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Hydra Nemesis 2 Plug and Play Tuning Instructions

Nemesis Installation Troubleshooting Primer Nemesis Tuning Primer
Wideband Installation Boost Control Installation Ignition Installation

The Hydra Nemesis 2 opens up a whole new world of possibilities to you. With it you can bring out of your engine everything it is capable of delivering in terms of power, drivability, fuel economy, and clean emissions. Provided you have sufficient fuel system capacity and proper heat management and oiling, practically anything is possible with your new setup. The Hydra Nemesis 2 can also be the fastest way to end up with a useless heap of expensive metal. Achieving the former without having to deal with the later is the subject of this tuning section.

Important Information you must know before attempting to tune

Early versions of the Hydra Nemesis 2.1 were shipped with a ground wire going to the B10 pin on the small blue connector. This was required to allows you to adjust the fuel and timing maps on the fly while the engine is running. If this pin has been pulled out as is suggested once your engine is tuned, you will want to put it back into place to allow you to make any on-the-fly adjustments required. Note that adjustments made to the fuel and spark maps in on-the-fly mode are completely forgotten by the Hydra Nemesis 2.1 and 2.5 versions when you shut the ignition power off unless you explicitly make them permanent by downloading the changes to the Hydra Nemesis unit through the 'Download button on the entry screen of the laptop software. Note that downloading will always stop the engine if it is running. This is normal. Just be aware of it so that you don't try to download while the car is moving. Pull off somewhere safe. Download the changes. Turn ignition power completely off for at least two seconds, and then turn the power back on and resume normal operation. Always upload the changes you just downloaded after you turn the ignition power back on so that you don't get a warning telling you that the laptop software and the unit may not be completely synched up with the same map settings.

You should be running at least the Nemesis 2.14 version of the laptop software and Nemesis firmware. If your system is still running on pre-2.14 software, please contact us and make arrangements to have your firmware upgraded.

Most of the numeric boxes in the program panels have an 'Enter' button next to them which must be pushed in order to have the new value you typed in sent to the Nemesis.

Any changes made to the 2D and 3D maps other than the fuel and spark map do not get sent to the Nemesis while in on-the-fly mode until you press the 'Return' key on your keyboard. The laptop software will remind you if you forget to press the enter key after making a change to one of these maps.

Regardless of which changes seem to take on-the-fly, always save your changes to a new file (so that you have old settings still available to go back and look at or download if your new settings create problems) and do an explicit download of the changes when the car is not moving at the end of your tuning or trouble shooting section.

You will get a message indicating that you do not have all of the password keys when you attempt to download changes to the Nemesis. This is normal as the trigger and output codes are locked out to prevent severe damage to the engine should these be improperly modified. If you have a need to change these factory settings, please contact us.

The Trigger

Let's start by familiarizing ourselves a little bit with the way that the Nemesis is connected to the 3S-GTE. The most critical input to the Nemesis is the cam and crank angle triggers. Without these inputs, the Nemesis would not know when to open the injectors and when to tell the ignition to produce a spark. The settings for the stock 3S-GTE trigger is pre-programmed into your Nemesis and locked so that you cannot alter these settings and get them wrong. The unit was tested on a real 3S-GTE engine before it was shipped to you and verified to work properly. There is nothing that you need to do to set up the trigger and the number of cylinders. To verify that the triggering is working properly, watch the RPM readout on the main screen while you crank the engine over with the starter. If the RPM readout stays at zero or go to wildly large values, there is a triggering problem. If it indicates about 200-400RPMs while the engine is cranking, the triggers are functioning properly.

The Injectors

Among the most important outputs is the four injector drivers. These are labeled INJ1-INJ4 on the Nemesis. The Nemesis is not aware of the actual firing order of the 3S-GTE, which is 1-3-4-2 and it does not need to know because it always starts with 1 and counts sequentially until it gets to 4 and starts over again. Because of this, you must remember that INJ1 on the Nemesis is connected to cylinder 1 on the engine, INJ2 is connected to cylinder 3, INJ3 is connected to cylinder 4 and INJ4 is connected to cylinder 2. If this doesn't make sense to you, go back, re-read this section and think about it until it makes sense. Once you have it figured out, upload the Nemesis map into your laptop and go to 'Select->Settings' and click the 'Injection' button. On the left side of this panel is the injector trims. The injector trims allows extra fuel to be directed to specific cylinders. You will notice that many of the base maps are set up to inject an extra 2% of fuel to cylinders 2 and 3 (remember that 2 is 3 and 4 is 2). This is done because the middle two cylinders on the genII engine receive a little extra air when using the stock intake manifold. If you are using an aftermarket intake manifold with good flow characteristics for the power levels you will run, you may want to not trim the injectors at all.

On the right side of the panel, there is a box labeled 'SEQUENTIAL INJECTION' which must be checked to enable sequential injection. If this box is not checked, the Nemesis will use batch injection. Batch injection fires all the injectors simultaneously while sequential injection fires each injector individually starting at some crank angle before the cylinder reaches TDC (determined by the Injection phasing map). Sequential injection should be used as it is more fuel efficient than batch injection. Should batch injection be selected, it is important that 'BATCH MIN PULSE (ms)' be set to a value very close to the true opening time of the fuel injectors. Fuel injectors require around 0.8-1.0ms to open if they are low impedance and 1.0-1.2ms to open if they are high impedance. This value will determine when the Nemesis will fire the injectors once per cylinder event (every other revolution) rather than once per cycle when in batch mode. This value has no impact on the function of the Nemesis when sequential injection is selected.

The 'THROTTLE BODY INJECTION' box should not be checked on the 3S-GTE because it uses port injection.

The 'LEAN UNDER LOAD BACKUP SPARK' box can be checked to enable the Nemesis to switch to the backup spark map if the Nemesis detects a lean condition under high load. To use this option, you must have a wideband O2 sensor. The target AFR table is consulted to determine if the engine is operating under a lean condition.

The 'DYNAMIC ENLEANMENT COEFFICIENT' determines how quickly the Nemesis will pull out fuel in situations where the throttle is released and the car is allowed to coast under engine braking. If this value is set too low, enleanment will happen slowly which is not very desirable as it will prevent fuel cutoff from cutting in when the throttle is released. This can lead to backfiring and popping from the exhaust. It can also greatly reduce the operating life of any catalytic converter in the exhaust system. Too large a value can result in bucking and lurching, especially at low speed in low gear as even tiny changes in throttle adjustment produce sharp fuel cutoff. Whenever there is an 'enter' button beside a numeric input box, you must click the button to send the updated value to the Nemesis.

The 'DYNAMIC ENRICHMENT COEFFICIENT' determines how much fuel the Nemesis will add when the throttle is quickly snapped open or the intake manifold pressure drops quickly. If this value is set too low, very little enrichment happens and the engine will hesitate and pop during fast throttle changes. If this value is set too high, the engine will feel boggy and lazy when quick throttle changes are made.

The 'MANIFOLD WETTING COEFFICIENT' is not used for port injection. It tells the Nemesis how much fuel condenses out into the manifold instead of reaching the intake valves.

The 'MANIFOLD CHARGING COEFFICIENT' indicates how much of a delay there is between the injectors and the intake valves. A value of 10-30 is appropriate for the 3S-GTE unless the entire injector and runner setup had been modified which changes the stock distance between the injectors and the intake valves, in which case some experimentation will be required to determine which value gives the best overall throttle response.

The Ignition

Another very important output (or outputs, if you requested a direct fire ignition setup) is the ignition. Go to 'Select->Settings' and click the 'Ignition' button. On this panel are various items that let you adjust the settings of the ignition.

The 'KNOCK RETARD STEP' indicates how many degrees of timing the Nemesis should retard the ignition for every poll of the knock sensor that exceeds the threshold signal value defined in the 'Select->Control 1->Knock threshold' voltage. The 'KNOCK RETARD MAX' value indicate the maximum number of degrees that the Nemesis will retard the ignition from the ignition map value due to excessive knock. Setting either of these two values to zero effectively eliminates knock retard but does not eliminate the backup spark map. The knock detection and protection capabilities of the Nemesis are fairly extensive and are explained in a separate knock detection section.

The 'RPM LIMIT SOFT' value indicates the maximum RPM value that the Nemesis will allow the ignition to continue supplying spark to the engine. The Nemesis will begin to introduce deliberate ignition misses around 200 RPMs before this RPM limit is reached. This will at first be a gentle reminder that you are approaching the rev limit and as you approach the limit the misses will increase to make it almost impossible for the engine to exceed the RPM limit on its own power. The 'RPM LIMIT HARD' should be set at or a little above the soft limit and this indicates the RPM point at which the Nemesis will stop injecting fuel. No 3S-GTE regardless of how seriously it is modified will continue to make power when fuel is completely cut.

The 'LAUNCH RPM SOFT' value indicates the maximum RPM that the engine will be allowed to rev to when the launch control is enabled. This is used with a clutch switch to allow the engine to rev up just fast enough to start spooling the turbo but no faster prior to launching the car in a drag race. It could also be used with a hidden switch as a valet rev limiter to prevent the engine from being over-revved by over-zealous parking lot attendants. The 'LAUNCH FUEL CUT % CYCLES' value indicates how many cycles to cut fuel out on when launch control is engaged and the RPMs reaches the launch RPM limit. The 'LAUNCH SPARK CUT % CYCLES' value determines how many misses are introduced when launch control is engages and the RPM limit is reached.

The 'BACKUP SPARK KNOCK COUNT' and the 'BACKUP SPARK KNOCK THRESHOLD VOLTAGE' values indicate the maximum amount of knock that will be tolerated before the Nemesis will turn on the check engine light output and drop to the spark backup map. This feature is disabled when the on-the-fly programming mode is on to prevent the Nemesis from constantly dropping to the spark backup map while the maps are being tuned. See the main installation instructions for details on how to disabled the on-the-fly mode and enable the spark backup feature once the Nemesis is properly tuned.

The 'DIRECT FIRE' checkbox should be checked in order to run a multi-coil ignition system. An appropriate setup of the plug and play system is required to run such an ignition setup as the standard kit is set up to run the stock ignition system. If the multi-coil ignition system is composed of two coils utilizing wasted spark, then the 'WASTED SPARK' checkbox should also be checked.

Idle Speed Control

The Idle speed control is used to control the speed of the engine when the throttle plate is closed. Go to 'Select->Settings' and click the 'ISC' button to access the idle speed control panel. It is important to note that you can waste a lot of time trying to get a perfect idle before your fuel and ignition maps are properly adjusted. It is recommended that you initially get the engine to idle so that it doesn't stall every time you let off the throttle when the engine is warm and not worry about getting perfect idle behavior until after the fuel and ignition maps are properly tuned for your engine.

The 'PROPORTIONAL' value determines how quickly the Nemesis attempts to react to idle speed changes. Set this value to the highest number that does not produce any wavering or hunting of the idle speed. This hunting will be particularly noticeable when the engine is first warming up. The 'INTEGRAL' value determines how much the Nemesis will flare the engine when the engine first starts and how quickly it attempts to recover idle speed when the engine is allowed to drop quickly back to idle. The 'DERIVATIVE' value determines how quickly the Nemesis will bring the idle down when the engine RPM is above the idle target. The target idle speed is defined in the map under 'Settings->Control 2->Idle speed target'

The 'MAX VACUUM (mmHg)' indicates the lowest vacuum that the Nemesis will attempt to control idle speed at. This should be set at no less than 50 mmHg below the normal idle vacuum produced by the engine when it is at normal operating temperature. For example, if your engine idles at around 550 mmHg, then set this value to 600-650 mmHg.

The 'AC STEPS UP (%)' value is used to allow a higher idle of the engine when the A/C compressor clutch is engaged. Older versions of the Nemesis plug and play system did not have a connection to the A/C signal and so this value will have no effect on idle control. If you are not sure if your system is aware of the A/C, go to 'View->Panel' when the engine is running and watch if the A/C indicator changes color when you switch the A/C compressor on and off.

The 'INTO DRIVE STEPS UP (%)' is also not used and pertains only to cars with automatic transmissions.

The 'VEHICLE MOVING STEPS UP (%)' value can be used to give the idle speed a little bump up when the throttle is released while the car is in motion. This can be used to offset the dip in idle speed that sometimes happens when the throttle is allowed to snap shut after the clutch is engaged.

The 'ANTILAG POSITION (%)' allows the idle valve to be opened when the antilag maps are selected. Setting up a real anti-lag requires the use of extremely retarded timing and extra fuel in addition to air in order to burn the fuel. Since antilag would usually be enabled while the throttle is closed and clutch is pushed in, the idle valve is likely to be the main source of air for the engine during that time.

The 'MIN PWM DUTY' and 'MAX PWM DUTY' values set the minimum and maximum range of the stock Toyota idle speed control valve. These values should allow the idle speed control valve sufficient freedom to control the idle speed when the engine is cold and warm. There are limits to how much air the valve controls, therefore the settings of the valve need to be adjusted in conjunction with the physical settings of the idle air bypass screw on the top of the throttle body and, in some cases, the setting of the idle stop screw. These values can be used to completely shut off the idle speed control so that the base idle speed setting of the idle screw can be properly set to a point that is just below the minimum desired idle speed when the engine is warm and the accessories are off. Once that is done, the engine should be able to run without stalling even if the idle speed valve is not operating. The idle speed will be affected by electrical loads such as the headlights, but the engine should receive enough air to prevent it from stalling when it is at normal operating temperature. Once that is accomplished, the idle speed valve can be given the freedom to maintain the desired target speed as the engine load changes and when the engine is cold.

The 'VALVE STEPS' setting is not used except if a special setup that includes a GM stepper motor idle speed valve is requested, in which case this value should indicate the number of steps required to move the valve from the fully closed to the fully open position.

The Throttle

The throttle position sensor input is used by the Nemesis to perform several useful functions. One of these is to determine when the idle speed control valve needs to operate to keep the idle speed of the engine constant under varying loads and when to keep the valve closed to allow normal engine operation. Another important function is to provide extra fuel to the engine during quick throttle transitions. Go to 'Select->Settings' and click the 'THROTTLE' button to access the throttle parameters.

The 'CLEAR FLOOD TPS (%)' value is used to provide a quick method for clearing the excess fuel out of a flooded engine so that it will start. Set this value to 90 so that if you push the throttle all the way or nearly all the way down to the floor while you crank the engine, the injectors will be completely turned off and the incoming air will quickly clear out the flooded cylinders.

The 'IDLE' and 'WOT' values indicate the closed and wide open settings of the throttle position sensor. In general, these should be calibrated using the 'TPS CAL' box. The 'IDLE' setting will generally be one or two greater than the actual throttle closed value to prevent any slight variations in the throttle values caused by heat to prevent the Nemesis from realizing that the idle speed control valve should be operating.

The 'TPS SENSITIVITY THRES' value determines how sensitive the Nemesis is to throttle changes in terms of initiating throttle pump and deceleration fuel cutoff events. The larger the value, the less sensitive the Nemesis becomes to throttle changes. In general, a value between 40 and 45 is probably best for most setups. If this value is too small, the engine may buck and surge at very low throttle settings as the deceleration fuel cut kicks in and out with only tiny throttle adjustments.

The 'MAP SENSITIVITY THRES' value determine how sensitive the Nemesis is to manifold pressure changes in terms of initiating throttle pump and deceleration fuel cutoff events. The larger the value, the less sensitive the Nemesis becomes to throttle changes. In most cases, a value of 50 is most appropriate.

The 'Range multiplier' value should be set to 100.

The throttle pump map determines how much additional fuel is injected by the Nemesis when the throttle is opened quickly. Go to 'Select->Control 1->Throttle pump' to view this map. When the throttle is snapped open, the vacuum in the intake manifold drops quickly. This causes some fuel to drop out of suspension which must be quickly replaced if the engine is to keep running without temporarily leaning out. The throttle map indicates how much additional fuel is to be injected immediately after a quick throttle movement. If the amount of fuel injected is insufficient, the engine will bog down and feel sluggish on quick throttle movements. Backfiring and popping during fast throttle changes and gear shifts is usually indicative of either insufficient throttle pump or too high a sensitivity threshold preventing throttle pump initiation.

The Outputs

The Nemesis is set up with various outputs to control all standard engine functions as well as some additional external functions that can be controlled with the Nemesis. The output panel can be reached by going to the 'Select->Outputs' screen. The Nemesis comes programmed with specific output functions which are matched to the plug and play harness and are locked to prevent them from being inadvertently misused in ways that may make it impossible to run the engine properly or safely.

The 'INJ1' through 'INJ4' outputs are set to drive the four main injectors.

The 'INJ5' output is used to control a proportional water injection system such as the Aquamist 2C. The output is set up to use the PWM MAP 9 which is a three dimensional map in which the X axis is boost controlled and the Y axis is RPM controlled. The map must be programmed by going to 'Select->3D pwm->PWM 9 MAP' and entering appropriate duty cycles to inject the desired amount of water at each point.

The 'INJ5' through 'INJ8' outputs may also be set up for staged injection if this was requested when the unit was purchased. When staged injection is used, the output values must be set appropriately to reflect the size of the staged injectors relative to the main injectors. The 'RATIO' value should be calculated as 100*main injector flow/staged injector flow. So, if the main injectors are 550cc and the staged injectors are 440cc, the RATIO value should be set to 125 (100*550/440) for all four staged injector outputs.

The 'PWM2' and 'PWM3' outputs are used to control the stock Toyota idle speed control valve.

The 'PWM4' output is set up to control the TVIS, which are the butterfly valves present on the intake manifold on the gen2 3S-GTEs. The RPM value should be set to the point above which the valve should be open. This value should be in the range of 3600-4200 RPMs depending on the amount of power that the engine is able to make. The optimal opening point can be best determined on a dyno by doing a pull with the valve open from a very low RPM value (like 1000) and a pull with the valve open at a high RPM value (like 5000) and finding the point at which the two torque curves intersect. On setups where the TVIS has been gutted, the TVIS wire can be used to control other devices such as a shift light and the RPM value used is the desired shift point. If a high-intensity LED is used as a shift light, it should be connected in the following way:

The 'PWM5' output is set up to control the turbo timer option available with the Nemesis. The 'TIMEOUT (S)' value can be adjusted to indicate how many seconds the engine should be allowed to idle before shutting off. The timeout starts whenever the throttle returns to the idle position. If installed as per the instructions, the turbo timer will only keep the engine running if the parking brake lever is in the lifted position.

The 'PWM6' output is used to control the boost control solenoid available with the Nemesis. This output is set up to use the 'PWM MAP 8' 2D map to produce the proper kinds of control pulses to run either internal or external wastegate setups. See the boost control installation instructions for details.

The 'PWM9' output is used to control the electric pump on MR2s equipped with this power steering. This output can be used in lieu of 'PWM4' to control a timing light if the PSCT signal wire is used instead of the TVIS signal wire.

The 'PWM10' output is used to switch the fuel pump from low voltage to high voltage mode. When the output is enabled, the pump is switched to low voltage mode. If the stock fuel pump is replaced with a Supra fuel pump, the value in the control box should be set to '0.0' to prevent the fuel pump relay from switching the higher-current Supra pump into low voltage mode. Be warned that setting the value to anything larger than about 20 can cause your engine to run lean since the fuel pump is not able to supply enough fuel pressure in low voltage mode to maintain a proper AFR during spirited driving and boosting.

The 'PWM11' output is used to control the check engine light. No user selectable settings are available. The check engine light will light when the ignition is turned on and the engine is not running. It will also light when the Nemesis wideband detects that the engine runs lean for more than about five seconds and when the backup spark map is in use because the maximum knock settings were exceeded.

The 'PWM12' output is used to control the TVSV on the stock boost control system. When the output is enabled, the stock turbo control system is placed in low boost mode. The default behavior is to keep the engine in low boost mode until it reaches an appropriate operating temperature. Since the TVSV is almost always disabled when an aftermarket boost controller is installed, this signal can be used to switch on a relay to control fans based on the engine coolant temperature. The temperature value in centigrade at which the output is enabled can be set.

The 'PWM13' output is used to control a simple on/off water injection system. The boost pressure above which this water will be injected can be set.

The 'PWM14' output is used to control the stock EGR valve. When this output is enabled, the EGR valve is allowed to function. The valve is prevented from functioning when the engine is warming up and when the engine is being started. The EGR signal can also be used to control a relay that will switch on cooling fans. It might be a better choice for this function than the 'PWM12' output because it also prevents the fans from running while the engine is off or starting. The temperature value in centigrade at which the output is enabled can be set.

The 'PWM16' output controls the fuel pump. The 'PRIMER (S)' value indicates how many seconds the pump will be switched on when the ignition key is turned on to prime the fuel system even if no attempt is made to start the engine.

The Fuel Map

Properly tuning the fuel map requires attention to detail and the help of a few tools. There is so much that can be said about how to tune a fuel map properly that saying most of it would fill a book. Unfortunately, this is out of the question, so this section hits the highlights. Classes on tuning are available from the EFI University and I recommend  them to aspiring engine tuners.

The essence of tuning the fuel map is to inject the appropriate amount of fuel under every RPM and load point to keep the AFR (air-fuel ratio) at the proper level at all times. What the proper AFR level is can vary across engines and here we consider the gasoline-powered 3S-GTE in particular. AFR is measured as a ratio of air vs. fuel present in terms of mass where fuel is always kept as 1. 14.0:1, therefore, means that there is 14 times as much air mass as fuel mass. The term rich when applied to AFR means that there is a substantial amount of fuel in the mixture while lean indicates that there is less fuel. Enriching indicates that you are adding more fuel for a given amount of air while leaning out (or enleaning) means that you are taking fuel out for a given amount of air.

At idle and under low load conditions, you can safely run the engine anywhere from as rich as 11.0:1 to as lean as 16.0:1 and get reasonable performance. 14.7:1 is stoichiometry, which is a fancy chemistry term that means we have just enough oxygen molecules to bind with all the available fuel molecules to produce complete burning with the fewest level of hydrocarbons left over. If you run leaner than 14:7:1, there will be a bountiful amount of oxygen to support combustion and the availability of so much extra oxygen means that combustion temperatures will be hotter than if less oxygen were available. More heat expands combustion gases more and under load can damage the engine. Under idle and low load, running lean does not produce enough extra heat to damage the engine, but it does cause larger amounts of nitrogen oxide (NOx) compounds to be produced. If the car is equipped with a catalytic converter, it is very important to be constantly switching from slightly lean to slightly rich of 14.7 which is what the closed loop feedback insures will happen provided the fuel map is properly tuned. This is so that the catalytic converter can store up oxygen during the lean part of the cycle to use to convert hydrocarbons to more benign substances during the rich part of the cycle. Without catalytic converters, it is may be advantageous to run the engine slightly lean under low-load cruising as it will improve fuel economy particularly on long highway trips.

As engine load increases above the 100mmHg vacuum range up to the 0mmHg range, extra fuel should be used to both keep the engine cool and to produce best torque. At these load points, an AFR target of around 14.0:1 under some vacuum richening to about 13.5:1 at zero vacuum is appropriate.

Under boost, even more fuel is required to keep cylinder temperatures from quickly destroying the engine and to prevent detonation, which is the explosive, uncontrolled burning of the air-fuel mixture from blowing apart the most vulnerable parts of the engine. How rich depends on the octane rating of the fuel and many other factors, but a good rule of thumb is to aim to be no leaner than 12.0:1 when using premium pump gas. As a tuner, I prefer to keep the AFR as close as possible to 11.5:1 on street applications for what I consider to be the best compromise between longevity and power. Even then, be mindful that every engine is different and some may require a little more fuel to prevent detonation, particularly in hot climates. While engines in general differ in what high load AFR they require and make best torque at, the 3S generally will produce more torque under high load when the AFR is at least 11.5:1 or leaner but it does not tend to produce very much more torque when you go much leaner than 11.5:1. For this reason, 11.5:1 AFR above 5-6psi of boost pressure is what I recommend for most 3S setups, particularly if pump fuel is used.

The Nemesis has adjustable RPM and load points. The base maps provided for the 3S-GTE come with a full 32 by 32 set of load and RPM points which provide more resolution in the boost range and extend the RPM range out in the idle range and the spool range of most turbos. This will provide the tuner with all the control they would ever need in these critical areas. Obviously, the more load and RPM points you have the better the resolution, but the price you pay is that you will spend more time dialing each each cell to perfection. It is important to point out that when you change the RPM and load points by going to 'Select->Settings' and clicking on the 'GRIDX SETUP' and 'GRID Y SETUP' buttons the values in the maps do not move or change. If you desire to have load or RPM points others than those in the base maps, set these first before you go on to do any serious work on these maps and then immediately go into the maps and put in reasonable starting values for these new load and RPM points. It is also perfectly fine to set the RPM and load points so that you will only run in what is effectively only one quarter or one half of the available map.

The easiest area of the fuel map to adjust is the idle range and this is the best place to begin with on the Nemesis fuel map. Go to 'Select->Settings' and click on the 'CLOSED LOOP' button. Uncheck 'ENABLE CLOSED LOOP,' 'ENABLE LONG TERM LEARNING' and 'ENABLE AUTO-TUNE' if they are checked. This will prevent the closed loop correction from attempting to adjust your AFR while you are trying to tune the fuel map. Go to 'Select->Fuel' to bring up the main fuel map.Start the engine and allow it to warm up. Using either the internal wideband if you have one installed or an external one, determine what AFR the engine is idling at. If it is not within 14.6:1 to 14.8:1, some tuning is in order.

Both the RPM and load points can be placed in either track or hold modes. When they are in track mode, the blue box which highlights the cell on the map that is currently selected for adjustment tracks both the load and the RPM of the engine, which is the yellow box that moves around when these are both switched to hold mode. When in hold mode, you can use the left and right arrows to move the blue box to the load point that you want to modify. When you at a particular box, the page up and page down keys increase or decrease the amount of fuel in the selected cell by the amount shown in the resolution box below the fuel map. This box is either '0.005' or '0.05' and you can use the '-' and '+' buttons to the left and right of this number to switch between the two resolutions. The higher resolution is used to make coarse changes to the fuel map when the AFR is more than 0.1 or 0.2 off from your desired target. The low resolution mode is good for very fine tuning of the AFR once you are almost at your desired target AFR. You should be able to do all your tuning in the '0.05' resolution mode. The higher resolution mode may be required when using very large injectors to get a proper AFR around the idle region.

The engine is almost never at the exact load and RPM points represented by any of the cells on the map. The Nemesis calculates the desired base fuel amount by looking at the four cells that most closely match the true actual load and RPM at any instant in time and extrapolates between them to determine the right amount of fuel to inject. Because of this, you very rarely make an adjustment by just changing a single cell on the map unless you are holding RPM steady on a brake dyno, but rather you adjust a cell and its eight neighbors to keep the differences between adjacent cells small. When you view the map as a 3D surface as is shown in the middle of the screen, you want to see smoothly rolling terrain instead of sharp peaks and drop offs. Such features are almost always indicative of a poorly adjusted map.

With the engine warm and idling steady, move the selection box to the yellow highlighted cell on the map and adjust it and then its neighbors so as to either richen or lean out the AFR to move closer towards 14.7. If big changes need to be made, it is best to make them in passes over the center cell and its neighbors to avoid creating too large a difference between adjacent cell value as these can cause the engine to move away from the spot where it is idling in unpredictable ways. Even so, if your starting AFR is far from 14.7:1, you may find that the engine will naturally begin to seek a new idling point as you move towards the desired target. When it does so, let the engine steady itself again and move the center cell that you are adjusting to track it and continue the richening or leaning process until you reach your desired target with the engine idling at a steady point. If the idle speed moves higher or lower than the desired range, you may have to readjust the idle settings as explained in the idle speed control section to bring the idle point back in the desired range.

This is probably a good time to point out that there are things that can produce inaccurate AFR readings. An oxygen sensor is measuring how much oxygen remains in the exhaust system at the point where the sensor is located. Consider what happens to the oxygen content of the exhaust if one cylinder is not firing. That errant cylinder is effectively pumping air from the intake manifold into the exhaust manifold. The oxygen in that air is unburned and causes the oxygen sensor to give a lean reading. If you have a cylinder that is not firing, or your ignition system is missing a lot of cylinder events and passing oxygen into the exhaust system, you will read a lean AFR but as you richen it up to try to hit your target you will cause the working cylinders to run very rich. They might actually start to run so rich and produce so much unburned hydrocarbons that the exhaust will smell rich, spit little black hydrocarbon droplets and maybe even produce wisps of black smoke even though the AFR doesn't indicate a rich condition. These are all sure indications that you have to locate and fix the cause of the miss or the faulty cylinder. There is little sense moving on until this problem is resolved. Also, you will get lean readings if there is an exhaust leak large enough to allow air to enter the exhaust system before the oxygen sensor. Catalytic converters also affect the AFR readings from a wideband sensor, so it is always essential to have the sensor located before any catalytic converters in the exhaust system.

If you do not have a wideband sensor, you can still do an excellent job of adjusting the idle AFR to 14.7:1 using the stock narrowband oxygen sensor. Instead of looking at the AFR value on the Nemesis laptop screen, look at the left bar on the O2 indicator. This bar will almost always indicate either 1, which means the AFR mixture is rich or 0 which means that the mixture is lean. If it reads lean, use the process given above to richen it up. Stop enriching immediately when you see the O2 bar switch to 1. If it is rich, lean it out slowly until you see the O2 bar go to 0. Then, come back slowly until it just switches back to 1. At this point you should be very close to 14.7:1.

Once you have managed to set the idle AFR right where you want it, you can now move on to the low-load cruising range, which is the area where vacuum is below 100mmHg and the RPMs are above idle. The ideal way to tune this range is to put the car on a brake dyno that can load the engine at a particular RPM and load point and then simply "walk" the car through every load and cell point that you can reach without putting the valve cover through the engine lid and repeat the same leaning or enriching process across the map. You don't really want to hold the engine at very high RPMs for a long time, so the best thing to do it to tune the car at up to around 5000-6000 RPMs this way and then copy the highest tuned row of RPM settings up to the limits of the map. These setting will actually work quite well for cruising at high RPMs. You might also notice that it is almost impossible to reach the highest levels of vacuum except when the engine is in deceleration mode and even there you will probably not go much below 600mmHg. Set these values so that they have about 0.8-1.0 and leave them alone as they will not even be used when deceleration cutoff is enabled.

If you don't have a load based dyno, find someone who you trust and is willing to drive the car and follow directions. Install a good vacuum/boost gauge in the car that the driver can see if you don't already have one. Find a nice stretch of the emptiest, flattest road you can and get them to drive the car gently up to 3000RPMs and then hold it steady at that RPM point. While they do this, use the same technique to bring the AFR to 14.7:1. Then, have them very lightly ride either the main brakes or the parking brake while holding steady at 3000RPM (it can take some practice to get good at this) to move you up a load point so that you can adjust that. Be sure to explain to them which vacuum point on the boost gauge they need to keep the engine at so that they can keep the car right where you need them to. Work as quickly as you can and give the brakes a cooling off period between every setting to keep them from self-destructing. If you can find a long, steady uphill grade that is even better for reaching the higher load points than the brakes are. Once you have as many of the load points that you can reach on the 3000RPM row up to almost 100mmHg dialed in, stop the car and copy the 3000RPMs cells up to the highest RPM settings on the map and down to 2000 RPMs.

Once you have reached this point, the car should idle well and drive well (at least once it is in motion). If you have the wideband feature, you can use the 'Tools->Log data' panel in the highest speed setting to locate the remaining rich and lean spots in the drivability range. Again, it is probably still helpful to get someone else to drive the car under your direction as you run the datalog and make changes based on the analysis of the results but you can do this by yourself if you prefer. Because of throttle pump and deceleration enleanment effects, you want to consider only those rows on the datalog where the 'tps %' is fairly steady over at least five to size rows at the highest sample speeds. If you spot RPM and load ranges that consistently show rich or lean AFRs, go into the fuel map and adjust those and then repeat the datalog experience until those spots give you the desired AFR readings.

If you work through this patiently, you should end up with a fuel map that idles well, accelerates well and drives well at or below the 100mmHg load point. This is a big accomplishment, and although you will get better at it the more often you do it, it should give you a sense as to why a lot of tuners shy away from doing drivability tuning in favor of the sexier and easier power tuning.

For tuning anything above 100mmHg on the map, a wideband is required. If a dyno is not available, the load range between 100mmHg and 0mmHg can be tuned by dataloging on an open stretch of road. Put the car in third gear and starting around 2500RPMs, accelerate while keeping the vacuum gauge as close to 50mmHg as possible until a maximum safe velocity is reached. The datalog will then show the AFR across at least part of the RPM range for this load point. Adjust the 50mmHg cells according to the results either up or down depending on whether the AFR was higher or lower than 14.0:1. Repeat the process until the AFR is as close to the desired AFR as possible. The process should then be repeated at 0mmHg with the target AFR being between 13.7:1 and 13.5:1.

Tuning the boost range absolutely requires a wideband. Start with the boost control set to the lowest possible setting, which is usually that of your wastegate spring. With the datalog on and set to the maximum logging speed, do a third gear pull from about 2500RPMs to redline. Have someone watch the AFR readings as you do the pull and either call or wave you off if the AFRs climb above 12.0:1 once you are boosting. Once the pull is finished, stop the datalog and look at the AFR across the pull. The AFR should start in the 14s and drop into the 11's by the time you hit full boost. Make adjustments to the fuel map to keep the AFR as steady as possible somewhere between 11.5:1 and 11.8:1 on pump gas. There is not much to be gained power-wise from going much leaner than 11.8:1, so it is better to stay on the conservative side. Note that there is usually a small delay between the map and the AFR readings depending on how far the wideband oxygen sensor is from the exhaust valves. If there is a drop in the AFR at 5100RPMs, the right point on the map to adjust is closer to 4900 or 5000RPMs. Practice is essential in reducing the number of pulls that you will have to make at a particular boost level to end up with a nice, flat AFR curve, so don't be too disappointed if it takes you a while to get it right at first. Once you have the curve right where you want it, raise the boost by 2psi and repeat the process working on the next row of the fuel map. Continue this process up to the maximum boost level that you wish to tune. When tuning above 18psi, it is recommended that race fuel or a mix of race and pump fuel be used to provide additional safety in case the AFR runs a little too lean. In all cases, make sure that the person controlling the vehicle can either see the AFR readings or that there is a system of communications set up to get them quickly off the throttle if the AFRs go too lean. As you finish each pull and review the datalog, take a close look at the injector duty cycles near the end of the pull. If the duty cycles get to 90% or higher when the AFR is set to the desired level, it is time to stop increasing boost as there is not enough fuel left to give any margin of safety beyond this point. Ideally, the injector duty cycles should be no greater than 85% at redline at the highest boost level that you will ever run.

Manifold Air Temperature

After spending so much time and effort getting your fuel maps to give you perfect AFRs, it would be very disappointing to see the AFR be way off by the next day. This can and will happen if you do not have the air temperature corrections properly dialed in. Go to 'Select->Control 1->Air temp trim' to see your correction settings. Air is denser (thus heavier) the colder it is. Denser air means that there are more molecules packed into the same amount of volume and more fuel must be injected to maintain the desired AFR (remember that AFR is the ratio of air vs. fuel in terms of mass). The exact change in the mass of air can be calculated as (base temp in Centigrade + 273) / (new temp in Centigrade + 273). Let's assume the base temp (the air temperature at which you adjusted your fuel map) to be 30C. If you run the engine on a cold morning or evening and the intake air temperature is 10C, the air entering the engine is 303/283 or 7.1% more dense than the air entering the engine when it was adjusted. That means that if you set the 30C point on the air trim map at 0, that the 10C point should be at 7.1. If you calculate for a very cold morning at -20C, he difference is 303/253 or nearly 19.8% denser. You will note, however, that the air trim map doesn't give you this much range. The reason why is that you never actually need it. In actuality, there is going to be a difference in the temperature of the air entering the cylinders (the charge temperature) and the temperature of the air at the location of the air temperature sensor in the intake manifold (the manifold air temperature). The major difference comes from the mixing of the fuel and the air in the intake port just prior to the opening of the intake valve. Since the fuel does not tend to cool off or heat up as much and as quickly as the intake air, the droplets of fuel tend to cool the air temperature down when the air is very hot and warm it up when it is very cold. Also, when the air entering the intake manifold gets very hot, it is appropriate to not lean out the intake fuel as much in order to produce a somewhat richer AFR which will give the engine more protection against pre-ignition and detonation under these extreme operating conditions. The base maps contain some very conservative adjustments to combat detonation under heat. When your maps are well tuned, I recommend air trim settings closer to these:

Air temp -20C -10C 0C 10C 20C 30C 40C 50C 60C 70C 80C 90C 100C 110C 120C 130C
Enrichment% 12.7 12 10.6 8.4 5.6 2.5 -0.6 -3.2 -5.7 -8.1 -10 -11.1 -11.6 -12 -12.3 -12.5

Starting

Although it is obviously essential that the engine be started before it can be tuned, you should not concern yourself too much with perfecting the starting behavior of the engine until you have properly tuned the fuel and ignition maps since most of the starting parameters rely on these values to start the engine properly under all conditions.

It comes to many as a surprise that gasoline is actually not that easy to ignite. You can throw a lit match into a pool of well-ventilated gasoline and the chances are very high that it will just snuff out. To reliably ignite gasoline, you need to obtain a suspension of very fine droplets of fuel in oxygen-bearing air. The colder the air, however, the harder it is to get a good, consistent suspension of fine fuel droplets. What happens in cold air is that the fuel droplets tend to be larger and do not burn as easily. Also, bigger droplets tend to condense out into the runners, valves and combustion chamber walls where they are less likely to ignite and more likely to just be pushed out into the exhaust stream unburned. For these reasons, a cold engine needs more fuel to start and run when it is cold.

The Nemesis has a rather significant set of features that are intended to provide for very quick and reliable starts under any environmental condition. The process of starting the engine actually starts before the starter is even engaged. When the Nemesis is first powered on, the fuel pump is switched on for the number of seconds defined by the 'PWM16' 'PRIMER (S)' output value. This raises the fuel pressure in the fuel line and fuel rail so that the fuel injectors will inject a fairly consistent amount of fuel from the first time that they are opened by the Nemesis.

The very first step of starting the engine takes place the instant that the Nemesis notices that the engine is cranking. This will usually happen as soon as a couple of the 24 teeth in the distributor pass by the G0 sensor. This will happen as soon as the crank rotates through about 60 degrees of a single rotation. At this point, the Nemesis will consult the start primer map (go to 'Select->Control 2->Start primer') and depending on the coolant temperature sensor reading, the Nemesis will pulse all four injectors open for the amount of milliseconds indicated in the start primer map. The purpose of the start primer pulse is to wet the intake ports and jump start the process of building an appropriate suspension of fine fuel droplets in the intake ports. Since the start primer map indicates a pulse width, the size of the injectors and the base fuel pressure is going to affect how much fuel is actually going to be delivered during cold start and so any changes in either injector size or fuel pressure is going to require the start primer map to be readjusted for best starting effect. The colder the engine is, the more gasoline that is going to require. Above 80C, the engine will most likely want no start primer.

When cranking initiates, there manifold pressure in the intake manifold will be equal to ambient atmospheric pressure. This will be between 50 mmHg and 0 mmHg unless you are at high altitudes. The easiest way to tell is to power up the Nemesis and then look at the load dial in the upper left corner of the Nemesis screen to determine what the MAP sensor is reporting. When the engine is cranked, the manifold pressure will drop very slightly because the cylinders will remove some air from the manifold as they open and suck in air. Since the engine cranks at very low RPMs, there will be a lot of time for the ingested air to be replaced in the manifold through the idle valve and so very little vacuum will be produced. After the Nemesis finishes injecting the start primer pulse, it will wait up to two crank revolutions for the G2 cam sensor to determine when the #1 cylinder is in its cycle and then it will start to consult the base fuel map at the RPM (probably around 200-250RPMs for cranking speed) and near ambient atmospheric pressure to determine the base amount of fuel for the next fuel pulse. Generally, these cells should contain values that are very close to the pulse widths required to properly operate the engine at the same load points in the 1000-2000 RPM range.

As long as the engine continues to crank under 400 RPMs, the Nemesis will inject fuel into each cylinder on every cylinder cycle based on the base fuel value in the fuel table for the load and RPM point that the engine is operating under plus whatever percentage of enrichment indicated in the cranking enrichment map based o the current coolant temperature sensor reading. To view the cranking enrichment maps, go to 'Select->Control 2->Cranking enrichment.'  Like the start primer, it will take more enrichment to start a cold engine while an engine that is at 80C or warmer will probably need zero enrichment over the base map values. If you find that you have to provide enrichment at 80C and above to start the engine, then you should increase the values in the base fuel map in the 0 RPM column until you can start the engine reliably when it is hot with zero enrichment. In very cold temperatures, you might need as much as 80-100% enrichment to reliably start the engine.

Once engine speed reaches 400 RPMs, the Nemesis stops consulting the cranking enrichment map and begins consulting the post start enrichment map. To view and edit this map, go to 'Select->Control 1->Post start enrichment.' The values in the post start enrichment map indicate the percentage of enrichment of the base fuel map that the Nemesis will apply immediately after the engine reaches 400 RPMs. This enrichment decays linearly over a short period of time (20-60 seconds) depending on how fast the engine is rotating. As with the start primer and cranking enrichment, the colder the engine, the more post start enrichment will be required to reliable keep the engine running right after it initially starts. If your engine starts reliably but tends to stall after a second or two after you have properly tuned your fuel map, then the chances are that you need to adjust the post starting enrichment map.

From the moment the engine cranks until the moment it stops, the Nemesis also consults the coolant temperature trim map to determine if any enrichment should be added to the base fuel based on the reading of the coolant temperature sensor. To view this map, go to 'Select->Control 1->Coolant temp trim.' In general, only a little bit of enrichment will be required to keep the engine running after the post start enrichment cycle is over. Tuning this map often requires several days of work. Let the engine cold soak overnight (if it is summer, you may need to finish this when winter arrives) and then start the engine and wait about one minute for the post start enrichment to wear off. Then drive the car normally and add or subtract fuel as the engine goes through each temperature range to obtain the best drivability possible. Obviously, other factors such as a weak ignition system or exhaust leaks can cause the engine to run poorly when it is cold regardless of the coolant temp trim map settings. Any such issues will need to be addressed before the coolant temp trim maps can be properly adjusted. The map should be set so that there is zero enrichment in the normal warm operating temperature range of the engine (80-100C). Some tuners will generally add enrichment at and above 110C to help cool down the engine in the case that the cooling system should find itself unable to maintain normal operating temperatures.

Just as the zero RPM column on the fuel map dictates the base fuel requirements of the engine during start, the same column in the spark map indicates how much timing advance to use when cranking the engine. The engine does not need very much timing to crank since things are happening so slowly during this time. Generally, ten degrees of timing is going to start the engine quite well under all conditions.

The coolant temperature trim map allows more or less ignition timing to the base spark map based on the coolant temperature sensor reading. To view this map, go to 'Select->Control 2->Coolant temp spark trim.' It is generally useful to add a few degrees of ignition timing when the engine is cold since poorly atomized fuel is going to burn more slowly that well atomized fuel. In some cases, it may also be useful to be able to retard timing a few degrees to reduce the potential for detonation when the engine overheats.

Knock Detection

The Nemesis has integrated knock detection which can be used to retard ignition timing and add fuel when any hint of knock is detected. Knock detection on the 3S-GTE consists of a knock detector, which is a microphone tuned to a very specific range of frequencies, installed on the engine block under the intake manifold right near the middle of the #3 cylinder. When detonation happens, a very sharp ringing sound akin to a hammer striking metal is produced. This sound has a very strong component in the specific frequency range that the knock detector is tuned to listen to. The sound in turn produces a corresponding voltage that is amplified by the Nemesis and measured as a value between 0 and 5 volts, where 0 is no signal at all and 5 is very certain and probably quite audible knock. Unfortunately, the system is not perfect and normal engine sounds also have some frequency components that show up as a signal in the knock detection circuit. For this reason, the knock response must be tuned on the Nemesis to properly fit the natural signal levels that are produced by the engine while it is under load.

Go to 'Select->Control1->Knock threshold' to see the knock threshold curve. At the bottom of the map, you will note a small, white cross. As you start the engine and drive around, this cross will start to move and leave behind it a train of crosses indicating the level of the knock signal detected. Carefully boost a few times and note where the crosses go. Ideally, the knock threshold curve should be set so that the white crosses almost but not quite touch the threshold curve when the engine is not exhibiting any signs or detonation. The best way to do this is to load up either a map that keeps the engine very rich (say 10:1 AFR) while it is boosting or to drop in a tank of very high octane race fuel.

Whenever the knock signal represented by the white cross touches or goes above the knock threshold curve, ignition timing ill be retarded by the number of degrees indicated in the 'KOCK RETARD STEP' box in the 'Select->Settings->Ignition' panel. For every engine cycle that the knock signal stays above the threshold, the ignition timing is further retarded by the indicated step until the retard level reaches the 'KNOCK RETARD MAX' setting. If either the step or the max values are set to zero, knock retard will be effectively eliminated. This is not recommended on a turbocharged engine.

In addition to retarding the ignition timing, the Nemesis can also be programmed to add fuel while knock is being detected. The 'Select->Control 3->Knock fuel add' map specified how much additional fuel to add depending on how much ignition retard is being applied. While small amounts of detonation can usually be quickly curtailed with a small amount of timing retard, the combination of timing retard and addition fuel to cool down the cylinders should very quickly quench any detonation before it does serious damage to the engine.

Once you have set the threshold appropriately across the RPM range, go to the 'Select->Settings->Ignition' panel and adjust the 'BACKUP SPARK KNOCK THRESHOLD VOLTAGE' so that it is a few tenths higher than the highest level of the knock threshold curve. Set the 'BACKUP SPARK KNOCK COUNT' at 16. This will then provide a level of safety under conditions where the Nemesis detects excessive knock. If the black wire going to the B10 pin of the small blue connector has been removed, the Nemesis will turn on the check engine light and will switch to the backup spark timing map which can be adjusted by going to 'Select->Spark backup.' On the base maps, this map is set to extremely conservative timing values which will allow you to limp home. If the black wire is still connected, the Nemesis will not consult the backup spark map, but it will blink the check engine light once every ten seconds until ignition power is cycled.

Regardless of the effectiveness of the knock detection system, I always prefer to tune the car so avoid detonation under all conditions rather than to allow some detonation to happen and react to it quickly when it does. The former technique produces a setup with more consistent and predictable power delivery, even though its peak power output might not be quite as high as the later technique.

The Timing Map

Proper ignition timing is very critical to obtaining good drivability, maximum safe power and excellent fuel economy. An understanding of ignition timing and how it affects the engine is critical to anyone who wishes to properly tune their timing maps. To understand timing you must keep in mind that the combustion process starts when a high voltage spark jumps across the spark plug's electrode but that it takes a while for that process to work its way across the entire air-fuel charge. The spark initiates a flame front which moves away from the point of ignition oxidizing the air-fuel mixture (that is, combining the oxygen with the gasoline molecules to produce exhaust gasses and release heat) leaving exhaust behind it as it moves towards the cylinder walls and piston top. While this flame font works its way across the cylinder, the piston continues to move from the point at which ignition started towards the point at which the heat and pressure created by the combustion pressure begins to build and ultimately push most strongly against the piston to produce torque at the crankshaft. The faster the engine is turning, the sooner the ignition process must start in order for peak cylinder pressures to happen at about 12-15 degrees after top dead center, which is when the piston is in the ideal location to translate pressure into torque. Sounds very simple, but there are several complicating factors.

Intake pressure, AFR and humidity affect how quickly the flame front propagates. Denser air fuel charge combusts more quickly and requires that the ignition point be delayed in order to prevent peak pressure from taking place too soon. For this reason, ignition must be retarded as vacuum turns to boost in the intake manifold. Very rich fuel mixture takes longer to combust because the extra fuel that can find no oxygen to combine with acts to cool the combustion process and slow it down. The same is true of octane additives and humidity, whether in the form of atmospheric or intentionally injected water. A fuel mixture that is somewhat to much leaner than stoichiometric also takes longer to combust as there are fewer fuel molecules around to combine with the available oxygen and produce heat. For these reasons, a little more timing will be required to produce the same amount of torque when the AFR is rich or when water injection is used as an anti-detonant. The presence of nitrous oxide in the air fuel mixture speeds up the combustion process by providing large amounts of free oxygen that must be fed fuel (otherwise it will turn its attention to the metal in the cylinder walls and piston top to satisfy its hunger) and increases the speed of the combustion process.

Detonation is the process whereby the air fuel mixture stops combusting at a deliberate pace and large portions of it explode in a very short (relatively speaking) span of time. This produces very high amount of heat and pressure too early in the combustion cycle at which point the piston is not in proper position to smoothly convert it into torque and the pressure attempts to lift the cylinder head off the engine block, crush the rod bearings and smash its way past the compression rings and the head gasket. Too much of this, particularly when the engine is under boost and you'll soon be looking at building a new engine. Detonation is usually caused when cylinder temperatures are allowed to rise beyond the point at which the octane rating of the fuel used can keep the combustion process from devolving into an explosion.

Although 12-15 degrees ATDC is the optimal point at which peak pressure needs to occur in order to make best torque, limits in engine design, the condition of the engine (carbon deposits, imperfections in the combustion chamber surfaces, too hot a spark plug), insufficient cooling (coolant temperature, oil temperature), octane rating of the fuel and other external conditions (intake manifold temperature) sometimes prevent ignition from initiating early enough to make best torque. When an engine is under such conditions, it is "knock limited" to running less than the optimal ignition advance and thus from producing less than optimal torque. The 3S-GTE when properly assembled, maintained and fueled with premium gasoline is not knock limited in any off-boost state. Caution, however, needs to be exercised when the engine is under boost, particularly near its point highest volumetric efficiency when running with anything other that the highest octane race fuels.

Since the 3S-GTE is turbocharged, some mention of the impact that ignition timing can have on the turbo needs to be made. Because a turbine runs on heat and pressure, timing can be manipulated in certain areas of a timing map to increase or decrease spool. At low RPMs when the intake manifold pressure is reaching zero vacuum but exhaust volume is not yet sufficient to spin the turbo fast enough to produce boost, a judiciously applied amount of ignition retard can actually cause the turbo to produce boost faster. The reason for this is that when the ignition point is delayed, less pressure and heat goes into producing torque and more of it is left around inside the cylinder when the exhaust valve opens and the blow down phase begins. This increases EGTs and provides more energy to spin the turbo. As long as ignition is not retarded beyond the point where EGTs climb to levels that damage the turbine and stress the cooling system, boost can be produced a few hundred RPMs sooner and the available area under the torque curve can be increased. In situations where compressor surge is occurring because a particular compressor is being driven into its surge zone, additional ignition timing in conjunction with a richer AFR mixture can sometimes be used to slow down the turbo enough to avoid compressor surge.

Do not bother to adjust the ignition map to perfection until you have properly tuned the fuel map to produce the desired AFRs at all RPM and load points. While it is the case that ignition timing will have practically no effect on AFR, the opposite is definitely not the case. This means that you will need different ignition timing values depending on the AFR at a particular load point so there is no sensor in finding that timing unless the AFR is at the desired point for that cell. Also, be sure that you have closed loop operation turned off while you are adjusting the ignition timing.

Before manipulating your timing maps, you will need to gain access to some tools. The first tool is a dyno that can hold the engine at a specific RPM while showing the amount of torque the engine is producing. This is either done through water or eddy current braking. Dynojet 224xLC dynos, Mustang dynos and Dynapack dynos are suitable for this. The second tool is a mechanic's stethoscope with a tube long enough to reach the engine compartment. The purpose of the stethoscope is to detect the onset of detonation before it reaches the stage where it is audible in the passenger cabin above the engine noise. Finally, I should not have to stress the importance of having used a timing light to verify that you are getting the timing that you are requesting on your timing map and that you can get back to that same timing should you ever need to remove the distributor. Before checking and adjusting your base timing, start the engine and wait for it to reach normal operating temperature.

Start with setting the idle timing. The intent of idling is not to make torque, but to run the engine as smoothly as possible and to produce least amount of pollution possible while you're at it. Idle timing should be between 14 and 20 degrees for most applications with larger cams requiring a bit more timing than stock cams. For large cams, I advance timing until I reach the highest amount of vacuum that I can and stop advancing once the vacuum stops responding. Remember that the idle range is more than just a single cell on the map. Use the brake pedal, headlights and the A/C compressor to put the engine at different idle load points and make sure that they all give a good, steady idle.

After adjusting the idle things get a little bit more difficult to do without tools. Ideally, this is the time to take the car to a brake dyno and start determining what the optimal timing is going to be for the driving range of the map. With the car strapped or bolted on to the dyno, set the dyno to hold you as close to one of the RPM points of the map as possible. Now starting at the lowest load point that you can get a consistent torque reading from, retard timing until you see the torque drop and then advance it until torque stops improving. If you continue to advance timing beyond this point, torque will at first stay fairly constant and then start dropping. If the load point is high, you might even start to get detonation, so set the timing to the lowest value that gives you best torque and no more.

Because the Nemesis maps are so large, it could take quite while to set best torque on each individual load cell in the driving range. Fortunately, there is no need to do this. It is sufficient to skip most points and then go back and manually extrapolate the right timing and fuel values in between the cells that you actually calibrated. You should spend more time and get more real points in the areas of the map that you will be spending the most time on when you are driving. The area just above and to the right of the idle region is where the engine will go when you accelerate from a stop. These timing values are critical to tune properly in order to make the engine feel strong when you pull away from a stop. The areas in the 2800-4000RPM range are where you will spend 99% of your time during highway driving. Getting these dialed in very accurately is critical to getting the best gas mileage possible from your map.

As you tune the maps on the brake dyno, keep a careful eye on the coolant temperature since the radiator will probably not be getting as much air flow across it while on the dyno as it would on a real highway. If the temperatures reach 100C, let the engine idle and cool for a while before continuing.

What can you do if you do not have access to a load dyno? In this case you will not be able to dial in the best possible timing, but you may be able to do a little bit by having someone drive the car on the flattest road that you can find with the cruise control set to maintain a steady speed. While you do so, you can adjust the timing at several load points to find the least timing that gives you the greatest vacuum (least load) required to hold a steady velocity. This will be a rough setting at best.

You will probably not be able to use the brake dyno RPM hold approach to find best torque much above a couple pounds of boost pressure unless you are using extremely high octane fuel. Putting the engine under this much load for the amount of time required to find the best torque above this is hard on the motor and will quickly produce detonation. Basically, in the boost region, you will be knock limited and rather than looking blindly for best torque, you need to look for the most torque you can get two or three degrees before the onset of detonation. This is the perhaps the most dangerous part of the tuning process. It is not for the faint of heart but if you do it well you will unleash more torque from your setup than you ever thought you would be able to get.

While setting ignition timing in the boost area of the map, the stethoscope is indispensable. One approach which can be used is to hold the engine at several high load cells and quickly but carefully advance the timing until the telltale sound of detonation just starts and then backing off two or three degrees. Do so very carefully and make sure that you give the engine and the intercooler plenty of time between each of these sessions to cool off. What you will note is that the timing accepted by the engine will drop by a degree every two or three additional pounds of boost and will increase by two to three degrees between the 4000 RPM and 7500 RPM region. That is, you will be able to get away with about two or three degrees of timing more near redline than you will right after the turbo has reached the desired boost setting.

After you have an idea of how much timing the engine will safely accept at several load and RPM points, you can extrapolate across the rest of the boost portion of the map and then you should perform several pulls to redline with the datalog and the stethoscope to verify that you are getting the ignition timing values you want and that there is no hint of knock at any time during the pulls. Patience is a great virtue and the careful tuner will be able to unlock the maximum potential from the engine here because ignition timing has a much greater impact on torque than AFR does.

Once the ignition map is properly adjusted for all load points, you might consider pulling out several degrees of timing in the region of the map where the turbo starts to spool. This area is going to usually consist of the rows between 0 and 5 pounds of manifold pressure. Be sure to document your efforts on the dyno so that you can determine whether your efforts are having the desired impact. If your cams are small, there may not be much of an effect because the cams simply open far too late for a few degrees of ignition timing to make that big an impact on the cylinder temperature and pressure at the start of the blowdown phase. Be careful not too retard timing too much under any conditions as this will increase the amount of heat that the exhaust valves are exposed to when they are unseated and if taken to an extreme can literally result in a burned valve.