996 Twin Turbo / GT2

Tuning Guide and Table Definitions

This tuning guide is broken into the basic components of tuning a Porsche 996 TT and the tables associated with each of these components. The guide outlines basic tuning strategies and defines tables for each major tuning category, such as boost control, fueling, and ignition timing.

Step 1 – What is the mechanical configuration of the vehicle?

The first step in tuning a Porsche 996 TT is choosing a COBB Tuning Off-The-Shelf (OTS) calibration that most closely matches the mechanical components and modifications of the vehicle to be tuned.

The Stage1 calibrations are designed for vehicles with no aftermarket parts at all. The Stage2 calibrations are designed for vehicles with an upgraded turbo-back exhaust system. Deviation from the outline configurations will impact the pumping efficiency of the motor and critically impacts all major aspects of tuning (boost, fuel, and ignition).

Step 2 – What fuel is the vehicle using?

Note that COBB Tuning offers calibrations for three different fuels: 93 octane (98 RON), 91 octane (95 RON), and ACN91 (91 octane from Arizona, California, or Nevada). Higher octane ratings indicate higher quality fuel that burns more slowly and can support higher cylinder pressure. This difference in fuel will determine how the car is tuned. Higher octane fuels support more ignition timing, higher boost levels, and leaner air-to-fuel mixtures compared to lower octane. Using a map designed for high octane with low octane fuels can result in damage to the motor.

Step 3 – What type of air intake is on the vehicle?

The 996 TT utilizes a mass air flow (MAF) sensor located downstream to the air filter and before the turbo to measure the amount (mass) of air entering the motor. This air flow measurement is CRITICAL for boost control, ignition timing, and fuel. This sensor reports the amount of air entering the motor, which is used to determine load. Many tables inside the ECU use Load and RPM as their axes. Therefore, it is important that the car is free of leaks of any kind before or after the MAF to be sure of proper running condition. Boost leak tests or smoke tests are needed due to the age of the vehicles. A crucial part of getting the car to run correctly is verifying the mechanical integrity of the vehicle.

Step 4 – Calibration refinement on a chassis dynamometer.

A: Perform initial testing at low boost.

After selecting the most appropriate initial calibration, prepare to test and refine the calibration on a chassis dynamometer. When creating a custom tune, it is best to begin testing under low load conditions by lowering values in the map Maximum Requested Load and Maximum Requested Load Late Cam Position as well as Target Cylinder Filling.

B: Connect the Accesstuner software to the Accessport equipped 996 TT

Open the selected starting calibration in the Accesstuner software then configure the Accesstuner software to connect to your vehicle. Attach the OBDII connector to the vehicle and to your Accessport (if applicable), then connect the associated USB cable to your computer. Press "Ctrl+F" to configure the program. Select the directory in which to store your data logs under the "Logging" tab.

C: Log critical engine parameters while testing.

Accesstuner software allows the user to sample and record critical engine parameters including sensor information and commanded engine function. Open Accesstuner and load the calibration currently flashed to the vehicle. Attach the OBDII cable from the vehicle to the Accssport. Then attach the USB cable from the Accessport to the the computer. Press "Ctrl+F" to configure the logged parameters in the "Log List" tab, and those displayed in the Accesstuner "Dashboard" through the "Gauge List" tab. The Dashboard, a screen that reports active engine and sensor parameters, can be accessed by pressing "Ctrl+B." It is critical to actively monitor the condition of the motor during tuning and this screen is the single best way to do so. These data monitors allow the tuner to determine if a calibration is performing correctly. Accurate and deliberate assessment of logged parameters is the only way to avoid conditions that may damage the motor.
If more than 12 parameters are selected at any one time, the logging can slow down. The Porsche can log 12 parameters around 20 Hz, so the less non-essential parameters the better.

D: Tuning for appropriate Air to Fuel Ratios (Lambda)

The ideal air to fuel ratio (AFR) depends upon fuel quality, engine design, fueling model (port injection, DISI, diesel, etc.), heat exchanging abilities, and other variables. Higher octane fuels are more stable at higher cylinder pressures, and are more resistant to preignition. Leaner AFRs can produce higher power, but also create more heat that may lead to unsafe preignition. Lower octane fuels, such as 91(95 RON) and ACN91 (Arizona, California and Nevada 91 octane), are less resistant to detonation and require a richer (fewer parts air per parts fuel) AFR for safer operation. Richer AFRs produces less heat, protect against detonation (due to a cooling effect of the excess fuel) and usually produce less power. We have found that the 996 TT motor is tuned on the leaner side from Porsche. After some initial testing we have found that just by richening the fuel target, the car picked up power. So we suggest a target AFR of 11.4:1 or a Lambda of around .78.

Air to fuel ratios for these vehicles are directly impacted by several tables. The Porsche fuel control system operates a closed loop control strategy. This means that the car runs a set of wideband air fuel sensors, and is constantly adjusting the fuel targets based on a collection of variables. The fuel target under wide open throttle is dictated by the Target Fuel Map for Component Protection. Setting a target in this table will yield the desired Air Fuel you are aiming for as long as there are no leaks in the system. This differs from the 997.1 as the Target Fuel Driver Demand was the main table for closed loop fuel target. We recommend that you still set the Target Fuel Driver Demand to what you want the values to be as a backup. This table will not be used though unless the modeled exhaust gas temperature falls below 45 degrees C. (This is not possible)

Since the car uses a closed loop system to control fuel, the ECU is constantly monitoring and adjusting short term and long term fuel trims. You can make changes to the short term corrections by adjusting the Fuel Correction Maps. These maps are dependent on valve timing to determine which map is being used at which time. They are a basic multiplier set up so 1.00 = 0 in terms of percentage of a correction. Anything above 1.00 IE. 1.10 is adding fuel, so in this case it would be an additional 10% fuel, .9 would be a -10% correction. Changes are generally linear for fuel correction so a 5% correction should yield a 5% change to the tables.
A fuel mixture that is too lean will contribute to uncontrolled combustion, excessive heat, detonation and possible engine damage. The objective is to run the car at the richest air to fuel mixture possible that does not sacrifice power. Ultimately, the best air to fuel can only be determined in concert with changes to ignition timing. For example, some cases a comparatively rich air to fuel mixture can be run with more ignition timing than a leaner mixture. This combination may produce higher power than a lean mixture with less ignition timing. Generally speaking, the air to fuel and ignition timing combination that produces the best power while minimizing heat is the desired calibration. Of course, this ideal is not limited to ignition timing and fuel, but is also a balance of variable cam timing and boost pressure.

E: Tuning Ignition Timing

The ignition control strategy in the Porsche 996 TT is very dynamic and has a lot of contributing variables to determine the overall ignition timing value. Since the car is always trying best to calculate an overall best efficiency, it does this for ignition timing by using the optimal ignition timing maps and using a target lambda (ʎ) =1 as a base for the efficiency. Additional corrections in the ECU get calculated to produce "optimal timing." This is the basis for all the ignition calculations in the 996. The Porsche uses a strategy of two states of cam timing as well. These points will dictate which of the ignition timing maps are used. The actual ignition timing will be based off of the base timing tables. When at WOT the ECU will try to run the commanded base ignition timing depending on cam position. There are other variables in the ECU that can affect cam timing. However, the biggest contributor to differing timing values (from commanded to actual) is caused by knock per cylinder being active. Most of the timing changes in tuning will be done in the Base Ignition Timing High Lift 1&2 maps. Do not make changes to the Optimum Timing Maps as this is going to have more of an effect on load calculation as opposed to timing advance changes.

F: Knock Control System

The knock control strategy on the Porsche 996 TT is very complicated and uses individual cylinder knock control to make changes to the ignition timing at all times. The system is very sensitive and thus almost always has some sort of feedback. You can monitor knock retard and ignition correction in each cylinder. This is the best way to check for detonation, and to ensure a safe running vehicle. The closer to 0 the better, but if it sways into the negatives (-1 degrees and below) this is the car registering detonation. Since the car is very dynamic it is made to be sensitive. If you are getting values past -6 degrees you will want to try and lower ignition timing, or add more fuel to try and see if you can bring the values back closer to 0. Running a race fuel will also help in getting the knock control values closer to zero.

If running built engines you can change the knock detection thresholds in the software. By raising these tables you are de-sensitizing the knock control system. THIS SHOULD BE DONE WITH GREAT CARE AS DOING THIS CAN RESULT IN ENGINE DAMAGE AS KNOCK CONTROL BECOMES LESS ACTIVE!!

Generally speaking, higher ignition timing supports higher torque and greater power. However, ignition timing should be increased with great caution. Higher timing yields are limited by fuel quality and the mechanical limitations of the motor due to higher cylinder pressure. Too much timing will produce knock sums when fuel quality is the limiting factor. When fuel quality is high, ignition timing should ONLY be added when its addition produces a substantive increase in torque and power. If increased timing does not increase torque, the extra cylinder pressure is simply producing unnecessary stress on engine components.

G: Porsche Torque Control Strategy and Boost Control Relationship

The Porsche Bosch ME7.8. ECU uses torque control to influence how the car behaves on and off power. This system uses input from a wide variety of internal and external sensors to dictate how the car reacts in certain conditions. The boost control system works in this same manner, not by trying to use a "standard" boost control setup, but by trying to achieve a target cylinder filling value. This is dynamic and varies based on conditions, temperatures etc.
Several methods are employed by this ECU to control torque output. One method includes closing the throttle plate when the car overshoots a target torque table. Other methods include lowering ignition timing, or changing air fuel ratios. So you want to be sure that the car is optimally calibrated in all conditions.
From the factory the Porsche 996 TT is equipped with K16 turbos in the standard 996 and K24's in the X50 and GT2's. All Porsche 996 TT use a traditional wastegate setup (non VTG) and a N75 electronic boost control solenoid.
This control rhetoric is implemented by the ECU and changes boost pressure to meet the cylinder filling targets or specified load. The specified load does not have a direct correlation to boost pressure but can be close when trying to determine load vs boost pressure. The boost pressure setup works by outlining what you want the target load to be in the Target Cylinder Filling table and making sure that it is high enough not to close the throttles. You will want to make sure that the two Maximum Requested Load tables are high enough as not to cause the load to be limited by overshooting the maximum load. It is also advisable to try and mimic the natural curve of the turbo by not trying to taper the requested load towards redline on stock turbo's as the turbo's will probably not hold that load target and you might get errors for boost deviation.

If the throttle is closing for any reason then you probably need to revisit the Target Cylinder Filling tables or the Optimum Torque table and raise them so that the throttle stays open.

H: Integrating all tuning parameters for the ideal calibration

The ideal calibration for your Porsche 996 TT is a combination of all major tuning areas outlined above. Generally speaking, the Porsche 996 TT will make the most power when it runs a lean AFR with the maximum amount of ignition timing allowed by the ECU without detonating. Calibrations should be thoroughly tested on a chassis dynamometer, where the impact of tuning is easily measured. Such measurements help determine if the calibration changes are ideal for the vehicle, its mechanical components, and its fuel. For example, addition of ignition timing that does not result in increased torque is not ideal because it produces additional stress on engine components without a perceivable benefit. The same is true of boost and air to fuel ratio. If the vehicle can operate at a richer air to fuel ratio without losing power, it is ideal to do so. If increasing boost does not yield considerable power gain, the turbo may simply be out of its efficiency range and in this scenario, less boost is actually more power. For a basic idea of ideal tuning parameters for your fuel type and mechanical configuration, examine the COBB OTS map notes.

I: Precautions

Fuel – The stock fuel injectors are ~450cc. These vehicles have well designed fuel systems, but if run on ethanol fuel they will run out of injector on the stock injectors and fuel system. Stock fuel pressure is 3.8 bar in the Porsche so make adjustments accordingly.

Mechanical Checks – 996 Turbo models are older and we strongly encourage our customers to review the mechanical state prior to any tuning session. We've included a check off list highlighting mechanical components that should be reviewed here.

Folder: Boost Control

Subfolder: Torque Limits

Maximum Indicated Engine Torque

Table Description- Torque limiter that is correlated to percentage.

Tuning Tips- Raise this to be sure not to hit it as a limit.

Permissible Indicated Torque Limit

Table Description- A permissible torque limit based on a throttle percentage. For tiptronic cars you may need to raise this if there are torque interference errors.

Tuning Tips- Raise this to help add in an increase in torque at lower throttle positions.

Permissible Indicated Torque Limit before Filter

Table Description- A permissible torque limit based on a throttle percentage. For tiptronic cars you may need to raise this if there are torque interference errors.

Tuning Tips- Raise this to help add in an increase in torque at lower throttle positions.

Permissible Torque Post Start

Table Description- A permissible torque limit based on a throttle percentage. For tiptronic cars you may need to raise this if there are torque interference errors. This is based after starting.

Tuning Tips- Raise this to help add in an increase in torque at lower throttle positions.

Torque Limiting Table

Table Description- A torque limit map. The map is already very high and in most cases will not need to be raised.

Tuning Tips- This table can be used to try and limit boost per gear, as it is a per gear toque limit. May be helpful for drag racing.

Torque Offset Tolerance

Table Description- Torque offset tolerance based on a throttle percentage. For tiptronic cars you may need to raise this if there are torque interference errors.

Tuning Tips- Raise this to help add in an increase in torque at lower throttle positions.

Folder: Boost Control

Subfolder: Torque Tables

Engine Torque Drag

Table Description- Maximum amount of engine drag allowed. This is used to affect the lower bounds of the torque control. Used mostly for idle it will help for engine decel to raise this if you have larger cams or turbos and the car is stalling on idle.

Tuning Tips- If raising power levels you will need to increase this table in order for there to be no complications with torque control.

Engine Torque Drag Variant 2

Table Description- Maximum amount of engine drag allowed. This is used to affect the lower bounds of the torque control. Used mostly for idle it will help for engine decel to raise this if you have larger cams or turbos and the car is stalling on idle.

Tuning Tips- If raising power levels you will need to increase this table in order for there to be no complications with torque control.

Optimum Engine Torque

Table Description- This is one of the main maps for the torque control strategy. It is used in maximum torque efficiency calculation as well. This value works directly with the map, Target Cylinder Filling.

Tuning Tips- This table needs to be increased if you want to increase boost pressure. Because the ECU works on a torque based boost control strategy raising this table will also raise boost pressure, as long as the Target Cylinder Filling map is raised as well. You want to try and make a linear change to both tables to ensure the car runs correctly.

Target Cylinder Filling

Table Description- This table dictates the target load value. Raising this table requires the Optimum Engine Torque map to be raised as well. Otherwise a conflict with the torque control strategy will arise and the car will try and apply torque error correction. This table is one of the key proponents to increasing power. Increasing this table has a direct effect on increased boost pressure. Generally speaking, as target cylinder filling increases then more boost pressure is required.

Tuning Tips- Raise this value if you want to increase power, as this table has a direct correlation with the target torque strategy.

Precautions and Warnings – Be sure not to go too high without making appropriate changes to other limit tables, or else the car will run into errors.

Folder: Boost Control

Boost Control Integral Limitation

Table Description – This table acts as an integral boost control limit.

Tuning Tips – This table can be used to smooth boost control curves. Increase this table if boost control is not high enough. If target boost exceeds 22psi then extra pre-caution is warranted as the ECU will continue to ramp in boost pressure as it cannot see the boost increasing. If boost pressure exceed this threshold on an ECU based boost control then you will want to lower this number.

Delta Load Overboost Active

Table Description – This is a multiplier table that allows an active increase in the load based on a percentage if overboost or sport mode, is active.

Tuning Tips – Raise this table if increasing boost pressure to ensure that no errors are triggered.

Duty Cycle Replacement Value for Boost Control

Table Description –Wastegate duty cycle replacement values for the boost control system due to closed loop failure.

Tuning Tips- Use this in case closed loop boost control is no longer working

Lower Limit of Boost Control Duty Cycle (Min WGDC)

Table Description – The minimum wastegate duty cycle percentage allowed from 0-100%.

Tuning Tips- When non OEM turbos are equipped, you may want to set this this table to 0 if boost control is not going low enough or set it to 0 if you would just like the duty cycle to be decreased lower than stock.

Map for Linearization of Boost Pressure

Table Description – This is the WGDC post PID correction.

Tuning Tips – You can use this table as an open loop based boost control, which can be more desirable if using aftermarket turbos or open loop boost control is preferred. You will want to make the PID system a bit more unresponsive though if that is the case.

Max Airflow for Load Calculation

Table Description –This is a maximum airflow limit reading from the mass air flow sensor.

Tuning Tips- Raise these tables if raising the boost pressure so there are no airflow limit errors.

Maximum Allowable Pressure Ratio at the Throttle Plate for Boost Pressure Diagnosis

Table Description – The maximum amount of boost pressure based on RPM and throttle position before the throttle plate.

Tuning Tips- This value will need to be raised in to mitigate errors when increasing the boost pressure.

Maximum Diagnostic Airflow Limit and Maximum Diagnostic Airflow Limit Variant 2

Table Description –These are airflow tables based on mass air flow. If the mass air flow reading goes higher than these tables than the car will throw an error code

Tuning Tips- Raise these tables if raising the boost pressure so there are no airflow limit errors.

Maximum Requested Load and Maximum Requested Load Late Cam Position

Table Description – These tables control the maximum amount of load the ECU will allow before closing the throttles.

Tuning Tips- These values act as a ceiling. Your target cylinder filling tables should be lower than these tables, otherwise the ECU will be trying to target a much higher value.

Minimum MAF and Minimum MAF Variant 2

Table Description –These are airflow tables that is based on mass air flow. If the mass air flow reading goes lower than these tables than the car will throw an error code

Pressure Difference for Overboost Protection Diagnosis

Table Description – This table is used as an allowable amount of boost over what base is set to be.

Tuning Tips – If you are running more boost than stock than you will want to raise this table to ensure that you don't have issues with diagnostic codes from the ECU. You can raise this table or continue to use it as a safety feature.

Threshold Deviation for Boost Control Diagnosis

Table Description – This table is a 1D value that is a threshold deviation due to a boost deviation. If the deviation falls outside of this limit than the car will start diagnosis flags to try and sort out any issues with the boost control system. Raise this if raising boost to help aid in any deviation from target load to actual load.

Tuning Tips – Raise this if raising boost to help aid in any deviation from target load to actual load.

Time for Overboost Active

Table Description –Timer table that is used to allow an overboost amount for a certain period of time.

Tuning Tips- Raise this to be sure that there is no intervention from the ECU due to the overboost being too high for too long.

Upper Limit of Boost Control Duty Cycle (Max WGDC)

Table Description – The maximum wastegate duty cycle percentage allowed from 0-100%.

Tuning Tips- If trying to get as much out of the turbos as possible you may want to raise this value to 100%. Note that in order for this value to be hit you are going to have to make changes to the rest of the VTG tables.

Precautions and Warnings – Raising this value to 100% means that the turbos have the ability to run maximum boost pressure if the rest of the boost control tables are raised accordingly. Use caution when raising these table values.

Folder: Brake Boosting

Delay Time for Limit when the Brake Pedal is Pressed

Table Description- Amount of delay to closing the throttles when the brake pedal is pressed down.

Tuning Tips- Increase this value to ensure that the throttle does not close when trying to use brake boosting. We suggest still leaving a limit on this as to ensure that the car cannot be run for too long in this mode and to ensure that there is a still a safety device in place in the event the throttle is stuck in the open position.

Precautions and Warnings – Modify this at your own risk!! This is a safety device and should only be modified with the knowledge of how to turn a car off in the event of a throttle malfunction!!

Maximum Throttle Angle with Brake Pedal Pressed

Table Description- Maximum throttle percentage allowed while the brake pedal is pressed.

Tuning Tips- Increase this value to ensure that the throttle does not close when trying to use brake boosting. We suggest still leaving a limit on this as to ensure that brake boosting cannot be run for too long.

Precautions and Warnings – Modify this at your own risk!! This is a safety device and should only be modified with the knowledge of how to turn a car off in the event of a throttle malfunction!!

Minimum Engine Speed for Pedal Limit when the Brake Pedal is Pressed

Table Description- Maximum throttle percentage allowed while the brake pedal is pressed.

Tuning Tips- Increase this value to ensure that the throttle does not close when trying to use brake boosting. We suggest still leaving a limit on this as to ensure that brake boosting cannot be run for too long of a time.

Precautions and Warnings – Modify this at your own risk!! This is a safety device and should only be modified with the knowledge of how to turn a car off in the event of a throttle malfunction!!

Minimum Vehicle Speed for Pedal Limit when the Brake Pedal is Pressed

Table Description- Minimum speed the vehicle needs to be traveling in order to activate the throttle closure feature.

Tuning Tips- Increase this value to ensure that the throttle does not close when trying to use brake boosting. We suggest still leaving a limit on this as to ensure that brake boosting cannot be run at too high of a vehicle speed.

Precautions and Warnings – Modify this at your own risk!! This is a safety device and should only be modified with the knowledge of how to turn a car off in the event of a throttle malfunction!!

Folder: Compensations

Air Temperature Hot Limit

Table Description- This 1D value is the limit of the intake air temp threshold before the ECU considers the air temps to be too high and starts to aggressively trim power.

Tuning Tips- You can increase this temp if you are on the dyno and trying to calibrate a car and don't want as much compensation to effect the tuning. If you are always past this on the road the car may also be in need of an intercooler upgrade.

Precautions and Warnings – Raise this table with caution as it will change when the intake air temp compensations come in which are a good thing if the temperature is indeed too hot.

Target Exhaust Gas Temp 1 & 2

Table Description- These tables are exhaust gas temperature targets. Past this the car will try and trim the values back down by implementing methods such as closing throttles.

Tuning Tips- You can increase this temp if you are making big power and the exhaust gas temperature appears to be too high. This is a modeled temperature so the actual temperature values can vary. We suggest measuring EGTs if you are unsure of the actual temperature.

Load Correction Based on Intake Air Temp

Table Description - This table makes a correction to the load. This correction is based off of intake air temperatures.

Tuning Tips - If you are running larger turbos or higher than normal intake air temps than you will want to modify this table so there is not a load correction beyond what you are requesting.

Folder: Fuel

Cold Start Enrichment

Table Description – This table references temp and is an additional fuel percentage above what is requested from the ECU when the car is warming up.

Tuning Tips – Raise this table if you are experiencing cold start issues. This table can be very useful in helping to start on ethanol fuels.

End of Injection Angle

Table Description – This table helps to adjust the end of injection timing for the fuel injectors. The z data values are in degrees BTDC. The idea of this table is to inject fuel with the intake valve open for best efficiency. This is changed to try and increase atomization but sometimes this can be hard. It is also sometimes best to inject fuel onto the closed inlet valve if you feel like the injectors you are using are not atomizing fuel well. This can help atomize the fuel in the intake port but fueling accuracy does decrease. This can also be helpful in starting cars as well. These tables are also useful if you have a car with larger injectors and they are producing black smoke under wide open throttle.

Fuel Correction Map 1 and Variant 1

Table Description – These are the tables that help to correct volumetric efficiency inconsistencies, as well as fuel system inconsistencies. If you need to adjust fuel due to the fuel trims being off, then you want to make fuel changes in the two fuel correction maps. These maps are defined by injector open time and cam timing lift.

Tuning Tips – Since the car utilizes a closed loop strategy you'll want to use this table to make changes to any corrections that are being applied. This is a linear percentage so you will want to make changes accordingly.

Injector Latency

Table Description – This table contains latency values used to tell the ECU how much latency is needed to properly control the fuel injectors; the breakpoints are in battery voltage. All fuel injectors require a certain amount of "dead" time to fully open which is referred to as Injector Latency. The amount of latency an injector requires is dependent on several factors, such as the size of fuel injectors, viscosity of fuel, manifold pressure, and fuel pressure. Lower battery voltage requires increased injector latency (dead time). Likewise, higher fuel pressure may also increase injector latency. The data in this table is represented in milliseconds. A higher value will open the fuel injector sooner, thus the total IPW will be greater; a lower value will open the fuel injector later, thus the total IPW will be less.

Tuning Tips – Most fuel injector manufacturers will be able to provide you with injector latencies by voltage. The drivers used to develop these latencies may be different than the injector drivers in the stock ECU, so further modification from the published values may be necessary and you should not be concerned if your final values differ from manufacturer documentation.

One way to find the correct latency (or at least the latency that works best with the injector drivers in the ECU and your particular injectors) is to begin with stock fuel pressure and the stock intake system, then set the proper scale value for the injectors you are using based of the scalar calculation. Once you have established a proper injector scalar value, start the engine and let the car warm up (coolant temperature between 170-200˚ F and intake air temperature +/- 15 degrees F of ambient temperature) then re-set the ECU so your fuel trims start at zero. Then, start the vehicle again and watch the SUM of your fuel trims, STFT + LTFT. If you see that the SUM of your fuel trims (STFT + LTFT) is positive, add injector latency until you see the SUM of your fuel trims come closer to zero. You will have to test this throughout the operating range of the engine. Try to avoid sudden throttle movements during this process to avoid corrections based on the Tip-in Enrichment tables. If you see that the SUM of your fuel trims is negative, reduce injector latency until you see the SUM of your fuel trims come closer to zero. Again, you will have to test this throughout the operating range of the engine - the entire MAF curve. Try to avoid sudden throttle movements during this process to avoid corrections based on the Tip-in Enrichment tables.

This is part of a calibration process that will bring you closer to the ideal settings necessary to properly control your fuel injectors. Please take into account that you will most likely have to calibrate the fuel correction maps to get the trims where you want them at different operating conditions.

Injector Scaling

Table Description – This table contains a singular value used to represent the fuel injector size or flow rate. Any changes to this value will affect ALL tables within the ECU related to fuel delivery and load calculations. This value DOES NOT need to be altered when using stock injectors with gasoline. When adjusting this value, a lower number represents a LARGER injector, whereas a larger scale value will represent a SMALLER injector. This value in the Porsche is a factor of total opening time. A larger injector will need less time open to supply the same amount fuel, hence the smaller number for a larger injector.

Tuning Tips – In order to calculate the injector open time Porsche uses a large equation to come to the final value. In this equation they calculate air density as well as a slew of other variables. One of these variables is calculating an injector constant with n-heptane. Since some injector companies don't use this as a calibration medium anymore, this can sway the final result of the injector scaling since the density of the two fluids is different. So depending on injector manufacturer you may need to adjust the scaling either up or down to come to a value that is close according to the fuel trims.

With that being said here is the best way to come up with the proper value range for larger injectors:
Y= 44.0901/X so in order to get a new injector constant value divide 44.0901 by your injector size.
Example- Injector Constant= 44.0901/1000(cc)
Injector Constant= .04409 or about .045.

Make sure to check your short term fuel trims at idle after scaling to make sure it is close. Make adjustments if they are not within your target short term fuel trim.

Lower Diagnostic Threshold for Lambda Control

Table Description – This data value is the lower range of the fuel system adaption. It can adapt up to 20% negative. .8 = -20%

Tuning Tips – Lower this if you feel that there needs to more room for the ECU to adjust fuel trims in the negative direction.

MAF Correction

Table Description – This table is used to correct for fluctuations in the MAF signal due to turbulent airflow. This can prove to be useful for cars that are using different intakes that have different size or geometry in relation to piping.

Minimum Injector Pulsewidth

Table Description – This table is the lowest injector pulse width the ECU will allow the injector to operate at.

Tuning Tips – If running an injector is very large like a 2000cc injector, then you may need to increase this value to make sure that the deviation of the injector at low pulse widths is within range. For example if using an Injector Dynamics 2000cc Injector then you would want to raise this value to around 1.0ms or something similar to make sure that the deviation is within a reasonable percentage.

Target Fuel Driver Demand

Table Description – This map is used when modeled EGT's are below the threshold. Since the stock threshold is set at 45 degrees C in the 996 TT this map is not really used, hence the 1.0 lambda target in the table stock

Tuning Tips – We still suggest that you set this to the same values as your Lambda Map for Component Protection table to be on the safe side, in case there is some error in the EGT system.

Target Fuel Map for Component Protection

Table Description – This table is used as protection maps incase temperature limits are reached. They are used as a precaution to cool down the cylinder by adding more fuel than what is requested in the Target Lambda Driver Demand Map. In the 996 Turbo this is the main fuel map as the switch over EGT modeled temp is 45 degrees C. Since this is so low this table will be the main lambda target used.

Tuning Tips – Set this to where you would want a safe air fuel mixture. Avoid setting this too rich as overly rich conditions and retarded ignition timing can cause high EGT's.

Upper Diagnostic Threshold for Lambda Control

Table Description – This data value is the upper range of the fuel system adaption. It can adapt up to 20% positive. 1.2 = 20%
Tuning Tips – Raise this if you feel that there needs to more room for the ECU to adjust fuel trims in the positive direction.

Folder: Idle Control

Target Idle Table

Table Description – Target idle requested for the car based on gear and coolant temperature. Set this higher if the car has cam shafts, or generally just need the idle to be higher.

Target Idle Table 2

Table Description – Target idle requested for the car based on gear and coolant temperature. Set this higher if the car has cam shafts, or generally just need the idle to be higher.

Folder: Ignition Timing

Base Ignition Timing 1,2 Base Timing High Valve Lift 1,2

Table Description – These are the base ignition timing tables. The High Valve Lift maps are used at WOT as they are dependent on the cam switch over. This will be the target ignition timing maps used with no outside influence. So as long as there is no knock then the car should be trying to target the values in these maps.

Tuning Tips – Make the same changes you want to be made to all 4 of these timing tables so you know the timing will be consistent in all operating ranges.

Base Ignition/Optimal Ignition Delta

Table Description – This table dictates the engine efficiency relative to MBT. The X axis is degrees of timing from optimum ignition while the input values are engine efficiency (%).

Tuning Tips – This table typically should not be modified.

Optimum Ignition Timing 1,2,3,4

Table Description – These are the most ideal timing values for the car, and are used in the whole ignition efficiency calculation. These are based on temperature and cam timing reference to select which map is used.

Tuning Tips – Typically you do not need to change these tables. If you need to make changes to the ignition timing, you want to make them to the Ignition Timing Base Tables.

Folder: Knock Control

Knock Detection Threshold Cylinder 1-6

Table Description – These thresholds are made to determine when the knock control system becomes active. Raising these thresholds will make the car less likely to pull timing when it hears something it deems as a knock event. Use this on built motors when the harmonics of the engine can change the amount of noise the knock sensor deems as knock, when in fact, it is just engine noise. The numbers are for each individual cylinder.

Maximum Timing Retard

Table Description – This is the maximum amount of timing that can be pulled out when the knock control is active throughout the RPM range.

Tuning Tips – – Change this if you feel that the car is pulling too much timing or too little timing depending on the knock event. USE THIS WITH GREAT CAUTION!

Timing Reduction per Knock Event

Table Description – The amount of timing retard in degrees that gets pulled during each knock event.

Tuning Tips – Change this if you feel that the car is pulling too much timing or too little timing depending on the knock event. USE THIS WITH GREAT CAUTION!

Timing Refresh Rate Post Knock Event

Table Description – This is a raw value for how fast timing comes back in after a knock event. Lower this value if you want the timing re instate to be faster, or increase it if you want it to decay for longer.

Folder: Limits