. Please note that every setup is different and while the parameters shown here work fine on my engine, they may not give ideal or even safe results on yours.

Setting up a TEC3 system to control your engine starts with the basic engine parameters screen:

Several values on this screen must be filled out in order to create a new BIN file which contains all the parameters and maps needed to control an engine. The first necessary value is the engine type. On a 3S-GTE with only a crank sensor the 4-cylinder, 4-stroke, Phased/Staged setting is correct. If a cam sensor is added, the Sequential/Staged mode should be used instead. Phased mode fires each injector on every revolution of the crank to inject half the amount of fuel needed by the engine. Sequential mode fires each injector only prior to the opening of the intake valve for its corresponding cylinder. Sequential allows higher top RPMs and better idle with very larger injectors because injector open and close times only need to be accounted for once for every two revolutions while Phased gives a little bit more torque and power due to the intercooling effects of having two sprays of fuel hitting the back of the intake valve per cylinder event. The TEC3 can operate with a 1, 2 or 3 BAR MAP sensor and this is the second value that must entered in this screen. The maximum engine RPM is the third required value. Once you have these values, you need to select a map size. I use 16 by 16 maps, but even 8 by 8 maps work well because the TEC3 interpolates the values between the cells rather than using a step function. The middle screen provides a calculator for estimating minimum injector size. The final and most difficult items to fill in are those that set up the fuel map. Given a User Adjustable Pulse Width (UAP) and a Pulse Width Offset Time (POT) a fuel map can be calculated. The UAP is the amount of time that the injectors should be kept open at maximum RPM and MAP. This is not very easy to determine, but it is fine to estimate it and adjust it later to get the engine to run properly. The POT value adds (or subtracts, if you put in a negative value) a specific amount of time from each pulse. The minimum injector turn-on time is used to indicate the minimum amount of time that the injectors can be pulsed. If you have high quality low-impedance injectors, you can usually control these down below 1.2 ms and sometimes as low as 1.0 ms. For high-impedance injectors, your minimum turn-on time is usually 1.5 ms or above.

Once these values are entered and a BIN file is created, you can go over to the ignition timing screen and adjust the ignition timing map:

This map is unique from the others in that you can actually edit the MAP and RMP points if you are not satisfied with those selected by the setup wizard. In the ignition timing map, you have total control of the ignition timing that will be chosen for every possible load point and speed point. The TEC3 smoothly interpolates values for points between the cells. The initial advance value is used when the engine is cranking. Note that, in general, you want to advance timing as RPMs increase so that you reach maximum advance by 3500 or 4000 RPMs but you want to decrease timing to prevent detonation as the boost pressure increases. The best approach to filling this map is to start with conservative values and then advance them while on a dyno to the minimum point where maximum torque is achieved.

Once the basic parameters and ignition timing are set up, the engine will run (although it will be hard to start when it is cold). The next stage is to tune the VE map to get the AFR close to a safe, desired point:

The base fuel injection pulse widths are set by the UAP and POT values and these would be sufficient if you had a thermodynamically linear engine, which is one that effectively flows the exact amount of air that the cylinders displace under all conditions. Since real engines don't do this, the VE map allows for an adjustment from the base fuel values. Negative values reduce the amount of fuel delivered at a point while positive values increase it. Despite its name, there is more to adjusting this map than just reflecting the actual VE of the engine. While an AFR of 14.3-14.7:1 is desirable for maximum fuel efficiency and minimum emissions at idle and normal cruising under low loads, more fuel is needed to keep cylinder temperatures lower and detonation in check under boost and this needs to be reflected in the VE map. Like the ignition map, the VE map should be set conservatively and then carefully tuned using a wideband O2 meter under various speed and load conditions. The TEC3 provides capabilities to use a oxygen sensor (preferably an accurate, fast acting wideband O2 meter) to automatically tune the VE table to the AFR values defined in the AFR map:

The desired AFR map is also used to adjust the injector pulse width while the computer is in closed loop mode. The TEC3 provides a wide range of control over closed loop mode operation depending on the speed and accuracy of the oxygen sensor. The EGO parameters screen is used to control closed loop operation:

The top part of this screen controls how quickly and how far the computer will go to adjust the AFR during closed loop operation. A properly tuned set of fuel maps should require very little adjustment, so an authority range of 10% is quite adequate. This also protects the engine from the danger that a failing oxygen sensor could present if an unlimited authority range is allowed. The bottom part of the screen defines the operating range of the closed loop mode. Most important when using the stock 4-wire oxygen sensor is to allow closed loop mode only when the engine is not boosting.

With the basic fuel parameters and the VE map properly filled and tuned using an appropriate oxygen meter, the resultant fuel map can be viewed:

This map cannot be adjusted directly, but it does highlight problems such as points where the injectors would open less than the minimum injector opening time. The TEC3 will not produce an injector pulse shorter than the defined minimum opening time, but if you have too much of the map under this value, you will experience poor operation in that range. In this case, the cells shown in red are rarely encountered in actual operation, so no real problems are experienced.

Once the fuel and ignition maps are properly tuned, the engine will operate very well in warm, steady state mode but you want more than that from a street car. A cold engine needs more fuel to start and operate than a warm one does, and the starting enrichments screen allows fuel to be adjusted during this period of engine operation:

On a stock 3S-GTE, the cold start injector switch and cold start injector provide an adequate temperature-based starting enrichment and very little needs to be done to this screen. In cases where the cold start injector is removed either to replace it with a MAT sensor or when upgrading to an aftermarket intake manifold, this screen can be used to provide an appropriate level of starting fuel through the main injectors. This screen allows for additional starting fuel both during cold and warm start operation. Also, this screen allows the fuel pump to be switched on when the ignition is turned to "ON" prior to cranking in cases where the fuel system needs time to pressurize. The values shown here took some time and experimentation to get right, but with some diligence you can always find a setting that gets the engine quickly started under any temperature condition without flooding. Once the engine is started and beyond the 20 second operating range of this screen, a cold engine will still require additional fuel until it warms up. This can be supplied through the warm-up parameters screen:

This screen is fairly straightforward. Depending on the coolant temperature, extra pulse width can be added above what is specified in the fuel map to operate the engine. Another aspect of proper fueling is adjusting for the impact of air temperature on air density. This is done through the MAT fuel enrichment screen:

Note that fuel is also being enriched when the manifold air temperature goes above 60C. The reason for this is to protect the engine against the increased risk of detonation when the air charge is hot.

So far, we have taken care of starting and warm-up adjustments to the basic fuel map. There are also adjustment that need to be made to allow the engine to run smoothly during acceleration and deceleration. Acceleration adjustments look like this:

The TEC3 can detect acceleration by either looking at throttle position changes or MAP changes. Since the 3S-GTE has a perfectly good TPS that is easily wired to the TEC3, that's the preferred method to use. The rate of position sensitivity determines how fast the throttle position has to increase for the system to go into acceleration mode. Once in acceleration mode, both a cold and regular temperature enrichment can be defined.

Along with an acceleration enrichment, a deceleration cutoff is needed:

The deceleration cutoff screen allows for fuel to be cut off while the engine is being decelerated as well as allowing extra fuel to be added to bring the engine back to normal operation after declaration completes.

The final adjustment that needs to be made to fueling is to adjust the injector pulse widths to compensate for battery voltage:

 Lower battery voltages means that more time will be required to open and close the injectors. The value of 75 us/V is fairly standard and should work perfectly with most injectors.

One final fuel related item is of importance only when a second set of fuel injectors is used to provide additional fuel. This configuration is known as staged injectors and the secondary injectors can be controlled by the TEC3 through the values in the staged injectors map:

There are also adjustments that can be made to the base ignition timing map based on the intake manifold air temperature:

This screen allows the timing to be advanced or retarded depending on the MAT sensor reading. This screen shows the timing being retarded to reduce the possibility of detonation under higher intake air temperatures. The ignition timing can also be adjusted based on the coolant temperature:

This could be used, for example, to increase timing to get a slightly faster idle when the engine is cold. Timing can also be altered to help the engine maintain a steady idle:

In this case a small advance or retard can be applied to keep the engine better centered on the desired idle speed even if an idle speed control motor is not used.

The TEC3 includes an integrated knock detection feature and the behavior of the system to the presence of knock can be easily configured with the knock detection screen:

The parameters entered into this screen determine how quickly system will retard ignition timing in response to a knock signal. Also, because false knock detection usually occurs when the engine RPMs rise above 5000 RPMs, it is a good idea to inhibit knock response at higher RPMs.

A rev limiter is also available:

As is an overboost fuel protection or cutoff feature:

The TEC3 also includes capabilities to control idle speed using a idle speed control motor and this feature can be controlled by the idle speed control screen:

This screen allows different idle speed targets to be selected during engine warm-up. It is also very important to properly set how quickly the idle control will responds to engine speed changes. With a stock flywheel, the 3S-GTE does take a while to change speed due to a change in the idle valve setting and so the system should be set to make small, slow changes so as not to cause wild oscillations in idle speed due to over-zealous control. The system provides for two speed control modes, fine and coarse. I actually found the system to work best when engine was allowed to idle without any fine control. This can be made to work very well if the idle speed screw is set to give the desired idle speed when the engine is warm. In this case, idle adjustment is only needed when the engine is cold or loaded by electrical accessories.

One other feature of the TEC3 that is of some interest is the cylinder trim feature:

This feature can be used to increase or decrease the fuel and ignition to a pair of cylinders. In cases where the engine is being pushed very hard to the edge of its abilities, it may be good to increase fuel or decrease timing a little bit on the number 2 and 3 cylinders which traditionally are the ones that always seem to break when something goes wrong.

Another feature of the TEC3 that is very useful is the ability to program the four general purpose outputs to control engine functions other than fueling and ignition timing. Particularly powerful is the ability to set up the first two general purpose outputs to have fully adjustable pulse widths at various frequencies depending on the speed and load on the engine:

In this particular case, which is actually a very simple application of what can be a very sophisticated level output, the first general purpose output is set up to control a water injection system. If a sophisticated valve such as that provided in the Aquamist 2s kit were connected to the TEC3, a much more sophisticated map could be developed to inject differing amounts of water depending on engine load and speed. Such an output could also be used with a VSV to act as a turbo boost controller.

Another common use of the general purpose outputs is to control engine fans. This can be done by putting one of the output in fan thermo control mode:

In this case, the system is set up to operate the intercooler fan so that it is switched on after the engine reaches an appropriate operating temperature. There are various other simple general output controls that can be easily selected and programmed including speed and boost selectable modes to operate the TVIS VSV or the EGR VSV.

The TEC3 also provides four general purpose inputs that can be set up to perform various functions or to just capture data for datalogging purposes. The following screen shows one of the general purpose inputs selected to increase idle speed when the A/C compressor is switched on:

Another use of another general purpose input is to log vehicle velocity when the input is properly connected to the speed sensor:

There are many other features and controls available on a sophisticated EMS such as the TEC3, but this section has captured everything needed to properly control a 3S-GTE under all real-world conditions.